HA— Health Advisory
HAD— Health Assessment Document
HAP— Hazardous Air Pollutant
HAPEMS— Hazardous Air Pollutant Enforcement
HAPPS— Hazardous Air Pollutant Prioritization
HATREMS— Hazardous and Trace Emissions
HAZMAT— Hazardous Materials
HAZOP— Hazard and Operability Study
HC— Hazardous Constituents; Hydrocarbon
HCP— Hypothermal Coal Process
HDD— Heavy-Duty Diesel
HDDT— Heavy-duty Diesel Truck
HDDV— Heavy-Duty Diesel Vehicle
HDE— Heavy-Duty Engine
HDG— Heavy-Duty Gasoline-Powered Vehicle
HDGT— Heavy-Duty Gasoline Truck
HDGV— Heavy-Duty Gasoline Vehicle
HDPE— High Density Polyethylene
HDT— Highest Dose Tested in a study.
HDV— Heavy-Duty Vehicle
HEAL— Human Exposure Assessment Location
HECC— House Energy and Commerce Committee
HEI— Health Effects Institute
HEM— Human Exposure Modeling
HEPA— High-Efficiency Particulate Air
HEPA— Highly Efficient Particulate Air
HERS— Hyperion Energy Recovery System
HHDDV— Heavy Heavy-Duty Diesel Vehicle
HHE— Human Health and the Environment
HHV— Higher Heating Value
HI— Hazard Index
HI-VOL— High-Volume Sampler
HIWAY— A Line Source Model for Gaseous
HLRW— High Level Radioactive Waste
HMIS— Hazardous Materials Information
HMS— Highway Mobile Source
HMTA— Hazardous Materials Transportation
HMTR— Hazardous Materials Transportation
HOC— Halogenated Organic Carbons
HON— Hazardous Organic NESHAP
HOV— High-Occupancy Vehicle
HP— Horse Power
HPLC— High-Performance Liquid Chromatography
HPMS— Highway Performance Monitoring
HPV— High Priority Violator
HQCDO— Headquarters Case Development
HRS— Hazardous Ranking System
HRUP— High-Risk Urban Problem
HSDB— Hazardous Substance Data Base
HSL— Hazardous Substance List
HSWA— Hazardous and Solid Waste Amendments
HT— Hypothermally Treated
HTP— High Temperature and Pressure
HVAC— Heating, Ventilation, and Air-Conditioning
HVIO— High Volume Industrial Organics
HW— Hazardous Waste
HWDMS— Hazardous Waste Data Management
HWGTF— Hazardous Waste Groundwater Task
Force; Hazardous Waste Groundwater Test Facility
HWIR— Hazardous Waste Identification
HWLT— Hazardous Waste Land Treatment
HWM— Hazardous Waste Management
HWRTF— Hazardous Waste Restrictions
HWTC— Hazardous Waste Treatment Council
Habitat— The place where
a population (e.g. human, animal, plant, microorganism)
lives and its surroundings, both living and
Habitat Indicator— A physical
attribute of the environment measured to characterize
conditions necessary to support an organism,
population, or community in the absence of
pollutants; e.g. salinity of estuarine waters
or substrate type in streams or lakes.
Half-Life— 1. The time
required for a pollutant to lose one-half
of its original coconcentrationor example,
the biochemical half-life of DDT in the environment
is 15 years. 2. The time required for half
of the atoms of a radioactive element to undergo
self-transmutation or decay (half-life of
radium is 1620 years). 3. The time required
for the elimination of half a total dose from
Halogen— A type of incandescent
lamp with higher energy-efficiency that standard
compounds with long atmospheric lifetimes
whose breakdown in the stratosphere causes
depletion of ozone. Halons are used in firefighting.
Hammer Mill— A high-speed
machine that uses hammers and cutters to crush,
grind, chip, or shred solid waste.
Hard Water— Alkaline water
containing dissolved salts that interfere
with some industrial processes and prevent
soap from sudsing.
Hauler— Garbage collection
company that offers complete refuse removal
service; many will also collect recyclables.
Hazard— 1. Potential for
radiation, a chemical or other pollutant to
cause human illness or injury. 2. In the pesticide
program, the inherent toxicity of a compound.
Hazard identification of a given substances
is an informed judgment based on verifiable
toxicity data from animal models or human
Hazard Assessment— Evaluating
the effects of a stressor or determining a
margin of safety for an organism by comparing
the concentration which causes toxic effects
with an estimate of exposure to the organism.
