The Association of Nonage Chronic Arsenic Exposure, Methylation Levels of Arsenic Metabolism Genes, and the Risk of Cancer Development

Previous studies reported that exposing to high level of arsenic from drinking water was related to increased risks of cancer. There is evidence showed that long-term arsenic exposure induced skin cancer, liver cancer, lung cancer, kidney cancer, bladder cancer and prostate cancer. Evidence from animal models showed that arsenic exposure can cause tumor growth and arsenic exposure in utero may affect carcinogenic. Therefore, this study will aim (1) to investigate the correlation between arsenic exposure before adulthood and the risk of cancer; (2) to investigate the correlation between arsenic metabolism-related genes and the degree of methylation of arsenic metabolism ability; (3) to explore the correlation between the arsenic metabolism-related gene methylation and arsenic exposure before adulthood. The main study cohort used in the study will be from the cohort of arsenic exposed area located on the northeastern of Taiwan established between 1991 and 1994. The data will link to National Health Insurance database, cancer registry files, death registry to identify the mortality rate and incidence rate in cancer. The the type of cancer will be determined by ICD9 and ICD10. Age of drinking well water less than 20 years old and arsenic exposure more than 50^g/L will be classified as arsenic exposure before adulthood. We will randomly selected 800 people to do urine test, and will randomly selected 500 people to do gene methylation analysis in those who did urine test before. Statistical analysis included Chi-square test, Student’s t-test, binomial test, logistic regression, cox proportional hazard model, and RERI. SAS 9.3 will be the statistic software used in this study. We expect those who exposure arsenic before adulthood have higher risk in cancer than those who exposure arsenic after adulthood. And those who exposure arsenic before adulthood have lower urinary arsenic metabolism capacity in the population who have do urine test. In the population who have do gene methylation analysis, we expect methylation level in arsenic metabolism genes will be different between those who exposure arsenic before adulthood and those who exposure arsenic after adulthood.