December 20, 2016

Lead and hope

The Flint water crisis is winding down: the city has been back on Detroit water for over a year, and in early December this year tests showed that nearly all the water supply was back within Federal standards for lead.  Criminal charges have been filed against some officials for their roles in creating or covering up the problems.

Flint residents were exposed to levels of lead in their drinking water that were well above the Federal safety threshold, and this translated, predictably, into higher levels of blood lead in children (and presumably in adults, too).  The proportion of kids under 5 with ‘elevated blood lead’, (>5μg/dL) increased from about 2% (close to the national average)  before the water crisis to about 4%.  Obviously, a national average of 2% means there are other places affected, but Flint was distinctive because the water-supply change was simple and deliberate.

On the other hand, lead is still one of the great victories over pollution. In the 2011-12 round of the US health survey NHANES, 95% of children had blood lead levels below 2.9 μg/dL.  In the 1976-1980 round(PDF), nearly 90% of  children had blood levels above 10 μg/dL, and 10% had levels above 30 μg/dL.  Abolishing lead in petrol has been a huge success and other restrictions have helped.  This year we’ve also seen signs that restricting CFCs has worked: the ozone hole may be slowly starting to heal.  Restricting CFCs was harder, and the improvement is slower, but we’re making progress.  It can work.



Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »