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The process in which molecules of a gas or liquid are taken up and incorporated into the physical structure of another solid or liquid.

A chemical substance with a PH less than 7 on a scale of 0-14. Acids can neutralize bases, and strong acids are corrosive.

Acid rain
Any rain, sleet, fog, dew, dust, or other precipitation with a pH less than clean rain (pH 5.6). Acid rain occurs when the by-products of combustion react chemically with air and water in the presence of sunlight to form mineral acids.

The process in which the molecules of a gas or liquid adhere to the outer surface of another solid or liquid. Adsorption may retard the diffusion of contaminants.

The transfer of an atmospheric property, such as temperature, by the movement of air, especially horizontally. In environmental science, the movement of water, either internally or externally, through a sediment bed.

Oxygen is present. Describes organisms requiring oxygen to live or environments where oxygen is present. Contrast with anaerobic.

Describes a group of organic compounds, including paraffins, olefins, and acetylenes

Alcohol resistant foam
Which may break down other types of foam.

Oxygen is not present. Describes organisms not requiring oxygen to live or environments where oxygen is not present. Contrast with aerobic.

An underground layer of earth that contains groundwater. Aquifers are a major source of drinking water.

A type of hydrocarbon, typified by benzene. The name comes from its usually strong odor.

A lung disease caused by exposure to asbestos fibers. assay
See bioassay.

A reduction or weakening of strength or toxicity.


A chemical substance with a pH greater than 7. Bases can neutralize acids, and strong bases like lime are corrosive.

Refers to a laboratory test.

A volatile hydrocarbon liquid found in solvents and gasoline. In significant quantities, benzene is considered a hazardous air and water pollutant.

To build up a large amount of a substance by ingesting small amounts over an extended period of time.

A test using plants, animals, or bacteria to determine the effect of a chemical substance.

The extent to which living organisms can extract toxic chemicals from sediments or other materials. If a substance is not bioavailable, it cannot cause toxic effects.

To naturally break down in the environment. Biodegradation is decay caused by light, temperature, humidity, and microorganisms.

Biological agents
Living organisms that cause disease, sickness and mortality in humans. Anthrax and Ebola are examples of biological agents. Refer to Guide 158.

The use of organisms such as bacteria to clean up contaminated areas, typically by providing nutrients to help them break down pollutants.

The use of natural processes to change or eliminate contamination without human intervention.

The natural activity of living organisms, such as worms, to move particles and porewater from inside soil or sediment beds toward the surface and circulate them in the upper layers.

Blister agents (vesicants)
Substances that cause blistering of the skin. Exposure is through liquid or vapor contact with any exposed tissue (eyes, skin, lungs). Mustard (H), Distilled Mustard (HD), Nitrogen Mustard (HN) and Lewisite (L) are blister agents.
Symptoms: Red eyes, skin irritation, burning of skin, blisters, upper respiratory damage, cough, hoarseness.

Blood agents
Substances that injure a person by interfering with cell respiration (the exchange of oxygen and carbon dioxide between blood and tissues). Hydrogen cyanide (AC) and Cyanogen chloride (CK) are blood agents. Symptoms: Respiratory distress, headache, unresponsiveness, seizures, coma.

A hole drilled into the earth, usually to determine the location of minerals or aquifers for wells.

An abandoned, idled, or underused industrial and commercial facility where expansion or redevelopment is complicated by real or perceived environmental contamination.

Refers to either a chemical or thermal burn, the former may be caused by corrosive substances and the latter by liquefied cryogenic gases, hot molten substances, or flames.


Placement of a covering (a cap) of one or more layers of sand, silt, rock, or geotextile fabric, over an established layer of contaminated sediment. The cap seals the sediments physically and chemically, preventing pollutants from migrating into the surrounding water.

A molecule combining a metal ion with two or more non-metal ions. Chelation may be used to remove ions from solutions and soils. 

Chemical Abstracts Service Number (CAS RN or CAS No.)
An internationally recognised registration number assigned by the Chemical Abstracts Service to uniquely identify either a chemical, a group of similar chemicals or a mixture, (including a fortuitous mixture such as an oil refinery product).
The CAS Number (sometimes described as a Registry Number or RN) consists of up to nine digits and provides an accurate way for retrieving a substance from a computer database. The CAS number is simply a reference number and, unlike the UN number, cannot be linked to any particular chemical or physical properties.

