Development of health-based exposure limits for radiofrequency radiation from wireless devices using a benchmark dose approach

Abstract

Background: Epidemiological studies and research on laboratory animals link radiofrequency radiation (RFR) with impacts on the heart, brain, and other organs. Data from the large-scale animal studies conducted by the U.S. National Toxicology Program (NTP) and the Ramazzini Institute support the need for updated health-based guidelines for general population RFR exposure.

Objectives: The development of RFR exposure limits expressed in whole-body Specific Absorption Rate (SAR), a metric of RFR energy absorbed by biological tissues.

Methods: Using frequentist and Bayesian averaging modeling of non-neoplastic lesion incidence data from the NTP study, we calculated the benchmark doses (BMD) that elicited a 10% response above background (BMD₁₀) and the lower confidence limits on the BMD at 10% extra risk (BMDL₁₀). Incidence data for individual neoplasms and combined tumor incidence were modeled for 5% and 10% response above background.

Results: Cardiomyopathy and increased risk of neoplasms in male rats were the most sensitive health outcomes following RFR exposures at 900 MHz frequency with Code Division Multiple Access (CDMA) and Global System for Mobile Communications (GSM) modulations. BMDL₁₀ for all sites cardiomyopathy in male rats following 19 weeks of exposure, calculated with Bayesian model averaging, corresponded to 0.27-0.42 W/kg whole-body SAR for CDMA and 0.20-0.29 W/kg for GSM modulation. BMDL₁₀ for right ventricle cardiomyopathy in female rats following 2 years of exposure corresponded to 2.7-5.16 W/kg whole-body SAR for CDMA and 1.91-2.18 W/kg for GSM modulation. For multi-site tumor modeling using the multistage cancer model with a 5% extra risk, BMDL₅ in male rats corresponded to 0.31 W/kg for CDMA and 0.21 W/kg for GSM modulation.

Conclusion: BMDL₁₀ range of 0.2-0.4 W/kg for all sites cardiomyopathy in male rats was selected as a point of departure. Applying two ten-fold safety factors for interspecies and intraspecies variability, we derived a whole-body SAR limit of 2 to 4 mW/kg, an exposure level that is 20-40-fold lower than the legally permissible level of 0.08 W/kg for whole-body SAR under the current U.S. regulations. Use of an additional ten-fold children's health safety factor points to a whole-body SAR limit of 0.2-0.4 mW/kg for young children.

Keywords: Benchmark modeling; Exposure guidelines; Radiofrequency radiation; SAR; Specific Absorption Rate.