Discontinuity in arsenic slope factor based on SW Taiwan data

The U.S. EPA (2010) cancer risk assessment bladder and lung cancers from inorganic arsenic ingestion is based on the Wu et al. (1989) study of 42 villages in the Blackfoot Disease-endemic area of Southwest Taiwan. Age-gender distributions were known for village person-year counts and cancer deaths. The EPA used a Poisson regression analysis, usually with the SW Taiwan reference population added as an additional data point and with the median village arsenic levels as the withinstudy exposure metric.