Probably the most important thing our society can do to protect our health is to ensure a clean and healthy environment. This is likely far more important in terms of both lives saved and illnesses prevented than ensuring access to health care, than delivering drugs, than targeting treatments based on genetic factors, or even than curing cancer. And yet we live in a world where some believe that the science behind many medical treatments or genetic risk prediction is more reliable than the science behind environmental regulation. In fact it's just the opposite.

Regulations to improve air quality are a perfect case in point. In 2012 the World Health Organization estimated that ambient air pollution killed about 3 million people a year worldwide. In the United States, an estimated 200,000 people die prematurely each year because of air pollution. However, dramatic reductions in air pollution in the United States that have resulted from regulations implemented under the Clean Air Act have saved hundreds of thousands of lives and protected many more from illness and disability.

A solid and interdisciplinary body of research, comprising laboratory animal experiments, human exposure studies, and sophisticated epidemiologic studies, have identified the effects of a number of air pollution exposures on health. The process through which the Environmental Protection Agency (EPA) uses this evidence to set regulatory standards is exemplary of the best use of science to make policy.

Under the Clean Air Act, the EPA is required to review the evidence on each criteria pollutant - carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide - every five years. This is an intense process involving extensive scientific and public input.

The EPA staff assesses the evidence for health effects based on a range of different types of scientific studies. They obtain expert advice and hear public comment from a range of organizations and individuals. They systematically and rigorously evaluate the impact of various regulatory standards on the health of large population groups. Ultimately, they make recommendations based on the best available evidence. The EPA administrator then considers the recommendations in the context of other relevant policy factors and makes a decision on any proposed changes to the standard.

The process works: The air we breathe has improved dramatically, and the economy has not suffered because of it.

Since the passage of the Clean Air Act more than 40 years ago, and despite an increase of more than 50 percent in the U.S. population and a 250 percent increase in the gross domestic product, there has been a 70 percent reduction in emissions of criteria air pollutants. Children have grown up healthier. It has been one of the great, silent public-health successes of the past 50 years.

This is government functioning at its best: protecting the public based on the best available scientific evidence, while using a transparent process that takes into consideration not only science but a broad set of social and economic factors.

The role of government in protecting the public from environmental harms is critical. These are not harms that the public knows about or can willingly avoid. They are things in the air we breathe, in the water we drink, in the houses we live in. Environmental hazards are silent killers that we often do not know about and cannot individually control.

Imagine a world without environmental regulation. We can get an inkling of what a world like this is like from what is happening in places such as China, where air pollution levels are often several times higher that internationally accepted maximum levels and about 1.6 million deaths a year have been attributed to air pollution (aside from the burden of air pollution-related illness).

The recent cuts proposed for the EPA in President Trump's budget could fundamentally affect government's ability to protect the health of the public.

The EPA has been an international model for smart and responsible environmental protection that has benefited all of us. Rolling back on environmental protection, and on the science we need to sustain it, is not the right thing for America.

Ana V. Diez Roux, M.D., is dean of the Dornsife School of Public Health at Drexel University and chair of the EPA's Clean Air Scientific Advisory Committee. The views expressed are her own.