Laboratory Terms

A glossary of science, chemistry, environmental and laboratory terms.

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Habitat: The place where a population (e.g. human, animal, plant, microorganism) lives...
Habitat Indicator: A physical attribute of the environment measured to characterize conditions n...
Half-Life: 1. The time required for a pollutant to lose one-half of its original coconce...
Halogen: A type of incandescent lamp with higher energy-efficiency that standard ones.
Halon: Bromine-containing compounds with long atmospheric lifetimes whose breakdown ...
Hammer Mill: A high-speed machine that uses hammers and cutters to crush, grind, chip, or ...
Hard Water: Alkaline water containing dissolved salts that interfere with some industrial...
Hauler: Garbage collection company that offers complete refuse removal service; many ...
Hazard: 1. Potential for radiation, a chemical or other pollutant to cause human illn...
Hazard Assessment: Evaluating the effects of a stressor or determining a margin of safety for an...
Hazard Communication Standard: An OSHA regulation that requires chemical manufacturers, suppliers, and impor...
Hazard Evaluation: A component of risk evaluation that involves gathering and evaluating data on...
Hazard Identification: Determining if a chemical or a microbe can cause adverse health effects in hu...
Hazard Quotient: The ratio of estimated site-specific exposure to a single chemical from a sit...
Hazard Ratio: A term used to compare an animal's daily dietary intake of a pesticide to its...
Hazardous Air Pollutants: Air pollutants which are not covered by ambient air quality standards but whi...
Hazardous Chemical: An EPA designation for any hazardous material requiring an MSDS under OSHA's ...
Hazardous Ranking System: The principal screening tool used by EPA to evaluate risks to public health a...
Hazardous Substance: 1. Any material that poses a threat to human health and/or the environment. T...
Hazardous Waste: By-products of society that can pose a substantial or potential hazard to hum...
Hazardous Waste Landfill: An excavated or engineered site where hazardous waste is deposited and covered.
Hazardous Waste Minimization: Reducing the amount of toxicity or waste produced by a facility via source re...
Hazards Analysis: Procedures used to (1) identify potential sources of release of hazardous mat...
Hazards Identification: Providing information on which facilities have extremely hazardous substances...
Headspace: The vapor mixture trapped above a solid or liquid in a sealed vessel.
Health Advisory Level: A non-regulatory health-based reference level of chemical traces (usually in ...
Health Assessment: An evaluation of available data on existing or potential risks to human healt...
Heat Island Effect: A "dome" of elevated temperatures over an urban area caused by structural and...
Heat Pump: An electric device with both heating and cooling capabilities. It extracts he...
Heavy Metals: Metallic elements with high atomic weights; (e.g. mercury, chromium, cadmium,...
Heptachlor: An insecticide that was banned on some food products in 1975 and in all of th...
Herbicide: A chemical pesticide designed to control or destroy plants, weeds, or grasses.
Herbivore: An animal that feeds on plants.
Heterotrophic Organisms: Species that are dependent on organic matter for food.
High End Exposure Estimate: An estimate of exposure, or dose level received anyone in a defined populatio...
High Intensity Discharge: A generic term for mercury vapor, metal halide, and high pressure sodium lamp...
High-Density Polyethylene: A material used to make plastic bottles and other products that produces toxi...
High-Level Nuclear Waste Facility: Plant designed to handle disposal of used nuclear fuel, high-level radioactiv...
High-Level Radioactive Waste HLRW: Waste generated in core fuel of a nuclear reactor, found at nuclear reactors ...
High-Line Jumpers: Pipes or hoses connected to fire hydrants and laid on top of the ground to pr...
High-Risk Community: A community located within the vicinity of numerous sites of facilities or ot...
High-to-Low-Dose Extrapolation: The process of prediction of low exposure risk to humans and animals from the...
Highest Dose Tested: The highest dose of a chemical or substance tested in a study.
Holding Pond: A pond or reservoir, usually made of earth, built to store polluted runoff.
Holding Time: The maximum amount of time a sample may be stored before analysis.
Hollow Stem Auger Drilling: Conventional drilling method that uses augurs to penetrate the soil. As the a...
Homeowner Water System: Any water system which supplies piped water to a single residence.
Homogeneous Area: In accordance with Asbestos Hazard and Emergency Response Act (AHERA) definit...
Hood Capture Efficiency: Ratio of the emissions captured by a hood and directed into a control or disp...
Host: 1. In genetics, the organism, typically a bacterium, into which a gene from a...
Household Hazardous Waste: Hazardous products used and disposed of by residential as opposed to industri...
Household Waste: Solid waste, composed of garbage and rubbish, which normally originates in a ...
Human Equivalent Dose: A dose which, when administered to humans, produces an effect equal to that p...
Human Exposure Evaluation: Describing the nature and size of the population exposed to a substance and t...
Human Health Risk: The likelihood that a given exposure or series of exposures may have damaged ...
Hydraulic Conductivity: The rate at which water can move through a permeable medium. (i.e. the coeffi...
Hydraulic Gradient: In general, the direction of groundwater flow due to changes in the depth of ...
Hydrocarbons HC: Chemical compounds that consist entirely of carbon and hydrogen.
Hydrogen Sulfide H2S: Gas emitted during organic decomposition. Also a by-product of oil refining a...
Hydrogeological Cycle: The natural process recycling water from the atmosphere down to (and through)...
Hydrogeology: The geology of ground water, with particular emphasis on the chemistry and mo...
Hydrologic Cycle: Movement or exchange of water between the atmosphere and earth.
Hydrology: The science dealing with the properties, distribution, and circulation of water.
Hydrolysis: The decomposition of organic compounds by interaction with water.
Hydronic: A ventilation system using heated or cooled water pumped through a building.
Hydrophilic: Having a strong affinity for water.
Hydrophobic: Having a strong aversion for water.
Hydropneumatic: A water system, usually small, in which a water pump is automatically control...
Hypersensitivity Diseases: Diseases characterized by allergic responses to pollutants; diseases most cle...
Hypolimnion: Bottom waters of a thermally stratified lake. The hypolimnion of a eutrophic ...
Hypoxia-Hypoxic Waters: Waters with dissolved oxygen concentrations of less than 2 ppm, the level gen...

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