The examples and perspective in this article may not represent a worldwide view of the subject. (June 2019) (Learn how and when to remove this template message)
Lead is widely understood to be highly toxic to multiple organs of the body, particularly the brain. Individuals exposed to lead at young ages are more vulnerable to learning disabilities, decreased I.Q., attention deficit hyperactivity disorder, and problems with impulse control, all of which may be negatively impacting decision making and leading to the commission of more crimes as these children reach adulthood, especially violent crimes. No safe level of lead in the human bloodstream exists given that any amount can contribute to deleterious health issues.
Proponents of the lead–crime hypothesis argue that the removal of lead additives from motor fuel, and the consequent decline in children's lead exposure, explains the fall in crime rates in the United States beginning in the 1990s. This hypothesis also offers an explanation of the earlier rise in crime in the preceding decades as the result of increased lead exposure throughout the mid-20th century.
The lead–crime hypothesis is not mutually exclusive with other explanations of the drop in US crime rates such as the legalized abortion and crime effect. Lead exposure during the years in question correlated with exposure to urban poverty, due to close residential or primary school proximity with high-density motor vehicle traffic burning leaded gasoline or from residing in older, poorly maintained housing stock, much of which contained high levels of lead in the form of lead paint, lead solder, or other lead-based building materials; additionally, municipalities with a low taxation base often continued to receive drinking water via degraded lead pipes rather than upgrading to modern infrastructure. The difficulty in measuring the effect of lead exposure on crime rates lies in separating the effect from other indicators of low socioeconomic status such as poorer schools, nutrition, and medical care, exposure to other pollutants, and other variables that are predictive of criminal behavior.
Lead is a naturally occurring metal of bluish-grey color that has been used for multiple purposes in the history of human civilization. Being soft and pliable, as well as resistant to corrosion compared to other metals, has resulted in lead being used for many different items across time. Some of the earliest items made from lead were beads and jewelry dating back to 7th millennium B.C. Its malleability made lead an ideal choice for the Romans to build pipes for transporting water. Furthermore, lead acetate (also referred to as "sugar of lead") has been reported to have been used medicinally in the past. However, it was also noted that exposure to lead may have health consequences. The botanist Nicander was one of the first to write about the uses of lead. Dioscorides would later report that "the mind gives way" in individuals exposed to lead. Nonetheless, despite the hazards posed by lead, its durability made it useful and it was added to items such as glass, paint, and eventually gasoline. The widespread substance is also able to function as a shield against various forms of radiation.
The use of leaded products such as lead paint and leaded gasoline have resulted in higher environmental levels of lead in the air and soil. Lead is also a stable element and does not break down in the environment, so it must be physically removed. Most cases of lead exposure occur via inhalation or ingestion, though transdermal exposure is also possible. Once in the body lead has a half-life of approximately 30 days if in the blood, but can remain in the body for 20 to 30 years if it has accumulated in bones and organs. Expanded scientific investigation into organolead chemistry and the varied ways in which human biology changes due to lead exposure took place throughout the 20th century. Although it has continued to be in wide use even into the 21st century, greater understanding of blood lead levels (BLLs) and other factors have meant that a new scientific consensus has emerged. No safe level of lead in the human bloodstream exists as such; any amount can contribute to neurological problems and other health issues.
Analyses of the role of lead exposure in the brain have been ongoing for the past few decades. Lead can interfere with numerous neurotransmitter systems in the brain, most likely because of its ability to mimic calcium. Exposure to lead can also alter brain structure and function. At the behavioral level, exposure to lead has been observed to cause increases in impulsive actions and social aggression, as well as the possibility of developing attention deficit hyperactivity disorder (ADHD). Those conditions likely influence personality traits and behavioral choices, with examples including having poor job performance, beginning a pattern of substance abuse, and undergoing teenage pregnancy. Evidence that lead exposure contributes to lower intelligence quotient (IQ) scores goes back to a seminal 1979 study in Nature, with later analysis finding the link particularly robust.
The heavy metal lead can be found readily in the environment, especially in urban and industrialized areas. The majority of modern day environmental lead contamination can be traced back to leaded paint and the addition of tetraethyllead and tetramethyllead to gasoline, though other sources have contributed as well. Though some of the hazards of lead exposure have been documented for centuries, recognition of the hazards posed did not appear to gain much traction until the 1960s with the Senate hearings of Edmund Muskie that would help lead to the phaseout of leaded gasoline and lead-based paint in the 1970s. Blood lead levels would drop notably soon after the phaseout. In the decades since, scientists have concluded that no safe threshold for lead exposure exists.
