The diminished intelligence of children exposed to mercury contamination before birth costs the U.S. economy $8.7 billion a year in lost productivity, according to a study published Monday in a government science journal.
The study estimates that between 317,000 and 637,000 of the 4 million children born each year in the United States are exposed in the womb to mercury levels above the Environmental Protection Agency’s safety level.
The IQ loss to children whose mothers’ blood level of mercury was at or above EPA’s safety level was subtle and varied depending on the mother’s exposure, according to the study in Environmental Health Perspectives, a journal published by the National Institutes of Health. The peer-reviewed study was done by pediatricians at the Mount Sinai School of Medicine and the Albert Einstein College of Medicine, both in New York.
Children with mothers whose mercury levels were at or near the safety level suffer an IQ loss of less than 1 point, while children whose mothers are among the 5 percent of the population most highly exposed suffer IQ losses ranging from 1.6 points to 3.21 points, the study said.
“While this diminution in intelligence is small in comparison with the loss of cognition that can result from other genetic and environmental processes, the loss resulting from (mercury) exposure produces a significant reduction in economic productivity over a lifetime,” the study said.
The estimate of $8.7 billion in annual economic impact from mercury was calculated using methodology employed in previous studies of the economic impact of lead exposure, which also lowers intelligence.
The health and societal impacts of mercury “are very analogous to lead,” said Dr. Philip Landrigan, a co-author of the study.
“When I started out in pediatrics we used to think of lead as an all- or-none disease _ either you had convulsions or other gross symptoms or no symptoms at all,” Landrigan said. “Then in the ’70s we realized that not everybody was obviously sick, but they were still injured through the loss of a few points of IQ, their attention span was not as long as could be or they had behavioral problems.”
Coal-fired power plants, the single largest source of man-made mercury emissions in the United States, are responsible for $1.3 billion of the economic loss, the study found.
Leonard Levin, mercury issue manager for the industry-funded Electric Power Research Institute, said the study relies on limited or flawed data in its calculation of the effect of mercury exposure on fetal intelligence.
“There is a huge uncertainty around whether there is any effect or not” on intelligence from low levels of mercury exposure, Levin said. The study also overstates the number of children exposed and exaggerates the contribution of power plants to mercury pollution, Levin said.
Mercury emissions from power plants, incinerators, industrial processes and natural phenomena like volcanoes settle in water bodies. Microbes transform the deposits into methylmercury, the most toxic form of mercury. The contaminant then works its way up the food chain.
People are exposed to mercury primarily by eating fish, especially large, predatory species like shark, swordfish and some species of tuna.
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