Answer to Question #12828 Submitted to "Ask the Experts"
Category: Micro/Radio Waves, Radar & Powerlines — Satellite Dishes
The following question was answered by an expert in the appropriate field:
I am an air traffic controller at a tower facility with an Airport Surface Detection Equipment Model 3 ground movement radar mounted on top of the tower cab. Our tower is ~20 years old, and over those years, two of ~80 individuals who have worked here long term have developed brain cancer. While I realize that there is no proven link between this radar and cancer, it has still caused me concern as this is a ground movement radar, not one projecting upward into the sky. My question is two-fold. First, could long-term exposure in close proximity to a powerful radar be detrimental to human health (we are approximately 20 feet below the radar)? And secondly, is there any device I could use to measure the amount of radiofrequency (RF) or electromagnetic frequency (EMF), or other potentially harmful energy penetrating the tower cab and operations level, and what values would be considered harmful? The radar specifications are listed below. Thank you for this helpful service you provide!
Specifications:
- Frequency: 15.7–17.7 GHz
- Pulse repetition frequency (PRF): 13–20 kHz
- Pulsewidth (t): 36 nanoseconds
- Peak power: 10 kW
- Instrumented range: 500–24,000 ft
- Beamwidth: ß=0.25; e=1.6 degrees
- Antenna rotation: 1 second (60 rpm)
To answer your first question, radar emits brief but high intensity pulses of RF radiation that is potentially hazardous at excessive exposure levels. However, despite some epidemiological studies of radar operators, there is no clear evidence that working near radar is hazardous, as long as exposures are within international safety limits (which are similar to those in the United States) The World Health Organization has a fact sheet on the topic.
Health agencies have some concern that long-term exposures to RF energy is associated with cancer. The International Agency for Research on Cancer (IARC) has classified RF energy as a "possible" carcinogen, but this indicates that evidence supports some level of suspicion, and is not a statement that such fields actually do cause or promote cancer. Most of the epidemiological evidence that IARC considered involved long-term use of cell phones, which is a very different exposure situation from the one you describe. Nearly all RF energy at 15 GHz that is incident on the body is absorbed within about 1 millimeter from the surface of the body, i.e., in skin. For all practical purposes this radiation does not reach the brain at all.
To respond to your second question, various instruments are available to measure RF exposures from the radar, ranging from inexpensive hobbyist-grade meters available online, to very expensive survey instruments from companies that specialize in RF safety. Hobbyist-grade meters are too unreliable to be useful. Professional-grade meters of the kind needed to accurately measure exposures to pulsed radar fields such as you describe are generally quite expensive and require considerable expertise to use, although some high-quality personal exposure monitors are available for about $2,000. Measuring RF exposures, particularly in occupational settings such as yours, should be done by a qualified expert with appropriate equipment, it is not a do-it-yourself project. If you think that you may be exposed to RF energy above safety limits by all means ask your industrial safety people to survey the fields.
Overexposure situations involving radar are usually associated with inadvertent exposures to workers in the main beams directly in front of the antennas, and I would guess that your exposure is well within safety limits. But that is only an educated guess, and if you have any concerns, the exposure should be directly measured by a qualified expert.
Kenneth R. Foster, PhD
Professor of Bioengineering
University of Pennsylvania