Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

American Conference of Governmental Industrial Hygienists is an organization of professional personnel in governmental agencies or educational institutions engaged in occupational safety and health programs. ACGIH establishes recommended occupational exposure limits for chemical substances and physical agents. See TLV.

Acid

Any chemical that undergoes dissociation in water with the formation of hydrogen ions. Acids have a sour taste and may cause severe skin burns. Acids turn litmus paper red and have pH values of 0 to 6.

Acute Effect

Adverse effect on a human animal that has severe symptoms developing rapidly and coming quickly to a crisis.

Acute Toxicity

Acute effects resulting from a single dose of, or exposure to, a substance. Ordinarily used to denote effects in experimental animals. LC50 expresses the toxicity of chemicals to fish or other aquatic organisms. In these aquatic studies, LC refers to lethal concentration of a chemical dissolved in water. LC means lethal concentration and its units are milligrams of a chemical per cubic liter of water. Basically what we are measuring is the impact that chemicals have on fish and bottom of the food chain species like daphnia and the impact on algae growth.

Acute Toxicity is categorized under WHMIS as:

•	Oral - Very Toxic Below 50 mg/kg; Essentially non toxic above 500 mg/kg
•	Skin - Very Toxic below 200 mg/kg; Essentially non-toxic above 1000 mg/kg. A LC50 is used to describe acute inhalation toxicity. It is also used to measure toxicity of chemicals to fish or other aquatic organisms.

Adenocarcinoma

A tumor with glandular (secreting) elements.

Adenosis

Any disease of a gland.

Adhesion

A union of two surfaces that are normally separate.

Aerosol

A fine aerial suspension of particles sufficiently small in size to confer some degree of stability from sedimentation (e.g., smoke or fog).

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.

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.

Alkali

Any chemical substance that forms soluble soaps with fatty acids. Alkalis are also referred to as bases. They may cause severe burns to the skin. Alkalis turn litmus paper blue and have pH values from 8 to 14.

Allergic Reaction

An abnormal physiological response to chemical or physical stimuli.

Amenorrhea

Absence of menstruation.

Anesthetic

A chemical that causes a total or partial loss of sensation. Overexposure to anesthetics can cause impaired judgment, dizziness, drowsiness, headache, unconsciousness, and even death. Examples include alcohol, paint remover, and degreasers.

ANSI American National Standards Institute

A privately funded, voluntary membership organization that identifies industrial and public needs for national consensus standards and coordinates development of such standards.

Antidote

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

API

American Petroleum Institute is an organization of the petroleum industry.

Appearance

A description of a substance at normal room temperature and normal atmospheric conditions. Appearance includes the color, size, and consistency of a material.

Aquatic Toxicity

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

Asphyxiant

A vapor or gas that can cause unconsciousness or death by suffocation (lack of oxygen). Most simple asphyxiants are harmful to the body only when they become so concentrated that they reduce oxygen in the air (normally about 21 percent) to dangerous levels (18 per cent or lower). Asphyxiation is one of the principal potential hazards of working in confined and enclosed spaces.

ASTM

American Society for Testing and Materials is the world's largest source of voluntary consensus standards for materials, products, systems, and services. ASTM is a resource for sampling and testing methods, health and safety aspects of materials, safe performance guidelines, effects of physical and biological agents and chemicals.

Asymptomatic

Showing no symptoms.

Atm

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

Atmosphere-Supplying Respirator

A respirator that provides breathable air from a source independent of the surrounding atmosphere. There are two types: air-line and self-contained breathing apparatus.

Auto-ignition Temperature

The temperature to which a closed, or nearly closed container must be heated in order that the flammable liquid, when introduced into the container, will ignite spontaneously or burn.

BAL British Anti-Lewisite

A name for the drug dimecaprol-a treatment for toxic inhalations.

Base

A substance that (1) liberates hydroxide (OH) ions when dissolved in water, (2) receives hydrogen ions from a strong acid to form a weaker acid, and (3) neutralizes an acid. Bases react with acids to form salts and water. Bases have a pH greater than 7 and turn litmus paper blue. See Alkali.

