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Abiotic

An abiotic system is one which is free of biological organisms. Abiotic transformations are those brought about by a non-biological mechanism. Thus, the modification of a chemical through heating or by the absorption of radiation is, strictly, an abiotic transformation or process.

Absolute risk

Absolute Risk is the excess risk due to an exposure to a hazard.

Absorb

To soak up. The incorporation of a liquid into a solid substance, as by capillary, osmotic, solvent, or chemical action.

Acceptable risk

The concept of Acceptable Risk is not particular easy to define. It is essentially a measure of the risk of harm, injury or disease arising from a chemical or process that will be tolerated by a person or group. Whether a risk is "acceptable" will depend upon the advantages that the person or group perceives to be obtainable in return for taking the risk, whether they accept whatever scientific and other advice is offered about the magnitude of the risk, and numerous other factors, both political and social.

Accumulation

Accumulation is the gradual build-up of a chemical as a result of repeated doses or exposure, where destruction or elimination of the chemical fails to keep pace with its introduction into the body. This will result in a gradual increase in concentration in an organism, organ or tissue which may cause toxic effects that can become more marked with successive doses. Factors that can enhance accumulation include selective binding of the chemical to particular types of molecules in the body, the progressive concentration of fat-soluble chemicals in body fat, complete failure or a slowing of metabolism which would otherwise reduce the concentration of chemicals, and slow excretion.

ACGIH

ACGIH stands for American Conference of Governmental Industrial Hygienists.

Acid

The definition which is most readily understood, due to Arrhenius, is that an acid is a chemical which produces hydrogen ions when dissolved in water. The strength of an acidic solution is usually measured in terms of its pH (a logarithmic function of the H⁺ ion concentration). Strongly acidic solutions have low pHs (typically around 0-3), while weakly acidic solutions have pHs in the range 3-6

Acidosis

Condition of decreased alkalinity of the blood tissues. Symptoms may include sickly sweet breath, headache, nausea, vomiting, visual disturbances. Tissues and CNS functions are disturbed.

Action level

Exposure level at which (USA) OSHA regulations take effect. This is generally one-half of the PEL.

Active ingredient

An active ingredient is the part of a product which actually does what the product is designed to do. It is not necessarily the largest or most hazardous part of the product. For example, an insecticidal spray may contain less than 1% pyrethrin, the ingredient which actually kills insects. The remaining ingredients are often called inert ingredients. Active ingredients are often used to determine which products must comply with the national Workplace Hazardous Materials Information System (WHMIS).

Acute

Acute means sudden or brief. Acute can be used to describe either an exposure or a health effect. An acute exposure is a short-term exposure. Short-term means lasting for minutes, hours or days. An acute health effect is an effect that develops either immediately or a short time after an exposure. Acute health effects may appear minutes, hours or even days after an exposure.

Acute effect

One which involves severe symptoms which develop rapidly and may quickly reach a crisis.

Acute exposure

A short-term exposure usually occurring at high concentration.

Acute hazard

One to which a single exposure may cause harm, but which is unlikely to lead to permanent damage.

Acute health effect

An effect that develops either immediately or a short time after exposure.

Acute toxins

A subset of Particularly Hazardous Substances as defined by the OSHA Laboratory Standard. These are defined as chemicals which may be fatal as a result of a single exposure or exposure of a short duration. 

Additive effect

An Additive effect is one in which the effect of two chemicals acting simultaneously is the simple sum of the effects that they would have if acting alone.

Adenocarcinoma

A tumor with glandular (secreting) elements.

ADR

ADR is a European agreement relating to the international carriage of dangerous goods by road.

Aerosol

An aerosol is a collection of very small particles suspended in air. The particles can be liquid (mist) or solid (dust or fume). The term aerosol is also commonly used for a pressurized container (aerosol can) which is designed to release a fine spray of a material such as paint. Inhalation of aerosols is a common route of exposure to many chemicals. Also, aerosols may be fire hazards.

AIHA

AIHA stands for American Industrial Hygiene Association.

