EMF Database abstract: RADIOFREQUENCY EXPOSURE AND MORTALITY FROM CANCER OF THE BRAIN AND LYMPHATIC/HEMATOPOIETIC SYSTEMS.

EMF Database sample abstract

Last modified on: Monday, July 31, 2000
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RADIOFREQUENCY EXPOSURE AND MORTALITY FROM CANCER OF THE BRAIN AND LYMPHATIC/HEMATOPOIETIC SYSTEMS.
(Eng.) Morgan, R. W.; Kelsh, M. A.; Zhao, K.; Exuzides, K. A.; Heringer, S.; Negrete, W. [Exponent Health Group, 149 Commonwealth Dr., Menlo Park, CA 94025 (RR/M.A.K., R.W.M., K.Z., K.A.E., S.H., W.N.)] Epidemiology 11(2):118-127; 2000
Funding: Motorola, Inc.

Possible associations between occupational radiofrequency radiation (RFR) exposure and mortality from brain and lymphatic/hematopoietic system cancers examined. The cohort consisted of 195,775 persons employed by US Motorola Corporation facilities for at least 6 mo, of which at least 1 day was between January 1, 1976 and December 31, 1996. Motorola employees were chosen for study because Motorola has been active in the design, manufacture, testing, and use of wireless devices (such as two-way radios, defense and space communication devices, pagers, and cellular telephones) for over 50 yr and it was assumed that its employees would have a higher probability of RFR exposure than the general population. Occupational exposure occurred at RF frequencies of 30, 150, and 450 MHz for two way radios (beginning in the 1960s), 800 MHz for cellular telephones, and higher frequencies for microwave communications devices. Most Motorola employees had no significant occupational exposures to extremely low frequency electromagnetic fields (ELF EMFs), ionizing radiation, or to solvents or other chemical agents. Such exposures were not evaluated in this study. The cohort was followed through December 31, 1996 at which time its vital status was determined through reviews of the Social Security Administration Master Mortality and the National Death Index and retrieval of death certificates for identified deceased workers. A job exposure matrix (JEM) was created to classify each of 9,724 job titles into one of 4 RFR exposure categories. The background exposure category, which involved exposures which were similar to RFR levels experienced by the general public, included persons in administrative and support jobs who rarely encountered workplace RFR exposures. Workers in the low exposure category had infrequent low-level RFR exposures and included those who had job titles such as assembler, inspector, operator, supervisor, and assembly technician. Moderate RFR exposure workers included persons who routinely used handheld radios or worked in RF product development. This group included security, maintenance, and some supervisory staff and, for some business sectors, engineers and technicians. Workers in the high RFR exposure category included technicians, testers, and engineers involved with RF product testing, antenna systems, and government communications projects. Standardized mortality ratios (SMRs) were computed using mortality rates of the general populations of Arizona, Florida, Illinois, and Texas, states where most Motorola facilities are located, as external referents. Mortality was also assessed using internal comparisons of workers with moderate or higher RFR exposures to workers with either background or low RFR exposures. Rate ratios (RRs) were computed using Poisson regression models. The Motorola workforce had a relatively high proportion of female employees (44%) and was relatively young, with nearly 59% of its workers born between 1950 and 1970. Women tended to be employed in operator/assembly jobs (with low or no RFR exposure), whereas men tended to work in jobs with moderate or high RFR exposures. The occupational cohort of 195,775 workers contributed 2.7 million person-yr of follow-up. At the end of 1996, the cohort contained 6,296 deceased workers, 72,775 active workers, and 116,704 retired or terminated workers. Most of the cohort (72.1%) had no RFR exposure above the background level. Only 8.6% had moderate or high levels of RFR exposure. A pronounced "healthy worker" effect was observed, the all-cause SMR adjusted for age, gender, and race being 0.66 (95% confidence interval (CI) 0.64-0.67). The adjusted SMR for all cancers was 0.78 (CI 0.75-0.82). The SMR for central nervous system (CNS)/brain cancers was 0.60 (CI 0.45-0.78) and for all lymphomas/leukemias was 0.77 (CI 0.67-0.89). The RF-exposed subcohort of 24,621 workers (with peak exposure classified moderate or high) had SMR values close to the cohort as a whole. Internal cohort comparisons indicated mortality from CNS/brain cancers and all lymphoma/leukemias was also not elevated, the adjusted RRs being near 1.0 and below 1.0, respectively. SMRs were slightly above 1 for malignant melanoma of the skin, ovarian cancer, and Hodgkin's disease in the high and moderate RF-exposed groups, but these findings were based on small numbers of cases and were not significant. Analysis by duration of exposure or using different latency periods showed no risk increases for any class of malignancy with increasing exposure duration or latency (5, 10, or 20 yr lag periods). The authors concluded that although this study has limitations (the cohort being relatively young, only a small proportion being deceased, the rarity of the cancers of interest, and only a small percentage of the workforce being exposed to moderate or high levels of RFR), the findings do not support an association between occupational RFR exposure and brain/CNS or lymphatic/hematopoietic malignancies. (57 Refs). [Copyright 2000, Information Ventures, Inc.]
AUTHOR KEY WORDS: Brain neoplasms, Healthy worker effect, Leukemia, Lymphoma, Occupational health, Radiofrequency exposure, Neoplasms

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