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A clutch of newish studies on the effects of lead exposure has helped. The hypothesis that lead damage to developing brains causes violence later in life is one of the great mysteries of social science—widely believed by those who plot the decline in violence against the decline in lead exposure and note how the two track each other; widely mistrusted by researchers who mutter about correlation and causation. Newer studies are more nuanced. One, by James Feigenbaum of Boston University and Christopher Muller of Berkeley, tried to control for other factors by comparing cities where the PH of the water supply was below seven, making it acidic, and causing lead to leach into water. The authors found acidic water tallied with more crime.
一系列關于鉛暴露影響的新研究起到了幫助作用。鉛對大腦發育的損害會導致日后的暴力行為，這一假說是社會科學的一大謎團。有些人普遍相信這一假說，他們同時也將暴力行為的減少與鉛暴露量的下降進行了對比，并指出兩者是如何相互作用的；而那些對相關性和因果關系喋喋不休的研究人員則普遍懷疑這一假說。新的研究更加細致。波士頓大學的詹姆斯·費根鮑姆和伯克利的克里斯托弗•穆勒開展的一項研究試圖控制其他因素，將PH值低于7、呈酸性、且含鉛的城市供水進行對比。研究提出者們發現酸性水與更多的犯罪相吻合。
Some cities flush chemicals—orthophosphates— into pipes, to coat them to stop lead getting into the water. Milwaukee spends $400,000 a year to do so. That helps, but disturbances—such as when mains pipes are replaced but service lines to homes are not—can shake out particulates that remain in water. Karen Dettmer, superintendent of water works in Milwaukee, says events in Flint spurred her city to stop all repairs of lead lines. They also found, in 2017, ten schools fed by lead lines that were promptly replaced. Nurseries run from private homes remain exposed.
一些城市將化學物質正磷酸鹽沖入水管中，以覆蓋管道，防止鉛進入水中。密爾沃基每年為此花費40萬美元。這是有幫助的，但是也會起到阻礙作用，水中殘留的顆粒物會滲出，比如，當總水管被更換，而到家庭的服務線路沒有被更換的時候。密爾沃基市水利工程負責人卡倫·德特默說，弗林特市發生的事件促使她所在的城市停止了對鉛線的所有維修。他們還發現，在2017年，有10所學校很快就更換了供水的鉛線。私人住宅開辦的托兒所仍然面臨著鉛暴露。
Milwaukee is trying to replace 1,100 lead lines each year—hoping to emulate cities such as Lansing, Madison and Green Bay which have recently replaced all their pipes. Pittsburgh, Newark and other cities also plan to do so. But the cost of replacing one pipe averages $11,000 in Milwaukee (it was lower elsewhere). And with service lines mostly on private land, the job involves negotiations and cost-sharing with owners. Doing it all “will take about 70 years, that’s not fast”, she says. Much housing stock is decades old and pipes inside homes may also be a source of lead.
密爾沃基正試圖每年更換1100條鉛線，希望效仿蘭辛、麥迪遜和綠灣等城市，這些城市最近都更換了所有的水管。匹茲堡、紐瓦克和其他城市也計劃進行水管更換。但在密爾沃基，更換一根水管的平均成本為1.1萬美元（其他地方的成本更低）。由于服務線路大多在私人土地上，這項工作需要與業主協商和分擔費用。她說，徹底完成“需要70年左右的時間，這并不快”。很多房屋都有幾十年的歷史了，房屋內的水管也可能是鉛的來源。
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