Air-Line Respirator 

A respirator that is connected to a compressed breathable air source by a hose of small inside diameter. The air is delivered continuously or intermittently in a sufficient volume to meet the wearer's breathing requirements. Respirators are to be considered a last resort after considering engineering or administrative controls.  Respirators may only be used as part of a respiratory protection program. 

Air-Purifying Respirator

A respirator that uses chemicals to remove specific gases and vapors from the air or that uses a mechanical filter to remove particulate matter. An air-purifying respirator must only be used when there is sufficient oxygen to sustain life and the air contaminant level is below the concentration limits of the device. Respirators are to be considered a last resort after considering engineering or administrative controls.  Respirators may only be used as part of a respiratory protection program. 

Air Supplied Respirator

A positive pressure forced air respirator approved by NIOSH.

Allergen

An Allergen is any material which produces an allergic reaction in an individual.

Allergic Contact Dermatitis

Allergic Contact Dermatitis is a type of skin hypersensitivity. Its onset may be delayed by several days to as much as several years, for weaker sensitizers. Once sensitized, fresh exposure to the sensitizing material can trigger itching and dermatitis within a few hours.

Allergy

An Allergy is the appearance of symptoms of disease, irritation or discomfort upon exposure to a material, often one which has little effect upon other people. Development of allergies is essentially an unwanted (or faulty) reaction of the immune system.

Allotrope

An element has Allotropes if it is found in two (or more) different forms. The most well-known example is graphite and diamond, both of which are allotropes of carbon.

Alopecia

Loss of hair.

AMA

AMA is an abbreviation for the American Medical Association.

Ames Test

Used to assess whether a chemical might be a carcinogen. It assumes that carcinogens possess mutagenic activity, and uses bacteria and mammalian microsomes to determine whether a chemical is a mutagen. Approximately 85% of known carcinogens are mutagens. The Ames test, therefore, is a helpful but not perfect predictor of carcinogenic potential.

Analgesic

An Analgesic such as aspirin is a chemical which reduces the body's sensitivity to pain.

Anorexia

Loss of appetite.

Anosmia

Loss of the sense of smell.

Anoxia

Lack of oxygen in blood or tissues

ANSI

ANSI stands for the American National Standards Institute.

Antidote

A remedy to relieve, prevent, or counteract the effects of a poison.

Anuria

Absence or defective excretion of urine.

Apnea

Temporary stoppage of breathing.

Aquatic toxicity
The adverse effects to marine life that result from being exposed to a toxic substance

Argyria or Argyrism

An irreversible blueish-black discolouration of the skin, mucous membranes or internal organs caused by ingestion of, or contact with, various silver compounds.

Asbestosis

Chronic lung disease caused by inhaling airborne asbestos fibers.

Asphyxiant

An Asphyxiant is a material capable of reducing the level of oxygen in the body to dangerous levels. Most commonly, asphyxiants work by merely displaying air in an enclosed environment. This reduces the concentration of oxygen below the normal level of around 19% which can lead to breathing difficulties, unconciousness or even death.

Asthma

Medical disorder which causes attacks of wheezing, chest tightness, shortness of breath, and/or coughing due to spasmodic contraction of the air passage.

Asymptomatic

Showing no symptoms.

Ataxia

Loss of muscular coordination of gait or movement.

Atm
Atmosphere, a unit of pressure equal to 760 mmHg (mercury) at sea level.

Atrophy

Reduction in size or function of tissue, organs, or the entire body caused by lack of use.

Auto-ignition Temperature

The auto-ignition temperature is the lowest temperature at which a material begins to burn in air in the absence of a spark or flame. Many chemicals will decompose (break down) when heated. The auto-ignition temperature is the temperature at which the chemicals formed by decomposition begin to burn. Auto-ignition temperatures for a specific material can vary by one hundred degrees Celsius or more, depending on the test method used. Therefore, values listed in documents such as a Material Safety Data Sheet may be rough estimates. To avoid the risk of fire or explosion, materials must be stored and handled at temperatures well below the auto-ignition temperature.

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