Anglo-American Naval DifferencesDuring World War Iby Dean .docx

Anglo-American Naval Differences
During World War I
by Dean C. Allard
U.S. Naval Historical Center
USS Pennsylvania, leading the Presidential convoy at sea, about
40
miles from Brest, 1919. U.S. Navy piyotograph.
APRIL 1980
A NGLO-American mihtary cooperation in World War Ihas been
the subject of a number of historical works. Scho-
lars such as David Trask have demonstrated, for example, that
the United States accepted the grand strategy of the Allies in
which the focus of the land campaign was on the Western Front
while the all-important naval mission was the Royal Navy's
blockade of the continent. Other writers have described the high
level of tactical cooperation achieved in the war zone between
American and Allied forces, including the notably harmonious
joint United States-British destroyer patrol operating from
Queenstown, Ireiand.'
But while cooperation was evident, there also were significant
differences between the Allies and the United States that influ-
enced the shape of America's miiitary contributions and re-
flected the nation's outlook toward the conflict as a whole. This
article wiil discuss several areas of tension that particularly
involved American and British naval efforts.= In developing
this
theme, the contrasting views of Washington officiais and Admi-
ral William S. Sims also will be explored. This is necessary

since
Sims, the well-known, popular, and effective American naval
commander in Europe,* substantially shared the perspective of
Great Britain.* In fact, the admiral based his entire approach to
the war on his long-held belief that American and British
security
interests were identical. Sims also recognized the unequaled
Royal Navy as the dominant naval factor in the conflict and the
leader of all other Allied maritime forces. As a consequence, it
was his opinion that the task of the United States fleet should be
to
augment British operations and most particularly to aid in de-
feating the German submarine counter-blockade of the British
Isles.'
Although Sims' outlook has sometimes been seen as typifying
the American Navy's approach to the war, his concepts were not
shared by officials in Washington who framed the nation's naval
policy. These leaders included Rear Admiral Charles J. Badger,
chairman of the influential advisory hody known as the General
Board; Secretary of the Navy Josephus Daniels; and President
Woodrow Wilson himself. The central figure, however, was Ad-
miral William S. Benson, the Chief of Naval Operations, who
under the direction of Secretary Daniels was responsible for the
"operations of the fleet" and the preparation of "plans for its use
in war."'
Benson has sometimes been viewed as an Anglophobe, but he
might more accurately he described as a nationalist who trusted
no state's benevolent intentions. This austere and relatively
little-known naval officer was noted for integrity, loyalty to
political superiors, and his sympathy for Wilsonian idealism.'
Although lacking the popular reputation of Sims, Benson obvi-
ously shared with the European commander the objective of
military victory. Where Benson differed was in refusing to set
aside other considerations in responding to the needs of the

Royal
Navy or any other ally. He once described his attitude in these
words; "My first thought in the beginning, during, and always,
was to see first that our coasts and our own vessels and our own
75
interests were safeguarded. Then . . . to give everything we
had . . . for the common cause. . . . " At another point, the Chief
of Naval Operations revealed his feelings of Wilsonian indepen-
dence by commenting that, "It is difficult and really impossible
for me to state [when] I felt that we must be involved with the
Allies. . . . In fact, I do not know that I ever fully came to that
conclusion.""
As indicated by Benson, the defense needs of the United States
received priority consideration. Upon America's entry into the
war, the Admiral's conviction that German submarines would
launch operations in the Western Hemisphere — an estimate
based on U-boat activities off the East Coast earlier in the
conflict
— led him to establish a patrol force of destroyers and other
light
craft to safeguard the American continent. To the British and
Admiral Sims, however, these steps seemed almost entirely un-
necessary since they saw submarine operations in American
waters as unlikely and, if they occurred, as diversions of little
military consequence." At the same time, Sims, deeply
concerned
that the^U-boats would force the United Kingdom to her knees,
was calling for the urgent dispatch of American patrol forces to
Europe.
When the German submarine threat in American waters did

not materialize during the Spring of 1917, the General Board
and
planning officers in Benson's office supported Sims' position
that
the United States should assign all possible anti-submarine
ships
to support the defense of Great Britain. As a result, over the
next
two months, about 70 percent of America's small force of
modern
destroyers was deployed to Queenstown, Ireland. Here, Sims
assigned the ships to the operational control of the Royal Navy
which primarily employed them in protecting Allied merchant
vessels in the danger zone surrounding the British Isles."
Admirai Wiiiiam S. Benson, U.S.N. Chief of Navai Operations
during
Worid War i. U.S. Navy photograph.
76
This early deployment appeared to indicate that the American
Navy's anti-submarine forces would serve as an auxiliary to the
British Fleet, a development that was entirely consistent with
the
thinking of Admiral Sims. But Sims soon was to be
disappointed.
Throughout the Summer of 1917, and indeed until the end of the
war, the admiral was critical of the Navy Department for re-
taining a relatively small number of destroyers and other light
craft in American waters for coastal defense." But, of more
fundamental importance, Washington naval authorities soon
began to stress the use of their anti-submarine units for a basi-
cally different mission than the protection of mercantile
convoys
supplying Great Britain.

This shift in emphasis began as early as the Summer of 1917
when the Navy Department became convinced that England
would survive despite the enemy's submarine attacks. The Ger-
man U-boat offensive had become less effective by that time,
but
American planners also concluded that the crisis depicted by
Sims and the British earlier in 1917 had been exaggerated. If a
national collapse actually had been imminent, they noted that
the
far superior Royal Navyhadupwardsof 300 destroyers, including
more than a hundred with its Grand Fleet that were not directly
committed to the anti-submarine campaign. In contrast, the
American Navy entered the war with 51 modern destroyers and,
even after a major building program, could claim a total of only
107 by November 1918."
I T was also in the middle months of 1917 that Americanleaders
recognized the feasibility and need of a national army
in Europe. As a result, the United States Navy became responsi-
ble for the massive task of transporting the American troops and
munitions that would allow America's land power to be exerted
on the Western Front. As early as May 1917, the President indi'
cated his personal concern with this effort by cautioning the
Navy
to reserve enough destroyers from Queenstown to protect troop
movements to the ports of western France. In the same month,
Wilson took the unusual step of personally reviewing and ap-
proving a technical military plan for the safeguarding of such
convoys. When it appeared that neither British officials nor
Sims
recognized the urgency of establishing a sizable American land
force on the continent, Washington officials sent repeated in-
structions to Sims to assign American ships based in the United
Kingdom to the primary task of protecting the lines of
communi-

cation to France, as opposed to their original mission of
guarding
cargo convoys supporting the British Isles. Sims, however, was
not personally convinced of that priority until the Summer of
1918."
In April 1918, as it became evident that the Allies faced a grave
crisis on the Western Front, Great Britain at last recognized the
importance of American ground reinforcements. At that time
and throughout the remaining months of the war, the British
finally made available from their unmatched inventory of pas-
senger liners a significant volume of shipping for the
transporta-
tion of the U.S. Army. As a consequence, and ironically consid-
ering the nationalistic outlook of the Navy Department, a
slightly
larger number of American troops eventually was carried to
Europe in English bottoms than in American vessels. Neverthe-
less, the American Navy was responsible for delivering without
a
single casualty more than 900,000, or 46 percent, of the two
million
Army personnel sent to the Continent."
These operations in support of the land campaign involved a
large fleet that was based largely in the United States. Forty-one
troop transports, operated by the Navy, formed the core of this
force. Protecting the liners on their Atlantic passage were some
30 destroyers — which Sims would have preferred to have had
under his command in Europe — the majority of America's 31
cruisers, and late in the war a number of older battleships. In
addition, approximately 350 cargo ships operated by the Naval
Overseas Transportation Service were used primarily to carry
MILITARY AFFAIRS

military supplies to the Continent. A notable supplement to the
more than 450 trans-Atlantic escort and transport vessels was a
group of 85 ships homeported in Brest, France, under the com-
mand of an American flag officer, that protected American ships
on the final leg of their passage to Western Europe. Setting
aside
the force at Brest, no more than approximately 275 of the
Navy's
other 1500 units and fewer than 15 percent of the Navy's
personnel
were in eastern Atlantic and Mediterranean waters at the time of
the Armistice."
The organization of the ships committed to the projection of
American land power to the Continent indicated that the Navy
Department was as sensitive to the amalgamation of its units
into
European formations as General Pershing was in regard to
American ground forces. The Queenstown destroyers and a
squadron of battleships that eventually operated with the Grand
Fleet were under British operational control. However, the es-
cort units based outside the British danger zone, including those
operating from the French coast, were exclusively in an Ameri-
can chain of command. In contrast to the mercantile convoys
proceeding from the United States to the United Kingdom,
which
were under British strategic direction, the troop convoys that
sailed to the Continent also were entirely American operations."
Following the war, in reviewing the American Navy's overall
contributions. Admiral Benson concluded that the "major part"
played was in "getting our troops and munitions and supplies
over there." He differentiated these operations from the general
defeat of the German submarine, stating that even if the U-boat

campaign had been maintained at its "maximum," the Ameri-
can Army would have been established successfully in France
due to the exceptional measures taken by the United States in
protecting the troop convoys." Captain William Veazie Pratt,
Benson's capable assistant in Washington, also felt that the ser-
vice's key mission had been to support the land component of
Allied grand strategy, focusing on the Western Front, rather
than
augmenting the naval campaign undertaken primarily by the
Royal Navy. He asserted that "our great naval contribution to
the
war lay not in the fighting ships we could throw to the front, but
in
our ability to mobilize and transport America's great reserve
power quickly to the European war front. . . ." Pratt, with his
usual astuteness, contrasted this effort with the perspective of
the Royal Navy and Admiral Sims by pointing out that "The
impelling reason of the British was protection to food and war
supplies in transit. Our basic reason was protection to our own
military forces in crossing the s e a s . " "
DURING 1917, the Navy Department was concernedwith
another aspect of American security that was tangen-
tial to the British maritime campaign in Europe. Upon its entry
into the war, the United States became associated with Japan,
Britain's long-time ally. But, despite the fact that the United
States and Japan were now co-belligerents. President Wilson
remained suspicious of the Pacific power. There was even grea-
ter apprehension by American strategists who bore in mind, for
example, the Japanese seizure during 1914 of positions in the
Marshall, Caroline, and Mariana Islands, a development which
obviously endangered American lines of communication to the
Far East. The two-ocean challenge perceived by U.S. planners
was revealed in a proposal made by Admiral Benson's office in
February 1917 to deploy American capital ships to the Pacific
wherctheir "potential as a fleet in being might be used to the

