The world's biggest investigation¹ on possible links between cell phone use and brain tumours² is inconclusive（非决定性的，无结果的） , according to a Canadian scientist who collaborated³ on the Interphone International Study Group. Jack⁴ Siemiatycki, a professor at the University of Montreal and an epidemiologist（流行病学家） at the University of Montreal Hospital Research Center, says restricted access to participants compromised（妥协，连累） the validity（有效性，正确性） of results of the study to be published in the May 18 International Journal of Epidemiology. "The findings of the Interphone Study are ambiguous（模糊不清的） , surprising and puzzling," he says. The Interphone International Study Group, which examined whether cellular⁵ radio frequencies could be correlated to brain tumours, was coordinated⁶ by the International Agency for Research on Cancer. The investigation was led by 21 epidemiologists from Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the United Kingdom. Over 10,000 people took part in the study: cell phone users; non cell phone users; cell phone users who survived brain cancer as well as brain cancer survivors⁷ who had never used cell phones.

Paradoxical（矛盾的） findings

"If we combine all users and compare them with non-users, the Interphone Study found no increase in brain cancer among users. In fact, surprisingly, we found that when we combine users independently of the amount of use, they had lower brain cancer risks than non-users," says Dr. Siemiatycki, who teaches in the University of Montreal Faculty⁸ of Medicine. "However, the study also found heavy users of cell phones appeared to be at a higher risk of brain tumours than non-users."

Why the discrepancy⁹（不符，矛盾） ? Simply put（简言之） , scientists are unsure. Attention has focused on the methodology（方法学） of the study and, in particular, on the representativeness of the study subjects who participated. With participation¹⁰ rates in the range of 50 percent to 60 percent of eligible¹¹（合格的，合适的） subjects, it is possible that the participants did not provide an accurate portrait（肖像，描写） of cell phone usage among cancer cases and among healthy control subjects. Dr. Siemiatycki argues this problem arose because of constraints¹²（限制，约束） imposed on researchers by ethics¹³ committees intended to protect potential research subjects.

"Ethics reviews are now so rigid¹⁴ that scientists from Canada, the United States and Europe are losing the kind of access to medical databases and to study subjects that is needed to conduct studies such as this one. Ethics committees increasingly require that researchers work through treating physicians, professionals who are already overworked, to recruit（招募） their patients. This may work for clinical research exploring treatment of cancer, in which physicians often have a professional or personal interest, but it does not work for investigations¹⁵ into the causes of cancer. This flawed system can produce biased¹⁶（有偏见的） study results."

Despite the inconclusive results of the Interphone Study, consumers should not panic about possible risks related to cell phones, stresses Dr. Siemiatycki. "If there are risks, they are probably pretty small. Should anyone be concerned about potential dangers of cell phones, they can remedy（治疗，补救） the issue by using hands-free devices and avoid exposure to radio frequencies around their head."