Lessons from the campaign on lead
It took far too long for countries to ban lead in petrol and paint. The same should not happen with mercury, argues Faye Flam.
The use of leaded gasoline stole five or more IQ points from those of us who grew up when contamination peaked in the 60s, according to some estimates.
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.
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, 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 travelled 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 with inspiring more studies that influenced the US Environmental Protection Agency to start phasing out lead in the
Thousands fell ill, dozens died, and dozens more, exposed in utero, were left with cerebral palsy and other permanent disabilities.
1970s. New Zealand didn’t fully ban leaded petrol until 1996, 20 years after a lead study was published in the NZ Medical Journal.
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 of it, 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 polar regions.
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 preindustrial 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 later pieced together, a chemical plant began dumping a 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 US 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 localised threat that comes from the use of mercury in gold mining in developing countries.
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 paralyse innovation by making it nearly impossible to introduce new drugs or 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 American crime around the 1980s, when those 60s children had reached young adulthood.
It’s a chilling thought. Perhaps leaded petrol 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 cent in exchange for those IQ points.