Wendy Wolfson
Newswire21.com

Next time you are worried whether some pastime, such as smoking, using a tanning salon or talking on a cell phone will give you cancer, try to get inside the mind of an epidemiologist.

Cancer is quite common, second only to heart disease as a killer of Americans. At this point, smoking as a cause is probably a no-brainer. But cancer is actually difficult to link to environmental exposures. 

According to Dr. Peter Shields, professor of Medicine and Oncology, at Georgetown's Lombardi Cancer Center, only 47 percent of cancers can be associated with known causes. Shields has done a lot of work on the epidemiology of smoking, as well as other cancer environmental risk factors.

Unlike journalists, who like reporting on breakthrough studies, epidemiologists prefer the accumulated weight of evidence. "The big news for an epidemiologist is when a tenth study comes out and reinforces all the others," said Shields, who spoke recently during a National Press Foundation seminar sponsored by Pfizer.

Back in 1965, a researcher named Austin Bradford Hill came up with some useful general guidelines to figure out environmental causations of disease. According to these principles, an epidemiologist will look for: consistency among studies; what kind of response you get from a certain dose; the timing of exposure; the strength of an association; the specificity, or likelihood for a very specific population at a specific site; coherence - does the epidemiological research match up with laboratory data, and if the toxin in question is structurally similar to other known toxins.   

Cancer Myths
Shields then went on to list some of the top cancer myths still floating around: 

• What you do when you are young doesn't affect your risk for cancer.
• Living in a polluted city is more dangerous than smoking.
• Taking vitamins reduces the risk for cancer. In one meta analysis, taking beta carotene supplements gave smokers more cancer.
• Electrical devices cause cancer.
• Injuries cause cancer.
• Cancer is more common today.

The association between tanning beds and cancer is still disputed, but the link between repeated tanning under lamps and skin damage is increasingly clear.

The link between cancer and cell phone use was deemed unlikely by several studies. But some issues never die:  there was a meeting on brain cancer and cell phones on Capitol Hill the same evening that Shields spoke.