EPA Releases Two Draft Risk Evaluations for Public Comment

EPA recently released draft risk evaluations for two isomers of dichlorobenzene. The documents present EPA’s preliminary determinations of risk for p-dichlorobenzene, a crystalline solid used to make plastic and other chemicals, and o-dichlorobenzene, a liquid used to make paints, dyes, and pigments as well as cleaning, degreasing, and painting products.

EPA found that inhalation or dermal exposure to p-dichlorobenzene presents unreasonable risk to workers in seven conditions of use. These COUs include manufacturing; incorporation into solvents, soap, or cleaning products; repackaging; and commercial use of air fresheners and laboratory chemicals. The health effects of p-dichlorobenzene exposure include neurotoxicity, developmental toxicity, respiratory toxicity, and liver toxicity.

The draft risk evaluation proposes occupational exposure values (OEVs) for p-dichlorobenzene of 0.039 ppm as an eight-hour time-weighted average and 16.8 ppm as a 15-minute, short-term ceiling value. OEVs represent “the exposure concentration below which exposed workers . . . are not expected to exhibit any appreciable risk of adverse toxicological outcomes.” EPA specifies that it may consider factors such as cost and technological feasibility if it proposes a risk management rule for p-dichlorobenzene. OSHA’s current permissible exposure limit for p-dichlorobenzene, adopted in 1971, is 75 ppm, and the ACGIH Threshold Limit Value is 10 ppm, both as eight-hour TWAs. Neither OSHA nor ACGIH has a short-term exposure limit for p-dichlorobenzene.

NIOSH does not have a recommended exposure limit (REL) for p-dichlorobenzene because it considers the substance to be a potential occupational carcinogen. EPA, in contrast, “determined that p-dichlorobenzene is not likely to be carcinogenic to humans,” according to the draft risk evaluation.

For o-dichlorobenzene, EPA found unreasonable risk to workers from 14 COUs, including repackaging, processing as a reactant, incorporation into soap, and industrial use of solvents. Health effects of o-dichlorobenzene include respiratory toxicity from inhalation exposure and liver toxicity from dermal exposure.

EPA proposes an eight-hour TWA OEV for o-dichlorobenzene of 0.022 ppm and a 15-minute short-term ceiling limit of 0.14 ppm. The OSHA PEL and NIOSH REL for o-dichlorobenzene are 50 ppm ceiling limits, while the ACGIH TLV is 25 ppm as an eight-hour TWA. ACGIH also identifies a STEL for o-dichlorobenzene of 50 ppm.

EPA’s notice in the Federal Register specifies an Oct. 9 deadline for comments on the risk evaluations. Refer to the agency website for more information about p-dichlorobenzene and o-dichlorobenzene.