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What Are the Effects of Early Childhood Exposure to Environmental Lead on Personality?

Published online by Cambridge University Press:  11 April 2025

Arthur Fraas
Affiliation:
Resources for the Future, Washington, DC, USA
Randall Lutter*
Affiliation:
Enveritas Inc, Old Greenwich, CT, USA
Joshua Murphy
Affiliation:
Ontario, Canada
Qinrui Xiahou
Affiliation:
Faculty of Business and Economics, The University of Hong Kong, Hong Kong
Jeff Potter
Affiliation:
Psychology, The University of Texas at Austin College of Liberal Arts, Austin, TX, USA
Samuel D. Gosling
Affiliation:
Manhattan Institute for Policy Research Inc, New York, NY, USA
*
Corresponding author: Randall Lutter; Email: rwlutter@gmail.com
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Abstract

In the first analysis purporting to causally link environmental pollution to personality, Schwaba and colleagues leveraged a natural experiment driven by the United States. They used the Clean Air Act to assess the impact of decreased atmospheric lead on the “big five” personality traits. Using data from an online personality test taken by more than 1.2 million U.S. residents, Schwaba et al. reported that people born after lead levels had peaked in their county of birth had more mature, psychologically healthy personalities in adulthood (higher agreeableness and conscientiousness, and lower neuroticism) than cohorts born earlier and exposed to higher levels of atmospheric lead. One concern with their findings is that personality differences among people born in different periods could come from factors unrelated to lead, for example, access to abortion and birth control, or demographic, cultural, or technological changes. Schwaba et al. recognized this possibility but did not fully explore it. When we account for cohort-wide changes by introducing birth year fixed effects into Schwaba et al.’s models, the estimated effects of the lead phaseout on personality largely disappear, becoming indistinguishable from zero while remaining precise. Meanwhile, the estimated birth year fixed effects are jointly significant, suggesting differences in personality traits across cohorts. These results indicate that any effects of the lead phaseout on more mature, psychologically healthy adult personalities are not consistently observable in the data used by Schwaba et al. More broadly, they caution against making causal inferences without controlling for time period effects.

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Article
Creative Commons
Creative Common License - CCCreative Common License - BYCreative Common License - NCCreative Common License - ND
This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives licence (http://creativecommons.org/licenses/by-nc-nd/4.0), which permits non-commercial re-use, distribution, and reproduction in any medium, provided that no alterations are made and the original article is properly cited. The written permission of Cambridge University Press must be obtained prior to any commercial use and/or adaptation of the article.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Society for Benefit-Cost Analysis
Figure 0

Table 1a. Associations between atmospheric lead concentrations during childhood and big five personality traits

Figure 1

Table 1b. Associations between atmospheric lead concentrations during childhood and big five personality traits

Figure 2

Table 2a. Shifts in personality traits after each county’s lead phaseout: estimates and 99% confidence intervals in ()

Figure 3

Table 2b. Shifts in personality traits after each county’s lead phaseout: estimates and 99% confidence intervals in ()

Figure 4

Figure 1. Effects of lead phaseout on big five personality traits

Figure 5

Figure 2. Birth year coefficients and standard errors in models of personality traits and the phaseout of airborne lead, with county random effects10

Figure 6

Table A1. Associations between atmospheric lead during childhood and adult personality in the United States: county and birth year fixed effects

Figure 7

Table A2. Associations between atmospheric lead during childhood and adult personality in the United States with county fixed effects: without and with birth year fixed effects