Hazard Communication Standard—
An OSHA regulation that requires chemical
manufacturers, suppliers, and importers to
assess the hazards of the chemicals that they
make, supply, or import, and to inform employers,
customers, and workers of these hazards through
Hazard Evaluation— A component
of risk evaluation that involves gathering
and evaluating data on the types of health
injuries or diseases that may be produced
by a chemical and on the conditions of exposure
under which such health effects are produced.
Determining if a chemical or a microbe can
cause adverse health effects in humans and
what those effects might be.
Hazard Quotient— The ratio
of estimated site-specific exposure to a single
chemical from a site over a specified period
to the estimated daily exposure level, at
which no adverse health effects are likely
Hazard Ratio— A term used
to compare an animal’s daily dietary
intake of a pesticide to its LD 50 value.
A ratio greater than 1.0 indicates that the
animal is likely to consume an a dose amount
which would kill 50 percent of animals of
the same species.
Hazardous Air Pollutants—
Air pollutants which are not covered by ambient
air quality standards but which, as defined
in the Clean Air Act, may present a threat
of adverse human health effects or adverse
environmental effects.Such pollutants include
asbestos, beryllium, mercury, benzene, coke
oven emissions, radionuclides, and vinyl chloride.
Hazardous Chemical— An
EPA designation for any hazardous material
requiring an MSDS under OSHA’s Hazard
Communication Standard. Such substances are
capable of producing fires and explosions
or adverse health effects like cancer and
dermatitis. Hazardous chemicals are distinct
from hazardous waste.
Hazardous Ranking System—
The principal screening tool used by EPA to
evaluate risks to public health and the environment
associated with abandoned or uncontrolled
hazardous waste sites. The HRS calculates
a score based on the potential of hazardous
substances spreading from the site through
the air, surface water, or ground water, and
on other factors such as density and proximity
of human population. This score is the primary
factor in deciding if the site should be on
the National Priorities List and, if so, what
ranking it should have compared to other sites
on the list.
Hazardous Substance— 1.
Any material that poses a threat to human
health and/or the environment. Typical hazardous
substances are toxic, corrosive, ignitable,
explosive, or chemically reactive. 2. Any
substance designated by EPA to be reported
if a designated quantity of the substance
is spilled in the waters of the United States
or is otherwise released into the environment.
Hazardous Waste— By-products
of society that can pose a substantial or
potential hazard to human health or the environment
when improperly managed. Possesses at least
one of four characteristics (ignitability,
corrosivity, reactivity, or toxicity), or
appears on special EPA lists.
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 reduction or environmentally
Hazards Analysis— Procedures
used to (1) identify potential sources of
release of hazardous materials from fixed
facilities or transportation accidents; (2)
determine the vulnerability of a geographical
area to a release of hazardous materials;
and (3) compare hazards to determine which
present greater or lesser risks to a community.
Providing information on which facilities
have extremely hazardous substances, what
those chemicals are, how much there is at
each facility, how the chemicals are stored,
and whether they are used at high temperatures.
Headspace— The vapor mixture
trapped above a solid or liquid in a sealed
Health Advisory Level—
A non-regulatory health-based reference level
of chemical traces (usually in ppm) in drinking
water at which there are no adverse health
risks when ingested over various periods of
time. Such levels are established for one
day, 10 days, long-term and life-time exposure
periods. They contain a wide margin of safety.
Health Assessment— An
evaluation of available data on existing or
potential risks to human health posed by a
Superfund site. The Agency for Toxic Substances
and Disease Registry (ATSDR) of the Department
of Health and Human Services (DHHS) is required
to perform such an assessment at every site
on the National Priorities List.
Heat Island Effect— A
“dome” of elevated temperatures
over an urban area caused by structural and
pavement heat fluxes, and pollutant emissions.
Heat Pump— An electric
device with both heating and cooling capabilities.
It extracts heat from one medium at a lower
(the heat source) temperature and transfers
it to another at a higher temperature (the
heat sink), thereby cooling the first and
warming the second.
Heavy Metals— Metallic
elements with high atomic weights; (e.g. mercury,
chromium, cadmium, arsenic, and lead); can
damage living things at low concentrations
and tend to accumulate in the food chain.
