Lead exposure in kids can lead to low IQ, poor social skills

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Traffic Jam Delhi, air pollution
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Study on people who grew up in era of leaded gasoline shows how lead affects mental development

Lead exposure in childhood appears to have long-lasting negative effects on mental health and personality in adulthood. These are the findings of a study of people who grew up in the era of leaded gasoline.

Previous studies have identified a link between lead and intelligence, but this study looked at changes in personality and mental health as a result of exposure to the heavy metal. The findings, appeared in JAMA Psychiatry, reveal that the higher a person’s blood lead levels at age 11, the more likely they are to show signs of mental illness and difficult personality traits by age 38.

The link between mental health and lead exposure is modest, according to study coauthor Aaron Reuben, a graduate student in clinical psychology at Duke University. But “it’s potentially important because this is a modifiable risk factor that at one point in time everyone was exposed to, and now, certain people in certain cities and countries are still exposed to,” he said.

In a previous study, Reuben and colleagues showed that higher levels of lead in childhood were linked to lower IQ and lower social standing in adulthood.

Both sets of findings suggest that lead’s “effects really can last for quite a long time, in this case three to four decades,” said coauthor Jonathan Schaefer, also a graduate student in clinical psychology at Duke. “Lead exposure decades ago may be harming the mental health of people today who are in their 40s and 50s.”

Because gasoline around the world was treated with high levels of lead from the mid 1960s until the late 1980s, most adults now in their 30s, 40s, and 50s were exposed as children. Lead from automotive exhaust was released into the atmosphere and soils

Because gasoline around the world was treated with high levels of lead from the mid 1960s until the late 1980s, most adults now in their 30s, 40s, and 50s were exposed as children. Lead from automotive exhaust was released into the atmosphere and soils. Today, high lead exposures are rarer, and most often found in children who live in older buildings with lead plumbing and paint.

The subjects of this study are part of a group of more than 1,000 people born in 1972 and 1973 in Dunedin, New Zealand, at a time when gasoline lead levels in New Zealand were among the highest in the world. They have regularly participated in physical and mental health evaluations at the local University of Otago.

Researchers measured blood lead levels — in micrograms per deciliter of blood (ug/dL) — when participants were 11 years old. Today, blood lead levels above 5 ug/dL will trigger additional clinical follow-up of a child. At age 11, 94 percent of participants in the Dunedin Study had blood lead levels above this cutoff.

“These are historical data from an era when lead levels like these were viewed as normal in children and not dangerous, so most of our study participants were never given any treatment for lead toxicity,” said Terrie Moffitt, the senior author of the study and Duke’s Nannerl O. Keohane University Professor of psychology & neuroscience and psychiatry & behavioral sciences.

The Duke research team also assessed participant mental health and personality at various points throughout their lives, most recently at age 38. Diagnostic criteria or symptoms associated with eleven different psychiatric disorders — dependence on alcohol, cannabis, tobacco, or hard drugs; conduct disorder, major depression, generalized anxiety disorder, fears and phobias, obsessive-compulsive disorder, mania, and schizophrenia — were used to calculate a single measure of mental health, called the psychopathology factor, or “p-factor” for short.