Impact of in utero airborne lead exposure on long-run adult socio-economic outcomes: A population analysis using U.S. survey and administrative data

Abstract

As a neurotoxin, early exposure to lead has long been assumed to affect socioeconomic outcomes well into adulthood. However, the empirical literature documenting such effects has been limited. This study documents the long-term effects of in utero exposure to air lead on adult socio-economic outcomes, including real earnings, disabilities, employment, public assistance, and education, using US survey and administrative data. Specifically, we match individuals in the 2000 US Decennial Census and 2001-2014 American Community Surveys to average lead concentrations in the individual's birth county during his/her 9 months in utero. We then estimate the effects of shocks to airborne lead conditional on observable characteristics, county fixed effects, county-specific time trends, and month-year fixed effects. We find a 0.5 μg/m3 decrease in air lead, representing the average 1975-85 change resulting from the passage of the U.S. Clean Air Act, is associated with an increase in earnings of 3.5%, or a present value, at birth, of $21,400 in lifetime earnings. Decomposing this effect, we find greater exposure to lead in utero is associated with an increase in disabilities in adulthood, an increase in receiving public assistance, and a decrease in employment. Looking at effects by sex, long-term effects for girls seem to fall on participation in the formal labor market, whereas for boys it appears to fall more on hours worked. This is the first study to document such long-term effects from lead using US data. We estimate the present value in 2020, from all earnings impacts from 1975 forward, to be $4.23 Trillion using a discount rate of 3%. In 2020 alone, the benefits are $252 B, or about 1.2% of GDP. Thus, our estimates imply the Clean Air Act's lead phase out is still returning a national dividend of over 1% every year.

Fig 1. Time trends in U.S. air concentrations of lead, 1973–1989.

The graph shows average weighted individual-level in utero air lead levels by year in our sample.

Fig 2. Selected point estimates and confidence intervals.

The graph shows the effects of exposure to an additional 1 μg/m³ of atmospheric lead, while in utero, on each outcome index, as well as selected index components.

Fig 3. Nonlinear effects on earnings.

This graph depicts effect of lead on earnings when the effect is modeled as a linear, quadratic, and cubic relationship.

Fig 4. Effects by sex.

This graph displays the effects of a change in lead exposure of 1 μg/m³ on the change in probability of select outcomes for boys and girls.