Subjects: Public health
In 2001, an additive placed in Washington DC’s water had the unintended effect of leaching lead out of the pipes and into the water supply. The plume didn’t resolve until 2005 and District residents have worried ever since what effect it had on their children.
To address the matter, Dana Best and colleagues from Children’s National Medical Center reviewed 28,000 lead level test results performed at their facility.
They found that among children younger than 16 months of age and hence most vulnerable to lead’s deleterious effects, the percent of tests that exceeded the official threshold for concern (10 micrograms) jumped from 0.5 to 4.8 by the peak of the crisis in late 2001.
By 2004, that fraction had dropped to 1.8%.
Best’s group used that and other data to estimate that in 2003-2004, an incremental 900 children developed dangerously high lead levels as a result of the tainted water supply.
A few extrapolations later, the scientists ventured to guess that these kids lost 2-3 IQ points on average and sustained a slightly increased risk of behavioral problems as a consequence.
The study is in Environmental Science & Technology.
The investigators warn however, that there is no legitimately “safe” level when it comes to lead exposure. Even at levels below 10 micrograms scientists have detected similar reductions in IQ.
That’s why Bruce Lanphear, a lead-poisoning expert at Simon Fraser University told the Washington Post, “we suspect that there are thousands, possibly tens of thousands, of children who have experienced harm as a result of increased lead exposure” in the District.
So is 2-3 IQ points a lot?
Best was optimistic. “With enrichment, with a good school environment, it is likely that the loss will not affect your child in a significant way,” she told the Post (leaving open the question as to whether these things were available to all kids in the District).