Occupational exposures to radiofrequency fields: results of an Israeli national survey

Abstract

Relatively high exposures to radiofrequency (RF) fields can occur in the broadcast, medical, and communications industries, as well in occupations that use RF emitting equipment (e.g. law enforcement). Information on exposure to workers employed in these industries and occupations is limited. We present results of an Israeli National Survey of occupational RF field levels at frequencies between ~100 kHz and 40 GHz, representing Industrial Heating, Communications, Radar, Research, and Medicine. Almost 4300 measurements from 900 sources across 25 occupations were recorded and categorised as 'routine', 'incidental', or 'unintended'. The occupation-specific geometric means (GMs) of the percentage of the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) for each of the three exposure scenarios are presented together with the geometric standard deviation (GSD). Additionally, we present estimates of occupation-specific annual personal exposures and collective exposures. The vast majority of the GM of routine exposures ranged from a fraction to less than 1% of ACGIH TLVs, except for Walkie-Talkie (GM 94% of ACGIH), Induction Heating (17%), Plastic Welding (11%), Industrial Heating (6%) and Diathermy (6%). The GM of incidental and unintended exposures exceeded the TLV for one and 14 occupations, respectively. In many cases, the within-occupation GSD was very large, and though the medians remained below TLV, variable fractions of these occupations were projected to exceed the TLV. In rank order, Walkie-Talkie, Plastic Welding, and Induction Heating workers had the highest annual cumulative personal exposure. For cumulative collective exposures within an occupation, Walkie-Talkie dominated with 96.3% of the total, reflecting both large population and high personal exposure. A brief exceedance of the TLV does not automatically translate to hazard as RF exposure limits (issued by various bodies, including ACGIH) include a 10-fold safety factor relative to thermal thresholds and are based on a 6 min averaging period.

Radiofrequency Exposure Amongst Employees of Mobile Network Operators and Broadcasters

“…Previous measurements in telecom and broadcasting have indicated that routine exposure is generally low 16 and though some spot measurements around the VHF antennas did exceed 100 V m −1 these were made at the rear of antennas close to steelwork where re-radiation can occur or at splitters where leakage was acknowledged. All of these measurements were made in the highly localised conditions of near-field radiation and are not necessarily indicative of whole-body exposure.…”

“…Traditionally occupational exposures have been assessed through the measurement of electric and magnetic field strength using portable hazard survey instrumentation 23 – 25 . However, the worker's exposure depends on the source's power, modulation scheme and field pattern, as well as the worker's behaviour and adherence to proper safety practice 16 .…”

“…More recently, personal monitors have been recommended as the best means of assessing individual exposures of those working in the telecommunication and broadcasting industries 26 , 27 . Their convenience means that they are suited for use in future epidemiological studies 14 , 16 .…”

“…Only a limited amount of research has been published on occupational RF exposures of workers in the telecommunication and broadcast industries 14 – 16 . Though the combination continues to evolve, the types of RF source have been established for some time and here results are presented from a study that explored the exposure of telecommunication and broadcast employees in the UK in the early 2000 s 14 .…”

Electromagnetic Dosimetry of Radiofrequency Portable Transceivers Used in Front of the Face

“…Peak values of 10-g average local SARs were calculated in various situations and found bellow 2 W/kg from distances of 8 cm onward. Analyzing the practical use of portable transceivers by professionals over a national survey focused on various occupations, in the article published in 2015 by an Israelian group [14], the authors concluded that the cumulative collective exposures over all workers within an occupation, portable transceivers exposure dominated with 96% of the total, conducting to field levels exceeding safe limits for incident field strengths and also to the highest SARs among all RF sources. In this regard, present approach aimed at presenting a series of dosimetric results coming from tests made in an accredited laboratory with one model of dual-band portable transceiver emitting in the UHF band and with a model of walkie-talkie, both emitting on the same frequency, for comparison of the results.…”