Though efforts to reduce environmental levels of lead were initially slowed down by the lead industry, the emergence of Clair Patterson in the 1960s would lead to more meaningful changes. The establishment of the United States Environmental Protection Agency in 1970 and the influence of the Consumer Product Safety Commission would help ensure that gasoline and paint could only contain trace amounts of lead. Furthermore, several major legislative acts were passed to help reduce the amount of lead being introduced into the environment, including the Clean Air Act of 1970 and the Lead Based Paint Poisoning Prevention Act.
The international process of trying to lower the prevalence of lead has been largely spearheaded by the Partnership for Clean Fuels and Vehicles (PCFV). The non-governmental organization partners with major oil companies, various governmental departments, multiple civil society groups, and other such institutions worldwide. Efforts to phase-out lead in transport fuel achieved major gains in over seventy-five nations. In discussions at the 2002 Earth Summit, institutions under the umbrella of the United Nations vowed to emphasize public–private partnerships (PPPs) in order to help developing and transitional countries go unleaded.
Research on lead–crime correlation
The lead-crime hypothesis arose out of the confluence of several events, primarily the decrease in crime rates in the 1990s and the reduction of environmental lead pollution in the 1970s. After decades of relatively steady increases, crime rates in the United States started to sharply decline in the 1990s. The trend continued into the new millennium. Multiple possible explanations have come about, with academic studies pointing to complex, multifactorial causation as different social trends occurred at the same time. The fact that in the United States anti-lead efforts took place simultaneously alongside falls in violent crime rates attracted attention from researchers. Changes were not uniform across the country, even while increasingly stringent Environmental Protection Agency rules went into force from 1970s onward. Several areas had far greater lead exposure compared to others for years.
While there is strong evidence indicating that genetics influence the development of violent and aggressive behavior, more recent attention has focused on environmental factors such as lead exposure. Though there is anecdotal evidence suggesting that knowledge of a relationship between lead exposure and behavior dates back centuries, direct observations would not be documented until the late 1800s. Research in the mid-1900s observed that children previously treated for lead poisoning displayed a series of aberrant behaviors, including violence and aggression. Further research has yielded similar results, finding that past lead exposure functions as a predictor for criminal activity. Nation-wide analyses have also demonstrated positive associations between air-lead concentrations and measures of criminality and homicide. A meta-analysis of studies examining the relationship between lead and conduct problems arrived at a similar conclusion, suggesting that the magnitude of the relationship between lead exposure and behavior is comparable to the relationship between lead exposure and I.Q. While the scientific literature suggests there is a relationship between lead exposure and behavioral issues such as delinquency and criminality, directly relating these observations to the decrease in overall criminality is more difficult.
According to Jessica Wolpaw Reyes of Amherst College, between 1992 and 2002 the phase-out of lead from gasoline in the U.S. "was responsible for approximately a 56% decline in violent crime". While cautioning that the findings relating to "murder are not robust if New York and the District of Columbia are included," Wolpaw Reyes concluded: "Overall, the phase-out of lead and the legalization of abortion appear to have been responsible for significant reductions in violent crime rates." She additionally speculated that by "2020, all adults in their 20s and 30s will have grown up without any direct exposure to gasoline lead during childhood, and their crime rates could be correspondingly lower." According to Reyes, "Childhood lead exposure increases the likelihood of behavioral and cognitive traits such as impulsivity, aggressivity, and low IQ that are strongly associated with criminal behavior".
A 2011 study by the California State University found that "Ridding the world of leaded petrol, with the United Nations leading the effort in developing countries, has resulted in $2.4 trillion in annual benefits, 1.2 million fewer premature deaths, higher overall intelligence and 58 million fewer crimes", according to the United Nations News Centre. The executive director of the United Nations Environment Programme (UNEP) Achim Steiner argued that "Although this global effort has often flown below the radar of [the] media and global leaders, it is clear that the elimination of leaded petrol is an immense achievement on par with the global elimination of major deadly diseases."
