Answer to Question #316 Submitted to "Ask the Experts"

Q

Are 10-15kW RF welding machines dangerous? They work at 27.12Mhz. How much heat can they induce into a human body? Can they affect male fertility?

A

From a response you gave to our follow-up question regarding what product is produced by the machines in question, we assume you are asking about a dielectric "welder" used to heat plastics. A dielectric "welder" is used to HEAT (melt) vinyl plastic materials, CURE glue (heat/evaporate water in glue) for furniture and wood products, etc. The RF (e.g. 27.12 MHz) dielectric heaters are commonly used to melt plastic (PVC) for products such as loose-leaf binders, rain apparel, waterproof containers, and packaging materials.

Proper exposure measurements are required before any definite conclusions can be reached about the particular heater(s) that you have in mind. However, without proper shielding of dielectric heaters, it is common for exposures to exceed recommended exposure limits (e.g. IEEE C95.1-1999). Proper shielding of heaters can reduce worker exposure to levels below recommended exposure limits. The human male reproductive system is sensitive to testicular heating. Testicular temperatures are normally several degrees below core body temperature, and it has been known for some time that male germ cells are sensitive to elevated testicular temperatures. Human male fertility may be affected by long-term RF exposure above the recommended limits if testicular temperature is substantially elevated. These effects of elevated temperature on sperm production are known to be reversible, not permanent. That is, recovery to normal function occurs after exposure is discontinued. More research is needed to better establish the degree of RF-induced testicular temperature elevation and other exposure conditions related to male infertility in humans.

David Conover
National Institute of Occupational Safety and Health