The Clean Air Act of 1970—long touted as one of the most significant federal environmental laws—was actually preceded by 15 years of air pollution legislation. But the 1970 Act was the first time the federal government set nationwide standards, goals, and enforcement methods for reducing and controlling air pollution. Since then, amendments have clarified, revised, and added provisions to the law.

This overview gives a sense of the structure of the Act, some of its notable successes, and some remaining concerns, particularly those related to electricity generation.

The basics

The federal Environmental Protection Agency (EPA) sets standards and identifies control technologies (ways to reduce pollution), and the states write permits and enforce the Act. EPA approves state plans for reducing pollution, which can apply more, but not less, stringent standards than federal standards

Pollution sources

The Act recognizes two main sources of air pollution: mobile sources like fossil-fuel burning vehicles and stationary sources like power plants. Mobile sources are regulated in three ways:

• controlling contents of the fuels (e.g., unleaded gasoline)
• requiring pollution capture or reduction technologies (e.g., catalytic converters)
• requiring operational efficiency standards (e.g., fuel efficiency)

Stationary sources have a much broader range of regulations, but they mostly fall into a similar scheme of reduction of pollutants in inputs, increased operational efficiencies, and pollution capture at the back end.

Air pollutants

The Clean Air Act began by regulating seven air pollutants (called “criteria” pollutants):

• carbon monoxide
• lead
• nitrogen oxides
• ozone
• particulate matter
• sulfur dioxide
• hydrocarbons

Additional pollutants

Substances that have not been regulated under the Act can become regulated after a series of research-based findings by EPA. First, EPA establishes that an unregulated substance endangers human health and the environment. Then the agency sets up a phased approach to controlling it, often starting with efforts that can either most easily and cheaply reduce emissions or will result in the largest reductions.

Phase-in

The new regulations could not be implemented across the country all at once without major economic disruption and an impossible political and administrative burden. They have been, and continue to be, phased in over long time periods, based on a number of factors, including size of the polluter, relative hazards of the pollutants emitted, and the available technology or techniques to eliminate or control the pollution.

Major successes: lead, particulates

The single greatest success of the Clean Air Act is the enormous reduction in lead emissions—98 percent by 1994. In the strong consensus days of the 1970s, the newly-formed EPA was successful in phasing out lead additives in gasoline, paint, and other items in daily use. By removing lead from emissions sources, particularly gasoline and paint, lead emissions are now an issue only in a few industries where  they can be mostly captured and kept out of the air.

The result of the Clean Air Act was striking: a drop of blood lead levels in children of 75 percent by 1994 and a corresponding increase in children’s’ IQ.

Particulates are tiny particles of microscopic matter emitted from sources like vehicle engines and factories. The Clean Air Act has successfully resulted in a dramatic drop in larger particulates—about 78 percent by 1994, mostly through use of taller smoke stacks and capture technologies. Unfortunately, fine particulates are more easily airborne and harder to capture. Increasing rates of asthma and other respiratory ailments are due in part to the continued emissions of fine particulates, mostly from burning fossil fuels.

Major failure: fossil fuel power plant exemption

In a huge blow to human health, the environment, and the economy, the Clean Air Act expressly exempted existing fossil fuel power plants from regulation. Since plants were not regulated until subject to major modifications or rebuilt altogether, many plants have kept running beyond any reasonable operational or economic lifespan. This has resulted in a relative failure to control air pollutants from power plants. For example, the reduction of sodium dioxide is much less impressive than for lead and particulate matter, and nitrogen oxides have increased substantially—almost entirely due to increased coal burning at power plants and the increase in the number of natural gas power plants.

Looking forward—the Clean Air Act and energy

After 20 years of lawsuits and waffling by various Administrations, EPA has followed a 1990 congressional directive to revisit the ongoing validity of power plant exemptions and is beginning to regulate air pollution from old power plants as well.

At the same time, the standards for nearly all of the criteria pollutants have been undergoing a multi-year updating, begun in the Clinton and G.W. Bush Administrations. The new standards for sodium dioxide and nitrogen dioxide were finalized in 2010. Ground-level ozone standards will be finished late in 2010. The fine particulate standard is expected to be finalized in mid-2011. All of these new standards will apply, although probably differently, to both existing and new power plants.

Greenhouse gases

A recent—and significant—issue in power plant pollution is the emission of carbon dioxide and other greenhouse gases. In 2009, EPA issued its finding that carbon dioxide and other identified greenhouse gases endanger human health and the environment. In October 2009, it required reporting emissions of these substances from some industries and activities. In 2011, EPA is expected to issue permit requirements and a requirement for use of control technologies for greenhouse gas emissions. The scope of this issue is massive because of the huge emissions of greenhouse gases, especially from power plants, other stationary sources, and motor vehicles.

Again, regulations will be phased in over time, beginning with requirements for mobile sources and moving on to stationary sources. Roughly one-third of all greenhouse gas emissions are from power plants, one-third from buildings, and one-third from motor vehicles. These new regulations will have a profound effect on at least the continued viability of fossil fuel-generated electricity and internal combustion engines for cars and trucks.

This overview gives a sense of the structure of the Clean Air Act, some of its notable successes, and some remaining concerns, particularly those related to electricity generation.