Chlorinated hydrocarbon
A hydrocarbon compound containing chlorine atoms. Chlorinated hydrocarbons such as pesticides persist in the environment and can accumulate within living organisms.

Chlorofluorocarbon (CFC)
A chemical compound containing chlorine, fluorine, and carbon, used in cooling systems and aerosols. CFCs absorb infrared radiation and consume ozone in the stratosphere.

Choking agents
Substances that cause physical injury to the lungs. Exposure is through inhalation. In extreme cases, membranes swell and lungs become filled with liquid (pulmonary edema). Death results from lack of oxygen; hence, the victim is "choked". Phosgene (CG) is a choking agent.
Symptoms: irritation to eyes/nose/throat, respiratory distress,nausea and vomiting, burning of exposed skin.

The thread-like strand of DNA that carries genetic information. 

Carbon dioxide gas.

Any of two chemical substances composed of the same elements in the same proportions but which have different properties because of different structures. Dioxins and PCBs have many cogeners. Similar to isomer.

Cold zone
Area where the command post and support functions that are necessary to control the incident are located. This is also referred to as the clean zone, green zone or support zone in other documents. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472)

A fibrous protein found in bone, tendons, or other connective tissue.

A suspension of fine particles into a continuous medium such as a liquid.

Combustible liquid
Liquids which have a flash point greater than 60.50C (141 degrees F) and below 93 degrees C (2OO degrees F). U.S. regulations permit a flammable liquid with a flash point between 38 degrees C (100 degrees F) and 60.50C (141 degrees F) to be reclassed as a combustible liquid.

Compatibility Group
Letters identify explosives that are deemed to be compatible. Class 1 materials are considered to be "compatible" if they can be transported together without significantly increasing either the probability of an incident or, for a given quantity, the magnitude of the effects of such an incident.

A Substances which are expected to mass detonate very soon after fire reaches them.

B Articles which are expected to mass detonate very soon after fire reaches them.

C Substances or articles which may be readily ignited and burn violently without necessarily exploding. 

D Substances or articles which may mass detonate (with blast and/or fragment hazard) when exposed to fire

E&F Articles which may mass detonate in a fire.

G Substances and articles which may mass explode and give off smoke or toxic gases.

H Articles which in a fire may eject hazardous projectiles and dense white smoke.

J Articles which may mass explode.

K Articles which in a fire may eject hazardous projectiles and toxic gases. 

L Substances and articles which present a special risk and could be activated by exposure to air or water. 

N Articles which contain only extremely insensitive detonating substances and demonstrate a negligible probability of accidental ignition or propagation. 

S Packaged substances or articles which, if accidentally initiated, produce effects that are usually confined to the immediate vicinity.

The process of keeping hazardous or radioactive wastes confined to a particular location, to prevent their accidental release into the surrounding environment.

Control zones
Designated areas at dangerous goods incidents, based on safety and the degree of hazard. Many terms are used to describe control zones; however, in this guidebook, these zones are defined as the hot/exclusion/restricted zone, warm/contamination reduction/limited access zone, and cold/support/clean zone. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472)

COSHH (the Control of Substances Hazardous to Health).
The object of the regulations is to promote safe working with potentially hazardous chemicals.

Cryogenic liquid
A refrigerated, liquefied gas that has a boiling point cold 90 degrees C,(-130 degrees F) at atmospheric pressure.

Cutaneous hazard
Is a chemical which may cause harm to the skin, such as defatting, irritation, skin rashes or dermatitis


Dangerous water reactive material
Produces significant toxic gas when it comes in contact with water.

Decomposition products
Products of a chemical or thermal break-down of a substance.

The removal of dangerous goods from personnel and equipment to the extent necessary to prevent potential adverse health effects. Always avoid direct or indirect contact with dangerous goods; however, if contact occurs, personnel should be decontaminated as soon as possible. Since the methods used to decontaminate personnel and equipment differ from one chemical to another, contact the chemical manufacturer, through the agencies listed on the inside back cover, to determine the appropriate procedure. Contaminated clothing and equipment should be removed after use and stored in a controlled area (warm/contamination reduction/limited access zone) until cleanup procedures can be initiated. In some cases, protective clothing and equipment cannot be decontaminated and must be disposed of in a proper manner.

Is the term generally used to describe the loss of resilience of material used for protective gloves. Degradation may cause the material to soften, swell, become hard and brittle, or - in severe cases - disintegrate.

The reduction or removal of halogens from a chemical compound. Contrast with halogenation.

Dense non-aqueous phase liquid (DNAPL)
See non-aqueous phase liquid.

