Pierre River Mine Project

HEALTH AENV SIRS 79 – 89
Section 14.1
• No or negligible change in predicted RQ values between the Base Case and
Application Case.
• The Base Case contributes most of the RQ values under the Application Case
and the PDC (99 to 100%).
• Risk quotients associated with methyl mercury, which is still the primary
contributor to the mixture RQ values, are conservative estimates based on the
assumptions made in the HHRA (see EIA, Volume 3, Section 5.3.3.3).
• Most of the RQ values under the Base Case were the result of the assumed
fish consumption.
• It was assumed that residents would obtain all (100%) of their food,
including fish, from the local, natural sources over their lifetimes.
Arsenic and Liver Carcinogens
The Base Case LCR values range from 19 to 21 for arsenic and the liver
carcinogens, signifying that lifetime exposure to background levels of
carcinogens via multiple pathway exposures could potentially account for up to
21 cases of cancer when calculated on a 100,000 person population basis. The
Base Case LCR values are up from those predicted as part of the HHRA (see
EIA, Volume 3, Section 5.3.3.3).
The regulatory benchmark of an acceptable incremental lifetime cancer risk of
one in 100,000 is policy-based. Regulators have not recommended an acceptable
cancer incidence rate (or LCR) for exposure to carcinogens associated with
background or “baseline” conditions. The “acceptability” of this potential
lifetime cancer risk from a public health perspective cannot be determined
following a conventional approach since an acceptable “benchmark” cancer risk
level for exposure to background levels of carcinogens is not available for
comparison.
In a recent study conducted on behalf of Alberta Health and Wellness, “baseline”
lifetime cancer risks were estimated to range from 17 to 33 in 100,000 (AHW
2007). Note that the risk estimates for the baseline scenario in the AHW study
are similar to those presented for the revised Base Case.
For the following reasons, the project is not likely to result in adverse health
effects associated with exposure to arsenic and the liver carcinogens, as a whole,
in the region:
• Incremental lifetime cancer risks for arsenic and the liver carcinogens did not
exceed the regulatory benchmark of 1.0.
• Use of the exposure limit adopted from Health Canada, which was derived
based on the premise that arsenic acts as a “non-threshold” carcinogen, may
overstate the carcinogenic potency of arsenic and subsequently the
carcinogenic potency of the liver carcinogens.
April 2010 Shell Canada Limited 14-33
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