Natural Resources Defense Council

Natural Resources Defense Council - "EPA's New Stealth Campaign to Kill Regulation of Harmful Air Pollutants": Volitale Organic Compounds like Acetone & now TBAC (tertiary butyl acetate)

BAD SCIENCE is no basis for HEALTH POLICY!!!

"The Exceptions: Acetone and TBAC

In 1995 EPA unaccountably exempted a compound, acetone, which is more reactive than ethane on a per-molecule basis. To reach this insupportable decision, the agency focused on the fact that a gram of acetone forms less ozone than a gram of ethane. In other words, EPA changed its units from per-molecule to per-gram for this particular reactivity analysis.

The change is baseless. Reactivity depends solely on the number of molecules available for a reaction, not the weight of those molecules. Changing units enabled the agency to place fewer molecules of the heavier acetone in its imaginary reaction chamber (because one gram of acetone comprises fewer molecules than one gram of the lighter ethane), thus generating fewer imaginary molecules of ozone. Voila! Acetone appears less reactive than ethane.

In late 1999, the agency again proposed adopting this flawed per-gram approach to assessing reactivity, this time to exempt TBAC from VOC regulations. The TBAC proposal came in response to a petition submitted on behalf of the chemical's manufacturer, Lyondell, by the company's attorneys at Latham & Watkins - a group that included Jeffrey Holmstead, then a chemical industry lobbyist and now EPA assistant administrator for air. (Holmstead recused himself from the TBAC matter when he joined the agency.)

Responding to Lyondell's petition at a meeting of EPA officials and Lyondell representatives, John Seitz, then-director of EPA's Office of Air Quality Planning and Standards, noted that the "reactivity per mole[cule] basis is the correct technical basis for comparing compounds to ethane for exemption purposes," and that "exempting TBAC on a gram basis" in reliance on the acetone rule "would be perpetrating an error." (Docket item III-E-04, summary of August 9, 2000, meeting.) The proposed TBAC rule made the same point: "[T]he per-mole[cule] basis is the proper scientific basis to use in comparing reactivity to ethane for decisions concerning negligible reactivity." (Air Quality: Revision to Definition of Volatile Organic Compounds - Exclusion of t-Butyl Acetate, 64 Fed. Reg. 52,731, 52,734.)

EPA even acknowledged the flaws in its reasoning in last week's final rule. The agency conceded that a " 'reactivity per mole[cule]' comparison is more consistent" with historical practice and "arguably more environmentally protective than a 'reactivity per [gram]' comparison" and admitted that using a reactivity-per-molecule approach would preclude an exemption for TBAC (which is 50 percent more reactive than ethane on a per-molecule basis). (Revision to Definition of Volatile Organic Compounds - Exclusion of t-Butyl Acetate, http://www.epa.gov/airlinks/pdfs/tbac.pdf, at 6, 13 (TBAC Exemption)).

In the end, however, EPA granted Lyondell's request that TBAC be exempted from VOC limits without providing any rationale, let alone a scientifically defensible one, for using a per-gram reactivity approach. As a result, public exposure to TBAC and TBAC-created smog will no longer be regulated. "