By Dr. Michael Honeycutt
Director, TCEQ Toxicology Division
The EPA is considering lowering the existing national eight-hour ozone standard from its current level of 75 parts per billion (ppb) to a much lower range, between 70 and 60 ppb. However, after an in-depth review of the EPA’s analysis, as well as a thorough study of the relevant scientific literature, the TCEQ has concluded that there will be little to no public health benefit from lowering the current standard.
Surprisingly, the EPA’s own modeling in 12 cities across the country indicates the net result will be increased mortality in some areas, including Houston and Los Angeles. The EPA did not perform the analysis for other cities in Texas.
There is no doubt that, at some higher level, ground-level ozone is harmful to human health. The question is, has the EPA adequately demonstrated that lowering the ozone standard to 70–60 ppb would actually have health benefits? We think that the EPA’s process of setting ozone standards has not scientifically proven this, and that further lowering of the ozone standard will fail to provide any measurable increase in human health protection.
The EPA’s own modeling in its Health Risk and Exposure Assessment (HREA) indicates that lowering ozone concentrations would actually result in more deaths in some cities (Appendix 7, page 7B-2 of the HREA). Either this indicates that lowering the ozone standard defeats its stated purpose of protecting human health, or it indicates that something is wrong with the EPA’s interpretation of the data. Either way, it’s not a good argument for lowering the ozone standard.
Further, the EPA is not very forthcoming about the increased deaths. It’s not mentioned in the executive summary of their policy analysis, but it’s found on page 115 of Chapter 3, more than one third of the way through the 597-page document.
Number of Premature Deaths in Houston Predicted by EPA
||Net Impact on Mortality
|Meeting current standard (75 ppb) from present day ozone levels
||47 more deaths
|Going from present levels to 70 ppb
||48 more deaths
|Going from present levels to 65 ppb
||44 more deaths
|Going from present levels to 60 ppb
||35 more deaths
This table, which was made using EPA’s own modeling, indicates that reducing ozone in the Houston area will actually result in increased premature deaths. Whether this predicted result is factual, or if it just highlights flaws in the EPA’s interpretation of the data, it casts doubt on the science being used to justify EPA’s proposed lower ozone standards.
Data collected from Texas hospitals indicates that admissions for asthma are actually highest in the winter, when ozone concentrations are normally lowest. This casts further doubt on the EPA’s assertion that ozone is an important driver of asthma symptoms.
The EPA’s proposed lower ozone standard derives much of its claimed benefits from associating ozone with worsening asthma. The problem with this association is that asthma diagnoses are increasing in the U.S., yet nationwide, air quality is improving. If asthma were actually tied to ozone, you would expect to see the instances of asthma decreasing, not increasing. In fact, data from Texas hospitals show that asthma admissions are actually highest in the winter, when ozone levels are the lowest.
The evaluation of the proposed ozone standard was performed by the TCEQ Toxicology Division, which consists of 10 Ph.D. and five master’s level scientists. Our scientists specialize in toxicology and risk assessment related to air contaminants, and set guidelines and toxicity factors that are adopted by many different states and countries.
The sciences (toxicology, molecular biology, biochemistry, cell biology, chemistry, just to name a few) used to set the EPA’s standards are complex and technical. Toxicology Division members Stephanie Shirley (Ph.D., UT MD Anderson Cancer Center, molecular carcinogenesis), Sabine Lange (Ph.D. UT MD Anderson Cancer Center, biochemistry and molecular carcinogenesis), Neeraja Erraguntla (Ph.D., LSU, physiology, pharmacology and toxicology), a