BCM

Blood-clotting mechanism effects.

Benign

Not recurrent or not tending to progress. Not cancerous.

Biodegradable

Capable of being broken down into innocuous products by the action of living things.

Biohazardous

Any material containing bacterial or viruses (germs) can cause disease in humans.

Biopsy

Removal and examination of tissue from the living body.

BLD

Blood effects.

Boiling Points-BP

The temperature at which a liquid changes to a vapor state at a given pressure. The boiling point usually expressed in degrees Fahrenheit at sea level pressure (760 mmHg, or one atmosphere). For mixtures, the initial boiling point or the boiling range may be given.

Flammable materials with low boiling points generally present special fire hazards. Some approximate boiling points:

Propane -44°F
Anhydrous Ammonia -28°F
Butane 31°F
Gasoline 100°F
Allyl Chloride 113°F
Ethylene Glycol 387°F

BOM, or BuMines

Bureau of Mines, U.S. Department of Interior.

Bonding

The interconnecting of two objects by means of a clamp and bare wire. Its purpose is to equalize the electrical potential between the objects to prevent a static discharge when transferring a flammable liquid from one container to another. The conductive path is provided by clamps that make contact with the charged object and a low resistance flexible cable which allows the charge to equalize. See Grounding.

Bulk Density

Mass of powdered or granulated solid material per unit of volume.

Centigrade, a unit of temperature.

C02

Carbon dioxide is a heavy, colorless gas that is produced by the combustion and decomposition of organic substances and as a byproduct of many chemical processes. C02 will not burn and is relatively nontoxic (although high concentrations, especially in confined spaces, can create hazardous oxygen-deficient environments).

Approximately.

CAA

Clean Air Act was enacted to regulate/reduce air pollution. CAA is administered by U.S. Environmental Protection Agency.

Canutec

Canadian Transport Emergency Centre. This 24 hour emergency service provides information in case of accidents or emergencies which may occur during the transport of dangerous goods.

Carcinogen

A substance or agent capable of causing or producing cancer in mammals, including humans. A chemical is considered to be a carcinogen if

•	It has been evaluated by the International Agency for Research on Cancer (IARC) and found to be a carcinogen or potential carcinogen; or
•	It is listed as a carcinogen or potential carcinogen in the Annual Report on Carcinogens published by the National Toxicology Program (NTP) (latest edition); or
•	It is regulated by OSHA as a carcinogen.

Carcinogenic Effects

This indicates if a chemical can cause cancer. Two organizations collect and report data on chemicals that are suspected and/or known carcinogens.

Carcinogenicity

The ability to produce cancer.

Carcinoma

A malignant tumor. A form of cancer.

CAS

Chemical Abstracts Service is an organization under the American Chemical Society. CAS abstracts and indexes chemical literature from all over the world in "Chemical Abstracts." "CAS Numbers" are used to identify specific chemicals or mixtures.

CAS - (Chemical Abstract Service number)

This is a unique identification number assigned to each ingredient. This number is the same in both the U.S.A. and Canada.

Caustic

See Alkali.

Cubic centimeter is a volume measurement in the metric system that is equal in capacity to one milliliter (ml). One quart is about 946 cubic centimeters.

Ceiling

This is the airborne concentration of a chemical that should not be exceeded during any part of the working exposure.

Ceiling Limit (PEL or TLV)

The maximum allowable human exposure limit for an airborne substance which is not to be exceeded even momentarily. Also see PEL and TLV.

Central Nervous System

The brain and spinal cord. These organs supervise and coordinate the activity of the entire nervous system. Sensory impulses are transmitted into the central nervous system, and motor impulses are transmitted out.

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act of 1980. The Act requires that the Coast Guard National Response Center be notified in the event of a hazardous substance release. The Act also provides for a fund (the Superfund) to be used for the cleanup of abandoned hazardous waste disposal sites.

