Lead–crime hypothesis

This warning on an old Lynnwood, Washington fuel pump notes how it used to dispense gasoline with tetraethyllead additives.

The hypothesis that crime rates and the prevalence of lead are related, with high levels of lead contributing to social disorder, has been advocated by numerous academic studies and various criminologists, with the research coming to complex, disputed results. Lead poisoning is widely understood to have highly negative results in multiple parts of the human body, particularly the brain. Concerns about even low levels of exposure began in the 1970s; currently, scientists have concluded that no safe threshold for lead exposure at all exists. Problems become particularly acute in terms of children.

Publications running material in support of the hypothesis include Advances in Pediatrics and The B.E. Journal of Economic Analysis & Policy. The official United Nations News Centre has also ran articles in support of anti-lead efforts, citing purported benefits in terms of reduced crime rates. However, writers from publications such as the science magazine Discover have expressed caution at making too much of the connection.

Background and research

Usage of lead in modern history

The affects of age and natural exposure on this bridge railing in northern France leach its lead paint into the air and water beside it.

Lead, a naturally occurring metal of bluish-grey color, has been used for multiple purposes in the history of human civilization. Advantages include being somewhat soft and pliable as well as resistant to corrosion compared to other metals. The widespread substance is also able to function as a shield against various forms of radiation.

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.

Medical analysis of the role of lead exposure in the brain note 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 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 2000 '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.

Analysis of lead prevalence in terms of crime rates

Brazilian-German economist Achim Steiner, speaking as then head of the U.N. Environment Programme, has lauded anti-lead efforts as a key sustainable development success.

In terms of crime, multiple commentators and researchers have noted that, after decades of relatively steady increases, crime rates in the United States started to sharply decline in the 1990s. The trend continued even 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.

Notable economists Steven D. Levitt and John J. Donohue III, of the University of Chicago and Stanford University, respectively, have argued that the decline in U.S. crime rates took place due to the combination of increases in the number of police, hikes in size of the prison population, waning of the spread of crack cocaine, and the widespread legalization of abortion from the 1970s onward. Possible other factors include changes in alcohol consumption. Later studies have upheld many of these findings while disputing others.

While noting that correlation does not imply causation, 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.

A 2007 report published by The B.E. Journal of Economic Analysis & Policy, authored by Jessica Reyes of Amherst College, found that 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," the author concluded that "[o]verall, 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."

In 2011, a report published by the official United Nations News Centre remarked, "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". The California State University did the specific study. Then U.N. Environment Programme (UNEP) executive director Achim Steiner argued, "Although this global effort has often flown below the radar of 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."

In a 2013 article, Mother Jones ran a report by Kevin Drum arguing:

"Needless to say, not every child exposed to lead is destined for a life of crime. Everyone over the age of 40 was probably exposed to too much lead during childhood, and most of us suffered nothing more than a few points of IQ loss. But there were plenty of kids already on the margin, and millions of those kids were pushed over the edge from being merely slow or disruptive to becoming part of a nationwide epidemic of violent crime."

Criticism of the lead and crime hypothesis often focuses on the fact that expanded police activity and widespread incarceration of people with past criminal records may override whatever effects anti-lead measures have. In particular, advocates of the 'broken windows theory' of policing, or of alternative theories such as 'community policing', have stressed the relative importance of local programs while not dismissing other factors. Academic debates on the statistical correlations around crime have gone on for decades in major Western nations with complicated results.

Author and Discover journalist Scott Firestone has cautioned, "It’s beyond debate that lead can have terrible effects on people. But there is no real scientific basis for calling the violent crime link closed". He has written that individuals should keep in mind the influence of both confirmation bias and the ecological fallacy in looking at trends in the data.

See also

• Environmental toxicology
• History of the tetraethyllead controversy
• Lead
  • Lead abatement
  • Lead poisoning
  • Organolead chemistry
• Legalized abortion and crime effect
• Pollution control
• Statistical correlations of criminal behavior

External link

• "How Lead Caused America's Violent Crime Epidemic" - Forbes.com