Excess Relative Risk of Solid Cancer Mortality after Prolonged Exposure to Naturally Occurring High Background Radiation in Yangjiang, China

Abstract

A study was made on cancer mortality in the high-background radiation areas of Yangjiang, China. Based on hamlet-specific environmental doses and sex- and age-specific occupancy factors, cumulative doses were calculated for each subject. In this article, we describe how the indirect estimation was made on individual dose and the methodology used to estimate radiation risk. Then, assuming a linear dose response relationship and using cancer mortality data for the period 1979-1995, we estimate the excess relative risk per Sievert for solid cancer to be -0.11 (95% CI, -0.67, 0.69). Also, we estimate the excess relative risks of four leading cancers in the study areas, i.e., cancers of the liver, nasopharynx, lung and stomach. In addition, we evaluate the effects of possible bias on our risk estimation.

A pilot study for dose evaluation in high-level natural radiation areas of Yangjiang, China

“…These studies did not find any statistically significant excess mortality due to cancer or non-cancer diseases [8,9]. The examinations were made mainly against external exposure.…”

“…A China-Japan cooperative study was organized and radiological and epidemiological studies were carried out [2,[5][6][7][8][9][10]. These studies did not find any statistically significant excess mortality due to cancer or non-cancer diseases [8,9].…”

Commentary on information that can be drawn from studies of areas with high levels of natural radiation

“…Occupancy factors were obtained from a questionnaire survey conducted from 1991 to 1993 on 5291 subjects living in over 88 hamlets. Individual external effective dose estimates were derived for each subject in the cohort based on the hamlet-specific indoor and outdoor air kerma rates and on sex-and agespecific occupancy factors [1]. Migration data were taken into account in the dose estimation.…”

Results of Yangjiang study in China and an experience of Ramsar survey in Iran

“…This fact enabled us to estimate individual dose rates from ambient radiation dose rates and occupancy factors. Using a similar indirect method for estimating individual doses, Sun et al [5] estimated the excess relative risk of solid cancer mortality in these HLNRAs, Yangjiang.…”