CFR

Code of Federal Regulations. A collection of the regulations that have been promulgated under United States Law.

Chemical

An element (e.g., chlorine) or a compound (e.g., sodium bicarbonate) produced by chemical reaction.

Chemical Cartridge Respirator

A respirator that uses various chemical substances to purify in haled air of certain gases and vapors. This type respirator is effective for concentrations no more than ten times the TLV of the contaminant, if the contaminant has warning properties (odor or irritation) below the TLV.

Chemical Family

A group of single elements or compounds with a common general name. Example: acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) are of the "ketone" family; acrolein, furfural, and acetaldehyde are of the "aldehyde" family.

Chemical Formula

The chemical formula gives information on the number and kinds of atoms in one unit (one molecule) of a pure substance.

Chemical Name

The name given to a chemical in the nomenclature system developed by the International Union of Pure and Applied Chemistry (IUPAC) or the Chemical Abstracts Service (CAS). The scientific designation of a chemical or a name that will clearly identify the chemical for hazard evaluation purposes.

Chemical Pneumonitis

Inflammation of the lungs caused by accumulation of fluids due to chemical irritation.

CHEMTREC

Chemical Transportation Emergency Center is a national center established by the Chemical Manufacturers Association (CMA) to relay pertinent emergency information concerning specific chemicals on requests from individuals. CHEMTREC has a 24 hour toll-free telephone number (800-424-9300) to help respond to chemical transportation emergencies.

Chronic Effect

An adverse effect on a human or animal body, with symptoms that develop slowly over a long period of time or that recur frequently. Also see Acute.

Chronic Exposure

Long-term contact with a substance.

Chronic Toxicity

Adverse (chronic) effects resulting from repeated doses of or exposures to a substance over a relatively prolonged period of time. Ordinarily used to denote effects in experimental animals.

Clean Air Act

See CAA.

Clean Water Act (CWA)

Regulates the discharge of non-toxic and toxic pollutants into waterways by municipal, industrial and other point sources and by non-point sources of pollution. Types of pollution include toxic substances, organic wastes, sediment washed from agricultural or construction operations, acid, bacteria and viruses, nutrients, heat and oil and grease. The act gives authority to the federal government and covers all surface waters in the United States.

Major provisions of the act that deal with chemicals are the following:
Section 303: Water quality criteria and standards
Section 301, 204 & 307: Effluent limitation and guidelines
Section 311: Control of discharges of oil and hazardous substances

CMA

Chemical Manufactures Association. See CHEMTREC.

Carbon monoxide is a colorless, odorless, flammable, and very toxic gas produced by the incomplete combustion of carbon. It is also a byproduct of many chemical processes. A chemical asphyxiant; it reduces the blood's ability to carry oxygen. Hemoglobin absorbs CO two hundred times more readily than it does oxygen.

COC

Cleveland Open Cup is a flash point test method.

Coefficient of Water/Oil Distribution

This number compares the amount of material that can be dissolved in oil with the amount that can be dissolved in water. This information is used when selecting the right kind of personal protective equipment.

Combustible

Materials which burn are called combustibles. A combustible liquid has a flash point greater than 37.8 C (100o F) but less than 93.3 C (200 o F). A flammable liquid has a flash point below 37.7C (100o F). Since flammable liquids have flash points close to or below room temperature (16 to 25 o C) they are considered more hazardous than combustible liquids.

Combustible

A term used by NFPA, DOT, and others to classify certain liquids that will burn, on the basis of flash points. Both NFPA and DOT generally define "combustible liquids" as having a flash point of 100°F (37.8°C) or higher but below 200°F (93.3°C). Also see "flammable." Non liquid substances such as wood and paper are classified as "ordinary combustibles" by NFPA.

Combustible Liquid

Any liquid having a flash point at or above 100°F (37.8°C), but below 200°F (93.3°C), except any mixture having components with flashpoints of 200°F (93.3°C) or higher, the total volume of which makes up ninety-nine (99) percent or more of the total volume of the mixture.