The release of an absorbed or adsorbed substance, as in contaminants that are released from particles of sediment back into adjoining porewater.

The spontaneous mixing of one substance with another, as for example, the movement of gas molecules to the nose and respiratory track or the spread of liquid contaminants through a sediment bed.

A class of chemical compounds containing carbon, hydrogen, oxygen and chlorine, part of a larger group called polycyclic halogenated aromatics. Dioxins are human-made by-products of industrial processes such as incineration, paper milling, pesticide manufacture, and smelting. One dioxin, TCDD, is the most toxic synthetic substance known.

Distribution coefficient (Kd)
A measure of how sorbed a substance is to soil or sediment particles, expressed as the ratio of the sorbed-phase concentration to the solution-phase concentration at equilibrium.

Deoxyribonucleic acid. A major component of living cells which contains the genetic code for the cell.

Dense non-aqueous phase liquid. See non-aqueous phase liquid.

Common abbreviation for the U.S. Department of Transportation, which regulates the transport of chemicals in the U.S.A.

DOT hazard code

1  Explosive
2.1  Flammable gas
2.2  Non-flammable gas
2.3  Poisonous gas
3  Flammable liquid
4.1  Flammable solid
4.2  Spontaneously combustible
4.3  Dangerous when wet
5.1  Oxidizer
5.2  Organic peroxide
6.1  Poison - keep away from food
6.2  Infectious material
7  Radioactive
8  Corrosive
9  Miscellaneous

Dry chemical

A preparation designed for fighting fires involving flammable liquids, pyrophodc substances and electrical equipment. Common types contain sodium bicarbonate or potassium bicarbonate.


The accumulation of an excessive amount of watery fluid in cells and tissues. Pulmonary edema is an excessive buildup of water in the lungs, for instance, after inhalation of a gas that is corrosive to lung tissue.

Effective Dose 50 (ED50)
Is the amount of material required to produce a specified effect in 50% of an animal population. (See qualification in the definition of LD50).

Outflow from a manufacturing or treatment process, in the form of finished products or wastes.

Acronym for European Inventory of Existing Commercial Chemical Substances.

Acronym for European List of Notified Chemical Substances.

Retard the growth or affect the development of the unborn child. In serious cases they can cause deformities or death. Mercury compounds and certain heavy metals, aflatoxin, formamide and radiation are known embryotoxins.

The point of termination or final step, when nothing more needs to be done.

Is an acronym for the Environmental Protection Agency, which is the US federal agency responsible for regulating environmental hazards.

To be in, or bring about, equilibrium.

The state of being at rest, in balance, or unchanged. For example, in the process of adsorption, toxic wastes in rivers may contaminate sediments until the wastes in the water and the wastes in the sediment reach a state of equilibrium.

Place where the mouth of a river reaches the ocean.

Etiologic agents
Microscopic organisms such as bacteria or viruses, which can cause disease

Removed from the site, not in place. Treatment of hazardous wastes by removing them to another location.


Fate and transport
The final outcome of a hazardous substance and the physical, chemical, or biological means by which this result occurs.

Fibers per cubic centimeter of air.
U.S. Food and Drug Administration.

Flammable liquid
A liquid that has a flash point of 60.5 degrees C (141 degrees F) or lower.
Occurs when the flame in a gas torch burns back into the torch or hose; this is often accompanied by a hissing or squealing sound, and a pointed or smoky flame.

Flash point
Of a chemical is the lowest temperature at which a flame will propagate through the vapor of a combustible material to the liquid surface. It is determined by the vapor pressure of the liquid, since only when a sufficiently high vapor concentration is reached, can it support combustion. It should be noted that the source of ignition need not be an open flame, but could equally be, for example, the surface of a hot plate, or a steam pipe.


Gas chromatography
A method of analysis which the components of a chemical mixture can be separated, identified, or purified. Also called gas-liquid chromatography (GLC), gas-solid chromatography (GSC), or vapor-phase chromatography (VPC).

See gas chromatography and mass spectrometry.

Greenhouse effect
The behavior of the earth's atmosphere to trap and hold heat near its surface, causing global warming.
Greenhouse gas Heat-trapping gases that cause global warming. Natural and human-made greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbons (CFCs).

Water that moves slowly underground in an aquifer. Once groundwater has been contaminated, it is nearly impossible to return it to its pure state. The main source of drinking water from wells and springs. 


