Cancer Mortality in the High Background Radiation Areas of Yangjiang, China during the Period between 1979 and 1995

Abstract

The objective of the present study was to estimate cancer risk associated with the low-level radiation exposure of an average annual effective dose of 6.4 mSv (including internal exposure) in the high background-radiation areas (HBRA) in Yangjiang, China. The mortality survey consisted of two steps, i.e., the follow-up of cohort members and the ascertainment of causes of death. The cohort members in HBRA were divided into three dose-groups on the basis of environmental dose-rates per year. The mortality experiences of those three dose groups were compared with those in the residents of control areas by means of relative risk (RR). During the period 1987-1995, we observed 926,226 person-years by following up 106,517 subjects in the cohort study, and accumulated 5,161 deaths, among which 557 were from cancers. We did not observe an increase in cancer mortality in HBRA (RR = 0.96, 96% CI, 0.80 to 1.15). The combined data for the period 1979-95 included 125,079 subjects and accumulated 1,698,316 person-years, observed 10,415 total deaths and 1,003 cancer deaths. The relative risk of all cancers for whole HBRA as compared with the control area was estimated to be 0.99 (95% CI, 0.87 to 1.14). The relative risks of cancers of the stomach, colon, liver, lung, bone, female breast and thyroid within whole HBRA were less than one, while the risks for leukemia, cancers of the nasopharynx, esophagus, rectum, pancreas, skin, cervix uteri, brain and central nervous system, and malignant lymphoma were larger than one. None of them were significantly different from RR = 1. Neither homogeneity tests nor trend tests revealed any statistically significant relationship between cancer risk and radiation dose. We did not find any increased cancer risk associated with the high levels of natural radiation in HBRA. On the contrary, the mortality of all cancers in HBRA was generally lower than that in the control area, but not statistically significant.

Cancer Mortality, State Mean Elevations, and other Selected Predictors

“…In high NBR areas in China cancer mortality was also lower compared to lower NBR areas (Tao et al 2000). On the other hand, a small increased risk of cancer has been found for nuclear workers exposed to low levels of radiation (Cardis et al 2005).…”

The proportion of childhood leukaemia incidence in Great Britain that may be caused by natural background ionizing radiation

“…36 Of these, only the Chinese study is well developed, and as yet there are no indications of an excess risk of childhood leukaemia. 33,34 The radon component of the overall RBM doses estimated by Simmonds et al, 9 is rather less than 10%, suggesting that, under the 70/30 ERR/EAR model mixture, only about 2% of childhood leukaemia cases in Great Britain are due to exposure to radon and its radioactive progeny. As noted in Supplementary Material A, the doses from radon and other internally deposited radionuclides are those used by Simmonds et al, 9 which are based on ICRP models that were in use at the time.…”

“…32 However, in neither the Danish nor the French study were individual dose measurements used. Ecological studies have been conducted in various high background areas, in particular those in China, 33,34 India 34,35 and Iran. 36 Of these, only the Chinese study is well developed, and as yet there are no indications of an excess risk of childhood leukaemia.…”

Association between Local External Gamma Rays and Frequency of Cancer in Babol-Iran

“…Tao et al (2000) have indicated that the mortality of all cancers in high background radiation areas (HBRA) in China have been lower than that in the ordinary background radiation area (OBRA), but these differences in incidences are not statistically significant. Sun et al (2000) reported an excess of relative risk (-0.11) of solid cancer mortality after prolonged exposure to natural high background radiation for the same geographical area and time period as the Tao et al (2000) study. Chen and Wei (1991) have reported that although the frequencies of chromosome aberrations in HBRA inhabitants compared with OBRA residents are higher, the differences in the cancer mortality rates for the HBRA and OBRA are not significant.…”

“…Some others have shown no association between low dose radiation and cancer mortality (Allwright et al 1983). There are also some reports indicating inverse relationship between radiation and cancer incidence (Nambi and Soman 1987;Tao et al 2000). This study is an effort to investigate a possible relationship between reported cancer incidence and external terrestrial radiation dose level in residential areas of Babol which are located in Mazandaran province in the north part of Iran.…”