Common Name

Any means used to identify a chemical other than its chemical name (e.g., code name, code number, trade name, brand name, or generic name). See Generic.

Compressed Gas

•	A gas or mixture of gases having, in a container, an absolute pressure exceeding 40 pounds per square inch (psi) at 70°F (21.1°C); or
•	A gas or mixture of gases having, in a container, an absolute pressure exceeding 104 psi at 130°F (54.4°C) regardless of the pressure at 70°F (21.1°C); or
•	A liquid having a vapor pressure exceeding 40 Dsi at 100°F (37.8°C) as determined by ASTM D-323-72.

Compressed Gas

This substance is a gas at room temperature but is transported and used under pressure in cylinders.

Conc

See Concentration.

Concentration

The relative amount of a substance when combined or mixed with other substances. Examples: 2 ppm hydrogen sulfide in air, or a 50 percent caustic solution.

Conditions to Avoid

Conditions encountered during handling or storage that could cause a substance to become unstable.

Confined Space

Any area that has limited openings for entry and exit that would make escape difficult in an emergency, has a lack of ventilation, contains known and potential hazards, and is not intended nor designated for continuous human occupancy.

Conjunctivitis

Inflammation of the conjunctiva, the delicate membrane that lines the eyelids and covers the eyeballs.

Container

Any bag, barrel, bottle, box, can, cylinder, drum, reaction vessel, storage tank, or the like that contains a hazardous chemical. For purposes of MSDS or HCS, pipes or piping systems are not considered to be containers.

Controlled Product

Any material, products or substance imported or sold in Canada and classed as one or more of the following: compressed gas, flammable and combustible material, oxidizing material, poisonous and infectious material, corrosive material or dangerously reactive material, under the Controlled Products Regulations.

Corrosive

A substance which will burn, etch, eat away, nut or destroy some materials including human tissue.

Corrosive

A chemical that causes visible destruction of, or irreversible alterations in, living tissue by chemical action at the site of contact. For example, a chemical is considered to be corrosive if, when tested on the intact skin of albino rabbits by the method described by the DOT in Appendix A to 49 CFR Part 173, it destroys or changes irreversibly the structure of the tissue at the site of contact following an exposure period of 4 hours. This term shall not refer to action on inanimate surfaces.

CPSC

Consumer Products Safety Commission has responsibility for regulating hazardous materials when they appear in consumer goods. For CPSC purposes, hazards are defined in the Hazardous Substances Act and the Poison Prevention Packaging Act of 1970.

Curettage

Cleansing of a diseased surface.

Cutaneous Toxicity

See "Dermal Toxicity."

CWA

Clean Water Act was enacted to regulate/reduce water pollution. It is administered by EPA.

Cyst

A sac containing a liquid. Most cysts are harmless.

Cytology

The scientific study of cells.

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Decomposition

Breakdown of a material or substance (by heat, chemical reaction, electrolysis, decay, or other processes) into parts or elements or simpler compounds.

Density

The mass (weight) per unit volume of a substance. For example, lead is much more dense than aluminum. - This is the measure of the heaviness of a material. Water has a density of 1 gram per milliliter.

Depressant

A substance that reduces a bodily functional activity or an instinctive desire, such as appetite.

Dermal

Relating to the skin.

Dermal Toxicity

Adverse effects resulting from skin exposure to a substance. Ordinarily used to denote effects in experimental animals.

DHHS

U.S. Department of Health and Human Services (replaced U.S. Department of Health, Education and Welfare). NIOSH and the Public Health Service (PHS) are part of DHHS.

Dike

A barrier constructed to control or confine hazardous substances and prevent them from entering sewers, ditches, streams, or other flowing waters.

Dilution Ventilation

Air flow designed to dilute contaminants to acceptable levels. Also see general ventilation or exhaust.

DOL

U.S. Department of Labor. OSHA and MSHA are part of DOL.

