Radio Frequency Nonionizing Radiation in a Community Exposed to Radio and Television Broadcasting

Article excerpt

Exposure to radio frequency (RF) nonionizing radiation from telecommunications is pervasive in modern society. Elevated disease risks have been observed in some populations exposed to radio and television transmissions, although findings are inconsistent. This study quantified RF exposures among 280 residents living near the broadcasting transmitters for Denver, Colorado. RF power densities outside and inside each residence were obtained, and a global positioning system (GPS) identified geographic coordinates and elevations. A viewshed model within a geographic information system (GIS) characterized the average distance and percentage of transmitters visible from each residence. Data were collected at the beginning and end of a 2.5-day period, and some measurements were repeated 8-29 months later. RF levels logged at 1-min intervals for 2.5 days varied considerably among some homes and were quite similar among others. The greatest differences appeared among homes within 1 km of the transmitters. Overall, there were no differences in mean residential RF levels compared over 2.5 days. However, after a 1- to 2-year follow-up, only 25% of exterior and 38% of interior RF measurements were unchanged. Increasing proximity, elevation, and line-of-sight visibility were each associated with elevated RF exposures. At average distances from > 1-3 km, exterior RF measurements were 13-30 times greater among homes that had > 50% of the transmitters visible compared with homes with [less than or equal to] 50% visibility at those distances. This study demonstrated that both spatial and temporal factors contribute to residential RF exposure and that GPS/GIS technologies can improve RF exposure assessment and reduce exposure misclassification. Key words: broadcasting, electromagnetic fields, exposure assessment, GIS, nonionizing radiation, radio, television. doi:10.1289/ehp.8237 available via http://dx.doi.org/[Online 20 September 2005]

**********

Public exposure to radio frequency (RF) fields from sources such as radio and television (TV) broadcasting is common in industrialized countries. As of 1999, an estimated 14,000 radio and TV stations were on the air in the United States [Federal Communications Commission (FCC) 1999]. Public concerns about the potential health effects of exposure to RF nonionizing radiation stem partly from the pervasiveness of these exposures. The primary toxicologic response associated with RF exposure occurs through tissue heating, and current exposure standards for the general public are based primarily on a thermal mechanism of action [FCC 1999; National Radiological Protection Board (NRPB) 2003]. Ambient RF power densities from telecommunications devices are typically well below these levels (NRPB 2003). However, the issue of whether health effects occur at nonthermal RF exposure levels in the general population remains controversial. Elevated cancer rates have been reported in some residential human populations exposed to radio and TV transmissions (Ahlbom et al. 2004). Nonthermal RF exposures may also be linked with hematologic, neurologic, reproductive, and cardiovascular disorders [NRFB 2003; World Health Organization (WHO) 1993]. Results from studies published to date have not established a clear cause-effect relationship between RF exposure from radio and TV broadcasting and adverse health outcomes in humans. Previous epidemiologic investigations of the relationship between residential RF exposure and human cancers have relied almost exclusively on distance to RF transmitters to characterize exposure (Ahlbom et al. 2004). Few studies have examined factors that contribute to spatial or temporal variation in residential RF exposure (Allen 1991; Anglesio et al. 2001; Dahme 1999; Mantiply et al. 1997; Tell and Mantiply 1980). Potential limitations with respect to exposure misclassification may therefore apply to previous studies of residential RF exposures and adverse health effects. …