Toxin Release Inventory and Styrene

Since 1987, the U. S. Environmental Protection Agency (EPA) has collected information annually on the release of selected chemicals by U.S. manufacturing facilities, and has made this information public through the Toxics Release Inventory (TRI). The TRI was established pursuant to Section 313 of the Emergency Planning and Community Right-to-Know Act (EPCRA) of 1986.

TRI reporting requirements cover 643 chemicals, 28 of which are categories of chemical compounds. The list represents materials ranging in toxicity from mildly toxic to severely toxic, and whose effects range from acute to chronic. In 1996, the environmental releases of all chemicals of the 21,626 reporting facilities totaled 2.43 billion pounds.

The TRI data are presented to the public primarily through a publicly accessible database, and through EPA publications. Due to the complexity of compiling these figures, the report data reflect chemical releases from the year two years prior to the date of publication. The annual publication of these data receives attention from federal, state, and local governments, citizens, communities, industry, and the news media, and occasionally will generate questions about styrene's inclusion on the list.

Reporting Requirements.

Facilities with more than 10 full-time employees which manufacture or process more than 25,000 pounds, or use more than 10,000 pounds, of any reportable chemical must report to the EPA, on an annual basis, the quantities of these chemicals released into the air, water, and soil. EPA then publishes these figures in the TRI, along with information on the maximum amount of the chemicals stored at reporting facilities during the year. The names and locations of off-site facilities to which toxic wastes were shipped also are reported, as are the treatment or disposal methods used for wastes, and estimates of their efficiency.

Styrene Emissions.

Styrene emissions are among those chemicals which must be reported to the EPA under TRI. Despite the fact that the EPA has not formally classified styrene as a carcinogen (nor has any other Federal agency), it currently is listed in the TRI as a "carcinogen" based on
the 1987 IARC reclassification (see International Regulation of Styrene), although SIRC has protested the use of IARC classifications in defining carcinogens. The following information is important to consider relative to styrene's inclusion in the TRI:

Emission estimates from styrene manufacturing facilities do not directly translate into or signify a threat to public health. Styrene has a very short half-life. One limitation of the TRI data, as stated by EPA in the Introduction section of the Toxics Release Inventory document, is that "TRI reports reflect releases of chemicals, not exposures of the public to those chemicals. Release estimates alone are not sufficient to determine exposure or to calculate potential adverse effects on human health and the environment." Such is the case with styrene.

The available evidence strongly suggests that styrene is not carcinogenic to humans. Extensive epidemiology studies of over 55,000 workers, over a total of 45 years, collectively show no link between styrene and cancer. These workers are exposed to styrene at levels more than 10,000 times higher than the extremely small levels to which the general public is exposed from environmental sources. In recent years the National Institute for Occupational Safety and Health (NIOSH), the Occupational Safety and Health Administration (OSHA), and scientists of the European Union (EU) all have reviewed the scientific data on styrene, and all three organizations have chosen not to classify or regulate styrene as a carcinogen. A recent draft risk assessment by the Health and Safety Executive for the United Kingdom also proposes that styrene should not be regulated as a carcinogen.

Even though styrene is identified in the TRI as a "carcinogen," the U.S. EPA has not formally classified styrene as a carcinogen. EPA's Office of Research and Development (ORD) has begun a review of styrene for its Integrated Risk Information System database, that will include the agency's formal carcinogen determination for styrene.

While not required by statute or regulation, EPA has chosen to characterize the health effects of the substances listed in the TRI Report. Rather than base these characterizations on its own findings for these substances, EPA has chosen to adopt by reference the classification system used in the Occupational Safety and Health Administration (OSHA) Hazard Communication Standard (HCS). Substances are considered carcinogens under the OSHA HCS if they are so categorized by: (1) OSHA, (2) the National Toxicology program (NTP), or (3) the International Agency for Research on Cancer (IARC). The TRI lists styrene based on OSHA's reference to IARC and that agency's controversial Group 2B "possible" carcinogen classification of styrene.

The IARC classification of styrene remains controversial. IARC's classification process represents a hazard evaluation only, and not a complete risk assessment. IARC's examination of the data is based on a strength-of-the-evidence approach (i.e., any positive study signals a concern, regardless of the number of negative studies or the shortcomings of the positive studies), versus the more inclusive weight-of-the-evidence approach (which would evaluate both positive and negative findings). SIRC continues to work to address both IARC's classification and their methodology, as well as the appropriateness of EPA's use of IARC classifications as a basis for inclusion in the TRI.

SIRC has actively promoted facility emission reductions within the styrene industry. In presentations to industry segments with traditionally high emissions, facilities are being urged to initiate proactive efforts to significantly reduce emissions in an effort to address styrene's continued inclusion on the TRI. Several industry segments currently are working with EPA on the establishment of Maximum Achievable Control Technology (MACT) for their industries, to significantly control styrene emissions.

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