Answer to Question #922 Submitted to "Ask the Experts"

• Background radiation and cancer incidence in Kerala, India: Karanagappally cohort study. Health Phys 96(1):55–66; 2009.
• Cancer and noncancer mortality among inhabitants in the high background radiation area of Yangjiang, China (1979–1998). Health Phys 102(2):173–81; 2012.
• Human exposure to high natural background radiation: what can it teach us about radiation risks? J Radiol Prot 29(2A):A29–42; 2009.

There have been several studies published in particular on the health of people who live in the high-background radiation area of Yangjiang, China. More discussion of this can be found in the Ask the Experts Question 1254.

Even though there are significant differences in background radiation doses across the United States and the world, mainly due to different cosmic and terrestrial components, there does not seem to be a direct correlation between background radiation and cancer rates. The background cancer rate in the United States is about 25–30 percent, depending on which cancers are included, and this number seems to be fairly constant from areas that have low background radiation to areas that are much higher. This is something that would not be expected if one were to follow the linear, no-threshold hypothesis; this is one of the pieces of evidence against this concept. But there is still controversy and continuing research in this area until we can better understand the long-term effects of low levels of radiation.

Kenneth Krieger, CHP