[ RadSafe ] A paper in the January 2009 issue of the Health Phys cancer incidence in highback ground radiation areas of Kerala

parthasarathy k s ksparth at yahoo.co.uk
Tue Dec 23 03:19:56 CST 2008

Dear radsafers,

An interesting paper on cancer incidence in high background areas of
kerala is published in the January 2009 issue of Health Physics. The
following abstract of the paper is available at:

A critical appraisal of the paper may be of great interest 



Health Physics.    96(1):55-66, January 2009.
Nair, Raghu Ram K. *; Rajan, Balakrishnan *; Akiba, Suminori +;
Jayalekshmi, P *++; Nair, M Krishnan [S]; Gangadharan, P [S]; Koga,
Taeko **; Morishima, Hiroshige **; Nakamura, Seiichi ++; Sugahara,
Tsutomu ++  
mdash;: The coastal belt of Karunagappally, Kerala, India, is known for
high background radiation (HBR) from thorium-containing monazite sand.
In coastal panchayats, median outdoor radiation levels are more than 4
mGy y-1 and, in certain locations on the coast, it is as high as 70 mGy
y-1. Although HBR has been repeatedly shown to increase the frequency
of chromosome aberrations in the circulating lymphocytes of exposed
persons, its carcinogenic effect is still unproven. A cohort of all
385,103 residents in Karunagappally was established in the 1990's to
evaluate health effects of HBR. Based on radiation level measurements,
a radiation subcohort consisting of 173,067 residents was chosen.
Cancer incidence in this subcohort aged 30-84 y (N = 69,958) was
analyzed. 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. Following 69,958
residents for 10.5 years on average, 736,586 person-years of
observation were accumulated and 1,379 cancer cases including 30 cases
of leukemia were identified by the end of 2005. Poisson regression
analysis of cohort data, stratified by sex, attained age, follow-up
interval, socio-demographic factors and bidi smoking, showed no excess
cancer risk from exposure to terrestrial gamma radiation. The excess
relative risk of cancer excluding leukemia was estimated to be -0.13
Gy-1 (95% CI: -0.58, 0.46). In site-specific analysis, no cancer site
was significantly related to cumulative radiation dose. Leukemia was
not significantly related to HBR, either. Although the statistical
power of the study might not be adequate due to the low dose, our
cancer incidence study, together with previously reported cancer
mortality studies in the HBR area of Yangjiang, China, suggests it is
unlikely that estimates of risk at low doses are substantially greater
than currently believed.
(C)2009Health Physics Society 
 Copyright © 2008, Health Physics Society. All rights reserved.
Published by Lippincott Williams & Wilkins.
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