2021 Volume 10 Issue 2 Pages 74-81
The coastal belt of Karunagappally, Kerala, India is known for high natural background radiation (HNBR) from thorium-containing monazite sand. A cohort of all residents in Karunagappally was established in the 1990s to evaluate the health effects of HNBR. Following the cohort of 149,585 residents aged 30-84 for 19.1 years on average, approximately 2,851,688 person-years of observation were accumulated. The cumulative radiation dose for each individual was estimated based on outdoor and indoor dosimetry of each household, taking into account sex- and age-specific house occupancy factors. Using Karunagapally cancer registry, 6,804 cancer cases excluding leukemia were identified by the end of 2017. Poisson regression analysis of cohort data stratified by sex, attained age, follow-up periods and the original/additional subcohorts estimated an excess relative risk of cancer excluding leukemia as -0.05 Gy-1 (95% CI: -0.33, 0.29) when adjusted for education, bidi smoking, tobacco chewing, and alcohol drinking in a statistical model. In site-specific analyses, no cancer site was significantly related to cumulative radiation dose. Leukemia was not significantly related to HNBR, either.