According to a May 2017 study, lead exposure in childhood substantially increased school suspensions and juvenile detention among boys in Rhode Island, suggesting that the phasing out of leaded gasoline may explain a significant part of the decline in crime in the United States beginning in the 1990s.
A 2018 longitudinal study conducted in New Zealand found only a weak association between childhood lead levels and criminal conviction, which was no longer significant after controlling for sex. In New Zealand, there is no correlation between lead exposure and socioeconomic status, thus social class does not act as a confounder. The authors conclude that "past studies of the association between BLL and crime, in which high BLL and low socioeconomic status were associated, may not have completely overcome confounding".
- Biosocial criminology
- Environmental toxicology
- Lead abatement
- Lead poisoning
- Organolead chemistry
- Pollution control
- Statistical correlations of criminal behavior
- Stretesky, Paul B.; Lynch, Michael J. (2004). "The Relationship between Lead and Crime". Journal of Health and Social Behavior. 45 (2): 214–229. doi:10.1177/002214650404500207. ISSN 0022-1465. PMID 15305761.
- Nevin, Rick (2007). "Understanding international crime trends: The legacy of preschool lead exposure" (PDF). Environmental Research. 104 (3): 315–336. Bibcode:2007ER....104..315N. doi:10.1016/j.envres.2007.02.008. ISSN 0013-9351. PMID 17451672.
- Marcus, David K.; Fulton, Jessica J.; Clarke, Erin J. (2010-02-26). "Lead and Conduct Problems: A Meta-Analysis". Journal of Clinical Child & Adolescent Psychology. 39 (2): 234–241. doi:10.1080/15374411003591455. ISSN 1537-4416. PMID 20390814.
- Wright, John Paul; Dietrich, Kim N; Ris, M. Douglas; Hornung, Richard W; Wessel, Stephanie D; Lanphear, Bruce P; Ho, Mona; Rae, Mary N (2008-05-27). "Association of Prenatal and Childhood Blood Lead Concentrations with Criminal Arrests in Early Adulthood". PLoS Medicine. 5 (5): e101. doi:10.1371/journal.pmed.0050101. ISSN 1549-1676. PMC 2689664. PMID 18507497.
- ATSDR. "Lead (Pb) Toxicity: Key Concepts | ATSDR - Environmental Medicine & Environmental Health Education - CSEM". www.atsdr.cdc.gov. Retrieved 2018-10-18.
- Stewart, W. F.; Schwartz, B. S.; Davatzikos, C.; Shen, D.; Liu, D.; Wu, X.; Todd, A. C.; Shi, W.; Bassett, S. (2006-05-22). "Past adult lead exposure is linked to neurodegeneration measured by brain MRI". Neurology. 66 (10): 1476–1484. CiteSeerX 10.1.1.408.1953. doi:10.1212/01.wnl.0000216138.69777.15. ISSN 0028-3878. PMID 16717205.
- Cecil, Kim M; Brubaker, Christopher J; Adler, Caleb M; Dietrich, Kim N; Altaye, Mekibib; Egelhoff, John C; Wessel, Stephanie; Elangovan, Ilayaraja; Hornung, Richard (2008-05-27). "Decreased Brain Volume in Adults with Childhood Lead Exposure". PLoS Medicine. 5 (5): e112. doi:10.1371/journal.pmed.0050112. ISSN 1549-1676. PMC 2689675. PMID 18507499.
- Sanders, T.; Liu, Y.; Buchner, V.; Tchounwou, P.B. (January 2009). "Neurotoxic Effects and Biomarkers of Lead Exposure: A Review". Reviews on Environmental Health. 24 (1): 15–45. doi:10.1515/reveh.2009.24.1.15. ISSN 2191-0308. PMC 2858639. PMID 19476290.
- Leviton, A.; Bellinger, D.; Allred, E.N.; Rabinowitz, M.; Needleman, H.; Schoenbaum, S. (1993). "Pre- and Postnatal Low-Level Lead Exposure and Children′s Dysfunction in School". Environmental Research. 60 (1): 30–43. Bibcode:1993ER.....60...30L. doi:10.1006/enrs.1993.1003. ISSN 0013-9351. PMID 7679348.
