This document discusses the selenium drinking water quality guideline (DWQG) in Canada and argues that the current guideline of 10 μg/L is overly protective and not scientifically justified. Most jurisdictions worldwide use 10 μg/L as the guideline, except for the United States and South Africa which use 50 μg/L. The Canadian guideline is based on outdated assumptions from 1992 that selenium is carcinogenic, but recent evidence shows it is not and may have anticarcinogenic properties. The document argues Canada and other countries should re-evaluate and revise their generic DWQGs in light of new scientific data, and consider developing site-specific, risk-based objectives in the interim.

1. Learned Discourses: Timely Scientific Opinions
Timely Scientific Opinions
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In a Nutshell. . .
Selenium
The Selenium Drinking Water Quality Guideline in Canada: The
Case for a Reevaluation, by Guy Gilron.
Historic drinking water quality guidelines are arguably over-
protective, except possibly in the United States and South Africa.
Analytical Chemistry
The Issue with Tissue—Does Size (of Uncertainty in Chemistry
Data) Matter?, by Barbara Wernick.
Analytical results, regardless of the number of significant
figures, are estimates; too much significance should not be
attributed to small differences.
Toxicity Testing
It’s in the Bag! Identification and Evaluation of Plastic Bag
Toxicity: Implications for Aquatic Toxicity Testing and Changes to
Testing Procedures, by Stanka Rkman-Filipovic, Ekatarina Mourzaeva-
Solomonov, Otto Herrmann, and David Rodgers.
Transport containers should be routinely tested for toxicity
unrelated to their contents.
Global Climate Change
Global Climate Change and Risk Assessment: Invasive Species,
by Peter M Chapman.
In the context of global climate change irreversible changes,
both positive and negative will become the norm.
Risk Assessment
Migration Patterns Affect Biomagnifying Contaminant Concen-
trations in Fish-eating Birds, by Raphael A Lavoie, T Kurt Kyser, and
Linda M Campbell.
A conceptual model is proposed for combining external and
chemical tracers to delineate biomagnifying contaminant
accumulation in migratory birds.
How Can Multiple Stressors Combine to Influence Ecosystems and
Why Is It Important to Address this Question?, by Eleonora Puccinelli.
One of the most interesting challenges in the future for
ecology will be to investigate the consequences of system
interactions across multiple scales in space and time.
Stress Syndromes: Heightened Bioenergetic Costs Associated
with Contaminant Exposure at Warm Temperatures in Teleosts,
by Chris J Kennedy and Peter S Ross.
Warming habitats of many cold water fish species due to
climate change suggests a ‘‘Summer Stress Syndrome,’’ not the
‘‘Winter Stress Syndrome’’ postulated by Lemly.
DOI: 10.1002/ieam.1272
Learned Discourses Editor
Peter M. Chapman
Golder Associates Ltd.
500-4260 Still Creek Drive
Burnaby, BC V5C 6C6, Canada
peter_chapman@golder.com
THE SELENIUM DRINKING WATER QUALITY
GUIDELINE IN CANADA: THE CASE FOR A
RE-EVALUATION
Guy Gilron*
Cardero Coal Ltd., Vancouver, British Columbia
*ggilron@cardero.com
DOI: 10.1002/ieam.1252
Selenium (Se), a naturally occurring inorganic nonmetal
found in sedimentary rock, can be—depending on its
chemical speciation and concentration—both essential and
toxic to organisms. Current standards and guidelines for Se in
drinking water in Canada and other jurisdictions summarized
in Table 1 indicate that most jurisdictions have established,
use, and apply a threshold value of 10 mg/L as a Se drinking
water quality guideline (DWQG); the 2 exceptions are the
United States and South Africa, both of which apply 50 mg/L
LearnedDiscourses:TimelyScientificOpinions Learned Discourses—Integr Environ Assess Manag 8, 2012
194 ß 2011 SETAC

2. as a DWQG. In Canada, all 10 provinces and 3 territories
apply 10 mg/L as a DWQG. Eleven of these jurisdictions
default directly to the current Health Canada (HC) DWQG
(Health Canada 1992). Two jurisdictions, Ontario and
Quebec, do not refer to the HC DWQG (Health Canada
1992) specifically. Ontario also applies the 10 mg/L DWQG,
but cites rationale related to using an estimate of 10% of the
total diet comprising drinking water (vs the HC range
estimate of 10% to 25% [Health Canada 1992]; see below).
