Now that the US EPA has classified
TCE as a carcinogen, and dangerous at levels previously
believed to be safe, what will happen to risk assessments and other
regulatory decision-making in Ontario? Noted risk assessor, Brett Ibbotson, tells me that the new numbers
are two to four times as stringent as the ones just adopted on July
1, 2011, in Ontario:
"The reassessment of TCE by the US EPA includes revising
its toxicity reference values (TRVs). For TCE, the most important
types of health effects are non-threshold effects such as cancer,
so this brief email does not discuss the TRVs for threshold
effects.
For exposures via ingestion and dermal contact, the
"new" US TRV is about 3.5 times more stringent than the
TRV used in the revised (July 2011) MOE standards. This means that
if you previously estimated a risk of say 5 x 10-7 that you thought
was acceptable, it will be 3.5 times higher or 1.8 x 10-6 and
therefore not acceptable.