- Caito, Samuel; Aschner, Michael (2017), "Developmental Neurotoxicity of Lead", Advances in Neurobiology, Springer International Publishing, 18: 3–12, doi:10.1007/978-3-319-60189-2_1, ISBN 9783319601885, PMID 28889260
- Lanphear, Bruce P.; Hornung, Richard; Khoury, Jane; Yolton, Kimberly; Baghurst, Peter; Bellinger, David C.; Canfield, Richard L.; Dietrich, Kim N.; Bornschein, Robert (2005). "Low-Level Environmental Lead Exposure and Children's Intellectual Function: An International Pooled Analysis". Environmental Health Perspectives. 113 (7): 894–899. doi:10.1289/ehp.7688. ISSN 0091-6765. PMC 1257652. PMID 16002379.
- P., Braun, Joe M. Kahn, Robert S. Froehlich, Tanya Auinger, Peggy Lanphear, Bruce (2006). Exposures to Environmental Toxicants and Attention Deficit Hyperactivity Disorder in U.S. Children. National Institute of Environmental Health Sciences. OCLC 678275247.
- Bellinger, David C (2008-05-27). "Neurological and Behavioral Consequences of Childhood Lead Exposure". PLoS Medicine. 5 (5): e115. doi:10.1371/journal.pmed.0050115. ISSN 1549-1676. PMC 2689677. PMID 18507501.
- Liu, Jianghong (2011). "Early health risk factors for violence: Conceptualization, evidence, and implications". Aggression and Violent Behavior. 16 (1): 63–73. doi:10.1016/j.avb.2010.12.003. ISSN 1359-1789. PMC 3052794. PMID 21399727.
- Olympio, Kelly Polido Kaneshiro; Gonçalves, Claudia; Günther, Wanda Maria Risso; Bechara, Etelvino José Henriques (2009). "Neurotoxicity and aggressiveness triggered by low-level lead in children: a review". Revista Panamericana de Salud Pública. 26 (3): 266–75. doi:10.1590/s1020-49892009000900011. ISSN 1020-4989. PMID 20058837.
- Dapul, Dr. Heda; Laraque, Dr. Danielle (August 2014). "Lead Poisoning in Children". Advances in Pediatrics. 61 (1): 313–333. doi:10.1016/j.yapd.2014.04.004. PMID 25037135. Retrieved 30 November 2016.
- Doleac, Jennifer L. (1 June 2017). "New evidence that lead exposure increases crime". The Brookings Institution.
- Steel, Daniel (2013). "Mechanisms and Extrapolation in the Abortion-Crime Controversy". In Chao, Hsiang-Ke; et al. (eds.). Mechanism and Causality in Biology and Economics. Springer Science & Business Media. p. 188. ISBN 978-9-40-072454-9.
- Farrell, Graham; Tilley, Nick; Tseloni, Andromachi (2014). "Why the Crime Drop?" (PDF). Crime and Justice. 43 (1): 421–490. doi:10.1086/678081. ISSN 0192-3234.
- Levitt, Steven D (2004). "Understanding Why Crime Fell in the 1990s: Four Factors that Explain the Decline and Six that Do Not". Journal of Economic Perspectives. 18 (1): 163–190. CiteSeerX 10.1.1.210.3073. doi:10.1257/089533004773563485. ISSN 0895-3309.
- Donohue, J. J.; Levitt, S. D. (2001-05-01). "The Impact of Legalized Abortion on Crime". The Quarterly Journal of Economics. 116 (2): 379–420. CiteSeerX 10.1.1.205.9648. doi:10.1162/00335530151144050. ISSN 0033-5533.
- Ludwig, J.; Duncan, G. J.; Hirschfield, P. (2001-05-01). "Urban Poverty and Juvenile Crime: Evidence from a Randomized Housing-Mobility Experiment". The Quarterly Journal of Economics. 116 (2): 655–679. doi:10.1162/00335530151144122. ISSN 0033-5533.
- Hsieh, Ching-Chi; Pugh, M. D. (1993). "Poverty, Income Inequality, and Violent Crime: A Meta-Analysis of Recent Aggregate Data Studies". Criminal Justice Review. 18 (2): 182–202. doi:10.1177/073401689301800203. ISSN 0734-0168.
- Cantor, David; Land, Kenneth C. (1985). "Unemployment and Crime Rates in the Post-World War II United States: A Theoretical and Empirical Analysis". American Sociological Review. 50 (3): 317. doi:10.2307/2095542. ISSN 0003-1224. JSTOR 2095542.