Quebec has also applied the 10 mg/L DWQG but does not
provide a specific rationale. The HC DWQG (Health Canada
1992), the basis for most of the Canadian provincial
DWQGs, is based on the following rationale:
Se is an essential element for human health.
A variety of clinical disorders have been correlated with
either over ingestion of, or insufficient ingestion of, Se from
the diet.
Current information makes it difficult to ascertain whether
or not Se can be considered a carcinogen.
The main source of intake of Se for humans is from food—
there is little specific information available on the toxicity
of Se in drinking water.
The Se DWQG (referred to as the ‘‘maximum acceptable
concentration’’) has been determined to be 10mg/L because,
at this concentration, ‘‘drinking water would be the source of
between 10 and 25% of total selenium intake’’ (i.e., 90% to
75% of Se in the diet would be from food intake).
Given that HC does not regard Se as a carcinogen
(therefore, the use of a less conservative uncertainty factor
in calculating a final guideline value would be justified)
(Health Canada 1992), it is paradoxical that 10 mg/L is still
used as a DWQG versus the more scientifically-defensible (as
explained below) US Environmental Protection Agency
criterion of 50 mg/L (USEPA 2002).
Integr Environ Assess Manag 8, 2012—PM Chapman, Editor 195
Table 1. Selenium drinking water quality guidelines—Review of international jurisdictions
Jurisdiction
Se drinking
water guideline
(mg/L) Source
Canada
British Columbia 10 http://www.env.gov.bc.ca/wat/wq/BCguidelines/selenium/selenium.html
Alberta, Manitoba,
Newfoundland,
Prince Edward Island,
Yukon Territory,
Northwest Territories,
Nunavut
10 http://www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs-sesc/pdf/pubs/
water-eau/selenium/selenium-eng.pdf
Saskatchewan 10 http://www.saskwater.com/WhatWeDo/pdfs/Drinking%20Water%20Standards.pdf
Ontario 10 http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_030169_e.htm
Quebec 10 http://www2.publicationsduquebec.gouv.qc.ca/dynamicSearch/
telecharge.php?type¼2file¼%2F%2FQ_2%2FQ2R40_A.htm
Nova Scotia 10 http://www.gov.ns.ca/nse/water/docs/
GuideonGuidelinesforCanadianDrinkingWaterQuality.pdf
New Brunswick 10 http://www.gnb.ca/0053/public_health/water-quality_guidelines-e.asp
International
United States 50 http://water.epa.gov/drink/contaminants/basicinformation/selenium.cfm
United Kingdom 10 http://www.legislation.gov.uk/uksi/2000/3184/schedule/1/made
Australia 10 http://www.nhmrc.gov.au/_files_nhmrc/file/publications/synopses/adwg_11_06.pdf
New Zealand 10 http://www.maorihealth.govt.nz/moh.nsf/0/
5A25BF765B400911CC25708F0002B5A8/$File/appendix1-mavs.pdf
South Africa Class 1:20
Class 2:50
http://www.dwaf.gov.za/Documents/Other/DWQM/DWQMFrameworkDec05.pdf
European Union 10 http://ec.europa.eu/environment/water/water-drink/index_en.html
World Health Organization 10 http://www.who.int/water_sanitation_health/dwq/GDW8rev1and2.pdf
Se ¼ Selenium.

3. In the late 1970s and early 1980s, there was significant
scientific debate in the literature related to the justification for
an originally proposed 10 mg/L drinking water criterion in the
United States; a still protective, but more scientifically-
defensible, 50 mg/L criterion was recommended (Hammer
1981; Lafond and Calabrese 1979). The rationale provided
during this debate, coupled with a scientific review by the
USEPA Metals Subcommittee of the Science Advisory
Board’s Environmental Health Committee, resulted in the
modification of the US criterion from 10 mg/L (pre-1980s) to
50 mg/L (post-1980s) (USEPA 2002). However, note that
Barron et al. (2009) have questioned the scientific defensi-
bility of such generic DWQGs (or criteria in the United
States) and suggest that the development of site-specific
objectives would be more appropriate.
The initial establishment of Se DWQGs in Canada (and
also presumably in other jurisdictions) was based on the
assumption that Se is carcinogenic, resulting in the use of a
relatively stringent safety factor. However, Se has not been
demonstrated to be carcinogenic, and in fact has been
demonstrated to have anticarcinogenic properties (Muecke
et al. 2010). Thus, historic DWQGs are arguably over-
protective, except possibly in the United States and South
Africa. Canada, and other jurisdictions, need to review and
revise their existing generic DWQGs based on the toxico-
logical and epidemiological data that have been generated
since those values were developed (1992, in the case of
Canada). In the interim, site-specific, human health-based
objectives for Se in drinking water should be developed and
derived, using a risk-based approach as recommended by
Barron et al. (2009) and following recent guidance from
USEPA (2000).
