土壤重金屬含量與口腔癌發生率之空間相關性探討

Abstract

口腔癌為臺灣地區急遽成長的癌症之ㄧ，男性成長率達17.89 %為近幾年來成長最快的癌症。本研究目的希望藉由統計分析方法初步找出導致口腔癌之可能環境影響因子，進一步提供未來臨床醫學及流行病學領域上相關研究方向之參考。以鄉鎮為單元，考慮環境因子土壤重金屬砷、鎘、鉻、銅、汞、鎳、鉛、鋅，以及生活習慣因子嚼食檳榔、抽菸為導致口腔癌之危險因子。結合Spearman等級相關和空間自相關Moran’s I檢定，挑選出與口腔癌呈現相關且具有空間特性之變數。最後比較不考慮空間特性的傳統迴歸模式與納入空間特性的空間誤差模式兩者結果之差異。許多研究已證實嚼食檳榔及抽菸之習慣因子皆會導致口腔癌，但在考慮空間特性之情況下，兩項致癌危險因子與口腔癌發生之間關係並不顯著，主要是由於兩致癌危險因子並無存在空間相關性，造成在此一研究模式下無法突顯出此兩項致癌危險因子的特性。而在環境因子中，唯獨土壤重金屬鎳與口腔癌的發生呈現顯著相關。推斷彰化地區為口腔癌高發區之原因，可能是因為在類似的嚼食檳榔及抽菸盛行率之下的鄉鎮單元，彰化地區當地土壤重金屬鎳濃度含量偏高所造成。導致彰化地區土壤鎳濃度較高的主因為早期急速工業化，工廠農地混雜且管理不當。因此推論工業化造成工廠集中、工廠管理不健全為促使居住於此環境污染下居民罹患口腔癌之風險增高。

The incidence rate of oral cancer in Taiwan is one of the rapidly growing cancers. For male, the increasing rate of oral cancer incidence is 17.89% between 2001 and 2005, and it is the fastest growing cancer. The purpose of this study was to find out the probably environmental factors of oral cancer by preliminary statistical methods step by step. These results can provide for areas of clinical medicine and epidemiology as a direction in the future. We took the soil heavy metal contents which include As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and the lifestyle factors which include betel quid chewing (BQC) and cigarette smoking (CS) as risk factors for oral cancer. Spearman rank correlation in combination with spatial autocorrelation analysis was used to determine variables which positively correlate with oral cancer and have spatial characteristics. Finally, we compared the differences between these results of ordinary least regression and spatial regression error model. Many studies have been confirmed that BQC and CS habits will lead to oral cancer, but these results of this study revealed that the two lifestyle factors and oral cancer incidence are not significant when taking account of spatial characteristics. These showed that the spatial statistical method or the statistical unit of data types were unable to highlight the characteristics of these two lifestyle factors. For the environmental factors, nickel is the only one heavy metal which significantly correlates to oral cancer. Changhua county is with the most serious nickel contamination, so we infer that is why Changhua with higher incidence of oral cancer than the other towns with similar BQC or CS rates. Residents living in contaminated areas who suffer from a higher risk of oral cancer. And this study reveals that there is the most significant correlation between the soil heavy metal nickel and oral cancer incidence.