best
political advantage." This deployment was not made, especially
due to the department's assessment early in the war that Britain
might well collapse, a contingency that could lead to a German
surfate fleet assault in the Western Hemisphere. That threat was
connected with Japan in an April 1917 study by Admiral
Badger's
General Board which noted that, in addition to the short-term
danger in fhe Pacific, consideration had to be given to a hostile
alliance between Japan and Germany in a "war resulting from
A P " " ' " ° "
State, War and Navy Building, 17th and Pennsylvania Avenue,
N.W.,
Washington, as it appeared during World War I. U.S. Navy
photo-
graph.
the present one." In the following month, the advisory body re-
commended to the Secretary of the Navy that every effort be
made to embroil Japan in combat on the Eastern Front since the
prospects of German-Japanese cooperation "will be minimized
on account of tbe resulting antagonism." During the Summer of
1917, attention also was given to reports that the British were
planning to transfer capital ships to bolster Japan's already for-
midable fleet. These rumors were particularly alarming since
the United States had elected to defer battleship construction for
the balance of the war in order to concentrate on building anti-
submarine and merchant vessels."
The various aspects of the Japanese problem received con-
centrated attention in October 1917 when the General Board
held
hearings on a British request that a squadron of battleships join
the Grand Fleet. The Board's witnesses indicated that American

confidence in short-term Japanese intentions was a precondition
to the commitment to European waters of any part of the battle
fleet which, up to that point, had been carefully reserved in
home
waters.'" Captain Pratt noted, for example, that the initial deci-
sion to hold the battleships on the east coast had resulted from
the
"unsettled state" of the "far Eastern Question." The captain
added, however, that he now had been reassured by Viscount
Ishii's mission to Washington. Therefore, Pratt urged that the
requested dreadnoughts be sent to Europe, especially since he
hoped that Japan would imitate America's example by sending
her own reinforcements to the war zone.
Another witness at the hearings. Captain Frank H. Schofield,
also saw the dispatch of American battleships to European wat-
ers in the context of American-Japanese relations. In his view,
this move would indicate the good will of the United States to
Japan. It also would place Great Britain in America's debt, thus
deflecting the British from transferring ships or offering other
assistance to Japan that might threaten American interests."
Benson did not immediately agree with Pratt's and Schof ield's
position, since he continued to feel that the battle fleet should
be
kept together to meet the anticipated postwar challenge of Japan
and Germany, a belief fueled by his pessimism that the Allies
could achieve a decisive victory over the Central Powers. But
later that Fall, as the Lansing-Ishii Agreement was signed which
appeared to commit Japan to the status quo in China, Japanese-
American tensions decliiled in the Pacific. Most U.S. ships were
77

moved to the Atlantic, and apparently congenial relations de-
veloped as the remaining American units cooperated with the
Japanese and British in patrolling that vast ocean area. In
November 1917, Benson also departed for Europe as a member
of
the House Mission for the purpose of discussing the war effort
with the Allies. While there he at last concluded that Japan's
immediate intentions and — as will be discussed later — his
desire to promote an offensive campaign against German sub-
marines, indicated that the American battleships could be as-
signed to the Grand Fleet. In the following month these four
dreadnoughts, later joined by a fifth unit, crossed the Atlantic
and reported to the British command. They represented about a
fourth of America's modern battleships.*"
Thus, after eight months of American participation in the
European war, American fleet deployments were no longer con-
strained by the immediate threat of Japan and her potential
allies. Yet Washington officials, who along with their Allied
counterparts were deeply concerned with national interests in
the postwar era, continued to fear aggression by Japan at a later
date. These apprehensions were reinforced by the limited naval
and military forces actually sent to Europe by Japan and the
distinct possibility until the latter part of 1918 that Germany
could
emerge from the conflict with her fleet intact. Very late in the
war, as it became evident that the Central Powers were on the
verge of collapse, the specter of a Japanese-German
combination
was replaced by a possible hostile alliance between the fleets of
Great Britain and Japan, a situation that influenced Wilson and
his naval leaders in opposing the distribution of German war-
ships to the Allies. All of these considerations obviously pre-
vented American naval leaders from riveting exclusive attention
on the Royal Navy's campaign in Europe."

I N the light of this sometimes detached perspective, itis
paradoxical that another fundamental difference between
Anglo-American naval policies involved United States efforts to
initiate a vigorous offensive in European waters. From the ear-
liest days of American participation in the war. Admiral Benson
and Josephus Daniels expressed profound disapproval of British
anti-submarine efforts, which they considered to be lethargic
and
essentially defensive. Although eventually accepting such mea-
sures as convoying, Washington officials emphasized the
critical
importance of attacking enemy submarines in their home ports,
or otherwise preventing them from reaching the high seas where
the tasks of detection and destruction were greatly compounded.
By the Summer of 1917, Washington proposed to British au-
thorities that a massive mine barrier be placed across the North
Sea as the first element of this campaign. In August, Admiral
Henry T. Mayo, Commander-in-Chief of the U.S. Atlantic Fleet,
was dispatched to Britain to discuss this scheme as well as
further measures to prevent the U-boats from proceeding to
their
attack areas."'
Woodrow Wilson personally spurred these efforts to impress
the American way of war on the campaign against the German
submarine. In July he forwarded a well-known message to Sims
demanding the formulation of bold plans supplementing British
methods, which the President noted "do not seem to us effec-
tive." Nevertheless, Sims' response indicated that he shared the
Royal Navy's pessimism regarding the feasibility of offensive
schemes. A month later, Wilson delivered his famous "Hornet's
Nest" speech to officers of the Atlantic Fleet calling for an
attack
on the nests, or bases, from which the submarines operated.
Prior to Mayo's departure on his European mission, the Presi-
dent reiterated this position to the admiral and added the impor-

tant requirement that the United States take the "lead" and "be
the senior partner in a successful naval campaign.""
Mayo's discussion with the British came at a time when pres-
sures for a more aggressive approach were growing within
British circles. This combination of factors led the First Sea
78
Lord, Admiral Sir John Jellicoe, to present a daring proposal for
the capture of the islands of Heligoland and Wangerooge guard-
ing the approaches to the German North Sea coast, followed by
the sinking of 83 old battleships and cruisers to block the
adjacent
river mouths used by the U-boats. The British offered to provide
31 of these block ships, but they expected the balance to come
froifl America, Japan, and the other Allies.""
Despite the President's stated desire to "do something auda-
cious in the line of offense," the North Sea scheme was entirely
unacceptable both to Woodrow Wilson and his naval advisors.
One member of Admiral Mayo's staff, who was none other than
Ernest J. King, the famed naval leader of a later world war,
summarized the naval reaction by terming the plan a "straw
man" developed by the British to demonstrate the enormous
dangers and costs of a maritime offensive. The President was
openly disgusted with the proposal since he felt the Germans
could easily blast new channels through the North Sea ship
obstructions."'
However, at the last moment during Mayo's mission, the
British took a step that was more consistent with American
views
by assenting to a mine barrage across the North Sea between
Scotland and Norway on the understanding that it would be un-
dertaken largely by the United States. During November and

December 1917, this proposal and the entire strategy of an
offen-
sive campaign were taken up personally by Admiral Benson
when he accompanied Colonel House's mission to Europe. Upon
his return to Washington, Benson, perhaps for the first time,
was
enthusiastic in his desire to employ American naval power on
the
maritime front lines of Europe since he now was convinced that
the British had accepted American naval thinking.""
Benson's optimism resulted in part from the decisions reached
during his visit to establish two bodies — the Allied Naval
Council
and the American Naval Planning Section in London — that
were
designed to improve inter-Allied cooperation. But, perhaps of
equal importance, these organizations were viewed by the ad-
miral and Colonel House as establishing American leadership in
shaping future operations in Europe. This opinion, which soon
proved to be in error, may serve as a remarkable example of
American innocence, considering the nation's recent entry in the
war and Britain's historic status as the world's great naval
power. But it was consistent with Wilson's instruction that the
House ]Vñssion take the "whip hand' ' in establishing an
effective
maritime campaign."'
In the case of the Allied Naval Council, British leadership ap-
peared to Benson to have been effectively replaced by the
United
States since, in his view, the Allies were "anxious that we
should
dominate the entire allied situation." The same principle can be
discerned in Benson's agreement to establish the London Plan-
ning Section. That step complied with a standing request of the

