(Bloomberg View) — The crisis in Flint, Michigan has focused attention on lead-tainted water flowing through taps in the U.S. as well as lead paint exposures that continue to plague cities such as Baltimore and Philadelphia.
While there's skepticism surrounding recent claims that lead poisoning rates are higher in Philadelphia than in Flint, there's no disputing that there's a serious problem in both cities and many others.
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The term "poisoning" is the source of some confusion.
Since Flint switched to a more corrosive source of water in 2014, bringing lead from pipes into the drinking supply, some residents have reported rashes, hair loss, fatigue and other classic symptoms of lead poisoning.
But scientists now believe that exposures too low to cause people to feel sick can do serious and possibly permanent neurological damage, especially in children.
Studies have found evidence of learning and behavior problems in children with blood lead levels of less than 10 micrograms per deciliter, which until a few years ago was considered safe.
That's well below the average of 15 micrograms per deciliter back in the 1970s, when people were exposed to lead from gasoline.
The biggest concern is for very young children and developing fetuses, scientists say, because lead can interfere with the way the brain develops. The effects, they say, are more likely to be permanent when exposure comes early.
That doesn't mean kids can't be helped. Some scientists have found that enriched learning environments mitigate lead's damage.
The CDC now considers anything above 5 micrograms per deciliter to be high enough for concern. Since the start of the lead crisis in Flint, the percentage of U.S. children measuring over that limit doubled to nearly 5 percent.
Meanwhile, some studies show that around a tenth of the children living in Philadelphia exceed that limit. But Flint's problem is uneven and unpredictable, with water contamination much worse in some homes than others.
A report from the American Chemical Society shows that while many cities safely rely on lead pipes, authorities in Flint failed to use required anti-corrosion additives–in particular, a phosphate compound that was recommended at a cost of $50,000. The result was that some samples of residents' tap water measured 900 times the allowable limits on lead.
Twentieth-century Americans couldn't have done a much more thorough job of maximizing lead exposure, said Harvard University neurologist David Bellinger. They coated the insides of homes with lead, used it to carry drinking water and burned it in cars.
Until recently, it wasn't widely appreciated that lead from pipes, paint and gasoline were exposing people to unnatural levels, said Chris Sellers, a historian specializing in environmental issues.
Lead is an element that is part of the earth's crust. In the early 20th century, people didn't know how much lead would naturally occur in air, water or dust.
That changed, said Sellers, after a mid-century geochemist named Clair Patterson started a project to calculate the age of the earth using the rate of decay of uranium to lead.
Patterson found he had to contend with a surprising amount of lead contamination and set to work investigating the source and consequences of it.
Using clues such as the abundance of lead in ancient layers of Greenland's icecap, he concluded that environmental lead had spiked.
"A prevailing belief is that industrial and natural sources contribute more or less equal amounts of lead to the body burdens of the general population," he wrote in 1965. "A new approach to this matter suggests that the average resident of the United States is being subjected to severe chronic lead insult." Manufacturers of leaded gasoline fought back, going so far as to offer his institution, the California Institute of Technology, an endowed chair if they would fire him, according to Bill Bryson's book, "A Short History of Nearly Everything."
Later, doctors started to make equally alarming findings. In one 1979 study, the physician Herbert Needleman measured lead in baby teeth from seemingly healthy children living near Boston.
He found that kids with higher-than-average lead levels showed more behavioral and learning problems. Lead-industry researchers disputed the finding, but other studies were starting to bolster the idea.
One study showed a connection between lead in umbilical- cord blood – an indication of prenatal exposure – with the IQ scores measured 30 years later.
In the early 21st century, studies were showing reduced IQs in kids, in some cases by more than 7 points.
It looks like most of us are not as bright as we would have been if leaded paint and gasoline had never been invented.
Lead is absorbed by the brain because the body mistakes it for necessary elements–zinc and calcium–said neuroscientist Tomas Guilarte. Once there, lead interferes with the mechanism of learning–a series of changes involving the brain's delicate system of chemical signaling and growth of new neurons.
In experiments on lab rats, he said, they found that the best countermeasure to lead exposure is not a chemical strategy.
What helped was exercise and stimulation – from toys and other challenges. In a study of children exposed to lead in Mexico, he said, adding an enriched learning environment was beneficial.
This could amount to going to museums, art and music lessons and physical exercise, he said, exactly the things that wealthy kids will get from their parents if not provided at school.
Guilarte says that just getting bottled water to Flint isn't enough.
Without extra help, kids there, whether sickened or not, could suffer long-term consequences from the months they drank contaminated water before the problem came to light. Enriched learning is the least the country owes them in compensation.
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