Childhood Exposure To Lead Can Blunt IQ For Decades, Study Suggests

Judith QuinnMar 30, 2017

As expected, the participants in the study who had low blood levels as children had an adult IQ that was as high as when they were kids.

These cities had consistently higher levels than global standards during the 1970s and 1980s, largely due to motor-vehicle exhaust fumes.

Study participants are part of a life-long examination of more than 1,000 people born in Dunedin, New Zealand in 1972 and 1973. Overall, the CDC estimates that about half a million children in the US from ages 1-5 have blood lead levels above 5-μg/dL.

Participants with childhood blood lead levels above 10 micrograms/dl had average adult IQ test scores 4.25 points lower than their peers with lower blood lead levels.

This study adds to a large body of research focusing on the risks associated with lead reinforces the message that people should be paying attention to these threats, and should be aware that they can be exposed not only via contaminated water, but also via contaminated soils and paint in their environment.

The U.S. Centers for Disease Control and Prevention recommends public health intervention for kids with 5 micrograms per deciliter of lead in their blood or more, noting there is no safe blood lead level for children.

The paper's senior author, Professor Terrie Moffitt of USA -based Duke University, said the data was from an era when such high lead levels were viewed as normal for children and not unsafe.

Childhood blood lead levels ranged from 4 to 31 micrograms/dl.

New Zealand eventually banned leaded gasoline in 1996, and it has also been phased out elsewhere in the world. "Children will continue to experience the greatest harm from lead exposure, and disadvantaged children will bear a disproportionate share of the burden".

In justifying their research, the team directly invoked the Flint crisis, which saw the town in MI deal with lead contamination (and outbreaks of Legionnaires' disease) following a cost-cutting change in their drinking water source and subsequent poor water treatment in 2014. Children playing outside either inhaled lead-laden dust or swallowed small amounts of leaded soil.

Lead is a powerful neurotoxin that can build up in children's bloodstreams and settle into bones, teeth and soft tissue.

If anything, that reality may only worsen the influence lead could have on developing children's brains today, since poverty often makes us all the more vulnerable to environmental toxins.

"It also suggests that lead exerts a downward pull on an individual's cognitive abilities over time regardless of where they start out in life", Reuben said by email.

Main author Aaron Reuben, a Duke PhD candidate, said the lower job status was "partially but significantly explained by the loss of IQ".

Some previous research has linked each 1-point decrease in IQ scores to $200 to $600 less in annual income, Moffitt said.

About half of the 11 year olds had levels in excess of 10 micrograms per deciliter of blood, which is slightly higher than the historical "level of concern" for lead exposure in the 1990s.

'The cognitive deficits associated with lead persisted for decades, and showed in the kinds of occupations people got, ' he said. Children who were over 10 micrograms of lead attained occupations with socioeconomic status levels four-tenths lower than their less-exposed peers.

The research unit is supported by the New Zealand Health Research Council and New Zealand Ministry of Business, Innovation and Employment.

Lead exposure in childhood could be linked to lower IQs as adults, a new study reveals.

This study was supported in part by grants from the US National Institute on Aging, as well as United Kingdom government grants.

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