Admiralty and Admiral Sims, but the proposal was modified by
the nationalistic Benson. Specifically, he assured that the
London
planning section was created as a separate entity which wotild
work closely with the British naval staff but not be
amalgamated
into it. Further, the Chief of Naval Operations directed that the
assigned American officers be "imbued with our national and
naval policy and ideas." Benson clearly saw the London staff as
a
tool to persuade the British to develop the type of aggressive
measures that, in Washington's estimation, had long been lack-
ing.-'
So far as specific operations were concerned, Benson "in-
sisted" that American agreement to undertake the North Sea
mine barrage be coupled with a vigorous British mining and
naval patrol campaign to close the alternate submarine transit
route through the Dover Straits." In making this proposal, how-
ever, the admiral and other Navy Department officials recog-
nized that the bulk of the British battle fleet needed to be con-
served for the critically important task of blockading the Conti-
nent and maintaining readiness for another Jutland-type fleet
MILITARY AFFAIRS
engagement, which conceivably could determine the entire out-
come of the war. Thus, in order to allow a supplemental
offensive
campaign to be undertaken, the United States expressed her
willingness to send capital ships to Europe. The battleship divi-
sion that Benson dispatched late in 1917 represented the first
increment of these forces. As has been noted, the decision to
send

this force was associated with declining Japanese-American
tensions. But the deployment also was linked with the
Wilsonian
offensive since the addition of American dreadnoughts to the
Grand Fleet allowed the British to decommission an equal
number of battleships. The crews of these units then were reas-
signed to anti-submarine ships, including those essential for the
Dover Straits barrage."
Besides the distant blockade of the submarine nests rep-
resented by the Dover and North Sea barriers, Benson was con-
vinced in December 1917 that he had won British assent to a
close-in surface ship assault against German seaports. And,
once
again, the admiral accepted the obligation to provide additional
units from the American battle fleet in order to make these
oper-
ations possible. At the conclusion of the House Mission, Benson
reported agreement on a "definite plan of offensive operations
[probably a reference to an attack by older battleships on the
German submarine bases in Belgium] in which our forces will
participate in the near future." Benson further noted that a
"tentative agreement" had been reached to send the "entire
Atlantic Fleet to European waters in the Spring provided condi-
tions warrant such action."""
Benson's naive optimism was soon dampened. To be sure, the
North Sea mine barrage, which was the most tangible realization
of the American naval offensive, was begun in the Spring of
1918.
Nevertheless, this ambitious project was not entirely completed
by the Armistice, even though some 57,000 American and
16,000
British mines were planted by that time."* American encourage-
ment may have been partially responsible for the British re-
vitalization of the Dover Straits barrage. Yet, despite the opera-

tion's increased effectiveness. Admiral Badger concluded that
the British never fully met their part of the bargain to close this
submarine transit zone."
The close-in attack on the German U-boat bases was almost
entirely abandoned and, as a result, the large American fleet
offered by Benson late in 1917 was not deployed. Although a
number of the American battleships that would have been com-
mitted to this operation later proved useful in protecting troop
convoys, Benson continued to regret that a seaport offensive
was
not undertaken. The most essential explanation for its absence
was the fact that the Admiralty — no doubt recalling its experi-
ences at Gallipoli in 1915 — could not accept the feasibility of
attacking fortified shore positions, despite Benson's hopes in
De-
cember 1917. The Royal Navy continued the strategic blockade
of
Europe and its containment of the German fleet, but for these
essential missions there was little need for additional capital
ships. This was especially the case since an American force
would have demanded logistical support by Allied shipping
which
was always in critically short supply. Admiral Badger of the
Secretarv's Advisory Council, 1917-1918. Left to right: Ma/.
Gen. George Barnett, Capt. William C. Watts, Asst. Sec. of
Navy Franjdm D.
B„n^^v/ii RAdm Samuel McGoivan, RAdm. Roberts. Griffin,
RAdm. David W. Taylor, VAdm. William S. Benson, RAdm.
Ralph Earle, Cdr. H. G.
Sparrow, RMm. Charles W. Parks, RearAdm. Leigh C. Palmer,
RAdm. William C. Bralsted, USN(MCj, and Sec. of Navy
Josepus Daniels, m his
office at'Navy Department. U.S. Navy photograph.

79
APpil IHRO
General Board also suggested one additional factor. Apparently
referring to Benson's offer of the entire Atlantic Fleet, he stated
that the British "never wanted" such a force "over there under
American command. They wanted the American aid to be in the
way of reenforcements to their own fleet."™
A prominent theme in all of these issues was theisolation of
American policy based on national self-interest
and distinctive strategic concepts. In contrast to the model de-
veloped by the British and Admiral Sims, Washington officials
—
often reflecting the personal views of President Wilson — did
not
believe that America's primary role was to provide unqualified
assistance to the Royal Navy. Instead, the United States fleet
gave priority to establishing and supporting an independent
American Army in France, an effort that was entirely separate
from the defense of the mercantile convoys serving Great
Britain
or of the general defeat of the German U-boat. Naval officials
were concerned to varying degrees with the defense of the
conti-
nental United States, preparedness to counter Japan in the
Pacific, and an expected challenge from Japan, Germany, or
even Great Britain in a conflict following the World War. There
was basic disagreement on an offensive against the submarine
bases and an attempt, that was only partially successful, to
shape
an aggressive campaign against these targets in accordance with
American concepts.

These unresolved differences offer at least a partial explana-
tion for the pattern of American naval deployments which saw
only a small percentage of the American Navy committed to the
Allied maritime campaign in European waters." But, of more
fundamental importance, Anglo-American naval tensions de-
monstrate once again the continuing independence of American
policy in World War I despite the fact that, in her own way, the
United States was committed to the defeat of Germany and the
other central powers.
Dean C. Allard is a senior his-
torian and archivist with the U.S.
Naval Historical Center, Wash-
ington, D.C. A graduate of
Dartmouth Coilege, he received
his Ph.D. degree from George
Washington University. His pub-
iished writings concentrate on
20th Century navai history and
n'avai bibiiography. This article
was accepted for publication in
December 1978.
REFERENCES
1. See David F . Trask's perceptive analysis in his Captains and
Cabinets: Anglo-American Naval Relations, 1917-1918 (Colum-
bia: University of Missouri Press, 1972), 360-65; and William
S.
Sims, The Victory at Sea (Garden City: Doubleday, Page,
1920).
2. For general discussions of Anglo-American differences, see
W. B. Fowler, British-American Relations, 1917-1918
(Princeton:

Princeton University Press, 1969), and Seth P. Tillman, Anglo-
American Relations at the Peace Conference of 1919 (Princeton:
Princeton University Press, 1961). This paper does not discuss
maritime and mercantile rivalries which are emphasized in Jef-
frey J. Safford, Wüsoman Maritime Diplomacy, 1913-1921
(New
Brunswick, Rutgers University Press, 1978); Edward B. Par-
sons, Wilsonian Diplomacy (St. Louis: Forum Press, 1978); and
Carl Parrini, Heir to Empire: United States Economic Diplo-
macy, 1916-1923 (Pittsburgh: University of Pittsburgh Press,
1969).
3. In addition to Trask and Sims, see the outstanding biography
by Elting E. Morison, Admiral Sims and the Modern Am,erican
Navy (Boston: Houghton Miffiin, 1942).
4. Trask, 83, 360, and Dean C. Allard, "Admiral William S.
Sims and United States Naval Policy in World War I," American
Neptune, 35 (April 1975), 99-103.
5. Allard summarizes Sims' views. See also Sims to Secretary
of the Navy (16 July 1917), Subject File UP, Box 580, Record
Group (RG] 45, U.S. National Archives.
6. Quoted in Julius A. Furer, Administration of the Navy De-
partment in World War I! (Washington: GPO, 1959), 6-7. Sims'
dominance in shaping policy is suggested, for example, in
Trask,
360-65.
7. Benson's Anglophobia is indicated in Trask, 48, 361. Ben-
son's outlook seems to this author to be similar to the
nationalism
described in John Milton Cooper, Jr., The Vanity of Power:
American Isolationism and the First World War, 1914-1917
(Westport: Greenwood, 1969), 3-4, 200, 203. See also the view

of
Benson in Safford, 224-47. There is no biography for Benson,
but
one is under preparation by Mary Klachko. Sims, who was no
admirer of Benson, referred to Benson's "inflexible honesty" in
Sims to Pratt (9 Nov. 1917), Pratt Papers, Box 1, Naval History
Division; and to his loyalty to his political superiors in Sims to
Mrs. William S. Sims (4 Nov. 1918), Sims Papers, Box 10,
Library
of Congress. Benson's sincere support of Wilsonian ideals is re-
flected in Benson to Daniels (10 Nov. 1918), Box 66, Daniels
Pap-
ers, Library of Congress.
8. U.S. Cong., Senate, Naval Affairs Committee, Hearings
Before the Subcommittee of the Committee on Naval Affairs
(66thCong.,2ndSess.) (Washington: GPO, 1920), 1959
(hereafter
cited as ¡Vaua! Investigation).
80
9. For Benson's views, see ffa^al Investigation, 1843 and E.
David Cronon, ed.. The Cabinet Diaries of Josephus Daniels,
1913-1921 (Lincoln: University of Nebraska Press, 1963), 135
(hereafter cited as Daniels Diaries). For the outlook of the
British and Sims, see Trask, 63, and Allard, 101.
10. General Board to Secretary of the Navy (28 April 1917),
File
425, General Board Records, Naval History Division (hereafter
cited as GB Records) ; Naval Investigation, 1340-42.
11. Trask, 79-90, 160, and AUard, 105.
12. Daniels to Wilson (3 July 1917), Box 110, Daniels Papers;

Trask, 127-28, 159-61; Wauai Investigation, 1083-85, 1167,
1471,
1482-83, 1561-62, and 1906; and Arthur J. Marder, Victory and
Aftermath, Vol. V of From the Dreadnought to Scapa Flow
(Lon-
don: Oxford University Press, 1970), 127.
13. The need for a national army is in, for example. Admiral
Mayo's statement in Naval Investigation, 610, and Thomas G.
Frothingham, The Naval History of the World War: The United
States in the War, 1917-1918 (Cambridge: Harvard University
Press, 1926), 98-102. See also Daniels Diaries, 145. The
Williams
document is enclosed in Benson to Commander Destroyer Force
Atlantic (29 May 1917), Area 11, Box 223, RG 45..The
instructions
to Sims are in Daniels to Sims (28 July 1917), Subject File UP,
Box
580, RG 45. See also Navy Department to Sims (8 July 1917),
Area
11, Box 223, RG 45; John J. Pershing, My Experiences in the
World War (New York: Frederick A. Stokes, 1931), I, 48-49, %;
Trask, 130,202-203 ; Sims message to Office of Operations (16
May
1918), Subject FUe UP, Box 580, RG 45; Trask, 202-203.
14. Pershing, I, 288-289, 388; Frothingham, 160n, 184, 160n,
161-62, 227-28. The British carried 49 percent of the troops and
other nations 6 percent.
15. Ibid., 156-60,174,188-89,285; "Summaryof ActivitiesofU.S.
Naval Forces Operating in European Waters," n.d., ZO File,
Naval History Division; Watia! investigation, 1003,1235-
36,1630;
and Albert Gleaves, A History of the Transport Service' (New
York: George H. Doran, 1921). Sims' request for the trans-

