Children exposed to lead have a lower IQ than others, according to the results of a study published in the Journal of the American Medical Association (JAMA). Lead is a metal that was present in gasoline in the 1970s.
Researchers at Duke University in North Carolina in the United States conducted a study with 500 children born in New Zealand in 1972 and 1973, a period when gasoline still ran on lead. This country was chosen because the lead content in fuel was among the highest in the world.
From birth to adulthood, study participants were regularly assessed to test their cognitive skills such as reasoning and working memory. At the age of 11, blood samples were taken and tested for lead.
Lead levels twice the values accepted today
Participants who carried more than 10 micrograms of lead per deciliter of blood by age 11 had an average IQ of 4.25 points lower by age 38 than their peers less exposed to lead. The study found that for every 5 microgram increase in lead in the blood, a person lost about 1.5 IQ points.
the lead level in the mean blood of children at age 11 was 10.99 micrograms per deciliter of blood, slightly higher than the historic “level of concern” for lead exposure.
Today, the benchmark recommended by the Federal Centers for Disease Control and Prevention (CDC) is half, 5 micrograms per deciliter, a level that 94% of children in the study exceeded.
“This is historical data from a time when lead levels like this were considered normal in children and not dangerous. So most of our participants never had special treatment, ”said Terrie Moffitt, lead author of the study and professor at the University of Psychology and Neuroscience and Psychiatry and Behavioral Sciences.
Today, leaded gasoline has been withdrawn from the market, although it can be found in some countries in Asia.
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