Abstract
The use of higher frequency microwave generating equipment has increased considerably since the development of radar and range-finder equipment in the early 1940's. Occupational exposure criteria were not officially proposed in the United States until 1958 when a maximum exposure of 10 milliwatts per square centimeter was established for United States Air Force operations. Since then, many organizations have proposed or adopted criteria which have expanded on the concept of a single exposure limit to incorporate other factors involved in a biological response. A review of representative exposure criteria used in the United States is presented along with those adopted in other countries such as England, Russia, and Poland, and others. Where criteria differ from United States guidelines, a short review of the scientific evidence is provided.