一次環境污染的教訓

本文內容轉自環境工程專家Andrew J. Whelton在資訊網站The Conversation的撰文：Toxic chemicals from Ohio train derailment lingered。

2023年2月，一列火車在俄亥俄州East Palestine鎮脫軌，裝滿危險物資的車廂破裂，引發化學火災。這場災難引起世界關注，兩個州的州長敦促疏散事故現場一英里。燃燒的化學物質發出刺鼻氣味。

三天後，在Norfolk南方鐵路公司的催促下，100萬磅氯乙烯從受損車廂釋放出來並點燃燒掉。聯邦調查人員後來結論，露天燃燒並引起黑蘑菇雲是不必要的，但為時已晚，有害化學物質散佈到俄州和賓州上空。

As an environmental engineers, I and my colleagues are often asked to assist with public health decisions after disasters by government agencies and communities. After the evacuation order was lifted, community members asked for help. 疏散令解除後，Andrew Whelton博士等環境專家應政府要求，協助做災後公共衛生決策。

In a new study, we describe the contamination we found, along with problems with the response and cleanup that, in some cases, increased the chances that people would be exposed to hazardous chemicals. It offers important lessons to better protect communities in the future. 新的研究報告描述了污染和處理方面的問題。

How chemicals get into homes and water: When large amounts of chemicals are released into the environment, the air can become toxic. Chemicals can also wash into waterways and seep into the ground, contaminating groundwater and wells. Some chemicals can travel below ground into nearby buildings and make the indoor air unsafe. 空氣會變得有毒。化學物質也會衝入水道並滲入地下，污染地下水和水井，從而進入建築物，使室內空氣也變得不安全。

Air pollution can find its way into buildings through cracks, windows, doors and other portals. Once inside, the chemicals can penetrate home items like carpets, drapes, furniture, counters and clothing. When the air is stirred up, those chemicals can be released again. 空氣污染可以從門縫、窗縫進入室內，隨即滲透和藏入地毯、窗簾、家具、櫃檯和衣服等家居用品中。

Evacuation order lifted, but buildings were contaminated: Three weeks after the derailment, we began investigating the safety of the area near 17 buildings in Ohio and Pennsylvania. The highest concentration of air pollution occurred in the 1-mile evacuation zone and a shelter-in-place band another mile beyond that. But the chemical plume also traveled outside these areas. 出軌事故3周後調查附近17棟建築物，污染最集中的地方是一英里內的疏散區和一英里外的就地避難區。

In and outside East Palestine, evidence indicated that chemicals from the railcars had entered buildings. Many residents complained about headaches, rashes and other health symptoms after reentering the buildings. At one building 0.2 miles away from the derailment site, the indoor air was still contaminated more than four months later. 疏散令解除後，許多居民重新進入樓房出現頭痛、皮疹等等症狀。有一棟樓，四個月後室內空氣仍然污染。

Nine days after the derailment, sophisticated air testing by a business owner showed the building’s indoor air was contaminated with butyl acrylate and other chemicals carried by the railcars. Butyl acrylate was found above the two-week exposure level, a level at which measures should be taken to protect human health. 出軌事故9天時，一位空氣測試技術業主測到樓內空氣受火車化學物質的污染，水平高於某個標準，應採取措施保護人體健康。

When rail company contractors visited the building 11 days after the wreck, their team left after just 10 minutes. They reported an “overwhelming/unpleasent odor” even though their government-approved handheld air pollution detectors detected no chemicals. This building was located directly above Sulphur Run creek, which had been heavily contaminated by the spill. Chemicals likely entered from the initial smoke plumes and also rose from the creek into the building. 事故發生11天時，鐵路公司承包工進入這樓，僅10分鐘他們報告有刺鼻的氣味，但他們手持政府批准的污染探測器卻沒有測到任何東西。

Our tests weeks later revealed that railcar chemicals had even penetrated the business’s silicone wristband products on its shelves. We also detected several other chemicals that may have been associated with the spill. Weeks after the derailment, government officials discovered that air in the East Palestine Municipal Building, about 0.7 miles away from the derailment site, was also contaminated. Airborne chemicals had entered that building through an open drain pipe from Sulphur Run. 幾周後的測試結果顯示，有害物質甚至滲入貨架上的硅膠腕帶產品中。附近一座市政大樓也測到空氣污染，空中毒氣會從開放式排水管進入樓房。