Heptachlor— An insecticide
that was banned on some food products in 1975
and in all of them 1978. It was allowed for
use in seed treatment until 1983. More recently
it was found in milk and other dairy products
in Arkansas and Missouri where dairy cattle
were illegally fed treated seed.
Herbicide— A chemical
pesticide designed to control or destroy plants,
weeds, or grasses.
Herbivore— An animal that
feeds on plants.
Species that are dependent on organic matter
High End Exposure (dose) Estimate—
An estimate of exposure, or dose level received
anyone in a defined population that is greater
than the 90th percentile of all individuals
in that population, but less than the exposure
at the highest percentile in that population.
A high end risk descriptor is an estimate
of the risk level for such individuals. Note
that risk is based on a combination of exposure
and susceptibility to the stressor.
High Intensity Discharge—
A generic term for mercury vapor, metal halide,
and high pressure sodium lamps and fixtures.
A material used to make plastic bottles and
other products that produces toxic fumes when
High-Level Nuclear Waste Facility—
Plant designed to handle disposal of used
nuclear fuel, high-level radioactive waste,
and plutonium waste.
High-Level Radioactive Waste
(HLRW)— Waste generated in core fuel
of a nuclear reactor, found at nuclear reactors
or by nuclear fuel reprocessing; is a serious
threat to anyone who comes near the waste
High-Line Jumpers— Pipes
or hoses connected to fire hydrants and laid
on top of the ground to provide emergency
water service for an isolated portion of a
High-Risk Community— A
community located within the vicinity of numerous
sites of facilities or other potential sources
of envienvironmental exposure/health hazards
which may result in high levels of exposure
to contaminants or pollutants.
The process of prediction of low exposure
risk to humans and animals from the measured
high-exposure-high-risk data involving laboratory
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
Hollow Stem Auger Drilling—
Conventional drilling method that uses augurs
to penetrate the soil. As the augers are rotated,
soil cuttings are conveyed to the ground surface
via augur spirals. DP tools can be used inside
the hollow augers.
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) definitions, an area of surfacing
materials, thermal surface insulation, or
miscellaneous material that is uniform in
color and texture.
Hood Capture Efficiency—
Ratio of the emissions captured by a hood
and directed into a control or disposal device,
expressed as a percent of all emissions.
Host— 1. In genetics,
the organism, typically a bacterium, into
which a gene from another organism is transplanted.
2. In medicine, an animal infected or parasitized
by another organism.
Household Hazardous Waste—
Hazardous products used and disposed of by
residential as opposed to industrial consumers.
Includes paints, stains, varnishes, solvents,
pesticides, and other materials or products
containing volatile chemicals that can catch
fire, react or explode, or that are corrosive
Household Waste (Domestic Waste)—
Solid waste, composed of garbage and rubbish,
which normally originates in a private home
or apartment house. Domestic waste may contain
a significant amount of toxic or hazardous
Human Equivalent Dose—
A dose which, when administered to humans,
produces an effect equal to that produced
by a dose in animals.
Human Exposure Evaluation—
Describing the nature and size of the population
exposed to a substance and the magnitude and
duration of their exposure.
Human Health Risk— The
likelihood that a given exposure or series
of exposures may have damaged or will damage
the health of individuals.
The rate at which water can move through a
permeable medium. (i.e. the coefficient of
Hydraulic Gradient— In
general, the direction of groundwater flow
due to changes in the depth of the water table.
Hydrocarbons (HC)— Chemical
compounds that consist entirely of carbon
Hydrogen Sulfide (H2S)—
Gas emitted during organic decomposition.
Also a by-product of oil refining and burning.
Smells like rotten eggs and, in heavy concentration,
can kill or cause illness.
The natural process recycling water from the
atmosphere down to (and through) the earth
and back to the atmosphere again.
Hydrogeology— The geology
of ground water, with particular emphasis
on the chemistry and movement of water.
Hydrologic Cycle— Movement
or exchange of water between the atmosphere
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 controlled by the pressure
in a compressed air tank.
Diseases characterized by allergic responses
to pollutants; diseases most clearly associated
with indoor air quality are asthma, rhinitis,
and pneumonic hypersensitivity.
Hypolimnion— Bottom waters
of a thermally stratified lake. The hypolimnion
of a eutrophic lake is usually low or lacking
Waters with dissolved oxygen concentrations
of less than 2 ppm, the level generally accepted
as the minimum required for most marine life
to survive and reproduce.