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Development of an inhalation unit risk factor for ethylene dichloride
1a Division of Toxicology , Texas Commission on Environmental Quality , Austin , TX , USA.
Inhalation Toxicology
|June 17, 2016
Summary
A new inhalation unit risk factor (URF) for ethylene dichloride (EDC) was developed using rat tumor data. This URF helps set safe air concentrations to protect the public from EDC
Area of Science:
- Environmental toxicology
- Chemical risk assessment
- Carcinogenesis research
Background:
- Texas Commission on Environmental Quality (TCEQ) performs chemical carcinogenicity assessments.
- Ethylene dichloride (EDC, CAS 107-06-2) is a chemical emitted in Texas requiring risk evaluation.
Purpose of the Study:
- To develop an inhalation unit risk factor (URF) for ethylene dichloride (EDC).
- To establish a health-protective air concentration for chronic EDC exposure.
Main Methods:
- Utilized data from a 2-year animal inhalation study (Nagano et al.).
- Identified combined mammary gland tumors in female rats as the most sensitive carcinogenic endpoint.
- Applied benchmark concentration (BMC) modeling to determine the 95% lower confidence limit (BMCL10) at 40.1 ppm.
- Calculated the URF based on the identified endpoint and BMCL10.
Main Results:
- The developed URF for EDC is 1.4E-02 per ppm (3.4E-03 per mg/m(3)).
- The lifetime air concentration for a 1 in 100,000 excess cancer risk is 0.71 ppb (2.9 μg/m(3)).
Conclusions:
- The established URF and associated air concentration are considered health-protective for the general public.
- This assessment provides a basis for managing potential carcinogenic risks from chronic EDC exposure in ambient air.
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