鉛毒進行式 研究:鉛暴露與少年反社會行為有關 | 台灣環境資訊協會-環境資訊中心

鉛毒進行式 研究:鉛暴露與少年反社會行為有關

2018年03月22日
摘譯自2018年3月13日ENS美國,麻塞諸塞州,劍橋報導;姜唯編譯;周念學審校

根據最新一期的《犯罪學》期刊研究,兩位哈佛大學種族生態學者研究發現,兒童時期的鉛暴露與青少年時期的反社會行為有關,顯示鉛暴露是一種環境不正義(environmental inequity),不過研究沒有發現鉛暴露與逮捕行為有直接關係。

Joseph Mietus(CC BY-NC 2.0)
美國今日還有400萬個家庭生活在高濃度的鉛暴露環境。圖片來源:Joseph Mietus(CC BY-NC 2.0)

研究:鉛暴露脫離不了貧窮、種族隔離

主要作者桑普森(Robert Sampson)博士是哈佛社會科學亨利福特二世教授、波士頓地區研究計畫的創辦人及主任、以及美國律師協會的合聘研究教授。

在這份研究中,桑普森和共同作者、哈佛大學社會學家溫特(Alix Winter)運用1995至2013年間超過100萬次芝加哥兒童血液檢測的全面性資料,與超過2300個地理區塊進行比對。

結果發現,當代鉛暴露在個人層面與弱勢族群和貧窮有關,在社區層面與種族隔離和集中貧窮區有關,「主要原因是含鉛塗料殘餘物的破舊住宅分佈不平均。」

「這些結果顯示,鉛暴露是生命歷程早期發展不良的觸發因素,相對的應當將環境納入犯罪行為的個體差異理論中。」作者總結道。 

公共衛生勝利喊得太早 鉛毒還沒遠離

作者描述,20世紀時,有很長一段時間人們普遍暴露於危險濃度的鉛中。雖然經歷環境改革,例如70年代禁止汽油和油漆含鉛,被認為是當時公共衛生的勝利,但鉛的毒性遠不是過去所想的,只是有毒而已,桑普森和溫特說。  

最近在美國數千個城市以及世界各地的已開發和開發中國家,都發現了高濃度的鉛暴露。

作者寫道:「2015年底密西根州弗林特的水中毒事件,以及2016年在印第安納州東芝加哥冶煉廠污染整個住宅區、導致居民必須撤離的事件,都顯示今日鉛危害並沒有遠離。」

無明顯症狀  全美400萬個家庭生活於高鉛環境

美國疾病預防控制中心(CDC)表示,今天至少有400萬美國家庭的孩子生活在高鉛環境中。

約有50萬個一至五歲美國兒童,血鉛濃度超過每分升5微克(μg/ dL),已經達到CDC建議啟動公共衛生措施的參考水準。

桑普森和溫特寫道,即便是父母也往往不了解孩子生活環境中的鉛含量,「儘管已被禁止,含鉛油漆仍然存在在數百萬個住宅中,經房屋裝修或被屋主用新塗料隱藏起來,在新的油漆層剝落時便會暴露出來。」

他們指出,鉛冶煉廠是當代土壤中鉛的主要來源,大部分鉛冶煉廠是幾十年前興建的,且已經關閉了一段時間。 

CDC警告,兒童血鉛濃度沒有安全值。鉛暴露可能影響身體中幾乎所有的系統。由於鉛暴露通常沒有明顯症狀,往往無法察覺。

當年黑人處於劣勢  鉛毒暴露驚人種族差異

為確保研究結論準確,作者評估了一系列可觀察的種族差異之結構性解釋,包括社會經濟狀況、住房類型和年齡、是否鄰近高速公路和鉛冶煉廠,以及對於住宅老化和鄰里失序的系統性觀察。

整體而言,作者寫道:「我們的理論框架假定,鉛毒是導致美國種族隔離之下,黑人處於劣勢的環境因素...我們的研究結果支持這一假設,即使在考慮到可能的結構性解釋之後,也顯示了鉛毒暴露的驚人種族差異。」

同時,研究者表示其縱向分析結果顯示,公共衛生政策是減少種族不平等的重要力量。 

這篇研究發表在最新一期的《犯罪學》期刊上。

Childhood Lead Exposure Linked to Teen Delinquency
CAMBRIDGE, Massachusetts, March 13, 2018 (ENS)

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.” 

※ 全文及圖片詳見:ENS

作者

姜唯

如果有一件事是重要的,如果能為孩子實現一個願望,那就是人類與大自然和諧共存。

周念學

親近大自然,精神上總是愉快的。