A non-metallic element, such as fluorine, chlorine, bromine, iodine, or astatine.

Incorporation of one of the halogens, usually chlorine or bromine, into a chemical compound. Halogenated compounds are more likely to be toxic. Contrast with dehalogenation. 

The potential for physical harm to life, health or property. See also risk.

Hazard codes
See UN hazard codes

Hazardous Area
Defined AS 2430, Classification of Hazardous Areas - Explosive Gas Atmospheres.

Hazardous ingredient
A hazardous ingredient;
1. Meets any of the health effects criteria of the National Commission's Approved Criteria (see Hazardous Substance and present at a concentration exceeding the specified cut-off level;
2. Dangerous good, i.e. meets the classification criteria of the ADG Code; or
3. Liberated or generated in the application or use in the workplace from any substance or article that complies with point 1.

Hazardous Materials
Include dangerous goods and hazardous substances as defined in state legislation, which includes other substances, which, on release could threaten health or the environment

Hazardous Substance
A substance which has the potential through being used at work to harm the health or safety of persons in the workplace including substances which may be produced in the workplace (eg. from welding rods, plastics processing etc.).
The National Commission has defined a Hazardous Substance as a substance that;
< Is included in the National Commission's List of Designated Hazardous
Substances (about eight hundred substances); or
< Meets the criteria for a hazardous substance in the National Commission's
Approved Criteria for Classifying Hazardous Substances.
It excludes certain substances whose presence or use is not related to a work activity, being foodstuffs, therapeutic agents, cosmetics, tobacco and its products and toiletries and toilet products.

Hazard zones (Inhalation Hazard Zones)
HAZARD ZONE A: LC50 of less than or equal to 200 ppm,
HAZARD ZONE B: LC50 greater than 200 ppm and less than or equal to
1000 ppm,
HAZARD ZONE C: LC50 greater than 1 000 ppm and less than or equal to
3000 ppm,
HAZARD ZONE D: LC50 greater than 3000 ppm and less than or equal to
5000 ppm.

Hazardous waste
A substance (gas, liquid, solid, or sludge) that causes, or contributes to, illness or death, or that may substantially threaten human health or the environment when not properly controlled. A waste may be hazardous because it is toxic, ignitable, corrosive, or dangerously reactive.

Heavy metal
Metals having a high density, such as lead, mercury, cadmium, arsenic, beryllium, cobalt, and chromium. Many heavy metals are toxic and since they do not easily break down, they can bioaccumulate in living organisms.

Hematopoietic agent
Is a chemical which interfers with the blood system by decreasing the oxygen-carryi! ng a bility of haemoglobin. This can lead to cyanosis and unconsiousness. Carbon monoxide is one such agent, familiar to smokers.

Is a chemical capable of causing liver damage.

Area immediately surrounding a dangerous goods incident which extends far enough to prevent adverse effects from released dangerous goods to personnel outside the zone. This zone is also referred to as exclusion zone, red zone or restricted zone in other documents. (EPA Standard Operating
Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472)

The Health and Safety Executive. The HSE web site can be reached through The HSE is responsible for proposing and enforcing safety regulations throughout UK industry and academia.
Publications are available on a wide variety of safety-related issues

A chemical compound containing hydrogen and oxygen. Hydrocarbons are found primarily in petroleum, natural gas, and coal products. See also aromatic and chlorinated hydrocarbon.

Water-loving. Refers to substances that have an affinity for and can dissolve in water, such as carbohydrates, gelatins, or collagens.

Water-hating. Refers to substances that cannot dissolve in water, such as fats or waxes.

Is a condition defined by a low supply of oxygen.


International Agency for Research in Cancer. The IARC home page is at

In this guidebook, means that a material does not mix readily with water.

An analytical technique that uses antibody molecules as binding agents in the detection and quantification of substances in a sample. Often used to detect hazardous substances in low quantities or demonstrate compliance with governmental standards.

In situ
Present at the site, in place. Treatment of hazardous wastes on site, without removing them to another location.

In vitro
Outside the body, such as a test in a laboratory.

In vivo
Inside the body. Contrast with in vitro.

Industrial hygiene
The study and practice of creating a safe workplace.

Materials that flow into a manufacturing or treatment system. Raw materials are often called influents. Contrast with effluent.

Is a material which is added to a chemical to prevent an unwanted reaction. For example, BHT (2,6-di-t-butyl-p-cresol) is often added to tetrahydrofuran to prevent potentially dangerous polymerization

Not containing hydrocarbons, or not related to living organisms. For example, metals are inorganic.