DOT

U.S. Department of Transportation regulates transportation of chemicals and other substances.

Dry Chemical

A powdered fire extinguishing agent usually composed of sodium bicarbonate, potassium bicarbonate, etc.

Dsyplasia

An abnormality of development.

Dysmenorrhea

Painful menstruation.

Dyspnea

A sense of difficulty in breathing; shortness of breath.

Ectopic pregnancy

The fertilized ovum becomes implanted outside of the uterus.

Edema

An abnormal accumulation of clear watery fluid in the tissues.

Endocrine glands

Glands that regulate body activity by secreting hormones.

Endometrium

The mucous membrane lining the uterus.

Engineering Controls

These are controls in the work environment that help minimize the levels of airborne chemicals.

Environmental Toxicity

Information obtained as a result of conducting environmental testing designed to study the effects on aquatic and plant life.

EPA

U.S. Environmental Protection Agency.

Epidemiology

Science concerned with the study of disease in a general population. Determination of the incidence (rate of occurrence) and distribution of a particular disease (as by age, sex, or occupation) which may provide information about the cause of the disease.

Epithelium

The covering of internal and external surfaces of the body.

Estrogen

Principal female sex hormone.

Evaporation Rate

The rate at which a material will vaporize (evaporate) when compared to the known rate of vaporization of a standard material. The evaporation rate can be useful in evaluating the health and fire hazards of a material. The designated standard material is usually normal butyl acetate (NBUAC or n-BuAc), with a vaporization rate designated as 1.0. Vaporization rates of other solvents or materials are then classified as:

•	FAST evaporating if greater than 3.0. Examples: Methyl Ethyl Ketone = 3.8, Acetone = 5.6, Hexane = 8.3.
•	MEDIUM evaporating if 0.8 to 3.0. Examples: 190 proof (95°/0) Ethyl Alcohol = 1.4, VM&P Naphtha = 1.4, MIBK = 1.6.
•	SLOW evaporating if less than 0.8. Examples: Xylene = 0.6, Isobutyl Alcohol = 0.6, Normal Butyl Alcohol = 0.4, Water = 0.3, Mineral Spirits = 0.1.

Explosion Power

This measures the amount of energy released for each kilogram of substance that is exploded.

Explosive

A chemical that causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pressure, or high temperature.

Exposure Limits

The most common exposure limits are TLV's (threshold limit values). TLV's are for airborne concentrations of material and suggest conditions which it is believed nearly all workers may be repeatedly exposed day after day without any harmful effects. However, because there is a large variation in the way people react to chemical exposures, this is only a guideline. There are three main types of TLV's. They are: (Time-Weighted Averages), (Short-term Exposure Limits and Ceilings).

Exposure or Exposed

State of being open and vulnerable to a hazardous chemical by inhalation, ingestion, skin contact, absorption, or any other course; includes potential (accidental or possible) exposure.

Extinction

This suggests types of fire extinguishers that can be used to fight fires or an explosion of material.

Extinguishing Media

The firefighting substance to be used to control a material in the event of a fire. It is usually identified by its generic name, such as fog, foam, water, etc.

Eye Protection

Fahrenheit is a scale for measuring temperature. On the Fahrenheit scale, water boils at 212°F and freezes at 32°F.

f/cc

Fibers per cubic centimeter of air.

FDA

U.S. Food and Drug Administration.

Fetal

Pertaining to the fetus.

Fetus

The developing young in the uterus from the seventh week of gestation until birth.

Fibers/cc

The number of fibers that can be filtered from one cubic centimeter of air.

Fibrosis

An abnormal thickening of fibrous connective tissue, usually in the lungs.

FIFRA

Federal Insecticide, Fungicide, and Rodenticide Act requires that certain useful poisons, such as chemical pesticides, sold to the public contain labels that carry health hazard warnings to protect users. It is administered by EPA.

First Aid

Emergency measures to be taken when a person is suffering from overexposure to a hazardous material, before regular medical help can be obtained. This section suggests which first aid treatment should be given should there be an accident or overexposure to the material.

