Since the passage of the Clean Air Act of 1970, the size of the economy has tripled, energy consumption has increased by half, and vehicle mileage has tripled. Even so, the six most commonly found airborne pollutants have decreased by more than half, air toxics from industrial plants have fallen by more than 70 percent, and new cars are 90 percent cleaner. Sound regulations and public protections don’t impede economic growth, but they can and do improve the quality of our lives. Here’s the story of one such piece of regulatory legislation, the nation’s Clean Air Act.

Today is the birthday of the Clean Air Act, legislation signed into law by President Richard M. Nixon 44 years ago. This law is the centerpiece and platform for protecting the quality of the air we breathe. It took decades of work to get clean air laws passed, and over time, amendments have been added to strengthen our air quality standards and to respond to new risks. This is the story of how we established standards to protect a public good that we all need, but most of us take for granted.

The Public Demands Clean Air: Cities Take the Lead

In America, public complaints about filthy air began in the middle of the 19th century. As cities grew more densely populated, coal and oil became the major energy source, and large factories released all manner of waste from industrial production into the neighborhoods where they were located. In 1881, Chicago and Cincinnati, then major manufacturing centers and transportation hubs, became the first U.S. cities to limit air pollution.

At this point in time, Cincinnati was the nation’s most densely populated city and one of the most industrialized. Factories churning out iron products, coupled with smoke-producing locomotives and river boats, produced particulate-laden air that choked the city’s 300,000 residents. In response, the southern Ohio city passed smoke control regulations in 1881, requiring operators of coal-fired boilers to adopt smoke prevention technologies. Most firms ignored the law, and air quality deteriorated further.

Two years later in 1883, St. Louis, another river town full of industry, learned from Cincinnati’s experience and passed legislation that combined new rules limiting smoke emissions with an office of inspectors to measure and enforce the new law. Rules and the resources to enforce them worked. The citizens of St. Louis were soon breathing easier.

Seeing St. Louis’ successes, citizens of Cincinnati began to clamor for their city to enforce its anti-pollution rules. In 1903, a new smoke ordinance was passed, and along with it, funding to hire a professional engineer to enforce the law.

The turn of the century heralded a new era of citizen activism (the progressive movement), and across the country, citizens organized to fight back against the consequences of unregulated industrialization. The Cincinnati Women’s Club helped organize the Smoke Abatement League in 1906, a dues-paying organization, and were able to pressure city leaders to pass a third city anti-pollution law in 1907. The new law established a four-person Office of the Smoke Inspector and mandated that it use umbrascopes, a new technological tool, to measure smoke throughout the city, and then look for the sources of pollution to demand that enterprises shift to safer alternatives.

In 1910, Massachusetts became the first state to adopt clean air regulations with laws regulating smoke emissions in Boston. Other cities and states followed these early efforts, and by the close of the Second World War, a patchwork of clean air rules and standards existed throughout the United States.

This prompted the federal government to act. In 1910, the Taft Administration created the Office of Air Pollution within the Interior Department’s newly formed Bureau of Mines. The office, whose purpose was to control coal emissions, was largely inactive and was closed a few years later, to the delight of factory owners.

Tragedy Shifts Public Opinion and Increases Public Demand for Action

In October 1948, the nation’s attention was intensely focused on the deadly problem of uncontrolled industrial pollutants when a thick cloud of smog hovered over the industrial town of Donora, Pennsylvania for five days. Donora residents were accustomed to the yellow smoke that poured from the town’s zinc smelter. But in 1948, cold air aloft held the thick smog cloud in place. Townfolk asked the plant operators to suspend operations until the cloud dissipated. They refused.

The decision was deadly. The hospital was so overwhelmed by people in respiratory distress that the first floor of the town’s hotel was converted into an emergency medical clinic, and the hotel’s basement was turned into a make-shift morgue. By the time the toxic stew cleared five days later, 20 people were dead and 6,000 of the town’s 14,000 residents had been sickened. The deadly effect of air pollution in Donora blared in headlines throughout the country.

Four years later, a black smog settled over London for five days in December. The smog from coal-burning homes and factories was being held down by a weather system; it was so thick that the city’s buses could not run without people with lanterns walking ahead of the buses to guide them through the haze. An estimated 12,000 people died from exposure to the Black Smog of 1952. Some people point to this incident as the beginning of the modern environmental movement, but a national law to reduce coal use was not passed in the UK for another four years.

Federal Government Starts to Investigate

Public pressure for action intensified in the United States. In 1955, Congress passed the Air Pollution Act, a bill that provided the Public Health Service $5 million annually to study the effects of air pollutants on human health and to propose solutions to address the problem.

Public awareness of the impact on industrial waste on human health and the natural world broke through to a new level with Rachel Carson’s best-selling book, Silent Spring, published in 1963. Carson translated and popularized a growing body of scientific evidence about the deadly dangers of toxic pollution and chemical exposures.

Within six months of the publication of Silent Spring, Congress passed the Clean Air Act of 1963, the first federal law to regulate air emissions. This act set emission standards for power plants, steel mills and other industrial polluters. The law did not address mobile sources of pollutants stemming from autos and trucks, a significant part of the air pollution problem. It did, however, inaugurate the practice of the federal government providing funding to states to enforce anti-pollution standards, providing $95 million ($733 million in 2014 dollars) over three years to help states create their own air pollution control agencies.