Institute for Occupational Safety and Health. IOSH has its home page at

Irreversible compartment
The portion of an adsorbed substance, such as a pollutant, that cannot be desorbed and made bioavailable.

Is a chemical which may cause reversible inflammation on contact.

Any of two chemical substances composed of the same elements in the same proportions but with different structures and different properties. Dioxins and PCBs have many isomers. Similar to cogener.

A graphical representation of a mathematical equation, such as the relationship of the concentration of a contaminant virus the mass that is adsorbed by soil particles. The Freundlich Isotherm represents a common equilibrium equation.


See distribution coefficient.

Related to motion and its energy. In physics, refers to the movement of atoms and molecules in solids, liquids, and gases. In chemistry, refers to the rates of chemical reactions.


Liquid chromotography. See gas chromotography.

Lethal Dose 50(LD50)
Is the dose of a chemical which kills 50% of a sample population. In full reporting, the dose, treatment and observation period should be given.
Further, LD50, LC50, ED50 and similar figures are strictly only comparable when the age, sex and nutritional state of the animals is specified.
Nevertheless, such values are widely reported and used as an effective measure of the potential toxicity of chemicals. (See also LC50).

Lethal Dose Low

A liquid formed by passing a solvent, such as water, through another substance. For example, rainwater passing through a landfill or contaminated soil can leach out toxic wastes.

Light non-aqueous phase liquid. See non-aqueous phase liquid.


A large molecule that is made up of hundreds or thousands of atoms.
Examples include proteins and polymers.

Mass explosion
Explosion which affects almost the entire load virtually instantaneously.

Mass spectrometry
A method of chemical analysis in which a substance is vaporized and exposed to strong electric and magnetic fields to separate and measure its components.

Maximum exposure limit (MEL)
Is the maximum permitted concentration of a chemical to which a worker may be exposed over an extended period of time. Typically, MELs are quoted in ppm f or an 8-hour reference period, though shorter periods may be quoted for some materials. MELs are, in many countries, enforceable by law. A list of chemicals for which MELs are defined in the UK is held at

Median lethal dose (MDL)
See LD50

Layer of tissue covering an organism, plant, or cell. See also synthetic membrane.

Containing metals, as in mineral deposits or ores.

An odorless, colorless, combustible natural gas, often found in landfills, swamps, and marshes.

Creating methane. Used to describe the anaerobic bacteria who produce methane during decomposition of organic matter.

A small system that is representative of a larger system.

In this guidebook, means that a material mixes readily with water.

Illness, the rate of incidence of a disease. Compare with mortality.

Death, the rate of incidence of loss of life. Compare with morbidity.

A widely used abbreviation for Material Safety Data Sheet, which contains details of the hazards associated with a chemical, and gives information on its safe use.

Is an agent that changes the hereditary genetic material which is a part of every living cell. Such a mutation is probably an early step in the sequence of events that ultimately leads to the development of cancer

Able to create mutations, and so potentially able to cause infertility or birth defects.

Small changes in genetic structure of a living cell.


prefix meaning very small, or 10 to the minus 9th power. For example, a nanogram is 0.0000000001 gram.

See non-aqueous phase liquid.

National Priorities List (NPL)
A list of Superfund hazardous waste sites identified by the Environmental
Protection Agency for cleanup.

Is a chemical which may cause kidney damage. Common examples include antimony compounds, dimethyl sulphoxide, dimethylformamide and tetrahydrofuran

Nerve agents
Substances that interfere with the central nervous system. Exposure is primarily through contact with the liquid (via skin and eyes) and secondarily through inhalation of the vapor. Tabun (GA), Sarin (GB), Soman (GD) and VX are nerve agents. Symptoms: Pinpoint pupils, extreme headache, severe tightness in the chest, dyspnea, runny nose, coughing, salivation, unresponsiveness, seizures.

A poison which damages or affects the nervous system of living organisms.

National Institute for Occupational Safety and Health. This sets OELs and provides services in occupational health and safety investigations in the USA. The NIOSH home page is at

Non-aqueous phase liquid (NAPL)
A chemical that does not dissolve well in water, typically an organic solvent. Dense non-aqueous phase liquids (DNAPLs) have a density greater than water. Light non-aqueous phase liquids (LNAPLs) have a density less than water. NAPLs, particularly DNAPLs can contaminate groundwater creating large underground plumes that persist for very long periods.