Atlantic destroyers is in Sims to Pratt (16 Nov. 1917), Pratt
Pap-
ers, Box 1.
16. Three officers (Wilson, Niblack, and Pratt) stress the na-
tional independence of these forces in Naval Investigation, 902-
03,
1028, 1256. See also Frothingham, 160, and "Summary of Ac-
tivities of the U.S. Naval Forces Operating in European
Waters,"
57.
17. Naval Investigation, 1957, 196'?.
18. William Veazie Pratt, "Autobiography," 204-205, 216-217,
Box 7, Pratt Papers. Benson makes the same point in Naval
Investigation, 1956-57. See also Roland A. Bowling, "Convoy
in
World War II: The Influence of Admiral William S. Sims, U.S.
MILITARY AFFAIRS
Navy" (MA thesis, San Diego State University, 1975), 209-216.
An
excellent biography of Pratt is Gerald E. Wheeler, Admiral Wil-
liamVeazie Pratt,U.S. Navy: A Sailor's Life (WasbingtOD-
.GPO,
1974).
19. Wilson's apprehensions are indicated in Arthur S. Link,
Wilson: Campaigns for Progressivism and Peace (Princeton:
Princeton University Press, 1965), 296, and Fowler, 246. For a
masterful discussion of the two-ocean challenge, see William R.
Braisted, The United States Navy in the Pacific, 1909-1922

(Au-
stin: University of Texas Press, 1971), 162, 289, 309, 441-43.
See
also Chief of Naval Operations [Benson] to Secretary of the
Navy,
"Estimate of the Situation" (Feb. 1917), Box 46, Daniels Papers.
William Veazie Pratt identifies himself as the author of this
paper
in Naval Investigation, 1311. For the 1917 study, see General
Board to Secretary of the Navy (20 April 1917), File 425, GB
Records. Fears of a British collapse are reflected in General
Board to Secretary of the Navy (5 April, 28 April, and 3 May
1917),
in Ibid., and Nauai Investigation, 1144. The long-standing fears
of
possible German aggression in the Caribbean are indicated in
Richard D. Challener, Admirals, Generals, and American
Foreign Policy, 1898-1914 (Princeton: Princeton University
Press, 1973), 399-400. See also General Board to Secretary of
the
Navy (19 May 1917), File 425, GB Records. Braisted, 302
mentions
these rumors.
20 See Naval Investigation, 1849-50.
21. General Board Hearings (19 Oct. 1917), 500-520, GB Re-
cords. P r p t t ' s quotation appears on 500.
22. Ibid., 490; Naval Investigation, 1880, 1904-1906. See also
Admiral FuUam's comments in Naval Investigation, 705, and
Braisted, 332-36. See Jellicoe to Lord Beatty (30 Nov. 1917), in
A.
Temple Patterson, ed.. The Jellicoe Papers (London: Naval Re-
cords Society, 1968), II, 229-30.

23. For an excellent discussion of the Navy's postwar con-
cerns, see Warner R. Schilling, "Admirals and Foreign Policy,
1913-1919" (Ph.D. dissertation, Yale Umversity, 1953). Suspi-
cions resulting from J a p a n ' s limited participation in the war
and
the thinking until late in the conflict that Germany would
emerge
with her fleet intact a r e suggested by the comments in General
Board Hearings (8 J a n . 1918), 30-31, GB Records ; P r a t t to
Chief of
Naval Operations (28 March 1918), Box 1, P r a t t P a p e r s ;
and
Planning Section London memorandum 21 (May 1917), Subject
File TX, Box 567, RG 45. The Planning Section's memorandum
65
(4 Nov. 1918) in ibid., refers to a British-Japanese combination.
24. See Benson's views in Daniels Diaries, 137 and Daniels'
attitude in his letter to G.S. MacFarland (15 June 1917), Box
622,
Daniels P a p e r s . See also "The Present War, Viewpoint of
the
Office of Operations" (23 June 1917), Area 11, Box 223, RG
45;
Frank Freidel, Franklin D. Roosevelt: The Apprenticeship
(Boston: Little, Brown, 1952), 312-16; and Acting Secretary of
State to American Embassy, London (28 July 1917), Area 11,
Box
224, RG 45.
25. Message, Wilson to Sims (4 July 1917), Box 110, Damels
Papers ; Wilson to Daniels (2 July 1917), Box 110, Daniels
Papers ;
Trask, 93-97, 131-132; Danieis Diaries, 191.
26. Arthur J. Marder, 1917: Year of Crisis, Vol. IV of From the

Dreadnought to Scapa Flow (London: Oxford University Press,
1969), 231-35; Lady Wester Wemyss, The Life and Letters of
Lord
Wester Wemyss (London: Eyre and Spottiswoode, 1935), 363-
66.
27. Wilson is quoted in Donieis Diaries, 227; see also 223. For
King's summary, see General Board Hearings (17 Oct. 1917),
459,
GB Records. The General Board dismissed the scheme in its
letter to Secretary of the Navy (24 Oct. 1917), File 425-5, GB
Records.
28. See Captain W. S. Pye's testimony in General Board Hear-
ings (16 Oct. 1917), 409-11, GB Records, and Jellicoe to
Benson
(Sept. 1917), in Patterson, 209-10. For Benson's enthusiasm, see
Charles Seymour, The Intimate Papers of Colonel House (Bos-
ton: Houghton, ]VIifflin, 1928), III, 303.
29. Trask 176. N. Gordon Levin, Woodrow Wilson and World
Politics (New York: Oxford University Press, 1968), is a
general
interpretation of WUson's desire for world leadership. His aver-
sion to following the British lead is indicated in Tillman, 16,
and
30 Trask 181 includes the domination statement. House takes
the same view in Daniels Diaries, 273. For the London Planning
Section see Office of Naval Intelligence, Historical Section,
The
American Naval Planning Section London (Washington: GPO,
1923), V, 489-92, and Trask, 165-66.
31. Seymour, III, 236.

32. Noua! Investigation, 1163-64, 1169, 1497; Seymour, III,
299-300 ; General Board Hearings ( 19 Oct. 1917), 500, GB
Records ;
General Board to Secretary of the Navy (29 Aug. 1917), File
420-2,
GB Records; Marder, 1917: Year of Crisis, 42-43.
33. Quoted in Seymour, III, 299. See also Seymour, 269;
!Va!;a!
Investigation, 1852.
34. Office of Naval Records and Library, The Northern Bar-
rage and Other Mining Activities (Washington: GPO, 1920),
121-127. For a modern assessment of World War I mining, see
Philip K. Lundeberg, "Undersea Warfare and Allied Strategy in
World War I: Part II, 1916-1918," Smithsonian Journal of
History,
I (Winter 1967), 65-67.
35. Naval Investigation, 1167. Marder refers to the increased
effectiveness of the barrage and its British origins in Victory
and
Aftermath, 39-45.
36. Naval Investigation, 1850,1888-89,1923. The British under-
took a daring but unsuccessful operation to block the Belgian
ports in April 1918, but there is no indication they requested or
needed American assistance. See Marder, Victory and After-
math, 58-63. Washington naval authorities later attempted to
launch an aerial bombing offensive against the German sub-
marine bases in lieu of a surface ship assault. See General
Board
Hearings (23 Aug. 1918), 956, and General Board letters to
Secret-
ary of the Navy (26 Feb. and 30 March 1918), File 425-5, all in
GB

Records; and "Summary of Activities of U.S. Naval Forces
Operating in European Waters," 50.
37. Another important factor was the incomplete status of the
Navy's mobilization of ships and men. At the end of the war, the
Navy was still training many of its new personnel and preparing
numerous new ships for service.
KANSAS STATE UNIVERSITY
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Military Affairs, 1 9 3 7 - 1 9 6 9 . 1969
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No. 9. Artiiur D. Larson Civil-Military Rela-
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No. 10. Alien R Milleti & B. F. Caaiing.
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CURRENT STRATEGIES FOR ENGINEERING CONTROLS IN
DEPARTMENT OF HEALTH AND HUMAN SERVICES
Centers for Disease Control and Prevention
National Institute for Occupational Safety and Health

Nanomaterial Production and
Downstream Handling Processes
ii Current Strategies for Engineering Controls in Nanomaterial
Production and Downstream Handling Processes
This document is in the public domain and may be freely copied
or reprinted.
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Mention of any company or product does not constitute
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Institute for Occupational Safety and Health (NIOSH). In
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external to NIOSH do not constitute NIOSH endorsement of the
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Suggested Citation
NIOSH [2013]. Current strategies for engineering controls in
nanomaterial production and
downstream handling processes. Cincinnati, OH: U.S.
Department of Health and Human
Services, Centers for Disease Control and Prevention, National
Institute for Occupational
Safety and Health, DHHS (NIOSH) Publication No. 2014–102.
DHHS (NIOSH) Publication No. 2014–102
November 2013
iii Current Strategies for Engineering Controls in Nanomaterial
Foreword
The National Institute for Occupational Safety and Health
(NIOSH) is charged with
protecting the safety and health of workers through research and
training. An area of
current concentration is the study of nanotechnology, the
science of matter near the atomic
scale. Much of the current research focuses on understanding
the toxicology of emerging
nanomaterials as well as exposure assessment; very little
research has been conducted on
hazard control for exposures to nanomaterials. As we continue
to research the health effects
produced by nanomaterials, particularly as new materials and

products continue to be
introduced, it is prudent to protect workers now from potential
adverse health outcomes.
Controlling exposures to occupational hazards is the
fundamental method of protecting
workers. Traditionally, a hierarchy of controls has been used as
a means of determining how to
implement feasible and effective control solutions.
� Elimination
� Substitution
� Engineering Controls
� Administrative Controls
� Personal Protective Equipment
Following this hierarchy normally leads to the implementation
of inherently safer systems,
where the risk of illness or injury has been substantially
reduced. Engineering controls are
favored over administrative and personal protective equipment
for controlling existing worker
exposures in the workplace because they are designed to remove
the hazard at the source,
before it comes in contact with the worker. However, evidence
of control effectiveness for
nanomaterial production and downstream use is scarce. This
document is a summary of
available technologies that can be used in the nanotechnology
industry. While some of these
have been evaluated in this industry, others have been shown to
be effective at controlling
similar processes in other industries. The identification and
adoption of control technologies
that have been shown effective in other industries is an
important first step in reducing
worker exposures to engineered nanoparticles.

