Residential radon and brain tumour incidence in a Danish cohort.
BACKGROUND
Increased brain tumour incidence over recent decades may reflect improved diagnostic methods and clinical practice, but remain unexplained. Although estimated doses are low a relationship between radon and brain tumours may exist.


OBJECTIVE
To investigate the long-term effect of exposure to residential radon on the risk of primary brain tumour in a prospective Danish cohort.


METHODS
During 1993-1997 we recruited 57,053 persons. We followed each cohort member for cancer occurrence from enrolment until 31 December 2009, identifying 121 primary brain tumour cases. We traced residential addresses from 1 January 1971 until 31 December 2009 and calculated radon concentrations at each address using information from central databases regarding geology and house construction. Cox proportional hazards models were used to estimate incidence rate-ratios (IRR) and 95% confidence intervals (CI) for the risk of primary brain tumours associated with residential radon exposure with adjustment for age, sex, occupation, fruit and vegetable consumption and traffic-related air pollution. Effect modification by air pollution was assessed.


RESULTS
Median estimated radon was 40.5 Bq/m(3). The adjusted IRR for primary brain tumour associated with each 100 Bq/m(3) increment in average residential radon levels was 1.96 (95% CI: 1.07; 3.58) and this was exposure-dependently higher over the four radon exposure quartiles. This association was not modified by air pollution.


CONCLUSIONS
We found significant associations and exposure-response patterns between long-term residential radon exposure radon in a general population and risk of primary brain tumours, adding new knowledge to this field. This finding could be chance and needs to be challenged in future studies.
Diet, Genes and Environment, Danish Cancer Society Research Centre, Copenhagen, Denmark ; Construction and Health, Danish Building Research Institute, Aalborg University, Aalborg, Denmark.
Elvira V
EV
Bräuner
Zorana J
ZJ
Andersen
Claus E
CE
Andersen
Camilla
C
Pedersen
Peter
P
Gravesen
Kaare
K
Ulbak
Ole
O
Hertel
Steffen
S
Loft
Ole
O
Raaschou-Nielsen
D001932:Brain Neoplasms / Q000453:epidemiology* / Q000209:etiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011886:Radon / Q000633:toxicity*
D011886:Radon