Breckenkamp J, Berg-Beckhoff G, Münster E, Schüz J, Schlehofer B, Wahrendorf J, Blettner M. Feasibility of a cohort study on health risks caused by occupational exposure to radiofrequency electromagnetic fields. Environ Health. May 29, 2009. Ahead of print.
The widespread use of cordless and cellular phones has raised concerns about their potential health effects due to exposure to radiofrequency electromagnetic fields (RF-EMF). Research activity on this subject has been intense, but the results are far from conclusive. A limitation of the cohort studies published to date is the short follow-up period which may not be long enough for many diseases to manifest themselves. In studies using occupational exposure data, it is often difficult or too expensive to determine individual level exposure data.
The aim of the present study was to examine the feasibility of conducting a study on the health risks of exposure to radiofrequency fields (other than from mobile phones) among a cohort of persons in which a reasonable exposure assessment was feasible and in which a potential for some high and long-lasting exposure was present.
Different occupational groups and amateur radio operators were considered potentially eligible. Necessary information was identified from professional organizations, visits of industry sites, contacts with committees and administrative bodies, as well as a literature review. Possible outcomes of the cohort study were identified by reviewing the literature. Morbidity and mortality outcomes were initially considered, but restricting to mortality would allow a retrospective design and was eventually decided upon. Eligibility criteria were applied to identified cohorts: (i) subjects must have been exposed continuously at a level higher than that of the general population over ten years or more and duration of employment as well as information about the affiliation to an occupation group must be available; (ii) prospective exposure estimates should be possible on an individual level and a retrospective estimate should be possible at least on an aggregated level; (iii) it must be possible to choose an unselected cohort from personnel records and demographic variables must be available; and (iv) follow-up of all members of the cohort must be feasible.
Twenty occupational settings and amateur radio operators were considered as potentially exposed to RF-EMF. Exposure levels were rated by experts such as occupational hygienists. Of the 21 situations described, 18 were not considered further for one or more of the following reasons: (i) exposure to RF-EMF rare or at a very low level; (ii) small number of exposed subjects; and (iii) automated and shielded working processes. The 3 groups of persons further considered were: (1) personnel of medium/short wave broadcasting stations; (2) amateur radio operators; and (3) workers on dielectric heat sealers.
Implications and Limitations
Most of the identified occupational cohorts cannot be realistically used for a cohort study. Further inspection of the three promising groups revealed major limitations, including low power, a low average exposure, and difficult exposure assessments. These results are based on the situation in Germany and are only partly transferable to other countries.
This feasibility study found that an occupational exposure study to investigate occupational RF-EMF exposure in Germany is not appropriate at this time.