- Why are residential epidemiology studies of radon so complicated?
There are many factors that must be considered when designing a residential radon epidemiology study. It is very expensive and often impossible to design a study that takes all the pertinent factors into consideration. These factors include:
Mobility: people move a lot over their lifetime; it is virtually impossible to go back and test every home where an individual has lived;
Housing Stock Changes: over time, older homes are often destroyed or remodeled, thus radon measurements will be non-existent or highly varied; a home's radon level may change, higher or lower, over time if new ventilation systems are installed, the occupancy patterns are substantially different, or the home's foundation shifts or cracks appear.
Inaccurate Histories: often a majority of the lung cancer cases (individuals) being studied are deceased or too sick to be interviewed by researchers. This requires reliance on second-hand information which may not be as accurate. These inaccuracies primarily affect:
Residence History: a child or other relative may not be aware of all residences occupied by the patient - particularly if the occupancy is distant in time or of relatively short duration. Even if the surrogate respondent is aware of a residence they may not have enough additional information to allow researchers to locate the home.
Smoking History: smoking history historically has reliability problems. Individuals may under-estimate the amount they smoke. Conversely, relatives or friends may over-estimate smoking history.
Other: complicating factors other than variations in smoking habits include an individual's: genetics, lifestyle, exposure to other carcinogens, and home heating, venting and air conditioning preferences.
- Are there any residential epidemiology studies finding increased risk of lung cancer due to radon?
Yes, several residential epidemiology studies have found an increased risk of lung cancer due to residential exposures (i.e. Sweden, New Jersey ) These studies are also just pieces of a much bigger puzzle that is being put together. The National Academy of Sciences' BEIR VI Report examines in detail the available studies of radon and lung cancer in homes, as well as the studies of underground miners.
- When will we know for sure about radon's health risk?
We already have a wealth of scientific data on the relationship between radon exposure and the development of lung cancer. The scientific experts agree that the occupational miner data is a very solid base from which to estimate risk of lung cancer deaths annually. While residential radon epidemiology studies will improve what we know about radon, they will not supersede the occupational data. Health authorities like the Centers for Disease Control (CDC), the Surgeon General, the American Lung Association, the American Medical Association, and others agree that we know enough now to recommend radon testing and to encourage public action when levels are above 4 pCi/L. The most comprehensive of these efforts has been the National Academy of Science's Biological Effects of Ionizing Radiation (BEIR VI) Report. This report reinforces that radon is the second-leading cause of lung cancer and is a serious public health problem. As in the case of cigarette smoking, it would probably take many years and rigorous scientific research to produce the composite data needed to make an even more definitive conclusion.
- Has the National Academy of Sciences (NAS) published a report on radon and lung cancer?
The NAS published its latest analysis of health research on radon, the Biological Effects of Ionizing Radiation (BEIR VI) Report in 1999. This is the most comprehensive review effort to date. The Committee was charged with:
reviewing all current miner and residential data, as well as all existing cellular-biological data,
comparing the dose per unit exposure effects of radon in mines and homes, and examining:
interactions between radon exposure and smoking, and
any exposure-rate effect (alteration of effect by intensity of exposure).
- What is meta-analysis, and does the Lubin/Boice meta-analysis prove that residential radon levels cause lung cancer?
Meta-analysis is a statistical attempt to analyze the results of several different studies to assess the presence or absence of a trend or to summarize results. Lubin and Boice conclude that the results of their meta-analysis are consistent with the current miner-based estimates of lung cancer risk from radon which place the number of radon-related deaths at approximately 15,000 per year in the United States.
Because meta-analysis has several inherent limitations (such as the inability to adequately explore the consistency of results within and between studies and to control for confounding factors) meta-analysis is NOT able to PROVE hat residential radon causes lung cancer, but it does provide additional GOOD SUGGESTIVE EVIDENCE. It is one more link in the "chain of evidence" connecting residential radon exposure to increased lung cancer risk.
Since the investigators performing a meta-analysis do not have access to the raw data on the individual study subjects, the analysis is based on the published relative risks and confidence intervals of the individual studies. Frequently, the impact of each study is weighted based on some factor which the meta-analysis authors feel is relevant to the reliability of each study's data. In the Lubin/Boice meta-analysis, the results of each individual study were weighted so that each study contributed in relation to the precision (relative lack of random or sampling errors) of its estimate.
The Lubin/Boice meta-analysis paper cites 5,000-15,000 lung cancer cases required for a single case-control study to have sufficient power to detect an exposure-response equal to that expected from miner studies. EPA has maintained that Public Health Service investigators claim 10,000-30,000 cases would be required.
- What has changed?
EPA asked Dr. Lubin this question. He indicated that nothing had changed, that the "science" of sample size estimation was something of a "black box," and that the number of cases required probably should be higher than the 5,000-15,000 cited in the paper.
If you are interested in finding a qualified radon service professional to test or mitigate your home, or you need to purchase a radon measurement device, you should:
Contact your State Radon Contact to determine what are, or whether there are, requirements associated with providing radon measurement and or radon mitigations/reductions in your State. Some States maintain lists of contractors available in their State or they have proficiency programs or requirements of their own.
Contact one or both of the two privately-run Radon Proficiency Program who are offering proficiency listing/accreditation/certification in radon testing and mitigation.