But progress was slow, and the public in large cities was anxious for relief. Research was also showing the impact of lead emissions from gasoline on the health and IQ of small children in neighborhoods near freeways or heavily trafficked bridges. In 1965, the Motor Vehicle Pollution Control Act was passed, which added emissions limits on cars and trucks. This amendment also provided funds to study trans-boundary pollution, the crossing of polluted air from Canada and Mexico into the United States. Amendments in 1966 expanded local air pollution control programs. Significant amendments were added in 1967 to establish Air Quality Control regions in order to deal with the fact that air flow patterns do not respect political boundaries. This was the federal government's first acknowledgement that a patchwork of state and local standards was simply unable to deal with the problem; one national standard was needed. The 1967 amendments also imposed a timetable for implementation.

In 1970, in the midst of public protests about the Vietnam War and racial inequality, Sen. Gaylord Nelson (D-WI) called for the first Earth Day, a day of public demonstrations. On April 22, 1970, 20 million Americans in cities and towns across the land joined to demand changes to protect their environment.

Before the year ended, Congress passed the Clean Air Act of 1970, a sweeping re-write of the 1963 law. The 1970 law established National Ambient Air Quality Standards, New Source Performance Standards that strictly regulated emissions from both newly constructed plants and older plants (that had previously been grandfathered in and exempted from compliance), and strengthened the limits on emissions from cars and trucks. Enforcement of the Clean Air Act was given to the U.S. Environmental Protection Agency (EPA_, the nation’s newest federal agency, which was formed earlier in the month. Importantly, it also gave citizens the right to sue any person, organization, or commercial entity for violation of clean air standards.

Backlash

In the wake of stronger regulation and enforcement of the nation’s air quality standards, the air did get cleaner and respiratory diseases declined as a result. Yet industry continued to complain that the costs of complying with pollution controls reduced profits and competiveness. In spite of business opposition, the EPA continues to monitor scientific research demonstrating the impact of various kinds of airborne pollutants on human health and nature and modifies standards accordingly.

Sometimes the science is ignored. In 1979, a National Academy of Sciences report found that lead from gasoline was the single largest pollutant in the atmosphere, but a year later, the Reagan administration tried to abandon a previously agreed-on phase-out of lead from gasoline. A huge public outcry ensured, and the administration was forced to speed up the phase-out timetable.

Business interests also use the courts to try to push back on air quality standards. In 1988, Wisconsin Electric Power sued the EPA on the grounds that its New Source Review standards did not set appropriate tests to measure compliance. Two years later, the Seventh Circuit Court of Appeals ruled mostly in the company’s favor. Large polluters continue to challenge both the standards and enforcement measures that EPA has established.

In the 1990, the Clean Air Act was amended to address the new threats from “acid rain” and to respond to growing concern about climate change. The amendments set limits on the emissions of chlorofluorocarbons (CFCs) that destroy the earth’s protective ozone layer and introduced the concept of Best Available Control Technology, which gives industry a range of options for compliance.

But even now, 44 years after the first legislation aimed at reducing air pollution was passed, coal-burning power plants are still operating in the U.S. – despite their known impacts on human health and the environment. Earlier this year, the EPA finally announced new limits on power plants – phased in over years. In another decade, the “dirtiest” coal burning power plants will likely be closed. This is progress. We need to transition the workers from these plants into new jobs and ensure the pensions of the retirees of these companies, but the closing of these plants is a win for clean air and public health.

Still Work to Be Done on Air Quality

Although there have been major and continuing improvements in our air quality over the last half century, nearly half of Americans today live in counties with levels of ozone or particulates that can be harmful to their health, according to the American Lung Association's 2014 State of the Air report.

We need more monitoring of compliance with existing standards, not less. But the omnibus spending bill signed into law by President Obama earlier this month reduced the EPA’s budget – again. Over the last five years, EPA’s budget has been cut by 21 percent, even as the agency has been asked to take on new responsibilities for monitoring greenhouses gases. Already, the EPA workforce has been reduced to 1989 levels, even though the economy is twice the size it was back then.

Engage to Defend the Progress We’ve Made

Over the next two years, the federal Environmental Protection Agency and the rules and standards it created and enforced to improve our air quality will be under serious attack. It is interesting to note that the agency was created by a Republican president, in response to 20 million citizens turning out for Earth Day demonstrations all over the country. When the public wants something badly enough, partisanship has a way of dissipating.

We’ve come a long way from the days of yellow smog over Donora, Pennsylvania or the Black Smog that killed 12,000 in London. While we are unlikely to see a return to those gloomy days, every year, we see the human damage from more volatile weather patterns (Hurricane Sandy, wildfires and droughts in the West) that scientists tell us are the result of increasing carbon emissions. To protect the progress that’s been made and continue our transition to cleaner energy sources, we’ll need informed, engaged citizens like you. Pay attention. On this issue, it’s up to all of us to protect our air today and for future generations.

Editor's note: This post has been updated since its original publication date.