Non-point source
A source that is so broad, it cannot be pinpointed. such pesticide runoff from farmland. Contrast with point source.

See "Immiscible".

These letters refer to not otherwise specified. The entries which use this description are generic names such as "Corrosive liquid, n.o.s." This means that the actual chemical name for that corrosive liquid is not listed in the regulations; therefore, a generic name must be used to describe it on shipping papers.

In this guidebook, means that a material may be harmful or injurious to health or physical well-being.

National Priorities List.

Is the (US) National Toxicology Program, which tests chemicals, and reviews evidence relating to the possibility that a chemical may act as a carcinogen.

Nuisance material
Is one which can cause transient irritation or discomfort, but which has no long-term or systemic effects.


Occupational exposure limit (OEL)
A (generally legally-enforcable) limit on the amount or concentration of a chemical to which workers may be exposed.

Odour threshold
Is the lowest concentration of a vapor in air which can be detected by smell

Containing hydrocarbons or related to living organisms.

A chemical which supplies its own oxygen and which helps other combustible material burn more readily.

A chemical compound formed by the action of sunlight on oxygen or automobile emissions. At ground-level and the troposphere, ozone can harm plants and humans. In the stratosphere, it blocks the sun's harmful ultraviolet rays. In the upper troposphere and lower stratosphere it acts as a greenhouse gas.


The letter "P" following a guide number in the yellow-bordered and blue-bordered pages identifies a material which may polymerize violently under high temperature conditions or contamination with other products. This polymerization will produce heat and high pressure buildup in containers which may explode or rupture. (See polymerization below'.)

See polycyclic aromatic hydrocarbon.

A minute particle. For example, the quantity of particulate in the air is a measure of air pollution.

See polychlorinated biphenal.

Permissible exposure limit (PEL)
Is a time-weighted average (TWA) or absolute value (usually prescribed by regulation) setting out the maximum permitted exposure to a hazardous chemical.

Peroxidizable materials
Can form peroxides in storage, generally when in contact with the air. These peroxides present their most serious risk when the peroxide-contaminated material is heated or distilled, but they may also be sensitive to mechanical shock. The quantity of peroxides in a sample may be determined using a simple peroxide test strip

Chemicals used to kill pests, such as herbicides to kill weeds and plants; insecticides to kill insects; or fungicides to kill fungi and other micro-organisms.

A measure of the concentration of hydrogen atoms, or the acidity of a chemical substance. pH is measured on a scale of 0 to 14, with 0 being a strong acid, 7 neutral, and 14 a strong base. The scale is logarithmic, with each number representing ten times the strength of the previous one.

Photoallergic contact dermatitis
Is a skin condition brought on by exposure to light following skin contact with certain types of chemicals, such as sulphonamides

The process of decaying or breaking down a substance using light or other radiant energy.

Describes chemical compounds that can be degraded by sunlight or other radiant energy.

Use of plants and vegetation in the bioremediation of hazardous wastes. An example would be the use of poplar trees to clean up DDT residues.

Widely-used pictorial representations of the hazards presented by chemicals.

Poison Inhalation Hazard. Term used to describe gases and volatile liquids that are toxic when inhaled. (Same as TIH)

Describes a test in the field, run as a pilot project.

An area of air, soil, or water containing pollutants released from a single point source. Plumes tend not to mix readily and move slowly, if at all.

Point source
A source that can be identified or pinpointed, such as wastes from a pipe or leak. Contrast with non-point source.

Poison class A or B
Poisons are classified by the DOT into two classes. Those in Class A are highly toxic materials which, even in very small quantities, present a hazard to life. Examples of such gases are cyanogen, phosgene and hydrocyanic acid. Class B poisons, though less toxic, are presumed to present a serious threat to health during transportation.

Characterized by a positive or negative electrical charge. Polar substances like benzene tend to dissolve in water, while non-polar substances such as pesticides tend to adsorb to soil particles.

The state of being either positively or negatively charged.

Polychlorinated biphenal (PCB)
A class of chemical compounds containing benzine and chlorine atoms. The toxicity of PCBs varies based on the degree of chlorination and the position of chlorine atoms in the overall structure. Examples are pesticides and fire-resistant coatings.

Polycyclic aromatic hydrocarbon (PAH)
A group of aromatic hydrocarbons having three or more aromatic nuclei in their structures.

Polycyclic halogenated aromatic
See dioxin.

A natural or synthetic macromolecule made up of combinations of repeating chemical units. Examples include cellulose and plastics.