Our hope is that this document will aid in the selection of
engineering controls for the
fabrication and use of products in the nanotechnology field. As
this field continues to expand,
it is paramount that the health and safety of workers is
protected.
John Howard, M.D.
Director, National Institute for
Occupational Safety and Health
Centers for Disease Control and Prevention
iv Current Strategies for Engineering Controls in Nanomaterial
Executive Summary
The focus of this document is to identify and describe strategies
for the engineering control
of worker exposure during the production or use of engineered
nanomaterials. Engineered
nanomaterials are materials that are intentionally produced and
have at least one primary
dimension less than 100 nanometers (nm). Nanomaterials may
have properties different
from those of larger particles of the same material, making them
unique and desirable
for specific product applications. The consumer products market
currently has more than
1,000 nanomaterial-containing products including makeup,
sunscreen, food storage
products, appliances, clothing, electronics, computers, sporting
goods, and coatings. As more
nanomaterials are introduced into the workplace and nano-

enabled products enter the market,
it is essential that producers and users of engineered
nanomaterials ensure a safe and healthy
work environment.
The toxicity of nanoparticles may be affected by different
physicochemical properties,
including size, shape, chemistry, surface properties,
agglomeration, biopersistence, solubility,
and charge, as well as effects from attached functional groups
and crystalline structure. The
greater surface-area-to-mass ratio of nanoparticles makes them
generally more reactive than
their macro-sized counterparts. These properties are the same
ones that make nanomaterials
unique and valuable in manufacturing many products. Though
human health effects from
exposure have not been reported, a number of laboratory animal
studies have been conducted.
Pulmonary inflammation has been observed in animals exposed
to nano-sized TiO2 and
carbon nanotubes (CNTs). Other studies have shown that
nanoparticles can translocate to
the circulatory system and to the brain causing oxidative stress.
Of concern is the finding that
certain types of CNTs have shown toxicological response
similar to asbestos in mice. These
animal study results are examples, and further toxicological
studies need to be conducted
to establish the potential health effects to humans from acute
and chronic exposure to
nanomaterials.
Currently, there are no established regulatory occupational
exposure limits (OELs) for
nanomaterials in the United States; however, other countries

have established standards
for some nanomaterials, and some companies have supplied
OELs for their products. In
2011, NIOSH issued a recommended exposure limit (REL) for
ultrafine (nano) titanium
dioxide and a draft REL for carbon nanotubes and carbon
nanofibers. Because of the lack
of regulatory standards and formal recommendations for many
nanomaterials in the United
States, it is difficult to determine or even estimate a safe
exposure level.
Many of the basic methods of producing nanomaterials occur in
an enclosure or reactor,
which may be operated under positive pressure. Exposure can
occur due to leakage from the
reactor or when a worker’s activities involve direct
manipulation of nanomaterials. Batch-
type processes involved in the production of nanomaterials
include operating reactors,
mixing, drying, and thermal treatment. Exposure-causing
activities at production plants
and laboratories employing nanomaterials include harvesting
(e.g., scraping materials out
of reactors), bagging, packaging, and reactor cleaning.
Downstream activities that may
release nanomaterials include bag dumping, manual transfer
between processes, mixing or
compounding, powder sifting, and machining of parts that
contain nanomaterials.
v Current Strategies for Engineering Controls in Nanomaterial

Hazards involved in manufacturing and processing
nanomaterials should be managed as
part of a comprehensive occupational safety, health, and
environmental management plan.
Preliminary hazard assessments (PHAs) are frequently
conducted as initial risk assessments
to determine whether more sophisticated analytical methods are
needed. PHAs are important
so that the need for control measures is realized, and the means
for risk mitigation can be
designed to be part of the operation during the planning stage.
Engineering controls protect workers by removing hazardous
conditions or placing a barrier
between the worker and the hazard, and, with good safe
handling techniques, they are likely
to be the most effective control strategy for nanomaterials. The
identification and adoption
of control technologies that have been shown effective in other
industries are important first
steps in reducing worker exposures to engineered nanoparticles.
Properly designing, using, and
evaluating the effectiveness of these controls is a key
component in a comprehensive health
and safety program. Potential exposure control approaches for
commonly used processes
include commercial technologies, such as a laboratory fume
hood, or techniques adopted from
the pharmaceutical industry, such as continuous liner product
bagging systems.
The assessment of control effectiveness is essential for
verifying that the exposure goals of
the facility have been successfully met. Essential control
evaluation tools include time-tested
techniques, such as airflow visualization and measurement, as

well as quantitative containment
test methods, including tracer gas testing. Further methods, such
as video exposure
monitoring, provide information on critical task-based
exposures, which will help to identify
high-exposure activities and help provide the basis for
interventions.
This page left intentionally blank
vii Current Strategies for Engineering Controls in Nanomaterial
Contents
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . iii
Executive Summary . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . iv
List of Figures . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . x
List of Tables . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . xi
List of Abbreviations . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. xii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . xiv

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . 1
1.2 Industry Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 3
1.3 Occupational Safety and Health Management Systems . . . . .
. . . . . . . . . . . . . . 3
1.3.1 Prevention through Design (PtD) . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 6
1.3.2 OELs as Applied to Nanotechnology . . . . . . . . . . . . . . . .
. . . . . . . . . . . . 7
1.3.3 Control Banding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 7
2 Exposure Control Strategies and the Hierarchy of Controls . .
. . . . . . . . . . . . . . . . . . 9
2.1 Elimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 9
2.2 Substitution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 10
2.3 Engineering Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 10
2.3.1 Ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 11
2.3.1.1 Local Exhaust Ventilation . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 12
2.3.1.2 Air Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 14
2.3.2 Nonventilation Engineering Controls . . . . . . . . . . . . . . .
. . . . . . . . . . . . 16

2.4 Administrative Controls . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 17
2.5 Personal Protective Equipment (PPE). . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 18
2.5.1 Skin Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 18
2.5.2 Respiratory Protection . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . 18
3 Nanotechnology Processes and Engineering Controls . . . .
. . . . . . . . . . . . . . . . . . . . . 21
3.1 Primary Nanotechnology Production and Downstream
Processes . . . . . . . . . . . 21
3.2 Engineering Control Approaches to Reducing Exposures . . .
. . . . . . . . . . . . . . 22
3.3 Ventilation and General Considerations . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 24
3.4 Exposure Control Technologies for Common Processes . . . .
. . . . . . . . . . . . . . . 25
3.4.1 Reactor Operation and Cleanout Processes . . . . . . . . . . . .
. . . . . . . . . . . . 27
viii Current Strategies for Engineering Controls in Nanomaterial
3.4.2 Small-scale Weighing and Handling of Nanopowders . . . .
. . . . . . . . . . . 30
3.4.2.1 Fume Hood Enclosures . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 31
3.4.2.2 Biological Safety Cabinets . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 33
3.4.2.3 Glove Box Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . 34
3.4.2.4 Air Curtain Fume Hood . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . 35
3.4.2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 36
3.4.3 Intermediate and Finishing Processes . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 37
3.4.3.1 Product Discharge/Bag Filling. . . . . . . . . . . . . . . . . . . .
. . . . . . . 38
3.4.3.2 Bag Dumping/Emptying . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . 41
3.4.3.3 Large-scale Material Handling/Packaging. . . . . . . . . . .
. . . . . . . 43
3.4.3.4 Nanocomposite Machining . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . 44
3.4.3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 44
3.4.4 Maintenance Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . 45
3.4.4.1 Filter Change-out—Bag In/Bag Out Systems. . . . . . . . .
. . . . . . 46
3.4.4.2 Spill Cleanup Procedures . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . 46
4 Control Evaluations . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. 47
4.1 Approaches to Evaluation . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 47
4.1.1 Identification of Emission Sources . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 47
4.1.2 Background and Area Monitoring . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 47
4.1.3 Air Monitoring and Filter Sampling . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . 48
4.1.4 Assessment of Air Velocities and Patterns . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 50
4.1.5 Facility Sampling and Evaluation Checklist . . . . . . . . . .
. . . . . . . . . . . . . . . . 52
4 .2 Evaluating Sources of Emissions and Exposures to
Nanomaterials . . . . . . . . . . . . . 57
4.2.1 Direct-reading Monitoring . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 57
ix Current Strategies for Engineering Controls in Nanomaterial
4.2.2 Off-line Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 58
4.2.3 Video Exposure Monitoring . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 58
4 .3 Evaluating Ventilation Control Systems . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.3.1 Standard Containment Test Methods for Ventilated
Enclosures . . . . . . . . . . 59
5 Conclusions and Recommendations . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1
5.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . 61
5.2 Control Banding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 61
5.3 Hierarchy of Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 62
5.4 Engineering Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 62

