Guidelines for styrene air emissions vary from state to state.
SIRC monitors all 50 states for regulatory activity on styrene. The 1990 federal Clean Air Act Amendments regulate air emissions for hazardous air pollutants through technology-based standards that do not address potential health effects. However, many states also have air toxics regulations for styrene that establish health-based emission standards or guidelines. In establishing these health-based standards, state officials must rely primarily on their own resources, which often are limited.
The proposed or promulgated health-based air regulations for styrene vary dramatically from state to state. For example, Colorado proposed a 0.0004 parts-per-million (ppm) fence-line standard for styrene, while North Carolina promulgated a 2.5-ppm standard. Louisiana uses a safety factor of 42, while Virginia's safety factor is 500.
A serious concern for SIRC and the styrene industry is that many of the more stringent state air standards for styrene are based on erroneous references to styrene as a group 2B carcinogen (possibly carcinogenic) in various EPA documents, including the 1989 Health Effects Assessment Summary Table. Even though EPA corrected this inaccurate reference, SIRC continued to address numerous state agencies' inappropriate use of the reference as a justification for treating styrene as a carcinogen.
Consideration of Styrene Under California's Proposition 65
Styrene currently is awaiting review under California's Safe Drinking Water and Toxic Enforcement Act of 1986 (better known as Proposition 65), which requires that the state publish annually a list of chemicals "known to the state" to cause cancer or reproductive toxicity. At this point, styrene is not listed under Proposition 65.
In 1999, the Office of Environmental Health Hazard Assessment (OEHHA) assigned a "high" priority for the review of the carcinogenic potential of styrene under Proposition 65. Because the U.S. Environmental Protection Agency (EPA) currently is reviewing styrene and is expected to classify its carcinogenic potential, if any, SIRC urged that OEHHA defer consideration of styrene until after the completion of the IRIS process (see U.S. EPA Regulation of Styrene). Indeed, Proposition 65 guidelines direct OEHHA to use the determinations of other authoritative bodies (including U.S. EPA) to avoid duplication of effort. The U.S. EPA is expected to finalize its IRIS styrene carcinogen classification in 2004 or 2005, after which time California is likely to resume its review of styrene's carcinogenic potential under Proposition 65. Even before Cal/EPA launched its review of styrene's potential carcinogenicity, OEHHA proposed that styrene receive a preliminary "medium-high" prioritization for review as a developmental and reproductive toxicant (DART). SIRC communicated with OEHHA indicating the scientific data do not support a "medium-high" prioritization for review as a DART. It is SIRC's understanding that only a "high" prioritization would mean that OEHHA would review styrene a substance for potential listing as a DART. At this point, OEHHA has not finalized a prioritization of styrene for review as a DART.
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