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 The study set out to address a flaw in much of the previous research
linking lead and crime: mainly that it’s hard to determine how much
of this connection might be explained by poverty and other
socioeconomic circumstances that can influence both criminal
activity and lead exposure.
Researchers followed 553 people born in Dunedin, New Zealand, in
1972 and 1973, when lead exposure was common among children of all
economic backgrounds because of widespread use of leaded gasoline.
All of the kids were tested for lead exposure when they were 11
years old, and the study team followed them until age 38 to see how
many of them were convicted of crimes.
By the end of the study, 154 participants, or 28 percent, had at
least one criminal conviction, the researchers report in JAMA
Pediatrics. But the odds of this happening were barely influenced by
the amount of lead exposure people had during childhood. Just being
male had a stronger effect than lead levels, the researchers note.
“Many studies have shown that higher exposure to lead could predict
more criminal behavior, but our study actually found that there
isn’t a clear connection between the two,” said lead author Amber
Beckley, a researcher at Duke University in Durham, North Carolina.
The reason for the different results this time is that the current
study found children from all walks of life had high lead levels,
Beckley said by email.
“In our study, socioeconomic status was not associated with
childhood lead exposure,” she added.
There’s no safe level of lead exposure. This toxin can damage the
developing nervous system in young children, and blood lead levels
as low as 5 micrograms per deciliter may lower intelligence quotient
(IQ), according to the World Health Organization.
Participants in the current study had average blood lead levels more
than twice that high when they were 11 years old in the early 1980s:
11.01 micrograms/dL.
Blood lead levels ranged from 4 to 31 micrograms/dL and didn’t vary
according to socioeconomic status.
To see how many of these kids were later convicted of crimes,
researchers searched police records and also interviewed
participants six times to inquire about any criminal activity.
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A total of 68 participants, or 12 percent, had a single criminal
conviction and another 86 people had more than one conviction, the
study found.
Only 53 people were violent offenders, while 101 participants were
convicted of non-violent crimes.
Childhood lead exposure didn’t appear to influence at all whether
people would commit violent crimes or become repeat offenders.
But it did appear to influence the odds that teens would participate
in criminal activity, though this connection was weak and didn’t
persist over time, the authors conclude.
One limitation of the study is that children only got one blood test
for lead exposure, and multiple assessments can give a more accurate
picture of total exposure, the researchers note. It’s also possible
that results would be different today, when children typically have
less exposure to lead than they did in the 1970s and 1980s.
It’s also possible that the connection between childhood lead
exposure and criminal behavior might be stronger than the authors
concluded, David Farrington of Cambridge University writes in an
accompanying editorial. It may not be appropriate to describe the
strength of the connection as “weak,” Farrington writes.
“More research is needed, of course, to investigate the independent,
interactive and sequential effects of blood lead levels in relation
to other risk factors for offending,” Farrington writes. He didn’t
respond to emails seeking comment.
SOURCES: http://bit.ly/2lo9xSh and http://bit.ly/2lniM51 JAMA,
online December 26, 2017.
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