Exploring the Correlation between Oral Cancer and Heavy Metal Pollution
Date Issued
2011
Date
2011
Author(s)
Chiang, Chi-Ting
Abstract
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.
Subjects
oral cancer
heavy metal pollution
betel quid chewing
spatial clustering
principal component analysis
spatial regression
SDGs
Type
thesis
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