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Lead, a Global Poison
When asked what has surprised them most during their careers investigating lead poisoning in the United States and beyond, experts at the AAAS annual meeting echoed the same sentiment: the misconception that we’ve gotten rid of it.
While efforts to reduce the blood lead levels in children in the United States have been largely successful with the elimination of leaded gasoline and restrictions on lead paint, lead pollution internationally remains a pressing issue.
Recycling of lead acid batteries, for example, is a major source of lead in developing countries. “There are neighborhoods outside Jakarta, Indonesia, where 300,000 tons of lead acid batteries are recycled each year in informal factories,” said Mary Jean Brown, Chief of the Centers for Disease Control and Prevention’s Healthy Homes/Lead Poisoning Prevention Branch. “There are no barriers between the people in those villages and the lead toxins the recycling process creates.”
Consumer products made with recycled lead find their way from developing nations into international markets, including the United States. In 2012, for example, U.S. customs officials seized 1,400 Halloween costumes imported from China that contained 11 times the permissible lead level.
Members of Dr. Howard Mielke's research team improve the soil environment at a New Orleans daycare center by spreading clean soil (less than 5 ppm lead) over a geotextile layer. Credit: Howard Mielke
Dr. Brown said that the knowledge and skills required to address the international lead issue currently exist. “Now we must develop the leadership in developing countries to disseminate information about lead safety concerns.”
Exacerbating the problem, lead is spread through the atmosphere; so, while lead pollution has gone down in some parts of the world, industrial activities elsewhere mean lead released into the environment in one country could easily spread somewhere else.
In the United States, one researcher is focusing on lead that has settled to the ground under our feet. Howard Mielke, professor of pharmacology at Tulane University School of Medicine, has studied the association between lead in the soil and lead in the blood of children. More specifically, he has investigated how high levels of lead in urban soils affect human welfare. Lead poisoning permanently affects the brain’s prefrontal cortex, where vital cognitive functions take place.
“Children who grow up in areas with high soil lead are both less successful in school and more aggressive later in life,” Mielke explained.
His work could shed light on changes in rates of violent crimes nationwide; in 2010, for example, researchers observed that cases of violent crime by young males in the United States had decreased sharply since the 1990s. Mielke’s work shows that the declines in aggressive behavior by 1990 more or less parallel the efforts begun in the early 1970s to reduce atmospheric lead from automobile exhaust, and in turn, in the blood lead levels of children born at that time.
The X-ray of a common loon killed by lead poisoning. The small bulb in the loon's stomach is a lead fishing angler. Credit: Mark Pokras
Mielke and his team have found high levels of soil lead (500-1000 parts per million) in neighborhoods of New Orleans. To advance lead poisoning prevention in the most at-risk locations, Mielke has developed methods for reducing lead in the topmost layers soil. One method involves placing a geotextile layer over the contaminated soil and then bringing in new, clean soil to lay over it.
The persistence of lead poisoning in the United States is underscored by results in animals. “I see five to eight cases of lead poisoning in my clinic per week,” said Dr. Mark Pokras, a veterinarian at Tufts Cummings School of Veterinary Medicine. “This is something that should be totally preventable.”
The lead Pokras finds in the animals he treats often comes from unexpected sources, like fishing tackle or bullets. Legislation to reduce the lead in hunting equipment is still being pursued.
“Given what we are learning about the many toxic effects of lead, there is every reason to develop and adopt non-toxic alternatives for fishing and hunting equipment,” Pokras said.
To accomplish this, he says all interest groups must work together to find safe alternatives and to develop new educational and policy initiatives.
17 February 2013