OSHKOSH, Wis. -- A controversial new hypothesis to be published later this year should make us alter our thinking about environmental pollution. Until now, any consideration of pollution usually brought to mind despoiled habitats, endangered species and human health consequences. While all of those problems remain serious, the work of Roger Masters of Dartmouth College raises yet another concern, one of frightening dimensions.
Dr. Masters has very convincing, but preliminary, data suggesting that high levels of toxic metal exposure might well be responsible for increased levels of crime in some communities. That is, high levels of pollution might lead to increased levels of homicide, assault, rape and robbery.
The underlying mechanisms are very straightforward. Scientists have already carefully documented that certain types of chemical exposure can lead to cancer, liver damage, brain damage, anemia and a host of other physical ailments. Dr. Masters' work extends this basic premise to point out that some types of pollution can alter human physiology in such a way that behavior is affected.
The two chemicals most studied, lead and manganese, have direct effects on brain function . High levels of lead, for example, damage the brain's glial cells, which, when functioning normally, play a "housekeeping" role, detoxifying and ridding the brain of unwanted chemicals.
High levels of manganese serve to lower the brain's ability to use both serotonin and dopamine, two neurotransmitters often associated with the control of impulsive behavior. Together, the effects of elevated levels of lead and manganese, Dr. Masters argues, so alters brain chemistry that affected individuals are significantly more likely to suffer from mood disturbances and poor impulse control, while being significantly more aggressive.
"It's the breakdown of the inhibition mechanism that's the key to violent behavior," he asserts. Even worse are some of the synergistic effects he proposes. Because increased levels of lead diminish the body's ability to detoxify poison, Dr. Masters believes exposure might heighten the behavioral effects of alcohol and drugs.
Equally frightening are data demonstrating that children's bodies are much more proficient at absorbing toxic metals than are adults'. That the differences are far from trivial is obvious: Children absorb 50 percent of the lead they ingest, while adults absorb only 8 percent.
With the basic biochemistry and physiology of toxicity well established, Dr. Masters' research is as breathtakingly simple as it is important. His goal was to explain why some communities have only 100 violent crimes per 100,000 people, while others have over 3,000. And his conclusions contradict some of the most basic ideas of criminologists who believe that social and economic factors are best able to explain crime statistics.
Social variablesHe compared FBI statistics on violent crimes for each county in the United States with U.S. census statistics and Environmental Protection Agency data on industrial releases of lead and manganese into the environment in each county. The variables from the census he selected for examination are those thought most likely to lead to crime: number of school dropouts; unemployment rate; race and ethnicity; number of people on welfare; number of people below the poverty level; population density; number of police officers per person, and others that might add to the "social deterioration" index of a community.
Dr. Masters found that the demographic variables were remarkably poor at predicting crime rates, while the pollution data worked surprisingly well. Counties with the highest levels of lead and manganese pollution had crime rates that exceeded the national average by three times. Dr. Masters concluded that "the presence of pollution is as big a factor as poverty" in predicting crime statistics.
If his hypothesis is correct -- it is being received favorably, but scientists are calling for additional work before passing final judgment -- the consequences and costs of industrial pollution will have increased dramatically. A company lax about controlling the amount of metal in its waste stream might well be responsible for helping to unravel the social fabric of the community surrounding its factory.
Perhaps conservatives who have long argued that it is time to get tough on crime will now join with environmentalists in their efforts to get tough on industrial polluters. If they do so, the world may well become a cleaner and safer place to live.
Michael Zimmerman is dean of the College of Letters and Science and professor of biology at the University of Wisconsin, Oshkosh. He is the author of "Science, Nonscience, and Nonsense: Approaching Environmental Literacy."
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