Lead Exposure In Childhood Linked to Lower IQ, Lower Status

CITATION: "Association of Childhood Blood Lead Levels With Cognitive Function and Socioeconomic Status at Age 38 Years and With IQ Change and Socioeconomic Mobility Between Childhood and Adulthood", Aaron Reuben, Avshalom Caspi, Daniel Belsky, Jonathan Broadbent, Honalee Harrington, Karen Sugden, Renate Houts, Sandhya Ramrakha, Richie Poulton, Terrie Moffitt.

After adjustments for maternal and childhood IQ and childhood socioeconomic status, each 5- higher level of lead at age 11 was associated with a significant 1.61-point lower adult IQ score (95% CI -2.48 to -0.74) at age 38, reported Aaron Reuben, MEM, of Duke University, and colleagues. On average, for every five-microgram increase of lead in a child's blood level, they lost about 1.6 IQ points into adulthood.

Public health officials have repeatedly said that there is no safe level of lead in a child's blood and that lead exposure can seriously affect the IQ and attention span of children, as well as cause other problems.

"This is despite the fact that in the 1970s this same study [the Dunedin Study] was one of the best in the world at showing that lead was damaging the IQ of children".

Ninety-four per cent of the children had blood-lead levels greater than five micrograms per decilitre, the level at which the United States' Center for Disease Control and Prevention now recommends a public-health intervention. People who had low lead exposure as children had either the same or slightly higher IQ than they'd had as kids, but, Reuben says.

The paper's senior author, Dunedin Study Associate Director Professor Terrie Moffitt of Duke University, says the data was from an era when such high lead levels were viewed as normal for children and not risky.

This is published unedited from the PTI feed.

And, he adds, "people who saw that decline also experienced downward social mobility". The definition of lead poisoning was different then too; it was only in 2012 that the CDC reduced the level of acceptable lead exposure someone could have by half (agencies like the EPA have stuck to the old watermark). The researchers estimate that the decline in IQ accounted for 40% of that link.

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Unfortunately, if you live in a low-income area your children may be at higher risk for lead exposure. "The cognitive deficits associated with lead persisted for decades, and showed in the kinds of occupations people got". Research out today suggests children exposed to toxic lead feel the effects throughout their lives.

The Dunedin Multidisciplinary Health and Development Research Unit is supported by the New Zealand Health Research Council and the New Zealand Ministry of Business, Innovation, and Employment.

"We will continue to have to deal with the impact of lead on children - and adults - until we address these legacy sources of lead that are still in our environment", Bellinger says. Also, they tend to have lower-skilled jobs than their parents or their own children.

"This is historical data from an era when lead levels like these were viewed as normal in children and not unsafe, so most of our study participants were never given any special treatment".

BICHELL: In the USA, it's been years since policies went into place limiting or eliminating lead in paint, plumbing and gasoline.

The latest research "underscores the story of lead is not over", she said, adding that although lead has always been banned in gasoline, paint and most plumbing fixtures, plenty of threats remain in the United States and particularly in other parts of the world.

BICHELL: And he says this study shows exposure to lead may be one more thing holding them back for decades to come.

  • Myrtle Hill