Radiofrequency in Five Vancouver Schools: Exposure Standards Not Exceeded

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Artnarong Thansandote, PhD; Gregory B. Gajda, MASc; David W. Lecuyer

The rapid growth of the cellular telephone industry has resulted in the installation of numerous "base stations"or radio transmitters to relay telephone calls. Base-station antennas are mounted on free-standing towers or attached to rooftops or the sides of buildings. Many communities are concerned about the possible health risks associated with the emission of radiofrequency (RF) radiation from these antennas.

In 1997, a base-station antenna was installed in a church cross located across the street from an elementary school in Vancouver. Some of the parents of the students became concerned that the RF radiation from this and other antennas could affect their children's health. In response, we conducted a survey on RF radiation in and around 5 schools selected in consultation with the concerned parents. Three of these schools were selected because they had a cellular telephone base-station antenna on or near the school property. The others, which were not located near a base station, were selected as controls.

Although the purpose of the survey was to determine the actual levels of RF radiation in the analog (first-generaion cellular phone) and personal communication services (PCS, the new generation of digital cellular phone) cellular base-station frequency bands, measurements also covered AM, FM and TV broadcast frequencies where possible. We present a brief report of the survey findings and compare the results with the exposure limits outlined in Health Canada's Safety Code 6¹.

The RF radiation exposure limits specified in the code are based on a review of the scientific research conducted over the past 30 years on the health effects of RF radiation exposure. Effects of exposure at levels well above the limits include burns, cataracts, behavioural changes and damage to the central nervous system². These effects could occur at very high environmental levels of RF radiation, such as on the axis of high-power stationary radar antenna at a few meters from teh source, which is unlikely to exist in the general environment. No health effects from chronic exposure to RF radiation below the limits defined in the safety code have been conclusively demonstrated.

The dose of RF radiation is related to the energy absored per unit mass. Unfortunately, dose measurements are possible only under well-controlled laboratory conditions. For the purposes of our survey, the "power density" of the radiation, expressed as microwatts per square meter (µW/m²), was taken as a practical indicator of exposure. More than 160 measurements were carried oiut at the selected schools at indoor and outdoor sites frequented by both staff and students.

The measured power densities did not exceed the safety code limits (Table 1). In light of the current scientific understanding of the risks of RF radiation exposures, we conclude that the levels measured during our study posed no health risk to the students, school staff or the general public in or around the 5 Vancouver schools involved.

Table 1: Maximum measured power densities of radiofrequency radiation in areas accessible by staff and students in 5 Vancouver schools

Power density, µW/m²

Frequency band	School 1*	School 2£	School 3¥	School 4§	School 5§	Safety Code 6 limit1
Analog	0.10	25 600	2250	0.12	2.90	5.9 million
PCS	1620	NA	0.23	0.25	0.51	10 million
AM	442	NA	37.1	51.0	87.2	208 million
FM	6	NA	9.16	0.64	0.99	2 million
TV	0.61	NA	0.05	0.012	0.011	2 million
Note: PCS = personal communication services (digital cellular phone service), analog = first-generation cellular phone service, NA = data not available because of measurement time limitation. * PCS antenna across street. £ Analog antenna on school roof. ¥ Analog antenna across street. § No antenna in vicinity.

Dr. Thansandote, Mr. Gajda and Mr. Lecuyer are with the Radiation Protection Bureau, Health Canada, Ottawa, Ont.

Competing Interests: None declared.

References

1. Limits of exposure to radiofrequency fields at frequencies from 10 kHz - 100 GHz: safety code 6 Ottawa: Department of National Health and Welfare; 1991. Cat. no H46-2/90-160.
2. Environmental health criteria 137: electromagnetic fields (300 kHz - 300 GHz). Geneva: World Health Organization; 1993. Also available from the Canadian Public Health Association, 400-1565 Carling Avenue, Ottawa, ON K1Z 8R1; fax: 613 725-9826; hrc-cds@cpha.ca.

This article was taken from the Canadian Medical Association Journal, May 4, 1999, 160(9), pp.1311-1312, Published by the Canadian Medical Association, 1867 Alta Vista Drive, Ottawa, ON, K1G 3Y6.

In CMAJ see:

• Radiofrequency radiation: What's safe?:  Letter 1;  Letter 2;  Letter 3
• Editorial:  Radiofrequency radiation exposure and other environmental concerns