NEW YORK (Reuters Health) Nov 30 - Rates of squamous cell carcinoma may be elevated in areas with naturally high levels of the radioactive gas radon, a UK study suggests.
Radon, produced from the decay of naturally occurring uranium in soil and water, is already considered a risk factor for lung cancer. The U.S. Environmental Protection Agency (EPA) estimates that radon contributes to about 21,000 lung cancer deaths each year -- although smoking is also involved in the majority of those cases.
For the new study, reported online November 10th in Epidemiology, UK researchers looked at skin cancer rates across 287 postal codes in southwest England.
They found that the rates of squamous cell carcinoma varied by postal code. In some areas, the yearly rate per 100,000 people was about 35 cases; in others, it was as high as 182 cases.
There was an association between an area's average household radon level and its rate of squamous cell skin cancer. Where the radon level topped 230 Bq/m3, rates were 76% higher than in areas with the lowest average radon levels.
In the UK, radon levels above 200 Bq/m3 are considered "action" levels -- that is, people are advised to take steps to cut their home's radon concentration, such as sealing off cracks in basements and floors, and installing ventilation systems.
In the U.S., the EPA suggests taking those steps if home radon levels are around 150 Bq/m3. (The agency uses a different unit, giving the threshold as 4 pCi/L.)
The current study did not measure actual exposure to radon, which would vary by household even within a postal code with a high radon level, according to lead researcher Dr. Benedict W. Wheeler of the University of Exeter.
"This type of study is at the population/area level, so we only know that areas with high average household radon tend to also have high population rates of squamous cell carcinoma," Dr. Wheeler told Reuters Health in an email.
"It is possible that this relationship does not exist at the individual level," he added.
The researchers also had no information on people's individual behavior -- including how much time they spent in the sun. But if people in high-radon areas tended to spend more time in the sun, you'd expect to see higher rates of basal cell carcinoma as well, Dr. Wheeler noted. Yet in this study, radon levels were unrelated to rates of basal cell cancer or melanoma.
Wheeler said it is plausible that radon could specifically raise the risk of squamous cell cancers. Those tumors form in the more superficial layers of skin, while basal cell cancers arise in deeper layers. And radioactive particles from radon would not be expected to penetrate that deeply into the skin; the particles, Wheeler said, can be stopped by a sheet of paper.
A radon expert not involved in the study agreed.
"Radon decay products deposit on skin in a similar manner to how they plate out on surfaces in a home," said Dr. R. William Field, a professor at the University of Iowa College of Public Health who studies the health effects of radon.
Some researchers have suggested that radon exposure could be behind 2% of non-melanoma skin cancers, he told Reuters Health in an email.
Now, Dr. Field said, more rigorous studies are needed to see whether people's individual exposure to radon is related to their skin cancer risk. Dr. Wheeler agrees.
The EPA suggests that all homes be tested for radon, due to the lung cancer risk. Some state programs offer free or low-cost test kits; the agency has information on state radon contacts at http://www.epa.gov/radon/radontest.html.
Radon, produced from the decay of naturally occurring uranium in soil and water, is already considered a risk factor for lung cancer. The U.S. Environmental Protection Agency (EPA) estimates that radon contributes to about 21,000 lung cancer deaths each year -- although smoking is also involved in the majority of those cases.
For the new study, reported online November 10th in Epidemiology, UK researchers looked at skin cancer rates across 287 postal codes in southwest England.
They found that the rates of squamous cell carcinoma varied by postal code. In some areas, the yearly rate per 100,000 people was about 35 cases; in others, it was as high as 182 cases.
There was an association between an area's average household radon level and its rate of squamous cell skin cancer. Where the radon level topped 230 Bq/m3, rates were 76% higher than in areas with the lowest average radon levels.
In the UK, radon levels above 200 Bq/m3 are considered "action" levels -- that is, people are advised to take steps to cut their home's radon concentration, such as sealing off cracks in basements and floors, and installing ventilation systems.
In the U.S., the EPA suggests taking those steps if home radon levels are around 150 Bq/m3. (The agency uses a different unit, giving the threshold as 4 pCi/L.)
The current study did not measure actual exposure to radon, which would vary by household even within a postal code with a high radon level, according to lead researcher Dr. Benedict W. Wheeler of the University of Exeter.
"This type of study is at the population/area level, so we only know that areas with high average household radon tend to also have high population rates of squamous cell carcinoma," Dr. Wheeler told Reuters Health in an email.
"It is possible that this relationship does not exist at the individual level," he added.
The researchers also had no information on people's individual behavior -- including how much time they spent in the sun. But if people in high-radon areas tended to spend more time in the sun, you'd expect to see higher rates of basal cell carcinoma as well, Dr. Wheeler noted. Yet in this study, radon levels were unrelated to rates of basal cell cancer or melanoma.
Wheeler said it is plausible that radon could specifically raise the risk of squamous cell cancers. Those tumors form in the more superficial layers of skin, while basal cell cancers arise in deeper layers. And radioactive particles from radon would not be expected to penetrate that deeply into the skin; the particles, Wheeler said, can be stopped by a sheet of paper.
A radon expert not involved in the study agreed.
"Radon decay products deposit on skin in a similar manner to how they plate out on surfaces in a home," said Dr. R. William Field, a professor at the University of Iowa College of Public Health who studies the health effects of radon.
Some researchers have suggested that radon exposure could be behind 2% of non-melanoma skin cancers, he told Reuters Health in an email.
Now, Dr. Field said, more rigorous studies are needed to see whether people's individual exposure to radon is related to their skin cancer risk. Dr. Wheeler agrees.
The EPA suggests that all homes be tested for radon, due to the lung cancer risk. Some state programs offer free or low-cost test kits; the agency has information on state radon contacts at http://www.epa.gov/radon/radontest.html.
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