Prenatal and postnatal blood lead concentrations are associated with higher rates of total arrests and/or arrests for offenses involving violence. This is the first prospective study to demonstrate an association between developmental exposure to lead and adult criminal behavior.
A cohort study done by researchers at the University of Cincinnati. Between 1979 and 1984, 376 infants were recruited. Their parents consented to have lead levels in their blood tested over time; this was matched with records over subsequent decades of the individuals’ arrest records, and specifically arrest for violent crime. Ultimately, some of these individuals were dropped from the study; by the end, 250 were selected for the results.
The researchers found that for each increase of 5 micrograms of lead per deciliter of blood, there was a higher risk for being arrested for a violent crime, but a further look at the numbers shows a more mixed picture than they let on. In prenatal blood lead, this effect was not significant. If these infants were to have no additional risk over the median exposure level among all prenatal infants, the ratio would be 1.0. They found that for their cohort, the risk ratio was 1.34. However, the sample size was small enough that the confidence interval dipped as low as 0.88 (paradoxically indicating that additional 5 µg/dl during this period of development would actually be protective), and rose as high as 2.03. This is not very convincing data for the hypothesis.
For early childhood exposure, the risk is 1.30, but the sample size was higher, leading to a tighter confidence interval of 1.03-1.64. This range indicates it’s possible that the effect is as little as a 3% increase in violent crime arrests, but this is still statistically significant.
For 6-year-olds, it’s a much more significant 1.48 (confidence interval 1.15-1.89). It seems unusual to me that lead would have such a more profound effect the older the child gets, but I need to look into it further.
We evaluate air Pb emissions and latent aggravated assault behavior at the scale of the city. We accomplish this by regressing annual Federal Bureau of Investigation aggravated assault rate records against the rise and fall of annual vehicle Pb emissions in Chicago (Illinois), Indianapolis (Indiana), Minneapolis (Minnesota), San Diego (California), Atlanta (Georgia), and New Orleans (Louisiana). Other things held equal, a 1% increase in tonnages of air Pb released 22 years prior raises the present period aggravated assault rate by 0.46% (95% CI, 0.28 to 0.64). Overall our model explains 90% of the variation in aggravated assault across the cities examined. In the case of New Orleans, 85% of temporal variation in the aggravated assault rate is explained by the annual rise and fall of air Pb (total = 10,179 metric tons) released on the population of New Orleans 22 years earlier. For every metric ton of Pb released 22 years prior, a latent increase of 1.59 (95% CI, 1.36 to 1.83, p < 0.001) aggravated assaults per 100,000 were reported. Vehicles consuming fuel containing Pb additives contributed much larger quantities of Pb dust than generally recognized. Our findings along with others predict that prevention of children's lead exposure from lead dust now will realize numerous societal benefits two decades into the future, including lower rates of aggravated assault. ► Ecological associations between lead (Pb) and violence are modeled at the scale of the city. ► U.S. cities, Chicago, Indianapolis, Minneapolis, San Diego, Atlanta and New Orleans were studied. ► The 1950–1985 fluctuation of Pb emissions explains 90% of the aggravated assault variation. ► Each 1% tonnage Pb increase 22 years prior raised aggravated assault by 0.46% (95% CI, 0.28 to 0.64). ► Childhood Pb prevention may yield numerous benefits in two decades, including less violence. PLOS Medicine – Decreased Brain Volume in Adults with Childhood Lead Exposure
Methods and Findings – Volumetric analyses of whole brain MRI data revealed significant decreases in brain volume associated with childhood blood lead concentrations. Using conservative, minimum contiguous cluster size and statistical criteria (700 voxels, unadjusted p < 0.001), approximately 1.2% of the total gray matter was significantly and inversely associated with mean childhood blood lead concentration. The most affected regions included frontal gray matter, specifically the anterior cingulate cortex (ACC). Areas of lead-associated gray matter volume loss were much larger and more significant in men than women. We found that fine motor factor scores positively correlated with gray matter volume in the cerebellar hemispheres; adding blood lead concentrations as a variable to the model attenuated this correlation. Conclusions - Childhood lead exposure is associated with region-specific reductions in adult gray matter volume. Affected regions include the portions of the prefrontal cortex and ACC responsible for executive functions, mood regulation, and decision-making. These neuroanatomical findings were more pronounced for males, suggesting that lead-related atrophic changes have a disparate impact across sexes. This analysis suggests that adverse cognitive and behavioral outcomes may be related to lead's effect on brain development producing persistent alterations in structure. Using a simple model, we found that blood lead concentration mediates brain volume and fine motor function.
The studies by Cecil and colleagues and Dietrich and colleagues expand the range of outcomes linked to increased lead exposure in the “subclinical” range and help to place the problem in a larger public health context. Lead’s detrimental effect on IQ, the outcome most often studied, is clearly only the “tip of the iceberg.”
