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Study links children's lead levels, SAT scores

A Virginia economist who pored over years of national data says there's an "incredibly strong" correlation, which adds to a growing body of research on lead's harmful effects.

The findings, to be published this winter in the journal Environmental Research, suggest that from 1953 to 2003, the fall and rise of the average SAT math and verbal score has tracked the rise and fall of blood lead levels so closely that half of the change in scores over 50 years, and possibly more, probably is the result of lead, says economist Rick Nevin.

He controlled for rising numbers of students taking SAT prep courses and for rising numbers of students who speak a foreign language at home — that would depress verbal scores.

Nevin estimates that lead explains 45% of the historic variation in verbal scores and 65% in math scores.

His analysis compared national snapshots of children's blood-lead test results with SAT scores 17 years later. As lead levels dropped, scores rose — and vice versa.

He also found that over a 56-year time frame, the drop in lead levels tracked consistently with decreases in mental retardation 12 years later.

The average amount of lead in children's blood dropped sharply in the 1970s and later, mostly because of a phaseout of leaded gasoline in the 1970s; at the same time, paint manufacturers phased out lead house paint.

Nevin made a splash a few years back with another provocative thesis: He found that unleaded gas probably did more to reduce crime in the 1990s than did any crime prevention strategy, such as higher concentrations of police on city streets.

Over 30 years, a large body of evidence has shown that lead is a potent neurotoxin, affecting IQ, impulsivity and other factors that determine academic achievement. Nevin's study is the first to tie lead to national SAT scores.

Bob Schaeffer of FairTest, a non-profit watchdog that tracks testing, says Nevin's study "makes a very strong case" for the role lead plays — and suggests how non-school factors affect poor kids' achievement.

"It shows that these kids are mentally handicapped from the start," and criticizing the kids and their teachers isn't going to solve the problem, Schaeffer says.

The study, which is planned for an upcoming Environmental Research issue, is available here.