population, including susceptible individuals, could experience life-threatening health effects or death.”4
Adaptation: The acquisition of modifications that fit a plant or animal to life in a new environment or under new conditions.1
AEGL:See acute exposure guideline levels.
Aerosol: A suspension of liquid or solid particles in a gas.5
Alveolar macrophage: A mononuclear phagocytic cell arising from monocytic stem cells in bone marrow whose function is to ingest and digest foreign matter in the alveoli.1
Area under the curve (AUC): A measure of exposure that includes both duration and concentration. It is calculated from the curve that results when the concentrations of the test substance in some biologic tissue, typically blood, are plotted versus the exposure time.
ATA:See atmosphere absolute.
Atmosphere absolute (ATA): One atmosphere absolute (1-ATA) is the average atmospheric pressure exerted at sea level, 14.7 pounds per square inch (psi). Two-atmosphere absolute (2-ATA) is twice the atmospheric pressure exerted at sea level. If a physician prescribes 1 hour of hyperbaric oxygen treatment at 2-ATA, the patient breathes 100% oxygen at two times the atmospheric pressure at sea level for 1 hour.
ATSDR (Agency for Toxic Substances and Disease Registry): The ATSDR is an agency of the Department of Health and Human Services that was created by Congress under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), commonly known as the Superfund Act. Its mission is to serve the public by using the best science, taking responsive public health actions, and providing trusted health information to prevent harmful exposures and disease related to toxic substances. ATSDR defines minimal risk levels (MRLs).6
AUC: See area under the curve.
CAMS:See central atmosphere monitoring system.
CDC (Centers for Disease Control and Prevention): The CDC is an agency of the Department of Health and Human Services. The CDC promotes health and quality of life by preventing and controlling disease, injury, and disability. The National Institute of Occupational Safety and Health (NIOSH) is part of the CDC.7
CEGL:See continuous exposure guidance level.
Ceiling concentration: A concentration that shall not be exceeded during any part of a working exposure.8