This term describes a chemical reaction which is generally associated with the production of plastic substances. Basically, the individual molecules of the chemical (liquid or gas) react with each other to produce what can be described as a long chain. These chains can be formed in many useful applications. A well known example is the styrofoam (polystyrene) coffee cup which is formed when liquid molecules of styrene react with each other or polymerize forming a solid, therefore changing the name from styrene to polystyrene (poly means many).

In geology, a minute space between particles of a solid, such as soil or sediment, which permits the passage of liquids or gases.

Water present in the spaces between soil or sediment particles.

Parts per billion. A measure of the concentration of a substance.

Parts per million. A measure of the concentration of a substance.

Protective clothing
Includes both respiratory and physical protection. One cannot assign a level of protection to clothing or respiratory devices separately. These levels were accepted and defined by response organizations such as U.S. Coast Guard, NIOSH, and U.S. EPA.
Level A: SCBA plus totally encapsulating chemical resistant clothing (permeation resistant).
Level B: SCBA plus hooded chemical resistant clothing (splash suit).
Level C: Full or half-face respirator plus hooded chemical resistant clothing (splash suit).
Level D: Coverall with no respiratory protection.

A material which ignites spontaneously upon exposure to air (or oxygen).

Pump and treat
A remediation method in which hazardous substances are removed from where they are, pumped off site (ex situ), and treated.

Pyrophoric materials
Ignite spontaneously in air. Since a wide variety of chemicals will burn if heated sufficiently, it is usual to define a pyrophoric material as one which will ignite spontaneously at temperatures below about 45 C.

The property of some substances to emit invisible and potentially harmful radiation.


Living organisms such as bacteria, algae, worms, or plants that can receive and absorb hazardous substances.

Oxidation-reduction. Used to describes any reaction in which oxygen combines chemically with another substance, or in which electrons are exchanged.

Reproductive toxin
Such as vinyl chloride or PCBs, is a chemical which may cause birth defects or sterility.

Area of soil or sediment in and around a plant's roots.

Right to know
The right granted by the Superfund Amendments and Reauthorization Act (SARA) for a community to be notified about the risks of materials used or produced within it.

Risk phrases
Coded in the form R34, R61 etc are now included in MSDS sheets for chemicals purchased in the UK. A list of the meaning of these codes is available at

Ribonucleic acid. A major component of living cells and viruses which plays multiple roles in synthesizing proteins and transmitting genetic information.

RTECS number
Is an identification number set by the US Registry of Toxic Effects of Chemical Substances. For further information, connect to the RTECS home page at


Soil material that accumulates in layers beneath water.

Is a chemical which may lead to the development of allergic reactions after repeated exposure.

A non-pumpable mixture of solids and liquids. Sludge is typically produced by waste treatment plants, water supply treatment plants, or air pollution control facilities.

A pumpable mixture consisting of waste particles and liquid.

Slurry reactor
In a laboratory, a beaker filled with soil and liquid where chemical reactions can occur.

The top layer of the earth surface not covered by water.

Solid waste
Garbage, refuse, sludge, and other discarded material resulting from industrial, commercial, mining, agriculture, or community activities.

To make substances like fats dissolve in water by the action of a detergent or surfactant.

A liquid capable of dissolving a substance and holding it in solution. For example, paint remover is a paint solvent.

To spray a liquid, or to introduce air or gas into a liquid.

Short Term Exposure Limit (STEL)
Is the maximum permissible concentration of a material, generally expressed in ppm in air, for a defined short period of time (typically 5 minutes). These values, which may differ from country try to country, are often backed up by regulation and therefore may be legally enforceable.

The part of the atmosphere more than five miles from the earth's surface.

A nickname for legislation which identified hazardous waste sites (the National Priorities List) and the funds for their clean-up.

Surface water
Water at the surface of the earth, including oceans, lakes, rivers, ponds, and streams

Surface active agent. A compound, such as a detergent, wetting agent, or emulsifier, that helps to reduce surface tension among liquids and solids.

Synthetic membrane
An artificial structure that mimics a cellular membrane, either to act as a filter or to test the bioavailability of a hazardous substance. Synthetic membranes are typically made from solutions of polymers and solvents.

Systemic poisons
Have an effect which is remote from the site of entry into the body


Any waste product remaining after a substance has been processed. For example, mill tailings are wastes from milling lumber. Mine tailings are wastes from processing ores.

Tetrachlorodibenzo-p-dioxin. The most toxic synthetic substance known.

