April 13, 2018

ENVIRONMENTALISM IS CONSERVATISM:

Brain-damaging lead found in tap water in hundreds of homes tested across Chicago, results show (Michael Hawthorne and Cecilia Reyes, 4/13/18, Chicago Tribune)

Amid renewed national attention to the dangers of lead poisoning, hundreds of Chicagoans have taken the city up on its offer of free testing kits to determine if they are drinking tap water contaminated with the brain-damaging metal.

A Tribune analysis of the results shows lead was found in water drawn from nearly 70 percent of the 2,797 homes tested during the past two years. Tap water in 3 of every 10 homes sampled had lead concentrations above 5 parts per billion, the maximum allowed in bottled water by the U.S. Food and Drug Administration.

Alarming amounts of the toxic metal turned up in water samples collected throughout the city, the newspaper's analysis found, largely because Chicago required the use of lead service lines between street mains and homes until Congress banned the practice in 1986.

New evidence that lead exposure increases crime (Jennifer L. Doleac, June 1, 2017, Brookings)

A recent investigation by Reuters found that lead exposure affects kids in communities across the country -- not just in high-profile cities like Flint, Michigan. This is worrisome, because elevated blood lead levels in kids have been linked to an array of developmental delays and behavioral problems. More ominously, this could also increase crime. Kevin Drum and others have argued that lead exposure caused the high crime rates during the 1980s and early 1990s. There has been suggestive evidence of such a link for decades, though it hasn't gained much traction in research or policy circles. But the case that lead exposure causes crime recently became much stronger.

The "lead-crime hypothesis" is that (1) lead exposure at young ages leaves children with problems like learning disabilities, ADHD, and impulse control problems; and (2) those problems cause them to commit crime as adults -- particularly violent crime. For many years, the major source of lead in the environment was leaded gasoline: car exhaust left lead behind to settle into dust on the roads and nearby land. When lead was removed from gasoline, lead levels in the environment fell, and kids avoided the lead exposure that caused these developmental problems. About 20 years later, when those kids became young adults, crime rates fell. This, proponents say, is what explains the mysterious and persistent decline in crime beginning in the early 1990s.

It's an intriguing idea -- particularly since we don't have a better explanation for the big changes in crime rates during this period. Several studies have found correlations between lead exposure and crime, at varying levels of geography (from neighborhoods to nations). But correlation, as we all know by now, does not imply causation.

The main challenge in measuring the effect of lead on crime is that lead exposure is highly correlated with a variety of indicators related to poverty: poor schools, poor nutrition, poor health care, exposure to other environmental toxins, and so on. Those other factors could independently affect crime. The challenge for economists has been to separate the effect of lead exposure from the effects of all those other things that are correlated with lead exposure. A true experiment -- where some kids are randomized to grow up with high lead exposure and others not -- is out of the question. So economists have gone hunting for natural experiments -- events or policies that divide otherwise-similar kids into comparable treatment and control groups.

And they've found them. 

Posted by at April 13, 2018 4:16 AM

  

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