- Werbach, M (1992). "Nutritional influences on aggressive behavior". J Orthomol Med. 7 (1): 45–51.
- R., Major, Ralph (1931). Some landmarks in the history of lead poisoning. OCLC 230983773.
- Terekhova, N. N. (1981). "The History of Metalworking Production among the Ancient Agriculturalists of Southern Turkmenia". Soviet Anthropology and Archeology. 19 (3–4): 313–324. doi:10.2753/aae1061-1959190304313. ISSN 0038-528X.
- Hodge, A. Trevor (1981). "Vitruvius, Lead Pipes and Lead Poisoning". American Journal of Archaeology. 85 (4): 486–491. doi:10.2307/504874. ISSN 0002-9114. JSTOR 504874.
- Boeckx, Roger L. (1986). "Lead poisoning in children". Analytical Chemistry. 58 (2): 274A–[288A]. doi:10.1021/ac00293a001. ISSN 0003-2700. PMC 2060893. PMID 13230485.
- Delile, H.; Blichert-Toft, J.; Goiran, J.-P.; Keay, S.; Albarede, F. (2014-04-21). "Lead in ancient Rome's city waters". Proceedings of the National Academy of Sciences. 111 (18): 6594–6599. Bibcode:2014PNAS..111.6594D. doi:10.1073/pnas.1400097111. ISSN 0027-8424. PMC 4020092. PMID 24753588.
- O., Nriagu, Jerome (1983). Lead and lead poisoning in antiquity. Wiley. ISBN 978-0471087670. OCLC 424313729.
- Warren, Christian (1999). "Toxic Purity: The Progressive Era Origins of America's Lead Paint Poisoning Epidemic". The Business History Review. 73 (4): 705–736. doi:10.2307/3116131. ISSN 0007-6805. JSTOR 3116131.
- Nriagu, Jerome O. (1990). "The rise and fall of leaded gasoline". Science of the Total Environment. 92: 13–28. Bibcode:1990ScTEn..92...13N. doi:10.1016/0048-9697(90)90318-o. ISSN 0048-9697.
- Kovarik, William (2005). "Ethyl-leaded Gasoline: How a Classic Occupational Disease Became an International Public Health Disaster". International Journal of Occupational and Environmental Health. 11 (4): 384–397. doi:10.1179/oeh.2005.11.4.384. ISSN 1077-3525. PMID 16350473.
- Registry., United States. Agency for Toxic Substances and Disease (2007). Toxicological profile for lead. U.S. Dept. of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. OCLC 819638920.
- Brubaker, Christopher J.; Schmithorst, Vincent J.; Haynes, Erin N.; Dietrich, Kim N.; Egelhoff, John C.; Lindquist, Diana M.; Lanphear, Bruce P.; Cecil, Kim M. (2009). "Altered myelination and axonal integrity in adults with childhood lead exposure: A diffusion tensor imaging study". NeuroToxicology. 30 (6): 867–875. doi:10.1016/j.neuro.2009.07.007. ISSN 0161-813X. PMC 2789851. PMID 19619581.
- Yuan, W.; Holland, S. K.; Cecil, K. M.; Dietrich, K. N.; Wessel, S. D.; Altaye, M.; Lanphear, B. P. (2006). "The impact of early childhood lead exposure on brain organization: a functional magnetic resonance imaging study of language function". Pediatrics. 118 (3): 971–977. doi:10.1542/peds.2006-0467. PMID 16950987.
- Byers, R. K.; Lord, E. E. (1944). "Late Effects of Lead Poisoning on Mental Development". The Journal of Nervous and Mental Disease. 100 (4): 420. doi:10.1097/00005053-194410000-00009. ISSN 0022-3018.
- Mendelsohn, A. L., Dreyer, B. P., Fierman, A. H., Rosen, C. M., Legano, L. A., Kruger, H. A., ... & Courtlandt, C. D. (1998). Low-level lead exposure and behavior in early childhood. Pediatrics, 101(3), e10-e10.
- Needleman, H. L.; McFarland, C.; Ness, R. B.; Fienberg, S. E.; Tobin, M. J. (2002). "Bone lead levels in adjudicated delinquents: a case control study". Neurotoxicology and Teratology. 24 (6): 711–717. doi:10.1016/s0892-0362(02)00269-6. PMID 12460653.
