The U.S. Environmental Protection Agency might be preparing to unveil a major air pollution rule change shortly after midterm elections. The new standards would reflect the latest science relating to the health and ecosystem impacts of ground-level ozone and could have significant impacts on infrastructure projects across the nation.

Ground-level ozone (a.k.a. tropospheric ozone or (O3) is not emitted directly into the air, but is formed via chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Majors sources of these ozone precursors include industrial facilities, power plants, motor vehicles, chemical solvents, and vapors from gasoline.

Ozone is regulated under the Clean Air Act. As a result, the U.S. Environmental Protection Agency (EPA) is required to set national ambient air quality standards (NAAQS) for this type of air pollution. Furthermore, the EPA must periodically review these standards to "ensure that they provide adequate health and environmental protection, and to update those standards as necessary."

In 2008, the NAQQS for ozone were set at an 8-hour average not to exceed 0.075 parts per million (ppm). This value was slightly lower than the 1997 ozone standard of 0.08 ppm 8-hour average concentration. These standards were challenged by the Utility Air Regulatory Group. But, the U.S. Supreme Court refused to hear their appeal earlier this month, maintaining that the EPA has adequate scientific evidence to tighten the standards for this air pollutant.

It is rummored that the updated ozone standards could include a drop to 0.06-0.07 ppm (8-hour average).

Public Health Concerns

According to the World Health Organization (WHO), ozone is an air pollutant “of major public health concern." In their 2013 review of evidence relating to the health effects of air pollution, the WHO identified several studies that link ozone exposure to respiratory and cardiorespiratory illnesses that lead to increased hospital admissions and premature death.

According to studies, both long- and short-term exposure to ozone can be dangerous for public health.

Researchers with the American Cancer Society found a strong link between long-term exposure to ozone and premature death due to respiratory illness (less conclusive evidence existed in this study regarding the link between long-term ozone exposure and cardiovascular illness) in their work. Other studies have shown that ozone exposure could be particularly dangerous for people with predisposing conditions like diabetes and congestive heart failure and can increase asthma attack incidence rates, severity, and difficulty of treatment for those with asthma.

For short-term ozone exposure, ample evidence exists to link short-term ozone exposure to a range of pulmonary and vascular illnesses and suggest an effect on cognitive development and reproductive health. In addition, all-cause, cardiovascular, and respiratory mortality and morbidity have been reported as being linked to short-term exposure to ozone.

Impacts on Ecosystems

Ground-level ozone can also affect vegetation and ecosystems including forests, parks, wildlife refuges, and protected wilderness areas. In particular, ozone can interfere with the ability of certain plants to produce and store food. Black cherry, quaking aspen, ponderosa pine, and cottonwood trees have shown a particular sensitivity to ozone exposure. Furthermore, this air pollutant can visibly damage the leaves on trees and other plants. Over time, long-term exposure to ozone can lead to increased levels of disease and insect damage, while decreasing the overall health of sensitive plants.

Some cheer, others express concerns

As with most regulations, there certainly exist diverging viewpoints regarding the advisability of updated ozone standards.

In the business community, some voices have expressed concerns regarding the impact of tougher ozone standards on competitiveness. According to Ross Eisenberg, Vice President of energy and resources policy at the National Association of Manufacturers (NAM) "You have to balance what you're trying to achieve environmentally with what you're trying to achieve in the economy." One (contentious) study from the NAM reported that strengthening the ozone standard under the Clean Air Act could cost industry $270 billion/year in compliance costs.

Conversely, in environmental and public health communities one seems to find wide support for tougher standards for ozone. And, as the science appears to support arguments for more strict standards, "it's a difficult situation, because the Clean Air Act says that the limits are supposed to be set purely based on health and to provide an adequate margin of safety,” according to Rice University's Professor Dan Cohan.

Photo Credit: US EPA