As the president of Shell Oil, John Hofmeister, recently said, “We cannot deal with 50 different [state] policies. We need a national approach to greenhouse gases.” By a “national approach,” he means a federal law that pre-empts state regulation.

Whether we line up with President Bush or Al Gore on global warming, we should be leery of federal laws that squelch state environmental protection measures. The country has been down that road before. Big businesses crave uniformity, but replacing 50 regimes with one big one can hurt public health, including in cities such as New York. I know this from personal experience.

Recall the 1960s, when some states and localities began to regulate air pollution. Among them was New York City, which had regulated coal burning power plants and was about to follow California’s example by regulating new cars. The coal and auto industries turned to Congress, which in 1965 and 1967 enacted the first important federal air pollution legislation. It stymied the states, while doing little to cut pollution.

Voters blamed Congress for the dirty air, and it responded by passing the 1970 Clean Air Act. It reduced some pollutants, but stymied states on others. In particular, it barred states and localities from regulating lead in gasoline. Invoking that provision, the major oil companies went to federal district court in Manhattan to stop the city from implementing an ordinance that banned lead in gasoline in the city, effective the end of 1973. As a result, the city could not enforce its ban and had instead to rely on federal regulation. Washington failed to ban leaded gasoline until 1985, 12 years behind the city’s schedule. The “national approach” on lead produced a public health disaster in New York City.

The 1970 Clean Air Act was slow to get the lead out of gasoline, even though it was the pollutant that had most worried voters. Here’s what happened. The 1970 legislation required auto manufacturers, from 1975 on, to include catalytic converters, a pollution-controlling device, in their cars. Catalytic converters cut many pollutants, but not lead — in fact, lead would ruin them. A Congress that required motorists to pay for the device and then let it be ruined by leaded gas would look foolish. So, out of concern for the well-being of catalytic converters and their own reputations, the legislators backed a rule requiring new cars to use only unleaded gasoline.

Children were exposed to lead from gasoline for many years after 1970. The rule did not take effect until 1975, and even then, older cars could still use leaded gas. In 1975, there were roughly 100 million leaded gas-burning cars on the road, and many of them remained there, emitting lead well into the 1980s.

To mollify voters demanding protection for children, Congress had to do more on lead in 1970. So Congress put another provision into the Clean Air Act authorizing the Environmental Protection Agency to regulate lead in the gasoline used by pre-1975 cars. As soon as it was enacted, the energy companies, supported by legislators from the left and the right, lobbied the EPA to do nothing. Instead of federal regulation to protect health from lead in gasoline, we had oil companies claiming that the Clean Air Act pre-empted state and local efforts to do so.

At this time, I was an attorney at the nonprofit Natural Resources Defense Council. New York City asked me to intervene in federal court in Manhattan to save the city’s ban on lead. My colleagues and I had already sued the EPA in federal court in Washington for its failure to regulate lead in gas used by pre-1975 cars. Opposing the oil companies in Manhattan, we argued that Washington could not pre-empt state and local authority to regulate this gasoline and then do nothing. The court in Manhattan ruled in our favor and we later won our own case in Washington. That victory prompted the EPA to regulate the lead content of gasoline used by pre-1975 cars across the country.

The federal regulation to protect health was, however, quite weak under Presidents Nixon, Ford, and Carter. That weak federal regulation did, however, pre-empt the city’s ban, postponing elimination of lead in gasoline in the city by a dozen years.

Meanwhile, in the mid-1970s, the median child in the city had blood lead levels at twice the level that the federal government now classifies as lead poisoning. Much, much higher still were the blood lead levels of the poor child who played in highly trafficked streets in New York and in other large cities, where street dust was as rich in lead as ore in lead mines. Many parents today who worry that their child may have been “poisoned” by an individual exposure to lead in a building renovation, themselves carried much higher levels of lead in their blood when they were children.

The EPA has now put together statistics on the health benefits achieved by its eventually taking lead out of gasoline. The EPA’s own data indicate that thousands of children in the city were killed or maimed for life.

For years, my conscience was troubled by this failure to save the city’s children. The toll on these children and its connection to our litigation was so painful to me that it fell from my memory. The damage came back to me only this year when the EPA invited me to give a lecture in its ceremonial hearing room at its Washington headquarters. There, I told the EPA staff how Washington had pre-empted the city’s ban on lead in gasoline.

John Tierney from the New York Times was covering the event. Before putting his column to press, he called to ask whether I was quite sure of this dreadful charge. I could not for the life of me recall any of the specifics, but somehow knew the charge was true and so said “yes” with a gulp. I woke up at 4:30 a.m. in a cold sweat, fearful that I was wrong, but again could not, for the life of me, dredge up the specifics. It was only later research that brought back the full story. That is why there is nothing of it in my recent book, “Saving Our Environment from Washington,” even though the story would have added powerful support to its thesis.

I am now resting easier having left the guilt for the federal government’s abuse of New York City children where it belongs — in Washington. Please remember this story the next time you hear a corporate president calling for an exclusive “national approach” to an environmental problem.

Mr. Schoenbrod is Trustee professor at New York Law School, senior fellow at the Cato Institute, and author of “Saving Our Environment from Washington: How Congress Grabs Power, Shirks Responsibility, and Shortchanges the People.”