- Goodlad, J. K.; Marcus, D. K.; Fulton, J. J. (2013). "Lead and attention-deficit/hyperactivity disorder (ADHD) symptoms: A meta-analysis". Clinical Psychology Review. 33 (3): 417–425. doi:10.1016/j.cpr.2013.01.009. PMID 23419800.
- Schwartz, B. S.; Stewart, W. F.; Bolla, K. I.; Simon, D.; Bandeen-Roche, K.; Gordon, B.; Todd, A. C. (2000). "Past adult lead exposure is associated with longitudinal decline in cognitive function". Neurology. 55 (8): 1144–1150. doi:10.1212/wnl.55.8.1144. PMID 11071492.
- Nation, Jack R.; Baker, Dorothy M.; Taylor, Betty; Clark, Donald E. (1986). "Dietary lead increases ethanol consumption in the rat". Behavioral Neuroscience. 100 (4): 525–530. doi:10.1037/0735-7044.100.4.525. ISSN 1939-0084.
- Nevin, Rick (2000). "How Lead Exposure Relates to Temporal Changes in IQ, Violent Crime, and Unwed Pregnancy" (PDF). Environmental Research. 83 (1): 1–22. Bibcode:2000ER.....83....1N. doi:10.1006/enrs.1999.4045. ISSN 0013-9351. PMID 10845777.
- Lane, Sandra D.; Webster, Noah J.; Levandowski, Brooke A.; Rubinstein, Robert A.; Keefe, Robert H.; Wojtowycz, Martha A.; Cibula, Donald A.; Kingson, Johanna E.F.; Aubry, Richard H. (2008). "Environmental Injustice: Childhood Lead Poisoning, Teen Pregnancy, and Tobacco". Journal of Adolescent Health. 42 (1): 43–49. doi:10.1016/j.jadohealth.2007.06.017. ISSN 1054-139X. PMID 18155029.
- Reyes, Jessica Wolpaw (2007). "Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime" (PDF). The B.E. Journal of Economic Analysis & Policy. 7 (1). doi:10.2202/1935-1682.1796. Retrieved 30 November 2016.
- Committee on Public Works, Hearings before a Subcommittee on Air and Water Pollution, United States Senate, 89th Congress, Second Section on S-3112 and S-3400, Washington, DC, 1966.
- Bellinger, D. C. (2006-03-23). "Childhood lead poisoning: the torturous path from science to policy". Journal of Clinical Investigation. 116 (4): 853–857. doi:10.1172/jci28232. ISSN 0021-9738. PMC 1421365. PMID 16585952.
- Annest, Joseph L.; Pirkle, James L.; Makuc, Diane; Neese, Jane W.; Bayse, David D.; Kovar, Mary Grace (1983-06-09). "Chronological Trend in Blood Lead Levels between 1976 and 1980". New England Journal of Medicine. 308 (23): 1373–1377. doi:10.1056/nejm198306093082301. ISSN 0028-4793. PMID 6188954.
- Health, National Center for Environmental (2018-10-11). "CDC - Lead - Home Page". www.cdc.gov. Retrieved 2018-10-12.
- Patterson, Clair; Ericson, Jonathon; Manea-Krichten, Mirela; Shirahata, Hiroshi (1991). "Natural skeletal levels of lead in Homo sapiens sapiens uncontaminated by technological lead". Science of the Total Environment. 107: 205–236. Bibcode:1991ScTEn.107..205P. doi:10.1016/0048-9697(91)90260-l. ISSN 0048-9697. PMID 1785050.
- Patterson, C. C. (1965). "Contaminated and natural lead environments of man". Archives of Environmental Health: An International Journal. 11 (3): 344–360. doi:10.1080/00039896.1965.10664229. PMID 14334042.
- Lewis, J (1985). "Lead poisoning: a historical perspective". EPA Journal. 11: 15.
- "LEGISLATIVE HISTORY OF LEAD-BASED PAINT" (PDF). U.S. Department of Housing and Urban Development. Retrieved November 30, 2018.
- "Phase-out of leaded petrol brings huge health and cost benefits – UN–backed study". United Nations News Centre. 27 October 2011.
- Carpenter, David O.; Nevin, Rick (2010). "Environmental causes of violence". Physiology & Behavior. 99 (2): 260–268. doi:10.1016/j.physbeh.2009.09.001. ISSN 0031-9384. PMID 19758571.
