鉛毒進行式 研究：鉛暴露與少年反社會行為有關

Two Harvard researchers who examined the racial ecology of lead exposure as a form of environmental inequity have concluded that lead exposure in childhood is linked to antisocial behavior in adolescence, although not directly linked to arrests.

Lead author Dr. Robert Sampson is the Henry Ford II Professor of the Social Sciences at Harvard, founding director of the Boston Area Research Initiative, and affiliated research professor at the American Bar Foundation.

For this study, Sampson and co-author Harvard sociologist Alix Winter drew on comprehensive data from over one million blood tests administered to Chicago children from 1995-2013 and matched to over 2,300 geographic block groups.

They found that contemporary lead exposure is linked to minority status and poverty at the individual level, as well as to racial segregation and concentrated poverty at the neighborhood level, “primarily because of the unequal distribution of dilapidated housing that contains remnants of lead paint.”

“The results underscore lead exposure as a trigger for poisoned development in the early life course and call for greater integration of the environment into theories of individual differences in criminal behavior,” the authors conclude.

Exposure to dangerous levels of lead was extensive for long stretches of the 20th century, the authors recount. Although environmental reforms such as the bans on lead in gasoline and paint in the 1970s were considered victories for public health at the time, lead toxicity is far from a hazard of the past, state Sampson and Winter.

High levels of lead have recently been found in thousands of cities in the United States and in both developed and developing countries around the world.

“The poisoning of the water in Flint, Michigan, in late 2015 and the evacuation in 2016 of an entire neighborhood contaminated by a smelting plant in East Chicago, Indiana, shone bright public lights on the contemporary perils of lead,” they write.

The U.S. Centers for Disease Control and Prevention, CDC, says that today at least four million U.S. households have children living in them that are being exposed to high levels of lead.

There are approximately half a million U.S. children ages one to five with blood lead levels above five micrograms per deciliter (µg/dL), the reference level at which CDC recommends public health actions be initiated.

Even parents are often unaware of lead levels in their children’s environments, write Sampson and Winter. “Lead-based paint has remained in millions of housing units despite being banned, sometimes stirred up by housing renovations or hidden by landlords with fresh coats of paint and then exposed when newer paint layers peel.”

They point out that lead smelting plants, most of which were built decades ago and have been shuttered for some time, are a major source of contemporary soil lead.

No safe blood lead level in children has been identified, the CDC warns. Lead exposure can affect nearly every system in the body. Because lead exposure often occurs with no obvious symptoms, it frequently goes unrecognized.

To make certain their conclusions are accurate, the authors assessed an array of structural explanations for observed racial disparities, including socioeconomic status, type and age of housing, proximity to freeways and smelting plants, and systematic observations of housing decay and neighborhood disorder.

Overall, the authors write, “our theoretical framework posits lead toxicity as a major environmental pathway through which racial segregation has contributed to the legacy of Black disadvantage in the United States.”

“Our findings support this hypothesis and show alarming racial disparities in toxic exposure, even after accounting for possible structural explanations,” they write.

At the same time, they say, our longitudinal results show the power of public health policies to reduce racial inequities.

The study is published in the current issue of the journal “Criminology.”