Radium-Contaminated Water: a Risk Factor for Cancer of the Upper Digestive Tract

There is a high incidence of oral, pharynx and esophagus cancer among males in Na Mom district in SongkhlaProvince in Thailand, an area where radium concentration in shallow well water is found to be higher than otherareas in this province. A population-based case control study was conducted from June to November 2004 to determinethe association of oral exposure to radium-contaminated water and cancer of the upper digestive tract in the district.Thirty-two confirmed cases and 128 sex and five-year birth cohort matched neighborhood controls were selected bymultistage sampling from six villages in four sub-districts. All subjects were verified to have been permanent residentsin the district for more than 10 years. Thirty cases were dead at the time of the study, thus their relatives wereinterviewed to determine their amount of water drinking, tobacco smoking, alcohol drinking, betel chewing andexposure to other potential risk factors in the past. The other two cases and all controls were directly interviewed.The concentration of radium in shallow well water at the subject’s houses was estimated using a contour map of Ra-226 in the water at the location of their residence. The results showed a strong and dose-dependent associationbetween consumption of radium-contaminated shallow well water and cancer of the upper digestive tract. Inmultivariate analysis controlled for important risk factors of the cancer, the odds ratios for exposure to oral radiumconsumption 50-100 mBq/day and >100 mBq/day compared with <50 mBq/day were 2.83 (95% CI: 0.50-16.19) and29.76 (95% CI: 4.39-201.6) respectively. The risk also increased with consumption of fresh water fish which mighthave been contaminated by dissolved radium in the water. This study offers the first evidence of the associationbetween radium and cancer of the upper digestive tract to the world literature. Further studies with other methodssuch as area-wide correlation of radium-uranium concentration and the incidence of the cancer and case-controlstudies in other populations are needed to confirm the evidence.