How soon we forget.

In 1970, speaking from badly polluted Los Angeles, Bob Hope cracked, “I don’t trust air I can’t see.” Most Americans could see too much of their air. So they demanded that Congress and the president do something about it.

Today the agency President Richard Nixon created in response to the public outcry over visible air pollution and flammable rivers is under siege. The Senate is poised to vote on a bill that would, for the first time, “disapprove” of a scientifically based finding, in this case that greenhouse gases endanger public health and welfare. This finding was extensively reviewed by officials in the administrations of presidents George W. Bush and Barack Obama. It was finalized by the Environmental Protection Agency in response to a 2007 Supreme Court decision that greenhouse gases fit within the Clean Air Act definition of air pollutants.

As former administrators of the EPA, both under Republican presidents, we have observed firsthand rapid changes in scientific knowledge concerning the dangers posed by particular pollutants, including lead additives in gasoline, benzene and the impact of contaminants on our drinking-water supply. In each of these cases, the authority of our major environmental statutes was essential to protect public health and the most vulnerable members of our society, even in the face of remaining scientific debate.

Earlier this year, the House of Representatives approved a bill that would cut the EPA’s budget by nearly a third and in certain areas impede its ability to protect our air and water.

The EPA was created out of recognition that pollution — largely an unwanted side effect of an increasingly industrialized society — needed to be controlled or America’s public health and environment would deteriorate. The public called on our national government to step in and halt what the states could not or would not do.

As the EPA was being established, Congress passed the Clean Air Act in a burst of nonpartisan agreement: 73 to 0 in the Senate and 374 to 1 in the House.

During the 1970s, many other laws were passed to deal with air and water pollution, drinking-water contamination, radiation, solid waste, pesticides and toxic substances. Sixteen major pieces of legislation were enacted to address aspects of industrial, municipal or human activity that were threatening public health or the environment. Most were passed by a Democrat-controlled Congress and signed into law by a Republican president, and the votes were seldom close.

The air across our country is appreciably cleaner and healthier as a result of EPA regulation of trucks, buses, automobiles and large industrial sources of air pollution. There are three times the number of cars on the roads today as in 1970, yet they put out a small fraction of the pollution.

Likewise, American waterways have shown marked improvement. Lakes and rivers across the nation have shifted from being public health threats to being sources of drinking water as well as places for fishing and other forms of recreation. Lake Erie was declared dead in 1970 but today supports a multimillion-dollar fishery.

Amid the virulent attacks on the EPA driven by concern about overregulation, it is easy to forget how far we have come in the past 40 years. We should take heart from all this progress and not, as some in Congress have suggested, seek to tear down the agency that the president and Congress created to protect America’s health and environment.

It has taken four decades to put in place the infrastructure to ensure that pollution is controlled through limitations on corporate, municipal and individual conduct. Dismantle that infrastructure today, and a new one would have to be created tomorrow at great expense and at great sacrifice to America’s public health and environment. The American public will not long stand for an end to regulations that have protected their health and quality of life.

Our country needs today what it needed in 1970: a strong, self-confident, scientifically driven, transparent, fair and responsible EPA. Congress should help America achieve that. It should do so not with lowered sights but lowered voices that will result in an EPA fully capable of helping fashion a prosperous, healthy America whose environment continues to improve.

William D. Ruckelshaus was administrator of the Environmental Protection Agency from 1970 to 1973 and 1983 to 1985. Christine Todd Whitman, a former Republican governor of New Jersey, was EPA administrator from 2001 to 2003.