環境中重金屬污染與口腔癌之關聯探討

Abstract

近年來，愈來愈多因暴露重金屬污染引起的癌病在全球各處陸續被發現，臺灣地區幅員狹小、人口密集，工廠遍布於生活周遭，所面臨之挑戰更為嚴峻；因此，環境因子與疾病發生之間的關聯性研究儼然成為重要的公共衛生議題。疾病地圖之繪製廣泛地用來瞭解疾病群聚與環境的相關性，進而探索可能的致病環境因子。口腔癌是台灣地區最常見的頭頸部惡性腫瘤，近年來罹患率居高不下且增加速度更躍居所有癌症之冠。流行病學研究已確認嚼食檳榔、抽菸、喝酒等生活習性與口腔癌的發生有密切關係，臺灣東部的臺東縣和花蓮縣，以及中部的雲林縣和彰化縣同為口腔癌高發區，惟彰化縣嚼食檳榔盛行率排名居臺灣本島22個縣市的中間位置。因此，可能另有導致口腔癌的致病因子存在，環境污染被懷疑在口腔癌發生的過程中扮演著重要的角色。由於土壤與人類都是環境污染的承受體，藉由土壤中重金屬含量來反映人類在日常生活環境中可能暴露的重金屬量甚為合適。因此，除了考慮嚼食檳榔及抽菸兩項致病因子外，另加入以土壤重金屬含量代表環境因子來探究臺灣地區口腔癌發生與環境中重金屬污染之間的關係。本論文主要探討內容如下：第四章：藉由性別差異健康指標發現臺灣地區口腔癌發生率的性別差異性極大，且顯著大於同樣具有嚼食檳榔習慣之國家(如印度和泰國)，顯示此現象背後隱含有其他重要的因素促成口腔癌發生。第五章：運用兩種不同的空間聚集分析方法繪製口腔癌發生率、嚼食檳榔與抽菸盛行率及土壤重金屬含量之疾病地圖，並判斷各變數之間的空間相關程度。發現彰化縣雖為口腔癌發生之熱區，卻不是嚼食檳榔和抽菸盛行之熱區；然而，彰化縣為土壤重金屬污染之熱區，推判土壤重金屬與口腔癌之間具關聯性。第六章：結合主成分分析和空間迴歸分析結果顯示由鉻、銅、鎳、鋅組成的主成分一與口腔癌具顯著相關。第七章：透過病例對照研究法發現口腔癌患者血液中重金屬含量顯著高於非口腔癌患者之項目，與影響臺灣土壤重金屬污染之主成分一中的重金屬項目完全相同，突顯環境重金屬污染與口腔癌之間的相關性。綜合上述研究結果可知，環境中的重金屬污染可能是造成彰化地區口腔癌發生率極高原因的促進因子，其中又以電鍍業及金屬表面處理業工廠所產生的鉻、鎳與口腔癌的關係最為密切。希冀能提供未來在臨床醫學及流行病學各相關領域新的研究方向與議題。

In recent years, more and more cancer-related deaths caused by exposure to heavy metal pollution have been discovered around the world.  Taiwan is a small and densely populated island nation where factories are distributed over human residence, which faces more severe challenges.  Therefore, studying the correlation between environmental factors and disease occurrence has solemnly become an important public health issue.   Disease mapping is extensively used to understand the correlation between disease clusters and pollution ‘hot spots’ and to further explore the pathogenic potential of environmental factors. In Taiwan, oral cancer (OC) is the most common head and neck malignancy, which displays persistently high incidence rates of OC lately and is one of the fastest growing malignancies.  The habits of betel quid chewing (BQC), cigarette smoking (CS), and alcohol drinking are closely correlated with OC occurrence that has been demonstrated by epidemiological studies.  The eastern (Taitung and Hualien Counties) and central (Changhua and Yunlin Counties) Taiwan have persistently high incidence rates of OC.   However, the prevalence rate of BQC in Changhua County only ranks in the middle position among the 22 Counties.  There may be another pathogenic factor for the development of OC, and environmental pollution is suspected to play an important role in the process of developing OC.  Soil and the human body are both recipients of environmental pollutants.  The contents of heavy metals in soil reflect the level of the potential human exposure to heavy metal in the living environment that may be very appropriate.  Thus, in addition to BQC and CS lifestyle factors, the contents of soil heavy metals as environmental factors is to explore the correlation between OC occurrence and heavy metal pollution in the environment in Taiwan.  The main content of discussion in this thesis is described as follows:Chapter IV:  The great difference in Taiwanese OC incidence between male and female was found by the sex differential health indicator, which significantly higher than those countries with the similar prevalence of BQC such as India and Thailand.  This result implied that there may be other important factors resulting in the development of OC.Chapter V:  We used two different spatial clustering methods to draw the disease maps of OC incidence rates, the prevalence of BQC and CS, and heavy metal contents of soil, and we determine the magnitude of spatial correlation among the variables.  The discovery of Changhua County is a ‘hot spot’ of OC incidence, which is not a “hot spot” of the prevalence of BQC and CS; however, Changhua County is a ‘hot spot’ of soil heavy metal pollution that infers a correlation between soil heavy metals and OC.Chapter VI:  The results of integrating principal component analysis and spatial regression analysis revealed a spatial correlation between OC and heavy metals Cr, Cu, Ni, and Zn, the major determinants of principal component 1 (PC1).Chapter VII:  The case-control study found that heavy metals concentration in the blood of OC patients was significantly higher than that the of non-OC patients, these heavy metals were the same with the major components of PC1 influencing heavy metal pollution in Taiwan soil, which indicates a correlation between heavy metal pollution in the environment and OC.To conclude, we found that heavy metal pollution in the environment may be a promoting factor causing the high incidence of OC in Changhua County, and the electroplating and metal surface treatment factories producing heavy metals Cr and Ni are most closely related to OC.  This study hopes to suggest the new directions in novel research and new issues in related fields such as clinical medicine and epidemiology in the future.