飲用水中的污染物與心理疾病有關


  【24drs.com】新研究顯示,產前和幼兒時期曝露於有機溶煤四氯乙烯(PCE)會增加某些精神疾病的風險,特別是躁鬱症、創傷後壓力異常(PTSD)與精神分裂症。
  
  這篇人口基礎、回溯出生世代研究顯示,Cape Cod這個地區的孩童曝露於受PCE(PCE是用於該市水管內襯的物質)污染的飲水,這些孩童的躁鬱症風險是一般人口的兩倍。
  
  這篇研究線上登載於1月20日的環境健康(Environmental Health)期刊。波士頓大學公衛學院的Ann Aschengrau博士等人在報告中指出,PCE是一種神經毒素,被廣泛用在工業界與乾洗業。
  
  PCE會穿過血腦障蔽,與中樞神經系統的親脂性組織有高親和力,其神經毒性的實際機轉還不清楚,但是包括細胞膜脂質的過氧化,改變了腦部的脂肪酸情況,失去髓磷脂,影響了神經元受體的活性。
  
  有研究指出曝露於PCE會引起此類型工作者的心情改變、焦慮與憂鬱,迄今,有關孩童曝露於PCE後的長期影響還不甚暸解,但有一些證據指出,任職於乾洗業者的孩童發生精神分裂症的風險增加。
  
  為了深入探討,波士頓的這個研究團隊研究了居住在Cape Cod 的婦女在1969-1983年生下的孩童,該市使用內襯乙烯石棉的水泥水管。這些水管是由公立水公司從1960年代後期至1980年代初期設置,目的是解決管線分配末端的鹼化問題,這些內襯是以乙烯樹脂和PCE的混合物灑佈,超過十年後,官方才發現大量的PCE滲入公共用水供應系統。
  
  1980年進行的調查發現,Cape Cod 飲用水中的PCE值範圍為1.5- 7750 μ/L,因為更換水管相當昂貴,採用全面沖刷方式將數值降低到40 μ/L以下,而這是當時的最大建議值範圍,現在,PCE的最大污染值上限為5 μ/L。
  
  Cape Cod世代包括了1,512人,包括831名在產前和幼童期曝露於PCE者以及547名未曾曝露者。研究對象提供有關心理疾病、人口統計學和醫療紀錄、溶煤的其他曝露源、出生後到1990年間的居住地等資料。
  
  作者們解釋,使用水管分布系統模組軟體分析乙烯塗層水管的PCE曝露,整合運算滲漏情況。
  
  研究者發現,那些產前和孩童時期曝露於PCE者並沒有有意義的憂鬱風險增加(風險比[RR],1.1;95%信心區間[CI], 0.9 - 1.4)。Aschengrau博士表示,這結果令人驚訝,也再度確認了之前的成年PCE曝露會增加憂鬱症風險的研究。
  
  不過,研究者發現,妊娠期和幼童期有任何曝露者之躁鬱症風險(RR,1.8;95% CI,0.9 - 3.5)和PTSD風險(RR,1.5;95% CI,0.9 - 2.5) 增加。曝露程度最高者,躁鬱症風險(RR,2.7;95% CI,1.3 - 5.6)和PTSD風險(RR,1.7;95% CI,0.9 - 3.2)更高。
  
  作者們指出,曝露者的精神分裂症風險也增加(RR,2.1;95% CI,0.2 - 20.0),但是案例數太少而無法做出確定結論。
  
  不過,2007年發表於精神分裂症研究期刊的研究發現,任職於乾洗業者的子代精神分裂症風險增加3.4倍(95% CI,1.3 - 9.2),校正混雜因素之後並未改變結果。
  
  紐約大學Langone醫學中心精神科與環境醫學助理教授Mary Perrin博士表示,沒有流行病學研究可以證明任何事情,我們必須建立證據,我個人的看法是,這是另一個證據顯示出我們真的需要嚴格管控環境中的這些物質,動物研究清楚地如此顯示。
  
  她指出,Cape Cod研究是一篇研究方法相當好的研究。作者闡述了你不能忽視的研究限制,並沒有誇大結果,這非常有趣。
  
  Aschengrau博士等人表示,他們的研究限制包括,曝露情況可能分類錯誤、缺乏關於飲水量和沐浴習慣的資料;採用自我報告的心理疾病資料;可能有其他混雜因素而導致忽略了心理疾病的某些風險因素。
  
  研究者指出,另一個限制是低回應率,可能是心理疾病患者忽略了參與的要求。這使最後的樣本數減少,不過,現有的證據認為,這不會導致取樣偏差。
  
  Aschengrau博士也指出,無法計算研究對象曝露的實際PCE量。她表示,紀錄的PCE值有高達目前建議之安全上限的1,550倍,雖然水公司採用沖洗方式來解決這個問題,乾洗業和紡織業者依舊曝露於PCE,消費者也是,因此心理疾病風險依舊可能存在。
  
  Aschengrau博士等人指出,需有獨立研究探討類似的曝露族群,藉以證實他們的研究結果。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6715&x_classno=0&x_chkdelpoint=Y
  

Contaminant in Drinking Water Linked to Mental Illness

By Megan Brooks
Medscape Medical News

January 30, 2012 — Prenatal and early childhood exposure to the organic solvent tetrachloroethylene (PCE) may raise the risk of certain psychiatric illnesses, particularly bipolar disorder, post-traumatic stress disorder (PTSD), and schizophrenia, later in life, new research shows.

The population-based, retrospective birth-cohort study showed that children in Cape Cod who were exposed to drinking water contaminated with PCE, which was used to line municipal water pipes, had almost a 2-fold increased risk for bipolar disorder compared with the general population.

