Pollution of water, land, and air is a widespread and growing concern of global proportions. Media reports of diseases and contamination caused by the improper treatment and disposal of waste products occur on a regular basis. In many countries, recycling initiatives are being seen at the individual, community, city, and state levels. Of particular concern are wastes that present problems in two areas: those containing potentially infectious microorganisms (sewage sludge, biomedical wastes, wastewater) and those contaminated with toxic chemicals. Basic types of irradiation systems which are currently being used in waste treatment operations, or are being studied for this purpose, include gamma, electron-beam, ultraviolet, and X-ray