EPA Region 9 Releases Interim Short-Term Indoor Air
Response Action Levels for TCE
New research on the toxicology of trichloroethylene (TCE) has prompted some regulatory agencies to issue action levels for short-term vapor exposures. These new requirements will likely increase the need for residential and workplace vapor monitoring. In certain cases, they may also result in the need to rapidly assess indoor air conditions and even potentially relocate occupants until interim measures are taken to mitigate vapor concentrations to acceptable levels.
The U.S. Environmental Protection Agency’s (EPA’s) Toxicological Review of Trichloroethylene (2011) provided an inhalation reference concentration (RfC) for TCE in its Integrated Risk Information System database, from which screening values for indoor air can be calculated. The TCE RfC of 2 μg/m3 is based on a midpoint of two RfCs, for critical effects on the thymus and the potential for birth defects (cardiac malformations) in a developing fetus. Although the RfC is based on laboratory animal studies, a recent epidemiology study conducted by the New York State Department of Health reported an association between exposure during maternal residence within a TCE plume area (i.e., pregnant women residing over groundwater plumes) and fetal cardiac defects.
Default Fish Consumption Rates Go Up, Water Quality Criteria Go Down
Recent developments at both the state and federal levels indicate a trend toward assuming higher fish consumption rates (FCRs) for regulating water quality. In the past, many state water quality criteria (WQC) were developed using an average FCR of 6.5 g/day. Today, some states are assuming rates as high as 175 g/day. Higher FCRs mean lower WQC, which in some cases are lower than detectable and naturally occurring background concentrations, or below concentrations that can be achieved with existing control technologies.
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