RE: Cancer Rates

["Sandy Perle" <sandyfl@EARTHLINK.NET>]

I am interested in comments regarding this study:



{PRIVATE "TYPE=PICT;ALT=Thyroid Ca/Radiation in Workplace"}Cancer Tied to Workplace Radiation Low doses might play a role in thyroid cancer



Medical workers exposed to low doses of radiation on the job might face an 

increased risk of thyroid cancer. So, too, might dental, various industrial and nuclear 

power workers, claims a new Canadian study that examined data on a half-million 

people. Linking radiation exposure to cancer is nothing new. It's well documented 

that atomic bomb survivors and those who've received high doses of radiation to 

treat non-cancerous diseases have a higher incidence of cancer later in life.



Now, however, the new study links higher incidence of cancer -- and specifically 

thyroid cancer -- to low-dose radiation. The researchers used data collected by the 

Canadian National Dose Registry, which has monitored radiation exposure of 

workers since 1951, and compared it to the Canadian Cancer Data Base.



They connected 3,737 workers with cancer (2,098 men and 1,639 women) to 

radiation exposure between 1969 and l988. Most victims were between the ages of 

21 and 85. "The thyroid cancer incidence ¦ is greater than would be expected, and 

the incidence in women is very significant," says lead researcher Willem N. Sont, of 

Canada's Radiation Protection Bureau.



Sont says this study is the first to focus on medical workers who are exposed to low-

dose radiation over a period of time. But he quickly adds that, despite all the linkages 

found, "we don't know the cause, [and] we cannot say for sure it's from radiation." 

"We can only speculate," Sont says. Findings appear in the current issue of the 

American Journal of Epidemiology.



Radiation exposure is measured in doses, taking into account both internal and 

external exposure to ionizing radiation, which includes gamma, beta and X-rays. The 

amount of radiation absorbed by a gram of tissue is expressed in millisieverts, or 

mSv. The average dose received by the study participants was 6.64 mSv, with men 

receiving a much higher average dose than women: 11.50 mSv vs. 1.75 mSv, the 

study says.



Not everyone agrees with the researchers' conclusions, however. John Boice, 

scientific director of the International Epidemiology Institute and a professor of 

medicine at Vanderbilt University, points out that people normally get between 1 mSv 

and 3 mSv a year from natural sources, like cosmic rays and the air we breathe. 

"Thyroid cancer is a major effect of radiation, [but] it comes from exposure in 

childhood, before the age of 20," Boice maintains.



The fact that the Canadian study finds excesses of thyroid cancers in adults may be 

attributable to "much better medical care and screening and advancements in 

detection" rather than radiation exposure, he says. Sont says the researchers also 

found a higher-than-expected link between low-dose radiation exposure and 

melanoma, a virulent form of skin cancer. But again, he says, "There are other 

factors which cause melanoma. A very obvious one is exposure to ultraviolet [light]." 

With that, Boice concurs. "Melanoma is not associated with ionizing radiation," Boice 

says. "Basal cell and squamous cell cancers have been linked to high dosages, but 

when melanoma pops up, we think of other potential causes." Sun exposure 

generally comes to mind, he says.



Incidence of other cancers -- including testicular, pancreatic and colon cancer -- also 

was found by the Canadian researchers, but they say it's not possible from this study 

alone to declare cause and effect. The next step, Sont says, is to look at dose 

information for workers after l988. "With smaller doses, the cancer is harder to find, 

and that's why this study will make contributions," he says. "But linking cancer to 

radiation exposure is more difficult, and more work needs to be done."











**************************************************************

*

Sandy Perle                           

Director, Technical                           

ICN Worldwide Dosimetry Service     

ICN Plaza, 3300 Hyland Avenue   

Costa Mesa, CA 92626             



Tel: (714) 545-0100 / (800) 548-5100  Extension 2306 

Fax: (714) 668-3149  



E-Mail: sperle@icnpharm.com      

E-Mail: sandyfl@earthlink.net                      

                 

Personal Website: http://sandy-travels.com/

ICN Worldwide Dosimetry Website: http://www.dosimetry.com/



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