Academic journal article Forum for Applied Research and Public Policy

Mercurial Standards: Before We Rush Headlong into Another Regulatory Regime, We Need to Gain a Better Scientific Understanding of Hazardous Air Pollutants

Academic journal article Forum for Applied Research and Public Policy

Mercurial Standards: Before We Rush Headlong into Another Regulatory Regime, We Need to Gain a Better Scientific Understanding of Hazardous Air Pollutants

Article excerpt

Current regulations have achieved significant reductions in the major polluting air emissions--notably sulfur dioxide and nitrogen oxides--from U.S. coal-fired power plants. Now, the emphasis from regulators and various environmental groups has broadened to include concerns about trace chemical releases from power plants. Does science justify this new emphasis? Do we know enough to decide if and how these hazardous air pollutants (HAPs) should be regulated? Should we be spending several billions dollars annually to control an environmental problem that may not exist or, even worse, risk creating a new environmental problem?

The U.S. Environmental Agency has targeted more than 600 chemicals for monitoring and reporting because of their potential adverse environmental and health effects. Among the HAPs of greatest concern to human health is mercury, which is thought to be converted to methylmercury by bacteria in oxygen-free sediments. Methylmercury is a neurotoxin that can bioaccumulate in the food chain. While coal-fired power plants do not release methylmercury, they do release mercury, which can be converted into methylmercury after it settles out of the air.

But power plants are not the sole source of mercury in the environment. It occurs naturally in air, soil, and water. In addition, thousands of tons of mercury were used annually in the United States in many common products through the middle decades of the 20th century. Its uses ranged from thermometers, to fluorescent and mercury vapor lights, to level switches in thermostats in homes and light switches in automobiles. Since mercury is an element and cannot be destroyed, mercury can enter the environment as these products are scrapped. In fact, recent research by Oak Ridge National Laboratories has indicated that mercury is being released from municipal landfills in the most dangerous methylmercury and dimethylmercury forms.

Changing Course

In the past, when EPA considered the potential health and environmental consequences of HAPs emitted by utilities, it concluded that HAPs from power plants were not a sufficiently significant health or environmental threat to warrant regulatory attention. Subsequently, EPA decided that HAP releases from coal- and oil-fired power plants should be reported under its Toxic Release Inventory (TRI) program, a program originally designed for the chemical industry. Under TRI, electric utilities began estimating and reporting their annual releases of the listed TRI chemicals, including HAPs, to the air, water, and land. Many of these substances are released into the air through the smokestack, but at such extremely dilute concentrations that they pose no significant risk to human health.

In 1998, EPA released its Electric Utility Hazardous Air Pollutant Study Final Report to Congress, as mandated by the Clean Air Act Amendments of 1990. This report generally confirmed that HAPs emissions from utilities were not sufficiently worrisome to warrant regulatory concern. EPA concluded, however, that mercury deserved further study. The agency then issued a mercury information collection request (ICR) that required all electric utilities to sample every sixth coal shipment to each plant and have these samples analyzed to determine the mercury content. In addition, a number of randomly selected coal-fired power plants were required to sample flue gas at the inlet and outlet of the last environmental control system. The purpose of this was to provide data on the mercury content of the coal burned and an estimate of the mercury air emissions from coal-fired power plants in the United States.

On December 14, 2000, EPA announced that mercury emissions and certain other HAPs from coal-and oil-fired power plants should be regulated, although EPA acknowledged that there was still insufficient information to determine how this should be done. Nevertheless, under a schedule established by EPA, regulation proposals are due in December 2003, after two years of further study, and a final regulation is to be promulgated by December 2004, with compliance required by December 2007. …

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