Many procedures generate hazardous air contaminants that can get into the air that people breath. Normally, the body can take in limited amounts of hazardous air contaminants, metabolize them and eliminate them from the body without producing harmful effects. When the average air concentrations repeatedly exceed certain thresholds, called exposure limits, adverse health effects are more likely to occur. A very small percentage of individuals experience some discomfort or adverse health effects at or below the exposure limit because of a wide variation in individual sensitivities or pre-existing conditions. Exposure limits for hazardous air contaminants are listed on the material safety data sheets for each product in use.
Many organizations research occupational exposures and establish recommended exposure limits.
Recommended exposure limits are not enforceable by law. Due to a federal court ruling, the OSHA permissible exposure limits updated in 1989 have been set aside, and the private sector is now governed by a PEL list generated in the early 1970's. Wisconsin has decided to adopt the more protective 1989 list of Permissible Exposure Limits for use with Wisconsin Public sector employees. Units of Measurement A workplace exposure level, such as a PEL or TLV, is expressed as the concentration of the air contaminant in a volume of air. The smaller the concentration number, the more toxic the substance is by inhalation.