5.5 Administrative Controls . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 62
5.6 Personal Protective Equipment . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . 63
References . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . 65
Appendix A: Sources for Risk Management Guidance . . . . .
. . . . . . . . . . . . . . . . . . . . . 75
Appendix B: Sources of Guidance for Control Design . . . . .
. . . . . . . . . . . . . . . . . . . . . 77
x Current Strategies for Engineering Controls in Nanomaterial
List of Figures
Figure 1 . Atomic structure of a spherical fullerene
Figure 2 . How control measures are incorporated into an
occupational safety and health
management system
Figure 3 . Worker reaching into drum
Figure 4 . Graphical representation of the hierarchy of controls
Figure 5 . Four primary filter collection mechanisms
Figure 6 . Collection efficiency curve: fractional collection
efficiency versus particle diameter
for a typical filter
Figure 7 . A large-scale ventilated reactor enclosure used to
contain production furnaces to
mitigate particle emissions in the workplace
Figure 8 . A canopy hood used to control emissions from hot
processes

Figure 9 . Schematic illustration of how wakes caused by the
human body can transport air
contaminants into the worker’s breathing zone
Figure 10 . Nano containment hood adapted from a
pharmaceutical balance enclosure
Figure 11 . A tabletop model of a Class II, Type A2 biological
safety cabinet (BSC)
Figure 12 . A glove box isolator for handling substances that
require a high level of
containment
Figure 13 . Air curtain safety cabinet hood that uses push-pull
ventilation
Figure 14 . Ventilated collar-type exhaust hoods for containing
dust during product discharge
or manual bag filling
Figure 15 . An inflatable seal is used to contain
nanopowders/dusts as they are discharged
from a process such as spray drying
Figure 16 . A continuous liner product off-loading system that
uses a continuous feed of bag
liners fitted to the process outlet to isolate and contain process
emissions and product
Figure 17 . A ventilated bag-dumping station that reduces dust
emissions during the
emptying of product from bags into a process hopper
Figure 18 . A laminar downflow booth for handling large
quantities of powders
Figure 19 . Bag in/bag out procedures. This photo shows the
removal of a dirty air filter from
a ventilation unit into a plastic bag to minimize worker
exposure to particles captured by the
filter unit
Figure 20 . Operating principle of a Pitot tube (left) and
different types of Pitot tubes (right)
Figure 21 . Smoke generator to visualize airflow

xi Current Strategies for Engineering Controls in Nanomaterial
List of Tables
Table 1 . Potential sources of emission from production and
downstream processes
Table 2 . Process/tasks and emission
Table 3 . Summary of instruments and techniques for
monitoring nanoparticle emissions in
nanomanufacturing workplaces
Table 4 . Checklist of controls for nanomaterial manufacturing
and handling
Table 5 . Comparison of the fume hood performance test
methods
xii Current Strategies for Engineering Controls in Nanomaterial
List of Abbreviations
ACGIH American Conference of Governmental Industrial
Hygienists
AIHA American Industrial Hygiene Association
ANSI American National Standards Institute
APF assigned protection factor
ASHRAE American Society of Heating, Refrigerating, and Air
Conditioning Engineers
BSC biological safety cabinet

BSI British Standards Institute
CAV constant air volume
CDC Centers for Disease Control and Prevention
cfm cubic feet per minute
CNF carbon nanofiber
CNT carbon nanotube
CPC condensation particle counter
CVD chemical vapor deposition
DMPS differential mobility particle sizer
ELPI electrical low pressure impactor
EPA Environmental Protection Agency
FFR filtering facepiece respirator
FMPS fast mobility particle sizer
fpm feet per minute
HEPA high efficiency particulate air
HSE Health and Safety Executive
IH industrial hygiene
kg kilogram
lbs pounds
LEV local exhaust ventilation
LPM liters per minute
MPPS most penetrating particle size
MSDS material safety data sheet
MUC maximum use concentration
NIOSH National Institute for Occupational Safety and Health
nm nanometer
OEL occupational exposure limit
PEL permissible exposure limit
xiii Current Strategies for Engineering Controls in Nanomaterial
PHA preliminary hazard assessment
PM preventive maintenance

PPE personal protective equipment
PtD prevention through design
R&D research and development
REL recommended exposure limit
SMACNA Sheet Metal and Air Conditioning Contractors’
National Association
SMPS scanning mobility particle sizer
SOP standard operating procedures
TEM transmission electron microscopy
TEOM tapered element oscillating microbalance
TLV® threshold limit value
TWA time- weighted average
VAV variable air volume
VEM video exposure monitoring
wg water gauge
µg microgram
µm micrometer
xiv Current Strategies for Engineering Controls in Nanomaterial
Acknowledgments
This document was developed by the NIOSH Division of
Applied Research and Technology
(DART), Gregory Lotz, PhD, Director. Jennifer L. Topmiller,
MS, was the project officer
for this document, assisted in great part by Kevin H. Dunn,
ScD, CIH. Other members of
DART instrumental in the production of this document include
Scott Earnest, PhD, PE,
CSP; Liming Lo, PhD; Ron Hall, MS, CIH, CSP; Mike Gressel,
PhD, CSP; Alan Echt,
DrPh, CIH; and William Heitbrink, PhD, CIH (contractor).
Elizabeth Fryer also provided

writing and editing support in the initial stages.
The authors gratefully acknowledge the contributions of the
following NIOSH personnel
who assisted with the technical content and review of the
document.
Division of Respiratory Disease Studies
Stephen B. Martin, Jr., MS, PE
Education and Information Division
Charles Geraci, PhD, CIH
Laura Hodson, MSPH, CIH
Health Effects Laboratory Division
Bean T. Chen, PhD
National Personal Protective Technology Laboratory
Pengfei Gao, PhD, CIH
Office of the Director
Paul Middendorf, PhD, CIH
The authors also wish to thank Cathy Rotunda, EdD, Brenda J.
Jones, and Vanessa Williams
for their assistance with editing and layout for this report.
Cover photographs are courtesy of
Quantum Sphere, Inc. and Bon-ki Ku, PhD, of NIOSH.
Special appreciation is expressed to the following who served as
independent, external

reviewers. Their input contributed greatly to the improvement
of this document.
Keith Swain, DuPont, Wilmington, Delaware
Richard Prodans, CIH, CSP, Abbott, Abbott Park, Illinois
John Weaver, Birck Nanotechnology Center, Purdue University,
West Lafayette, Indiana
Gurumurthy Ramachandran, PhD, CIH, University of
Minnesota, Minneapolis, Minnesota
Phil Demokritou, PhD, Harvard University, Boston,
Massachusetts
1 Current Strategies for Engineering Controls in Nanomaterial
CHAPTER 1
Introduction
The number of commercial applications of nanomaterials is
growing at a tremendous rate. As
this rapid growth continues, it is essential that producers and
users of nanomaterials ensure
a safe and healthy work environment for employees who may be
exposed to these materials.
Unfortunately, because nanotechnology is so new, we do not
know or fully understand how
occupational exposures to these agents may affect the health
and safety of workers or even
what levels of exposure may be acceptable. Given our current
knowledge in this field, it is
important to take precautions to minimize exposures and protect
safety and health.

This document discusses approaches and strategies to protect
workers from potentially
harmful exposures during nanomaterial manufacturing, use, and
handling processes. Its
purpose is to provide the best available current knowledge of
how workers may be exposed
and provide guidance on exposure control and evaluation. It is
intended to be used as a
reference by plant managers and owners who are responsible for
making decisions regarding
capital allocations, as well as health and safety professionals,
engineers, and industrial
hygienists who are specifically charged with protecting worker
health in this new and
growing field. Because little has been published on exposure
controls in the production and
use of nanomaterials, this document focuses on applications that
have relevance to the field
of nanotechnology and on engineering control technologies
currently used, and known to
be effective, in other industries. This document also addresses
other approaches to worker
protection, such as the use of administrative controls and
personal protective equipment.
1.1 Background
Nanotechnology is the manipulation of matter at the atomic
scale to create materials, devices,
or systems with new properties and/or functions. Around the
world, the introduction of
nanotechnology promises great societal benefits across many
economic sectors: energy, healthcare,
industry, communications, agriculture, consumer products, and
others [Sellers et al. 2009].
Some nanoparticles are natural, as in sea salt or pine tree

pollen, or are incidentally produced,
as in volcanic explosions or diesel engine emissions. The focus
of this document is engineered
nanomaterials, those materials deliberately engineered and
manufactured to have certain
properties and have at least one primary dimension of less than
100 nanometers (nm).
Nanomaterials have properties different from those of their bulk
components. For example,
many of these materials have increased strength/weight ratios,
enhanced conductivities,
and improved optical or magnetic properties. These new
properties make nanomaterial
development so exciting and are the reason they hold the
promise of great economic potential.
Nanomaterials are often classified by their physicochemical
characteristics or structure. The
four classes of materials of which nanoparticles are typically
composed include elemental
carbon, carbon compounds, metals or metal oxides, and
ceramics. The nanometer form
of metals, such as gold, and metal oxides, such as titanium
dioxide, are the most common
engineered nanomaterials being produced and used [Sellers et
al. 2009]. Nano-sized silica,
silver, and natural clays are also common materials in use. The
carbon nanotube is a unique
nanomaterial being investigated for a wide range of
applications. These tubes are cylinders

constructed of rolled-up graphene sheets. Another interesting
carbon structure is a fullerene
(also known as a Bucky Ball). These are spherical particles
usually constructed from 60
carbon atoms arranged as 20 hexagons and 12 pentagons. As
shown in Figure 1, the structure
resembles a geodesic dome (designed by architect Buckminster
Fuller, hence the name).
Nanomaterials are widely used across industries and products,
and they may be present in
many forms.
Significant international health and safety research and
guidance concerning the handling
of nanomaterials is underway to support risk management of
commercial developments.
Both risks and rewards are inherent in these new materials.
Scientists around the world are
conducting toxicological studies on these nanomaterials, and
initial findings are concerning.
Animals exposed to titanium dioxide (TiO2) and carbon
nanotubes (CNTs) have displayed
pulmonary inflammation [Chou et al. 2008; Rossi et al. 2010;
Shvedova et al. 2005]. Other
studies have shown that nanoparticles can translocate to the
circulatory system and to the
brain and cause oxidative stress [Elder et al. 2006; Wang et al.
2008]. Perhaps the most
troubling finding is that CNTs can cause asbestos-like
pathology in mice [Poland et al. 2008;
Takagi et al. 2008].
Figure 1. Atomic structure of a spherical fullerene