The study was published online January 20 in Environmental Health.

Used widely in industry and to dry clean clothes, PCE is a well-known neurotoxin, Ann Aschengrau, ScD, and colleagues from Boston University School of Public Health in Massachusetts note in their report.

PCE readily crosses the blood-brain barrier and has a high affinity for the lipophilic tissues in the central nervous system. The exact mechanisms for its neurotoxic effects remain unclear but include peroxidation of cell membrane lipids, alterations in the fatty acid profile of the brain, and loss of myelin and interactions with neuronal receptors.

Exposure to PCE has been shown to cause mood changes, anxiety, and depression in people who work with it. To date, the long-term effect of this chemical on children exposed to PCE has been less clear, although there is some evidence that children of people who work in the dry cleaning industry have an increased risk for schizophrenia.

To investigate further, the Boston team studied individuals born between 1969 and 1983 to married women who lived in towns in Cape Cod, Massachusetts, that had vinyl-lined asbestos-cement water pipes.

Dose Response

These pipes were installed by public water companies from the late 1960s through early 1980 to solve alkalinity problems in dead-end sections of their distribution systems. The liner was applied by spraying a mixture of vinyl resin and PCE. More than a decade elapsed before officials discovered that large quantities of PCE were leaching into the public water supplies.

Surveys conducted in 1980 found that drinking water supplies in Cape Cod had PCE levels ranging from 1.5 to 7750 μ/L. Because replacing the pipes was prohibitively expensive, systematic flushing and bleeding were used to reduce levels below 40 μ/L, which was the maximum recommended level at the time. The maximum contaminant level for PCE is now set at 5 μ/L.

The Cape Cod cohort included 1512 individuals. The participants included 831 persons with both prenatal and early childhood exposure to PCE and 547 persons who had not been exposed. Participants provided information on mental illnesses, demographic and medical characteristics, other sources of solvent exposure, and places of residence from the time of their birth through 1990.

PCE exposure from the vinyl-liner water distribution pipes was assessed using water distribution system modeling software that incorporated a leaching and transport algorithm, the authors explain.

The researchers did not see any meaningful increase in the risk for depression with prenatal and childhood PCE exposure (risk ratio [RR], 1.1; 95% confidence interval [CI], 0.9 - 1.4). This finding was "both surprising and maybe reassuring," Dr. Aschengrau told Medscape Medical News, given that earlier research in PCE-exposed adults suggested an increased risk for depressive disorders.

However, the researchers did find that individuals with any exposure during gestation and early childhood were at increased risk for bipolar disorder (RR, 1.8; 95% CI, 0.9 - 3.5) and PTSD (RR, 1.5; 95% CI, 0.9 - 2.5). Further increases in risk were observed for bipolar disorder (RR, 2.7; 95% CI, 1.3 - 5.6) and PTSD (RR,1.7; 95% CI, 0.9 - 3.2) among persons with the highest exposure levels.

The risk of schizophrenia was also elevated among exposed individuals (RR, 2.1; 95% CI, 0.2 - 20.0), but the number of cases was too small to draw reliable conclusions, the authors note.

"Risk Remains Real"

The researchers note, however, that a study published in 2007 in Schizophrenia Research found a 3.4-fold increased risk for schizophrenia (95% CI, 1.3 - 9.2) among the offspring of parents who worked as dry cleaners. Adjusting for confounding factors did not appreciably alter the finding.

Mary Perrin, DrPH, assistant professor of psychiatry and environmental medicine from the New York University Langone Medical Center in New York City, worked on that study. Medscape Medical News asked her for her thoughts on the Cape Cod study.

"No one epidemiological study is going to prove anything. You have to build evidence, and my personal opinion is that it's another brick in the wall showing that we really need tighter regulation of these substances in the environment. The animal literature is quite clear on this," said Dr. Perrin.

She added that the Cape Cod study is "methodologically a good study. The authors articulated the limitations of the study, which you can't ignore, and did not overstate the results, which are very interesting."

Dr. Aschengrau and colleagues say the limitations of their study include the possibility of exposure misclassification and a lack of data on water consumption and bathing habits; self-reported mental illness data; and possible residual confounding as a result of missing data on several risk factors for mental illness.

The low response rate is another limitation. It is possible that individuals with mental illnesses preferentially ignored requests to participate, the investigators note. This would have reduced the number of cases in the final sample. However, available evidence suggests that this did not introduce selection bias, the authors say.

Dr. Aschengrau also noted that it is not possible to calculate the exact amount of PCE the participants in the study were exposed to.

"Levels of PCE were recorded as high as 1550 times the currently recommended safe limit. While the water companies flushed the pipes to address this problem, people are still being exposed to PCE in the dry cleaning and textile industries and from consumer products, and so the potential for an increased risk of illness remains real," she said.

Dr. Aschengrau and her colleagues added that independent investigations of similarly exposed populations are needed to corroborate their findings.

The study was supported by the National Institute of Environmental Health Sciences. Study investigator David Ozonoff, MD, PhD, is Co-Editor-in-Chief of Environmental Health. Dr. Ozonoff recused himself from all decisions regarding acceptance and publication of the manuscript. In 1980, he served as a witness in bankruptcy court in a suit against the Johns-Manville Corporation, manufacturers of the vinyl-lined asbestos-cement water pipes. He has also testified in personal injury and property damage cases involving exposure to tetrachloroethylene and trichloroethylene. Three years ago, Dr. Aschengrau served as a consultant in a personal injury case involving chlorinated solvent contamination. None of the parties in any litigation supported, reviewed, or had knowledge of this study. The other authors of this study have disclosed no relevant financial relationships.

Environmental Health. 2012;11:2. Published online January 20, 2012.

    
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