The good news is that the blood lead levels at which reduced brain volumes and increased risk of arrest were observed are much less common among US children today than they were in the early 1980s, when the participants in the CLS were young children. The mean childhood blood lead level of CLS participants was 13 μg/dl, and ranged from 4 to 37 μg/dl. Currently, the median blood lead level among one to five-year-old US children is 1.5 μg/dl, and 5% have a level greater than 5.8 μg/dl . In Ohio, where the CLS study is based, the percentage of children less than six years of age who had a blood lead level of more than 10 μg/dl was 16.55% in 1997, but only 2.30% in 2006 . This is an impressive public health victory, but in light of clear evidence that a broad array of adverse effects occur at blood lead levels that are well below 10 μg/dl, it is a national disgrace that so many children continue to be exposed at levels known to be neurotoxic.
US Centers for Disease Control and Prevention (2005) Preventing lead poisoning in young children. Available: http://www.cdc.gov/nceh/lead/publications/pub_Reas.htm. Accessed 21 April 2008.
Cecil KM, Brubaker CJ, Adler CM, Dietrich KN, Altaye M, et al. (2008) Decreased brain volume in adults with childhood lead exposure. PLoS Med 5: e112. doi:10.1371/journal.pmed.0050112.
Wright JP, Dietrich KN, Ris MD, Hornung RW, Wessel SD, et al. (2008) Association of prenatal and childhood blood lead concentrations with criminal arrests in early adulthood. PLoS Med 5: e101. doi:10.1371/journal.pmed.0050101.
White LD, Cory-Slechta DA, Gilbert ME, Tiffany-Castiglioni E, Zawia NH, et al. (2007) New and evolving concepts in the neurotoxicology of lead. Toxicol Appl Pharmacol 225: 1–27.
Stewart WF, Schwartz BS, Davatzikos C, Shen D, Liu D, et al. (2006) Past adult lead exposure is linked to neurodegeneration measured by brain MRI. Neurology 66: 1476–1484.
Schwartz BS, Chen S, Caffo B, Stewart WF, Bolla KI, et al. (2007) Relations of brain volumes with cognitive function in males 45 years and older with past lead exposure. Neuroimage 37: 633–641.
Yuan W, Holland SK, Cecil KM, Dietrich KN, Wessel SD, et al. (2006) The impact of early childhood lead exposure on brain organization: A functional magnetic resonance imaging study of language function. Pediatrics 118: 971–977.
Denno D (1990) Biology and violence. New York: Cambridge University Press.
Nevin R (2000) How lead exposure relates to temporal changes in IQ, violent crime, and unwed pregnancy. Environ Res 83: 1–22.
Nevin R (2007) Understanding international crime trends: The legacy of preschool lead exposure. Environ Res 104: 315–336.
Stretesky PB, Lynch MJ (2001) The relationship between lead exposure and homicide. Arch Pediatr Adolesc Med 155: 579–582.
Reyes JW (2007) Environmental policy as social policy? The impact of childhood lead exposure on crime. Working Paper no. 13097. National Bureau of Economic Research. Available: http://www.nber.org/papers/w13097. Accessed 23 April 2008.
Needleman HL, Riess JA, Tobin MJ, Biesecker GE, Greenhouse JB (1996) Bone lead levels and delinquent behavior. J Am Med Assoc 275: 363–369.
Needleman HL, McFarland C, Ness RB, Fienberg SE, Tobin MJ (2002) Bone lead levels in adjudicated delinquents. A case control study. Neurotoxicol Teratol 24: 711–717.
Dietrich KN, Ris MD, Succop PA, Berger OG, Bornschein RL (2001) Early exposure to lead and juvenile delinquency. Neurotoxicol Teratol 23: 511–518.
Braun JM, Kahn RS, Froehlich T, Auinger P, Lanphear BP (2006) Exposures to environmental toxicants and Attention Deficit Hyperactivity Disorder in U.S. children. Environ Health Perspect 114: 1904–1909.
Lane SD, Webster NJ, Levandowski BA, Rubinstein RA, Keefe RH, et al. (2008) Environmental injustice: Childhood lead poisoning, teen pregnancy, and tobacco. J Adolesc Health 42: 43–49.
Rocha A, Valles R, Cardon AL, Bratton GR, Nation JR (2005) Enhanced acquisition of cocaine self-administration in rats developmentally exposed to lead. Neuropsychopharmacology 30: 2058–2064.
Canfield RL, Gendle MH, Cory-Slechta DA (2004) Impaired neuropsychological functioning in lead-exposed children. Dev Neuropsychol 26: 513–540.
Surkan PJ, Zhang A, Trachtenberg F, Daniel DB, McKinlay S, et al. (2007) Neuropsychological function in children with blood lead levels
Brian Wang is a Futurist Thought Leader and a popular Science blogger with 1 million readers per month. His blog Nextbigfuture.com is ranked #1 Science News Blog. It covers many disruptive technology and trends including Space, Robotics, Artificial Intelligence, Medicine, Anti-aging Biotechnology, and Nanotechnology.
Known for identifying cutting edge technologies, he is currently a Co-Founder of a startup and fundraiser for high potential early-stage companies. He is the Head of Research for Allocations for deep technology investments and an Angel Investor at Space Angels.
A frequent speaker at corporations, he has been a TEDx speaker, a Singularity University speaker and guest at numerous interviews for radio and podcasts. He is open to public speaking and advising engagements.