1.2 Industry Overview
In March 2006, the Woodrow Wilson International Center for
Scholars created an inventory
of 212 consumer products or product lines that incorporate
nanomaterials (http://www.
nanotechproject.org/inventories /consumer/analysis_draft/).
These products were broken
down into eight categories using a publically available
consumer product classification
system. As of March 2011, the number of consumer products
has increased by 521% (212 to
1,317 nano-enabled products) with products coming from more
than 24 nations [WWICS
2011]. These products include acne lotions, antimicrobial
treatment for socks, sunscreens,
food supplements, components for computer hardware (such as
processors and video cards),
appliance components, coatings, and hockey sticks. Of the
current 1,317 nano-enabled
products, the largest product category with 738 products was
health and fitness. The most
common type of nanomaterial used in these products was silver
(313 products), followed by
carbon (91 products) and titanium dioxide (59 products).
Roco [2005] reports that worldwide, the investment in
nanotechnology has increased
from $432 million in 1997 to about $4.1 billion in 2005. In this
same time period, the U.S.
government investment in nanotechnology has increased to
nearly $1.1 billion. Estimates
made in 2000 suggested that $1 trillion in products will use
nanotechnology in some way by

2015. The National Science Foundation estimates that the
number of workers in this industry
will increase to 2 million worldwide by 2015.
Currently, most production facilities are relatively small, with
lab, bench, or, at most,
pilot plant operations [Genaidy et al. 2009]. This is also
indicative of downstream users
(applications and product development). As new manufacturing
processes and technologies
are developed and introduced, novel materials with unknown
toxicological properties will
require effective risk management approaches. As more of these
products enter the market,
concern about the health and safety of the workers grows.
1.3 Occupational Safety and Health Management Systems
Control measures for nanoparticles, dusts, and other hazards
should be implemented
within the context of a comprehensive occupational safety and
health management system
[ANSI/AIHA 2012]. The critical elements of an effective
occupational safety and health
management system include management commitment and
employee involvement, worksite
analysis, hazard prevention and control, and sufficient training
for employees, supervisors,
and managers (www.osha.gov/Publications/safety-health-
management-systems.pdf ). In
developing measures to control occupational exposure to
nanomaterials, it is important to
remember that processing and manufacturing involve a wide
range of hazards. Conducting
a preliminary hazard assessment (PHA) encompasses a
qualitative life cycle analysis of an
entire operation, appropriate to the stage of development:

� Chemicals/materials being used in the process
� Production methods used during each stage of production
� Process equipment and engineering controls employed
� Worker’s approach to performing job duties
� Exposure potential to the nanomaterials from the
task/operations
� The facility that houses the operation
The steps taken to perform PHAs for specific operations should
be documented to let
others know what was done and to help others understand what
works. PHAs are frequently
conducted as initial risk assessments to determine whether more
sophisticated analytical
methods are needed and to prepare an inventory of hazards and
control measures needed for
these hazards. One or two individuals with a health and safety
background and knowledge of
the process can perform PHAs. As part of the assessment, the
health and safety professional
should evaluate the magnitude of the emissions (or potential
emissions) and the effects of
exposure to these emissions. PHAs are an important first step
toward developing control
measures that can be considered during the planning stage.
Essentially, hazard control
should be an integral component of facility, process, and
equipment design and construction.
This includes design for inherent process safety. The use of

engineering controls should be
considered as part of a comprehensive control strategy for
hazards associated with processes/
tasks that cannot be effectively eliminated, substituted for, or
contained through process
equipment modifications.
The standards for an occupational health and safety management
system, as outlined in
ANSI/AIHA Z10 [ANSI/AIHA 2012] and BSI 18001 [BSI
2007c], promote a continuous
improvement cycle (plan, do, check, act), which does not have
an exit point and is the basis
for worksite analysis. Figure 2 illustrates how control measures
are incorporated into an
occupational safety and health management system. The
continuous improvement loop is
applicable to all hazards in a process/facility (e.g., airborne
contaminant exposures, ergonomic,
combustible dusts, fire safety, and physical hazards). The
hazard assessment should be
reviewed during each cycle described by Figure 2 and
periodically updated when major
changes occur. Although the optimal time to undertake a PHA is
during the design stage,
hazard assessments can also be done during the operation of a
facility and have the benefit of
using existing data.
After the PHA is complete, the nanomaterial risk management
plan is designed to avoid
or minimize hazards discovered during the assessment. The
following options should be
considered:
� Automated product transfer between operations. A process

that allows for continuous
process flow to avoid exposures caused by workers handling
powdered or vaporous
materials.
� Closed-system handling of powdered or vaporous materials,
such as screw feeding or
pneumatic conveying.
� Local exhaust ventilation. Steps should be taken to avoid
having positive pressure
ducts in work spaces because leakage from ducts can cause
exposures. Ducts or pipes
should be connected using flanges with gaskets that prevent
leakage.
� Continuous bagging for the intermediate output from various
processes and for
final products. A process discharges material into a continuous
bag that is sealed
to eliminate dust exposures caused by powder handling. Bags
are heat sealed after
loading.
Figure 3. Worker reaching into drum
� Minimizing the container size for manual material handling.
Minimizing the size of
the container or using a long-handled tool is recommended so
that the worker does
not place his breathing zone inside the container (as shown in

Figure 3). NIOSH
recommends a maximum container depth of 25 inches [NIOSH
1997]. If large
containers are required, engineering controls to provide a
barrier between the container
and the breathing zone of the worker are recommended.
Figure 2. How control measures are selected, implemented, and
managed into an occupational safety
and health management system. (adopted from [ANSI 2005])
Photo by NIOSH
Many good resources are available on the occupational safety
and health risk management
of nanomaterials. Comprehensive documents have been
produced by a number of
organizations. Some of these are listed in Appendix A.
1.3.1 Prevention through Design (PtD)
The concept of Prevention through Design (PtD) is to design out
or minimize hazards,
preferably, early in the design process. PtD is also called
inherent or intrinsic safety, safety
by design, design for safety, and safe design. When PtD is
implemented, the control
hierarchy is applied by designers (e.g., engineers, architects,
industrial designers) and
business leaders (e.g., owners, purchasers, managers) who
consider the benefits of designing

safety into things external to the worker to prevent work-related
injuries and illnesses.
PtD strategies, like the hierarchy of controls, can take many
forms. Elimination and
substitution measures are desirable, but these strategies may be
difficult to implement
when working with nanomaterials because these materials are
likely being used for their
unique properties. The pharmaceutical industry has addressed
some of these challenges
since their products must be contained rather than removed or
eliminated from the process.
They have adopted a containment hierarchy of controls that
addresses designing inherent
safety into the process [Brock 2009]. The initial levels of
containment include elimination
and substitution as well as product, process, and equipment
modifications. Only after
efforts have been made to design the process to reduce potential
emissions sources should
engineering controls be considered.
Other PtD strategies can be considered:
� Limiting process inventories by producing the nanomaterials
as they are consumed
in the process.
� Operating a process at a lower energy state (e.g., lower
temperature or pressure),
which typically results in lower fugitive emissions and therefore
safer operation.
� Using fail-safe devices where possible. Fail-safe devices are
designed so that if they

fail, the system reverts to a safer condition. An example of a
fail-safe device is a
valve controlling a reagent for a reaction. If the safe condition
for the system is for
this valve to be closed, the fail-safe valve would automatically
close in the event of a
failure.
� Installing a closed transport system to eliminate worker
exposures during transport
activities.
PtD strategies typically do not include administrative controls
and personal protective
equipment (PPE) as the primary controls. These measures
require worker interaction with
the process or active steps to limit the extent of the hazard.
Most effective PtD approaches
reduce or eliminate hazardous conditions without relying on
input from workers. Humans
are generally recognized as being much less reliable than most
machines, particularly in
emergencies [Kletz 2001]. The use of administrative controls
and PPE in PtD strategies is
generally for redundancy—further safeguards should the
primary control fail.
The ideal time to develop a PtD strategy is during the
development phase of a process, material,
or facility. As the nanotechnology field is still in its relative
infancy, there are numerous

opportunities to implement PtD in the early stages. The manner
in which these materials are
handled and processed can largely affect the overall safety of
the process, and the health and
safety of workers may be significantly improved through the
implementation of a PtD strategy.
1.3.2 OELs as Applied to Nanotechnology
Occupational exposure limits (OELs) are useful in reducing
work-related health risks by
providing a quantitative guideline and basis to assess the worker
exposure potential and the
performance of engineering controls and other risk management
approaches. Currently,
no regulatory standards for nanomaterials have been established
in the United States.
However, NIOSH has recently published two current
intelligence bulletins (CIBs) regarding
occupational exposures to nanomaterials. In a CIB on titanium
dioxide (TiO2), NIOSH
recommends exposure limits of 2.4 mg/m3 for fine TiO2 and 0.3
mg/m
3 for ultrafine
(including engineered nanoscale) TiO2, as time-weighted
average (TWA) concentrations for
up to 10 hours per day during a 40-hour work week [NIOSH
2011]. In a CIB on carbon
nanotubes and nanofibers, NIOSH recommends that worker
exposure be limited to no more
than 1 µg/m3 [NIOSH 2013].
Other countries have established OELs for various
nanomaterials. For example, the British
Standards Institute recommends working exposure limits for
nanomaterials based on various

