Because of the report by an expert panel of the International Agency for Research on Cancer (IARC) describing radiofrequency electromagnetic fields (RF-EMF) from cell phone use as a “possible carcinogen”, and the controversy it has spawned [see cartoon at:

 http://long-island.newsday.com/walt-handelsman-1.812005?tags=cell+phones],

a special ad- hoc session was held during the Epidemiology Congress in Montreal in late June. Present at the meeting were Jonathan Samet who chaired the panel for the IARC, and Jack Siemiatycki who chaired the epidemiology work group. It was an opportunity for attendees to get a behind-the-scenes account of what transpired at the IARC to produce the report. The session was chaired by NCI’s Martha Linet, Chief of the Radiation Epidemiology Branch at the National Cancer Institute.

Concern about cell phones is justified by the large number of users and the change in patterns of use which have shown dramatic increases. According to IARC, the number of mobile phones is estimated at 5 billion globally.

The IARC Process

The presenters began by outlining the process for evaluating potential carcinogens at the IARC. In doing this work, the reviewers must abide by the existing classification scheme previously established for potential carcinogens. In this scheme, agents can be classified as category 1 when sufficient evidence exists to implicate them, or agents can be put in category 2. In this category, a distinction is made between probable carcinogens, agents for which the evidence is limited in humans but sufficient in animals, and possible carcinogens, agents for which the evidence is limited in humans and less than sufficient in animals. A third category is for agents for which the evidence is inadequate in humans and inadequate or limited in animals.

According to the presenters, there are 248 other agents in the 2b group, including coffee and Styrofoam.

Findings Reviewed

Among the findings that were considered by the group are the time trends in brain cancer which have failed to show a clear increase in brain cancer or glioma. Scientists reportedly disagree about whether or not we should expect an increase over time by now, with some saying yes and others no.

Another type of evidence examined was a large record link study in Denmark which followed persons from the mid 1990’s until 2002 for a median follow up of 8 years. This study produced a null result for gliomas as an endpoint (RR 1.04).

Other case control studies have been carried out in Sweden, the US, and Finland. These results have been negative with the exception of a study in Sweden. However, the methods in this Swedish study are not described in great detail and questions have been raised about the methods.

Perhaps the most critical study is the 13 country Interphone research which was negative except for the group with the largest amount of cumulative call time. According to Siemiatycki, the interpretation of these results was “difficult and controversial”.

Classification

The majority of the members of the IARC advisory group voted to classify cell phone in the 2b category with a minority against that conclusion and wanting to call cell phone risk “not classifiable”.

As noted by one lay observer at the Montreal session, the meaning of the term “possible” for the experts at the IARC review and for the epidemiologists in attendance at the Congress in Montreal is really quite different from the meaning attached to that designation by the general public outside the Congress. The difference is in the amount of uncertainty conveyed by the word “possible” which would appear to be much greater in the minds of the experts who reviewed the evidence carefully than what crops up in the minds of the general public when they hear the term “possible”.

New Results

Now the IARC report is likely to be questioned further following the release of a study in children and adolescents showing no increase in brain tumors, and a study published in the July 1 issue of the AJE which did not find evidence of tumors preferentially located in the areas of the brain with the highest exposure to RF-EMF. Because the IARC panelists had concluded, despite inadequate evidence, that cell phones could pose some risk, concern about children with multiple years of exposure was a concern. The current studies should help to further allay those concerns.