Journal of Toxiocology and Environmental Health (JTEH)

Residential Radon and Lung Cancer: End of the Story?

A large study of the risks of radon shows that it can cause cancer at levels even below those previously recommended, according to research published in a special issue of the Journal of Toxicology and Environmental Health, Part A (Volume 69, Numbers 7-8) in 2006 with Guest Editors Jan M. Zielinski and R. William Field.

The study, which pooled data from seven North American residential radon studies, showed that exposure to radon concentrations of 3.0 picocuries per liter (pCi/L) of air increased the risk of lung cancer 11 to 21 percent during an exposure period of five to 30 years. The U.S. Environmental Protection Agency's currently recommends reducing radon levels if they exceed 4.0 pCi/L.

“Findings from this large-scale epidemiologic study provide direct evidence that residential radon exposure is a major public health concern,” says William Field, one of the co-editors of the special issue and associate professor of occupational and environmental health and epidemiology at the University of Iowa.  “The findings of the study indicate that prolonged residential radon exposure even under the U.S. Environmental Protection Agency's action level of 4 pCi/L significantly increases lung cancer risk.”

Radon is a naturally occurring, odourless, radioactive gas that is generated by the decay of uranium in the soil and accumulates in enclosed areas such as basements.  It is the leading cause of lung cancer among nonsmokers, causing 21,000 deaths in the U.S. each year, according to the EPA.

It has been known since the 1970s from studies of miners and animals that high concentrations of radon are associated with lung cancer.  However, prior case-control studies of residential radon exposure have had conflicting results.  Some indicate a weak association between radon levels and lung cancer while others show no association.

The current study pooled data from seven studies conducted in Connecticut, Iowa, New Jersey, Missouri, and Utah, South Idaho, and Winnipeg, Canada.  A total of 3,662 cases and 4,966 controls represents the largest epidemiologic study of radon ever performed in North America.  Its results agree with a similar pooled study of data from 13 European studies involving 7,148 cases and 14,208 controls.
“The North American and European pooling provides unambiguous and direct evidence of an increased lung cancer risk even at residential radon exposure levels below the U.S. EPA's action level," says Dr. Field.

In addition to the combined analysis of the seven studies, the special issue of the Journal of Toxicology and Environmental Health, Part A includes papers on exposure measurement, radon dosimetry, and epidemiologic methods, as well as a section on radon risk management that includes reports on two recent workshops sponsored by Health Canada and the World Health Organization on the subject.

“Policies for testing and control can now be based with confidence in the assumption that risk increases with concentration and that a ‘safe’ concentration cannot be specified,” says Dr. Jonathan Samet of the Johns Hopkins University School of Public Health in his preface to the special issue.  Samet, who served as chair of the U.S. National Research Council Committee on the Biological Effects of Ionizing Radiation (BEIR VI), says that the studies suggest a linear, dose-response, non-threshhold relationship between exposure to radon and lung cancer risk.

Published twenty-four times per year, the Journal of Toxicology and Environmental Health, Part A features strictly refereed original research in the field of environmental toxicology in general as well as in special interest fields such as target organ toxicities, immunotoxicology, risk assessment, carcinogenesis, mutagenesis, ecotoxicology, environmental factors affecting health, and aquatic toxicology.

Subscription information for the Journal of Toxicology and Environmental Health, Part A or a sample copy can be obtained from the address below.  To view the special issue (Vol. 69, Numbers 7-8), go to www.tandf.co.uk/journals/titles/15287394.asp.