classifications such as solubility, shape, and potential health
concerns as related to larger particles
of the same substance [BSI 2007b]. Germany’s Institut für
Arbeitsschutz der Deutschen
Gesetzlichen Unfallversicherung, an institute for worker safety,
has published similar guidelines
[IFA 2009].
In the absence of governmental or consensus guidance on
exposure limits, some manufacturers
have developed suggested OELs for their products. For
example, Bayer has established an
OEL of 0.05 mg/m3 for Baytubes® (multiwalled CNTs) [Bayer
MaterialScience 2010]. For
Nanocyl CNTs, the no-effect concentration in air was estimated
to be 2.5 µg/m³ for an 8-hr/day
exposure [Nanocyl 2009].
Another approach that may be taken when OELs are absent is
the ALARA concept, As Low
As Reasonably Achievable. While ALARA is generally the goal
for all occupational exposures,
this concept is particularly useful when OELs are absent or in
the case of contaminants with
unknown toxicity.
1.3.3 Control Banding
Control banding is a qualitative risk characterization and
management strategy, intended to
protect the safety and health of workers in the absence of
chemical and workplace standards.
Control banding groups workplace risks into hazard bands based
on evaluations of hazard
and exposure information [NIOSH 2009b]. Note that control
banding is not intended to be a
substitute for OELs and does not alleviate the need for

environmental monitoring or industrial
hygiene expertise.
To determine the appropriate control scheme, one should
consider the characteristics of the
substance, the potential for exposure, and the hazard associated
with the substance. Four main
control bands, based on an overall risk level, have been
developed:
� Good industrial hygiene (IH) practice, general ventilation,
and good work practices
� Engineering controls including fume hoods or local exhaust
ventilation
� Containment or process enclosure allowing for limited
breaks in containment
� Special circumstances requiring expert advice
One basic principle of control banding is the need for a method
that will return consistent,
accurate results even when performed by nonexperts. Other
requirements include having a
user friendly strategy, readily available required information
(e.g., material safety data sheet
[MSDS]), practical guidance on applying the strategy, and
worker confidence in the results.
With the absence of OELs, control banding can be a useful
approach in the risk management
of nanomaterials [Maynard 2007; Schulte et al. 2008; Thomas et
al. 2006; Warheit et al.
2007]. Several control banding tools are available for use with

engineered nanomaterials. The
CB Nanotool, for example, bases the control band for a
particular task on the overall risk
level, which is determined by a matrix that uses severity scores
and probability scores [Paik et
al. 2008]. The severity score is based on the toxicological
effects of the nanomaterial, while the
probability score relates to the potential for employee exposure.
The health hazard categories
for some control banding approaches are based upon the
European Union risk phrases, while
exposure potentials include the volume of the chemical used and
the likelihood of airborne
materials, estimated by the dustiness or volatility of the source
compound [Maidment 1998].
CHAPTER 2
Exposure Control Strategies and
the Hierarchy of Controls
Controlling exposures to occupational hazards is the
fundamental method of protecting
workers. Traditionally, a hierarchy of controls has been used as
a means of determining how to
implement feasible and effective controls. Figure 4 shows one
representation of this hierarchy.
The idea behind the hierarchy of controls is that the control
methods at the top of the triangle
are generally more effective in reducing the risk associated with
a hazard than those at the

bottom. Following the hierarchy normally leads to the
implementation of inherently safer
systems, ones where the risk of illness or injury has been
substantially reduced. Designing out
hazards early in the design process is a basic tenet of PtD.
When PtD is implemented, the
control hierarchy is applied by designers and owners/managers
to include safety into the process.
The following sections discuss each element of the hierarchy of
controls—elimination,
substitution, engineering controls, administrative controls, and
PPE— and how it may relate
to nanotechnology.
2.1 Elimination
Elimination and substitution are generally most cost effective if
implemented when a process
is in the design or development stage. If done early enough,
implementation is simple and, in
the long run, can result in substantial savings (e.g., cost of
protective equipment, first cost and
operational cost for ventilation system). For an existing process,
elimination or substitution
may require major changes in equipment and/or procedures in
order to reduce a hazard.
Figure 4. Graphical representation of the hierarchy of controls
Elimination is the most desirable approach in the hierarchy of
controls. As its name implies,

the idea behind elimination is to remove the hazard. Eliminating
hazards is generally
easiest to accomplish at the design stage, while the material,
process, and/or facility is being
developed. An example of elimination in a process step might
be the removal of an incoming
inspection step for nanomaterials. An incoming inspection that
requires opening a package
containing nanomaterials leads to the potential of aerosolization
of those materials and
therefore a potential hazard to the inspector. Eliminating the
inspection step removes the
hazard, thus creating an inherently safer process.
2.2 Substitution
Within the hierarchy of controls, the purpose of substitution is
to replace one set of
conditions having a high hazard level with a different set of
conditions having a lower hazard
level. Examples of substitution could include replacing a
solvent-based (i.e., flammable)
material with a water-based material, substituting a highly toxic
material for one of lower
toxicity, or changing a process’s operating conditions so they
are less severe (e.g., reduced
pressure). Substitution of a nanomaterial may be difficult since
it was likely introduced for its
particular properties; however, some substitution may be
possible. Substituting a nanomaterial
slurry for a dry powder version will reduce aerosolization and
provide a level of protection for
workers handling the material. The specific nanomaterial should
also be assessed because in
some cases a less hazardous nanomaterial may provide the
desired performance.

2.3 Engineering Controls
Engineering controls protect workers by removing hazardous
conditions (e.g., local exhaust
ventilation that captures and removes airborne emissions) or
placing a barrier between the
worker and the hazard (e.g., isolators and machine guards).
Well-designed engineering
controls can be highly effective in protecting workers and will
typically be passive, that is,
independent of worker interactions. It is important to design
engineering controls that do
not interfere with the productivity and ease of processing for
the worker. If engineering
controls make the operation more difficult, there will be a
strong motivation by the operator
to circumvent these controls. Ideally, engineering controls
should make the operation easier
to perform rather than more difficult. A good mantra in
designing engineering controls is
to “make it easier to do it the safe way.” This also applies to
administrative controls that are
discussed later.
The initial cost of engineering controls can be higher than
administrative controls or personal
protective equipment (PPE); however, over the long term,
operating costs are frequently lower
and, in some instances, can provide a cost savings in other areas
of the process. The major
benefit of engineering controls over administrative controls or
PPE is, however, the inherent
safety of the worker under a variety of conditions and stress
levels. The use of engineering
controls reduces the potential for worker behavior to impact
exposure levels.

Thus, when elimination and substitution are not viable options,
the most desirable alternative
for mitigating occupational hazards is to employ engineering
controls. Engineering controls
are likely the most effective and applicable control strategy for
most nanomaterial processes.
In most cases, they should be more feasible than elimination or
substitution and, given
the potential toxicity of many nanomaterials, should prove to be
more protective than
administrative controls and PPE.
Engineering controls are divided into two broad categories for
discussion below: ventilation
and nonventilation controls.
2.3.1 Ventilation
The general concept behind ventilation for controlling
occupational exposures to air
contaminants, including nanomaterials, is to remove
contaminated air from the work
environment. The efficiency of the ventilation system can be
affected by its configuration and
flow volumes of both the air supplied to and the air exhausted
from the work space. Effective
ventilation applies to a wide range of applications including
office heating, ventilating, and air
conditioning (HVAC); infection control in healthcare; and
control of emissions in industrial
processes. Ventilation for occupant comfort, HVAC, is a

specialized application of dilution
ventilation and is not within the scope of this document.
Filtration is a topic directly affecting
ventilation; exhaust air laden with nanomaterials may need to be
cleaned before being released
into the environment.
General ventilation can be used to achieve several goals for
workplace contaminant control.
A properly designed supply air ventilation system can provide
plant ventilation, building
pressurization, and exhaust air replacement. As new local
exhaust hoods are installed in the
production area, it is important to consider the need for
replacement air, the location of the
hood installation, and the need to rebalance the ventilation
system. In general, it is necessary
to balance the amount of exhausted air with a nearly equal
amount of supply air. Without this
replacement air, uncontrolled drafts will occur at doors,
windows, and other openings; doors
will become difficult to open due to the high pressure
difference, and exhaust fan performance
may degrade. In addition, turbulence created through high
pressure differentials can defeat
the design intent of the ventilation. Placement of the air supply
registers in relation to other
exhaust ventilation systems is important so that they do not
negatively impact the desired
performance. The use of general ventilation for dilution of
contaminants being generated in
the space should be restricted in its use depending on several
factors discussed below.
General ventilation used for dilution of contaminants by its
nature is inefficient. One of two

methods, recirculated air or single-pass air, may be used for this
purpose. As the terms imply,
recirculated air involves the treatment of exhaust air prior to its
being returned to the area
from which it was exhausted. Single-pass air is exhausted to the
outside and may or may not
require treatment prior to discharge. Both of these methods are
expensive—the treatment of
the recirculated air involves both first-cost and operating-cost
penalties, while makeup-air
treatment for single-pass air is inherently costly.
According to the American Conference of Governmental
Industrial Hygienists (ACGIH)
Industrial Ventilation: A Manual of Recommended Practice for
Design (hereafter referred to as
the Industrial Ventilation Manual), dilution ventilation (i.e., air
changes) to control exposure
should be used only under specific conditions. Dilution
ventilation for controlling health
hazards is restricted by four limiting factors: (1) the quantity of
contaminant generated must
not be too great or the airflow rate necessary for dilution will be
impractical, (2) workers must
be far enough away from the contaminant source or the
evolution of contaminant must be
in sufficiently low concentrations so that workers will not have
an exposure in excess of the
established threshold limit values (TLV®), (3) the toxicity of
the contaminant must be low,

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