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1. SHOP FLOOR MONITORING
I. It is essential to evaluate the risk that may arise as a
result of a worker carrying out a task involving a toxic
substance. Let us first define 'hazard' and 'risk', and also
'safe.
HAZARD : the adverse consequence to health of contact with a
biological, chemical or physical substance or process. This
includes energy, like sound, radiation.
*
RI»SK : a quantitative measure of hazard.
SAFE : something is safe if there is a general acceptance that
the risk invoved in its use is a reasonable one.
Thus it is clear that mere presence of a toxic substance does not
constitute a risk to health. There are three ways in which
health or body can be affected, as follows:-
INHALATION: leading to absortion into the body via the
bronchial system or to direct action on the lung itself.
SKIN CONTACT: leading to absorptioon into the body by
penetration through the skin (like organic lead) or to direct
effect on the skin itself (like hexavalent chromium)
INGESTION: leading to direct absorption into the body.
Ingestion is an uncommon source of ill health. Most common route
of entry into the body is through inhalation of the airborne
toxic substance. Standards have been laid for the airborne
concentration of different toxic substances such that a person
working in an atmosphere containing that level of the toxic
substance for 8 hours in a day is unlikely to suffer any
risk. These standards are variously called TLV's, Expposure
Limits, Permissible Levels in work environment, etc. The unit
used for gaseous substances is parts per million or ppm and for
particulates and fumes it is milligrams per cubic metre or mg/m .
The unit for fibrous substances, like asbestos, is fibres per
millilitre or f/ml.
There are various factors that influence effect on humans, as
follows:-
1) chemical characteristics
toxicity rating
physical characteristics-particle size will determine its
deposition in the Respiratory Tree.
For example, particulate contaminants (aerosols) can be
classified in two different ways.

2. PHYSICAL CLASSIFICATION
mechancical dispersoid
condensation dispersoid
dust
spray-
fume
mist
fog
smoke
smog.
PHYSIOLOGICAL CLASSIFICATION
nuisance and/or inert
inert pulmonary reaction producing
minimal pulmonary fibrosis producing
extensive pulmonary fibrosis producing
chemical irritant
systemis poison
allergy producing
febrile reaction producing.
2) Exposure
dose, concentration and volume of administration
routee, rate and site of administration
duration of freguency
A worker carrying out light work breathes in about 30
litres/m, for medium work about 50 1/m, and for heavy work 80-90
1/m. Thus, in the case of a heavy worker, the intake of the
toxic substance will be much higher, and conseguent greater
damage to health.
3) Individual susceptibi1ity
age, sex,
body weight - a larger body will need more oxygen and will
have a higher breathing rate
nutritional status (diet factors etc.)
presence of disease
other habits (smoking, drinking, etc.)
4)Particle deposition in the Respiratory Tree
SITE particle size
nasopharynygeal
trachea and bronchial region
aleveolar region
5-30 micron
1-5 micron
1 micron

3. Effects on the body can be of two types:
Acute is an initial short term response to exposure; e.g.
carbon monoxide causes confusion, headache. It can be very
harmful too.
Chronic is a long term prolonged response; e.g. fibrosis of
lung.
Body can excrete toxic substances via the following routes:-
in urine from the kidneys
expired air from the lungs
sweat
faeces
to a small degree throough hair and nails.
IIMEASUREMENTS
It is clearly essential to make measurements of airborne
toxic substances.
Envirotech have developed two simple instruments to make such
measurements. They are Personal Sampler Envirotech APM 800 and
Handy Sampler Envirotech APM 820 (fig.l and 2 ). Both work off
in-built rechargeable Ni-Cad batteries and will sample for
minimum 8 hours with ful ly' charged batteries., Both have in-built
rotameters also to measure the flow rate; there is a provision
for its adjustment.
Personal Sampler is light enough to be carried on one's 'belt with
the clip provided. Its sampling head which holds a filter is
attached to one's collar or nearby so that the air being sampled
is the same as being breathed by the worker. Particulates and
fumes etc. will be collected on the filter. At the end of
samplling concentration of the pollutant can be calculated from
the increase in weight of the filter and the volume sampled.
Handy Sampler can sample gaseous substances also through their
absorption in suitable reagents contained in the two impingers
connected to the pump. These reagents are analysed at the end of
sampling and the concentration of the gases or vapours calculated
from the volume sampled.. A sampling head can be connected after
the impingers for determination of particulates and fumes etc.
The substance collected on the filter can be further analysed, if
required, to determine the concentration of particular pollutants
(like metals etc.)
In the case of a fibrous material, like asbestos, a . gridded
membrane filter is used for smapling. At the end of sampling a
slide of the filter is prepared and the number of fibres on it
are counted under a phase contrast microscope.

4. IllSAMPLING
When embarking upon a sampling campaign to asess the risk to
which a worker may be exposed, it is necessary to ask several
questions, as follows:-
1. What to sample? This involves a review of the materials,
processes and operating procedures/work practices, coupled with a
discussion with management and safety personnel. A brief 'walk
through1
survey can also be useful as a guide to the extent of
sampling that may be necessary.
When the background work has been completed, it can then be
decided, what is to be measured.
2.On whom? The answer to this question obviously depends on the
size and diversity of the group of interst. The individual
selected must be representative, but selecting the individual
with the highest exposure can be a reasonable starting point.
If the group is large, then random sampling may have to be
employed, but care has to be exercised with this approach.
3.How long do we sample for? Many considerations have to be made
when answering this guestion, viz. what are the exposure limits,
is the hazard acute or chronic, what is the limit of detection of
the method employed, or simply what resources we have at our
disposal.
4.How often do we sample? The value of measurement of personal
exposure decreases as exposures become further removed from the'
exposure limit. For example, regular monitoring where
concentrations are below one-tenth or greater than 20 times
Exposure Limits are of little value.
5.How many samples should be taken? This is a very important
consideration to be made at the initial stage, i.e. when sampling
is done for the first time. It must be remembered that one
sample may give fortutous, or rogue, result. Therefore, the
sample must be repeated until a norm is established. Thereafter,
only one periodic sample should be sufficient to assure that
all is well. Another very important fact to remember is that it
is much more difficult to prove a negative; e.g. the results are
always below the Exposure Limit. Initially half a dozen samples
will be necessary to substantiate this belief. Once the fact is
established, one periodic sample will be enough as long as the
result obtained is as expected.

5. 6.How to monitor? The particular strategy to follow is outlined
in the-
following table:-
Environmental measurements
required to determine
Suitable types of
measurements
Hazard Personal
measurements
dose
Environmental control
status
Background monitoring
Whether area is safe to enter Direct reading
instrument
IV.CONTROL
l.Once the sampling is completed and the evaluation of results
done, it will be necessary to provide remedial measures where
the concentrations of polutants are above permissible levels.
2.Following control methods can be employed:-
-substitution with less toxic material
-enclosure of harmful process, and making it automatic
-isolation of harmful process with appropriate protection for
people in that area
-use of a hood with exhaust ventilation and having transparent
front/top so that the worker can insert his hands inside to
work and be able to see what he is doing
-local exhaust ventilation
-general ventilation
-wet methods (to control dust)
-decreasing the daily exposure
-Respiratory Protectivee Equipment (RPE), but this should be the
last resort, when other control methods are not possible
-personal hygiene
-use of protective cream (against effect on the skin)
-housekeeping and maintenance
-warnings and publicity
3.Success is possible only through Management Commitment and
Staff Cooperation. Management will have to allocate financial
and manpower resources , and also ensure training of the staff in
safer working methods.