See trichloroethylene.

TD50 may be defined as follows: for a given target site(s), if there are no tumors in control animals, then TD50 is that chronic dose-rate in mg/kg body wt/day which would induce tumors in half the test animals at the end of a standard lifespan for the species. Since the tumor(s) of interest often does occur in control animals, TD50 is more precisely defined as: that dose-rate in mg/kg body wt/day which, if administered chronically for the standard lifespan of the species, will halve the probability of remaining tumorless throughout that period. A TD50 can be computed for any particular type of neoplasm, for any particular tissue, or for any combination of these. The range of statistically significant TD50 values for chemicals in the CPDB that are carcinogenic in rodents is more than 10 million-fold.

Is a chemical which may cause genetic mutations or malformations in the developing foetus

Thermal pollution
The release of heated waters into natural environments, a process that reduces oxygen levels, harming fish and other living organisms.

Threshold limit value (TLV)
Is the maximum permissible concentration of a material, generally expressed in parts per million in air for some defined period of time (often 8 hours).
These values, which may differ from country to country, are often backed up by regulation and therefore may be legally enforceable.

Time Weighted Average (TWA)
This term is used in the specification of Occupational Exposure Limits (OELs) to define the average concentration of a chemical to which it is permissible to expose a worker over a period of time, typically 8 hours.

Ceiling exposure limit - an exposure limit which should not be exceeded under any circumstances

The condition of being poisonous or harmful to life.

See fate and transport.

Trichloroethylene (TCE)
A volatile organic compound used as a common solvent.

The part of the atmosphere up to five miles from the earth's surface.

Toxic Substances Control Act (TSCA)
This regulates the manufacture, transport and use of toxic substances in the

Treatment, storage, and disposal facilities for hazardous wastes
UN Hazard codes
Class 1 Explosive
Class 2 Gases
Class 3.1 Flammable liquids, flash point below -18C
Class 3.2 Flammable liquids, flash point between -18C and 23C
Class 3.3 Flammable liquids, flash point between 23C and 61C
Class 4.1 Flammable solids
Class 5.1 Oxidizing agents
Class 5.2 Organic peroxides
Class 6.1 Poisonous substances
Class 7 Radioactive substances
Class 8 Corrosive substances
Class 9 Miscellaneous dangerous substances
NR Non-regulated


Is a chemical which, if it can escape from the vein, causes extensive tissue damage, with vesicle formation or blistering.

Volatile organic compound (VOC)
Any hydrocarbon (except methane and ethane) which is able to change quickly to a gas. Chlorofluorocarbons (CFCs) are an example.


Warm zone
Area between Hot and Cold zones where personnel and equipment decontamination and hot zone support take place. It includes control points for the access corridor and thus assists in reducing the spread of contamination. Also referred to as the contamination reduction corridor (CRC), contamination reduction zone (CRZ), yellow zone or limited access zone in other documents. (EPA Standard Operating Safety Guidelines, OSHA 29 CFR 1910.120, NFPA 472)

Substances which may produce flammable and/or toxic decomposition products upon contact with water.

Water spray (fog)
Method or way to apply or distribute water. The water is finely divided to provide for high heat absorption. Water spray patterns can range from about 10 to 90 degrees. Water spray streams can be used to extinguish or control the burning of a fire or to provide exposure protection for personnel, equipment, buildings, etc. (This method can be used to absorb vapors, knockdown vapors or disperse vapors. Direct a water spray (fog), rather than a straight (solid) stream, into the vapor cloud to accomplish any of the above).
Is particularly effective on fires of flammable liquids and volatile solids having flash points above 37.8 degrees C (100 degrees F).
Regardless of the above, water spray can be used successfully on flammable liquids with low flash points. The effectiveness depends particularly on the method of application. With proper nozzles, even gasoline spill fires of some types have been extinguished when coordinated hose lines were used to sweep the flames off the surface of the liquid. Furthermore, water spray carefully applied has frequently been used with success in extinguishing fires involving flammable liquids with high flash points (or any viscous liquids) by causing frothing to occur only on the surface, and this foaming action blankets and extinguishes the fire.

Water table
The level of groundwater below the earth's surface. The height of a water table is the depth needed to reach groundwater. The higher the water table, the easier it is to get at the water, but the harder it is to keep it unpolluted.

An area that drains into one or more river systems or bodies of water.


Foreign to the human body or living organisms. Often used to describe hazardous substances such as pesticides.