EESA10 H3-S L30
"HUMAN HEALTH AND THE ENVIRONMENT"
Assignment #2

Issued: Monday, March 9th

Dept. of Environmental Sciences, University of Toronto Scarborough, Toronto, Canada

Due: Monday March 23th at 5pm, box outside SW-511A

TA: Steven Huryn
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Question 1:

Reference dose or RfD, is the maximum amount of acceptable oral dose of a toxic substance set by the EPA (United States Environmental Agency).( Agency for Toxic Substances and Disease Registry, 2009) The EPA uses RfD as a benchmark to set other regulations to prevent people from being exposed to amount exceeding the RfD standard. The EPA also has a unique RfD for every substance it evaluates. However, often separate acute and chronic RfDs are determined for the same substance. (US Environmental Protection Agency, 2014)

Cancer slope Factor, or CSF, is used to approximate the potential risk of cancer associated with exposure to a carcinogenic or potentially carcinogenic substance. (US Environmental Protection Agency, 2014) This approximation is usually expressed in units of a population affected per mg of substance/ kg body-weight/ day. A toxicity value that defines quantitatively the relationship between dose and response, or the slope factor, is calculated when the chemical is a known or probable human carcinogen. And different than RfD, High-quality Human data, or an epidemiological studies, on carcinogens is preferable to animal data. However, when human data is limited, the attention is given to the species that is the most sensitive.

Risk assessors use a reference dose to quantify non-carcinogenic toxicity, and cancer slope factor to quantify carcinogenic toxicity is because the RfD assumes "a dose below which no adverse non-carcinogenic health effects should result from a lifetime of exposure" (US Environmental Protection Agency, 2014) RfDs are usually derived from animal studies