- Baker, L. A.; Jacobson, K. C.; Raine, A.; Lozano, D. I.; Bezdjian, S. (2007). "Genetic and environmental bases of childhood antisocial behavior: a multi-informant twin study". Journal of Abnormal Psychology. 116 (2): 219–35. doi:10.1037/0021-843x.116.2.219. PMC 1913189. PMID 17516756.
- Baker, L. A.; Raine, A.; Liu, J.; Jacobson, K. C. (2008). "Differential genetic and environmental influences on reactive and proactive aggression in children". Journal of Abnormal Child Psychology. 36 (8): 1265–1278. doi:10.1007/s10802-008-9249-1. PMC 2609906. PMID 18615267.
- Raine, A. (2014). The anatomy of violence: The biological roots of crime. New York: NY, Vintage.
- Gibson, J. L., Love, W., Hardie, D., Bancroft, P., & Turner, A. J. (1892). Notes on lead-poisoning as observed among children in Brisbane. In Proceedings of the Third Intercolonial Medical Congress, Sydney, Australia (pp. 76-83).
- PIHL, R. O. (1990). "LEAD AND CADMIUM LEVELS IN VIOLENT CRIMINALS". Psychological Reports. 66 (3): 839. doi:10.2466/pr0.66.3.839-844. ISSN 0033-2941.
- W., Denno, Deborah (2010). Biology and Violence : From Birth to Adulthood. Cambridge University Press. ISBN 9780511752803. OCLC 900190649.
- Needleman, Herbert L. (1996). "Bone Lead Levels and Delinquent Behavior". JAMA: The Journal of the American Medical Association. 275 (5): 363–369. doi:10.1001/jama.1996.03530460029026. ISSN 0098-7484.
- Stretesky, Paul B.; Lynch, Michael J. (2001-05-01). "The Relationship Between Lead Exposure and Homicide". Archives of Pediatrics & Adolescent Medicine. 155 (5): 579. doi:10.1001/archpedi.155.5.579. ISSN 1072-4710. PMID 11343501.
- Aizer, Anna; Currie, Janet (May 2017). "Lead and Juvenile Delinquency: New Evidence from Linked Birth, School and Juvenile Detention Records". NBER Working Paper No. 23392. doi:10.3386/w23392.
- Beckley, Amber L.; Caspi, Avshalom; Broadbent, Jonathan; Harrington, Honalee; Houts, Renate M.; Poulton, Richie; Ramrakha, Sandhya; Reuben, Aaron; Moffitt, Terrie E. (2018-02-01). "Association of Childhood Blood Lead Levels With Criminal Offending". JAMA Pediatrics. 172 (2): 166–173. doi:10.1001/jamapediatrics.2017.4005. ISSN 2168-6203. Retrieved 2020-08-06.
- Carpenter, David O.; Nevin, Rick (February 2010). "Environmental causes of violence" (PDF). Physiology & Behavior. 99 (2): 260–268. doi:10.1016/j.physbeh.2009.09.001. PMID 19758571.
- Casciani, Dominic (21 April 2014). "Did removing lead from petrol spark a decline in crime?". BBC News.
- Drum, Kevin (11 February 2016). "Lead: America's Real Criminal Element". Mother Jones.
- Feigenbaum, James J.; Muller, Christopher (October 2016). "Lead exposure and violent crime in the early twentieth century" (PDF). Explorations in Economic History. 62: 51–86. doi:10.1016/j.eeh.2016.03.002.
- Firestone, Scott (8 January 2013). "Does Lead Exposure Cause Violent Crime? The Science is Still Out". Discover.
- Knapp, Alex (3 January 2013). "How Lead Caused America's Violent Crime Epidemic". Forbes.
- Nevin, Rick (19 December 2012). "The Answer is Lead Poisoning".
- Nevin, Rick (2016). Lucifer Curves: The Legacy of Lead Poisoning. BookBaby. ASIN B01I3LTR4W.
- Vedantam, Shankar (8 July 2007). "Research Links Lead Exposure, Criminal Activity". The Washington Post.
- Wakefield, Julie (October 2002). "The lead effect?". Environmental Health Perspectives. 110 (10): A574–A580. doi:10.1289/ehp.110-a574. ISSN 0091-6765. PMC 1241041. PMID 12361937.