探討台灣地區發生兒童白血病與居住地暴露於石化與交通空氣污染的相關性

Association of Childhood Leukemia with Residential Exposure to Petrochemical and Traffic Air Pollution in Taiwan

翁旭惠(Hsu-Huei Weng)

指導教授 ： 楊俊毓

共同指導教授 ： 吳聰能(Trong-Neng Wu)

高雄醫學大學/健康科學院/職業安全衛生研究所/博士(2009年)

摘要

石化工業是主導我國整體經濟發展的主要產業，它在我國工業中佔了相當大的比重。在台灣，石化產業已被認為是主要的工業空氣污染來源，其造成的環境污染問題也相當嚴重。而隨著經濟與科技的進展，機動車輛數目與日俱增，機動車輛需使用石化產品、也會排放廢氣，故伴隨著工業化與現代化而來的交通空氣汙染也日益嚴重。過去國際間有關石油、石化工業暨交通空氣汙染對人體長期之健康效應的研究，以癌症的論述最多。由石化工業排放之污染物，已被確認為環境致癌物質。國際癌症研究所(IARC)亦將汽、柴油引擎廢氣列為可能致癌物。石油及石化污染物逸散於居住環境中，是否對居住於工業區或工廠附近、毗鄰交通要道或繁忙道路、加油站附近居民長期健康造成影響，甚至致癌，是目前各國學者所亟欲探知的問題。因此，本文即以三種不同的環境汙染指標來探討台灣地區石化工業暨交通空氣汙染與兒童白血病之關係。
第一部份是以配對病例對照研究法探討石化工業空氣污染與兒童白血病之關係。我們由行政院衛生署得到1995至2005年之台灣地區居民死亡資料檔，再以病例對照的方式來進行研究，病例組的條件為：所有0-19歲死於白血病的兒童；對照組則排除癌症及呼吸道疾病者，依照性別、年齡、隨機抽樣採一對一配對。不論病例組或對照組，此年齡層大部分屬於在學學生，以避免職業暴露的干擾。且居住及死亡地點必須為同一個地區，用以確定研究對象確實居住於該地區。並以1989年製造工廠的僱用人數做計算，以(該地區所有僱用石化工人數目總和)除以(該地區所有人口數)，當做該地區石化工業的百分比，以此做為居民暴露於石化工業污染的指標。將所有個案組及對照組居住地點，由上列方法求出個別的石化工業百分比，再平均分割為三等分以利比較。結果發現，經調整可能干擾因子後，石化工業區高污染暴露區得兒童白血病的勝算比都比低污染區高，且都達到統計學上顯著差異。
第二部分是以配對病例對照研究法探討交通空氣污染與兒童白血病之關係。我們由行政院衛生署得到1995至2005年之台灣地區居民死亡資料檔，再以病例對照的方式來進行研究，病例組的條件為：所有0-14歲死於白血病的兒童；對照組則排除癌症及呼吸道疾病者，依照性別、年齡、隨機抽樣採一對一配對。不論病例組或對照組，此年齡層大部分屬於在學學生，以避免職業暴露的干擾。且居住及死亡地點必須為同一個地區，用以確定研究對象確實居住於該地區。並以二氧化氮(NO2)濃度來當做居民暴露於與交通工具有關的空氣污染的指標。將所有個案組及對照組居住地點，由上列方法求出個別的二氧化氮暴露量，再平均分割為三等分以利比較。結果發現，經調整可能干擾因子後，高度與中度空氣污染區的兒童白血病的勝算比都比低度污染區高，且都達到統計學上顯著差異。並且二氧化氮濃度上升與兒童白血病的風險，有一個顯著且愈來愈大的趨勢。
第三部分是以配對病例對照研究法探討交通空氣污染與兒童白血病之關係。我們由行政院衛生署得到1996至2006年之台灣地區居民死亡資料檔，再以病例對照的方式來進行研究，病例組的條件為：所有0-14歲死於白血病的兒童；對照組則排除癌症及呼吸道疾病者，依照性別、年齡、隨機抽樣採一對一配對。不論病例組或對照組，此年齡層大部分屬於在學學生，以避免職業暴露的干擾。且居住及死亡地點必須為同一個地區，用以確定研究對象確實居住於該地區。並以加油站密度(PSD)來當做居民暴露於與交通工具有關的空氣污染的指標。將所有個案組及對照組居住地點，由上列方法求出個別的加油站密度，再平均分割為三等分以利比較。結果發現，經調整可能干擾因子後，高PSD與中PSD鄉鎮的兒童白血病的勝算比都比低PSD高，且都達到統計學上顯著差異。並且加油站密度愈大與兒童白血病的風險，有一個顯著且愈來愈大的趨勢。

關鍵字

兒童白血病 ； 空氣污染 ； 居住地 ； 石化 ； 交通

並列摘要

Leukemia is the most common cancer in childhood. Studies to date failed to firmly establish risk factors for childhood leukemia except for ionizing radiation, chemotherapy agents, and certain inherited genetic disorders. Benzene has been identified as a cause of leukemia. A number of studies have reported that childhood leukemia is associated with exposure to high levels of traffic-related air pollution. In Taiwan, petrochemical industry and road traffic are the major sources of ambient air pollution in urban areas. The evidence for an association between exposure to petrochemical- or traffic-related air pollutants and the development of childhood leukemia is still inconclusive. Matched case-control studies were conducted using childhood deaths that occurred in Taiwan. Data on all eligible childhood leukemia deaths were obtained from the Bureau of Vital Statistics of the Department of Health. The control group consisted of children who died from causes other than neoplasms or diseases which were not associated with respiratory complications. The controls were pair matched to the cancer cases by gender, year-of-birth, and year-of-death. Each matched control was selected randomly from the set of possible controls for each case. Three different exposure indicators were applied to evaluate the exposure-response relationship. (1) The proportion of a municipality’s total population employed in the petrochemical industry in a municipality was used as an indicator of a resident's exposure to air emissions from the petrochemical industry. The subjects were divided into three levels (≦25th percentile; 25th–75th percentile; >75th percentile) according to the levels of the indicator. After controlling for possible confounders, results showed that children who lived in the group of municipalities characterized by the highest levels of petrochemical air pollution had a statistically significant higher risk of developing leukemia than the group that lived in municipalities with the lowest petrochemical air pollution levels. (2) Air quality data for recorded concentrations of nitrogen dioxide (NO2) from study municipalities for 1995–2005 were obtained as an indicator of a subject's exposure to air emissions from motor vehicles. The subjects were divided into tertiles according to the levels of NO2 in their residential municipality. The results showed that there was a significant exposure-response relationship between exposure to traffic exhaust pollutants and the risk of leukemia among young children after controlling for possible confounders. (3) Data on the number of petrol stations in study municipalities were collected from the two major petroleum supply companies, Chinese Petroleum Corporation (CPC) and Formosa Petrochemical Corporation (FPCC). The petrol station density (per square kilometer) (PSD) for study municipalities was used as an indicator of a subject’s exposure to benzene and other hydrocarbons present in evaporative losses of petrol or to air emissions from motor vehicles. The subjects were divided into tertiles according to PSD in their residential municipality. The results showed that there was a significant exposure-response relationship between PSD and the risk of leukemia development in young children after controlling for possible confounders. In conclusion, the findings of our studies suggest that further investigation is warranted in establishing the association between petrochemical or traffic-related air pollution exposure and childhood leukemia.

並列關鍵字

childhood leukemia ； air pollution ； residential ； petrochemical ； traffic

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