More than a month after the evacuation order was lifted, the Ohio Environmental Protection Agency acknowledged that multiple buildings in East Palestine were being contaminated as contractors cleaned contaminated culverts under and alongside buildings. Chemicals were entering the buildings. 疏散令撤消一個多月後，俄州環保署承認，由於承包工清理樓底和旁邊受污染的涵洞，鎮上多棟建築物正受到污染，化學物質正在進入樓房。

Contaminated water can cause contaminated air: The creek that flowed through town became heavily contaminated by the spill. More than 43,000 fish died downstream, and chemicals traveled 270 miles (435 kilometers) down the Ohio River. As tainted water flowed downstream, light chemicals like butyl acrylate naturally left the creek and entered the air by a process called volatilization. 被污染的溪水流過435公里進入俄亥俄河，引起4萬3千多條魚死亡，並且有害的化學物質揮發，進入大氣成為空氣污染。

Unnaturally however, the equipment used for cleaning the creeks also transferred chemicals from the water into the air. Residents near aeration equipment, which injects air into water, in part to help fish survive, complained of odors entering their homes and experiencing health problems. Our study shows the chemicals in the air may have been up to 2 to 25 times higher near these aerators. 用於清潔過濾溪水的設備把水中有害化學物質送入空中，影響到向水曝氣的設備運作，附近居民聞到氣味並出現健康問題。

Over the four-month study period, rain and the actions of contractors increasing and decreasing water flow also stirred up the creeks, releasing more chemicals into the air. 四個多月的研究期間，降雨以及承包工活動也攪動小溪，將更多的化學物質釋放到空中。

Steps to protect public health in future disasters: As with past disasters, what happened in East Palestine offers many lessons for communities. One of the most important is for communities to demand an exposure pathway diagram immediately after a chemical incident occurs. An illustration can help the community recognize potential threats, whether from the air or from culverts beneath their buildings, and see where testing and guidance are needed. 這次環境污染事故給我們很多教訓。其中最重要的是，社區立即需要毒氣暴露的路徑圖，無論是空中還是樓底涵洞，讓人看到哪裡需要測試和指導。

Monitoring the health of people exposed to the chemicals is also crucial. Because so many people became ill in and around East Palestine, and because testing overseen by government agencies did not pinpoint the exact conditions responsible for the illnesses, we recommend long-term medical monitoring for those affected. 建議對受到影響的人進行長期醫療監測。

People closest to the disaster site – those who lived in, worked in or visited buildings that became contaminated – likely experienced the greatest exposures. Railroad workers, government workers, cleanup workers, visitors and residents in Ohio and Pennsylvania were among those reporting health problems. Norfolk Southern and one contractor were cited for failing to protect workers from exposure. 俄州和賓州的鐵路工人、政府工作人員、清潔工人、遊客和居民都報告了健康問題。Norfolk南方鐵路公司和一名承包工因未能保護工人而受到指控。

Indoor building contamination can be a long-term problem. Just like with wildfire smoke, affected buildings need to be professionally cleaned because the chemicals can remain for months. Building exteriors also need to be decontaminated. Chemicals may continue to release from surfaces into the air. 室內污染需要專業清潔，因化學物質可能存留幾個月。樓外也需要淨化，免得毒氣繼續釋放，進入大氣。

There is also a need for better methods and evidence-based policies to rapidly identify chemical exposures. The U.S. Environmental Protection Agency, months after approving the use of handheld air testing devices to screen homes, determined that those chemical detectors could not have reliably alerted to butyl acrylate at all levels that can cause health problems. Not all the chemicals spilled were monitored for in buildings. 我們還需要開發比較好的技術來快速識別化學品接觸。已經批准使用的手持式空氣檢測設備不能可靠地發出警報，有些洩漏的化學品在室內沒有進行監測。

For complex disasters, we recommend calling in experts from outside the responding agencies and companies involved to provide the needed specialized expertise. 召集外面響應機構的專家與涉事公司的專家合作。