Complex science increasingly drives major policy decisions. The U.S. Environmental Protection Agency so acted last month to replace the relatively new 85-parts-per-billion (ppb) ozone standard with a far stricter 75-ppb standard.

As a longtime observer of EPA’s determination of air quality standards, I am struck by the extent of scientific objection to this dramatic change. Many credentialed experts sharply question whether the lower standard will provide additional health benefits beyond today’s standard.

Clinical, epidemiological and toxicological science is used to calculate a maximum ozone level to protect human health. In 2001, the U.S. Supreme Court clarified that the EPA must not use cost as a balancing factor. The Clean Air Act dictates that the EPA must establish health-based standards that “accurately reflect the latest scientific knowledge.”

With Dallas-Fort Worth’s current ozone design value of 94 ppb, the new 75-ppb standard is formidable. And although legally irrelevant, the EPA has conceded that the cost of attaining the new standard will outweigh the health benefits by $20 billion in 2020.

The new standard will classify 400 new counties nationwide into nonattainment. In Texas, five additional urban areas will join the Dallas-Fort Worth and Houston-Galveston regions under the federal nonattainment shackle. Characterized by the EPA as perhaps its most expensive rule ever, this 75-ppb standard begs for solid scientific justification.

Many prominent scientists and physicians question whether any new science exists since the EPA promulgated the 85-ppb standard in 1997. The author of the single, new, peer-reviewed study of 2006, Dr. William Adams of the University of California at Davis, concluded that there was no significant statistical correlation between lung function and ozone exposures at levels below the current standard. EPA staff reinterpreted Dr. Adams’ study and reached the opposite conclusion. Although Dr. Adams and a member of the EPA’s Scientific Advisory Committee challenged the staff’s manipulation, its conclusion remained.

Dr. Roger McClellan, former Scientific Advisory Committee chairman, testified that so lowering the standard “is a policy judgment based on a flawed and inaccurate presentation of the science that should inform policy decision.” Dr. McClellan and other scientists found serious flaws with EPA’s reliance onepidemiological studies with vague correlations – and no demonstrated causation – between monitored ozone levels and adverse health effects.

Ozone levels measured at a monitor are a poor measure of actual inhalation. Assumptions of 24-hour exposure to a monitored level are completely unrealistic and inappropriate for an ozone standard calculated on the basis of an eight-hour average. Indoor ozone levels are much lower.

Financial cost may not be part of EPA’s decision, but the magnitude of cost demands empirical data demonstrating health effects, not vague correlations. However expensive such studies might be, they pale in comparison to the EPA’s estimated implementation cost of $7 billion to $14 billion per year.

Ozone levels in North Texas have dramatically improved. With an aggressive state plan full of regulatory controls, the area should reach today’s 85-ppb standard by 2010. Over the next four years, new federal engine standards will yield sizable emission reductions from the mobile sources so dominant inthe region. These reductions, however, will not be enough to reach the 75-ppb standard.

So why worry if the EPA’s science does not justify lowering the standard? If the purpose is to protect human health, doesn’t even a slight chance of greater health benefits provide a sufficient basis? No. Massive unnecessary costs matter and matter for health.

The state, local governments and businesses have spent billions reducing ozone. Health and longevity are positively affected by income and economic growth. The most effective way to reduce ozone in the area is the purchase of new vehicles with cleaner burning engines, which requires a healthyeconomy.

America is a rare nation, prosperous enough to impose mandatory standards to protect human health regardless of cost. This is a wild luxury for most of the world’s population. But solid science and economics matter – and matter for human health.

Kathleen Hartnett White is director of the Center for Natural Resources at the Texas Public Policy Foundation. She served six years as chairwoman and commissioner of the Texas Commission on Environmental Quality.