Learning From the Fight Against Lead

As policymakers work to curb mercury pollution, they should consider the history of another dangerous metal.

Their side won ... eventually.

Photograph: PA Images/Getty Images

According to some estimates, the use of leaded gasoline stole five or more IQ points from those of us who grew up in big U.S. cities during the 1960s and early 1970s, when contamination peaked. Studies show that children with higher levels of lead in their baby teeth do worse on tests of reading ability, grammatical reasoning, vocabulary, reaction times and hand-eye coordination. And the doses back then were massive -- typical kids had blood levels five times what’s known to cause brain damage. In case there was any doubt, newer studies confirm that lead’s damaging effects on children are permanent.

Eventually, science moved policymakers to take action. Now people around the world face the same challenge with mercury -- another metal that’s toxic to children’s brains. Do we stall and debate while risking harm, or act with a greater level of precaution? The lessons of the past offer some guidance.

One reason 20th-century companies were able to spew so much lead into the environment was that the onus was on scientists to prove it was dangerous. Food and drug manufacturers, at least, had to demonstrate their products were safe before they hit the market, said Gerald Markowitz, a historian and co-author of the book “Lead Wars: The Politics of Science and the Fate of America's Children.” But for environmental pollutants and chemicals that people were exposed to in their jobs, industry generally didn’t act until a substance was proven hazardous. That was supposed to change in the 1970s with the Toxic Substances Control Act, he said, but in reality, it didn’t.

Regulating lead posed an additional challenge, since unlike DDT or plutonium, some lead is produced by natural sources. Industry scientists claimed that it was possible the lead found in people’s bloodstreams had nothing to do with their products.

That seemed plausible -- until scientists started looking into the matter. During the 1940s, a geologist named Clair Patterson stumbled across some of the most damning evidence by accident, while trying to calculate the age of the earth. Patterson was using the radioactive decay of uranium isotopes into lead as a sort of natural clock. In the process, he discovered there was lead everywhere in his lab, including on his clothes and hair. After he figured out the age of the earth 1 , he turned his attention to the lead contamination he’d discovered.

Patterson reasoned that car exhaust was the obvious source. But to really pin it down, he needed to figure out how much lead had been in the environment before the automobile age. Through the late 1950s and 1960s, he traveled around the world, collecting ancient sediments, deep ice cores and ancient bones. By the mid-1960s, he was able to compile a world history of lead exposure, showing a steep rise in the 20th century. He estimated that the level in children’s bodies was 400 to 600 times the natural background level. Children were not getting low doses -- they were getting massive amounts. Historians credit Patterson inspiring more studies that finally influenced the U.S. Environmental Protection Agency to start phasing out lead in the 1970s.

Natural mercury is even more challenging to measure than lead. Mercury gets into the world’s oceans from coal burning and gold mining, but volcanoes are also responsible for some portion of what’s out there, according to Carl Lamborg, an oceanographer at the University of California, Santa Cruz. And unlike lead, mercury tends to move around, going back and forth between the atmosphere and the oceans and accumulating in the Arctic.

Lamborg led an eight-year effort to estimate the degree of global mercury contamination by taking samples at different levels around the world’s oceans, and examining the way mercury was distributed compared with other elements. The result, published in 2014 in the journal Nature, was that the world’s oceans hold three times the mercury of pre-industrial era.

What's more, some people are getting much higher exposures than others, since mercury builds up in the tissues of fish and can pose a threat to people with seafood-heavy diets. That’s what happened in the last century in the small city of Minamata in Japan. As reporters would later piece together, a chemical plant began dumping a particularly toxic mercury compound into Minamata Bay in the 1930s. By the 1950s, people, pets and wild animals were coming down with a strange illness that affected their vision, hearing and coordination. Thousands fell ill, dozens died, and dozens more, exposed in utero, were left with cerebral palsy and other permanent disabilities.

This month marked the first meeting of the parties of an international treaty to curb mercury pollution -– the Minamata Convention. The treaty was negotiated so it wouldn’t change U.S. policy, said Boston University environmental policy professor Henrik Selin, but it will likely force China to cut back on emissions from coal-fired power plants, which can send pollution as far as the California coast. The treaty will also restrict the more localized threat that comes from the use of mercury in gold mining in developing countries.

Today in the U.S., mercury emissions are regulated under a hodgepodge of regulations, since much of it is emitted as air pollution but ends up as a water pollutant and food hazard. The Obama administration issued more coherent standard, which would require coal-burning power plants to install scrubbers, but the coal industry is continuing to fight it in court, said Selin.

Historians such as Markowitz say the lessons of the past point to the need to employ the precautionary principle -- requiring some proof of safety before substances are released into the environment. Critics say that would paralyze innovation by making it nearly impossible to introduce any new drugs or other products. But Selin says employing a moderate precautionary principle would simply move the burden of proof, making it easier to regulate or ban potentially dangerous substances.

It wouldn’t have taken extreme precaution to have prevented much of the trouble caused by lead and mercury. Patterson had already gathered a damning case against lead long before it was phased out of gasoline and paint. He worried that lead had robbed a generation of ability to think clearly and rationally. And in fact, some have suggested that lead contributed to a peak in crime around the 1980s, when those ’60s children had reached young adulthood.

It’s a chilling thought. Perhaps leaded gasoline was good for the car industry and therefore the world economy. But if I’ve benefited from any of it, I’d still give back every penny in exchange for those IQ points.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

  1. 4.55 billion years, in case you're curious.

To contact the author of this story:
Faye Flam at

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