Acknowledgment—The work upon which this article is
based was funded by the Mining Association of British Colum-
bia. The author wishes to thank Adriana Macleod (Peace River
Coal) and Claire Thomson (Mining Association of British
Columbia) for assistance with literature review, and Peter
Chapman (Golder Associates) for insightful comments on
an earlier version of this article.
REFERENCES
Barron E, Migeot V, Rabouan S, Potin-Gautier M, Se´by F, Hartemann P, Le´vi Y,
Legube B. 2009. The case for re-evaluating the upper limit value for selenium in
drinking water in Europe. J Wat Health 7:630–641.
Hammer MJ. 1981. An assessment of current standards for selenium in drinking
water. Ground Wat 19:366–369.
Health Canada. 1992. Guidelines for Canadian Drinking Water Quality—
Supporting Document for Selenium. Ottawa, ON: Health Canada.
Lafond MG, Calabrese EJ. 1979. Is the selenium drinking water standard justified?
Med Hypoth 5:877–899.
Muecke R, Schomburg L, Buentzel J, Kisters K, Micke O. 2010. Selenium or no
selenium—That is the question in tumor patients: A new controversy. Integr
Cancer Ther 9:136–141.
[USEPA] US Environmental Protection Agency. 2000. Methodology for deriving
ambient water quality criteria for the protection of human health.
Washington, DC: USEPA. EPA-822-B-00-004.
[USEPA] US Environmental Protection Agency. 2002. National primary drinking
water regulations. Washington, DC: USEPA. 67 FR 19029.
THE ISSUE WITH TISSUE—DOES SIZE (OF
UNCERTAINTY IN CHEMISTRY DATA) MATTER?
Barbara Wernick*
Golder Associates Ltd, Burnaby, British Columbia
*bwernick@golder.com
DOI: 10.1002/ieam.1262
It is widely acknowledged that analytical data are not
‘‘true’’ values; they are inherently uncertain estimates. For
tissue chemistry data, commonly collected in baseline studies
and environmental monitoring programs, the most apparent
and most often cited sources of uncertainty are natural
variability and field sampling error. However, the environ-
mental scientist designing, undertaking, or evaluating such a
field study may have less appreciation of the uncertainty that
arises after the samples reach the laboratory. Failing to
acknowledge these laboratory sources of uncertainty in
analytical data (also called ‘‘measurement uncertainty’’) can
result in incorrect decisions.
In a recent project involving the assessment of a long-term
set of fish tissue data, I was reminded of the importance of
understanding what analytical results do and do not mean.
Statistical analysis of data from a reference location indicated
that the more recent results were significantly higher than
earlier results, suggesting that reference conditions may have
changed. A reviewer for the project noted a higher recovery
of analytes in a certified reference material (CRM) associated
with the more recent samples and suggested that this caused a
bias upward in the time-series data, even though the CRM
results were within the laboratory’s data quality objectives
(DQOs). The comment implied that the laboratory data for
the later fish tissue samples somehow missed the true value
(i.e., were not accurate), as reflected in the CRM recovery.
However, like all analytical data, CRM results are inherently
uncertain estimates that are expected to fall within a range
of values (the measurement uncertainty) that contains the
true value. This highlights the importance of understanding
the precision (i.e., degree of repeatability) of laboratory data
and the weight that a particular CRM result should be given
when interpreting associated data. Given this inherent
uncertainty, perhaps a more relevant question is whether or
not the difference among years was large enough to be
considered ‘‘real,’’ regardless of CRM results or statistical
analysis.
Uncertainty in laboratory measurement occurs for a
number of reasons (Eurachem and CITAC 2000), including
but not limited to:
Heterogeneity of subsampling is likely the largest source of
uncertainty, particularly for tissue samples. The homoge-
nization process may not completely blend a sample,
especially for whole body fish samples that include soft
tissues and bone. As such, aliquots from a single tissue
sample will vary in composition, and this variation will
carry over into the laboratory quantitation.
Day-to-day variability of instrumentation and measure-
ments of calibration standards and reagents (e.g., sensitivity
of instruments and glassware to variations in temperature)
can be substantial.
The sample matrix may affect recovery if it is complex or
changes with a changing thermal regime during analysis.
196 Integr Environ Assess Manag 8, 2012—PM Chapman, Editor