Flammable

A chemical that includes one of the following categories:

•	"Aerosol, flammable." An aerosol that, when tested by the method described in 16 CFR 1500.45, yields a flame projection exceeding 18 inches at full valve opening, or a flash back (a flame extending back to the valve) at any degree of valve opening;
•	"Gas, flammable." (1) A gas that, at ambient temperature and pressure, forms a flammable mixture with air at a concentration of 13 per cent by volume or less; or (2) A gas that, at ambient temperature and pressure, forms a range of flammable mixtures with air wider than 12 percent by volume, regardless of the lower limit;
•	"Liquid, flammable." Any liquid having a flashpoint below 100°F (37.8°C), except any mixture having components with flashpoints of 100°F (37.8°C) or higher, the total of which make up 99 percent or more of the total volume of mixture.
•	"Solid, flammable." A solid, other than a blasting agent or explosive as defined in 1910.109(a), that is liable to cause fire through friction, absorption of moisture, spontaneous chemical change, or retained heat from manufacturing or processing, or which can be ignited readily and when ignited burns so vigorously and persistently as to create a serious hazard. A solid is a flammable solid if, when tested by the method described in 16 CFR 1500.44, it sustained flame at a rate greater than one tenth of an inch per second along its major axis.

Flammable material will burn when heated or contacts a source of ignition. A flammable material has a flash point below 37.8 C (100°F).

Flashback

When a flame travels back along a vapor trail after being ignited by a spark or ignition source, it is called Flashback.

Flashback Occurs

when flame from a torch burns back into the tip, the torch, or the hose. It is often accompanied by a hissing or squealing sound with a smoky or sharp-pointed flame.

Flashpoint

The minimum temperature at which a liquid gives off a vapor in sufficient concentration to ignite when tested by the following methods:

•	Tagliabue Closed Tester (see American National Standard Method of Test for Flash Point by Tag Closed Tester, Z11.24 1979 [ASTM D56-79]).
•	Pensky-Martens Closed Tester (see American National Standard Method of Test for Flash Point by Pensky-Martens Closed Tester, Z11.7-1979 [ASTM D93-79]).
•	Setaflash Closed Tester (see American National Standard Method of Test for FlashPoint by Setaflash Closed Tester [ASTM D 3278-78]).

This is the lowest temperature at which a flammable or combustible liquid will emit enough vapor to burn when it comes into contact with an open flame or spark.

Foreseeable Emergency

Any potential occurrence such as, but not limited to, equipment failure, rupture of containers, or failure of control equipment which could result in an uncontrolled release of a hazardous chemical into the workplace.

Formula

The scientific expression of the chemical composition of a material (e.g., water is H20, sulfuric acid is H2S04, sulfur dioxide is S02).

Freezing Point

This is the temperature at which a material changes from a liquid to a solid under normal conditions of pressure.

Fume

A solid condensation particle of extremely small diameter, commonly generated from molten metal as metal fume.

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Gram is a metric unit of weight. One ounce U.S. (avoirdupois) is about 28.4 grams.

g/kg

Grams per kilogram is an expression of dose used in oral and dermal toxicology testing to denote grams of a substance dosed per kilogram of animal body weight. Also see "kg" (kilogram).

General Exhaust

A system for exhausting air containing contaminants from a general work area. Also see Local Exhaust.

Generic Name

A designation or identification used to identify a chemical by other than its chemical name (e.g., code name, code number, trade name, and brand name).

Genetic

Pertaining to or carried by genes. Hereditary.

Gestation

The development of the fetus in the uterus from conception to birth; pregnancy.

Grounding

water pipe or to a grounding bus and ground rod. See Bonding.

Gynecology

The study of the reproductive organs in women.

Hand Protection

Specific type of gloves or other hand protection required to prevent harmful exposure to hazardous materials.

Hazardous Chemical

Any chemical whose presence or use is a physical hazard or a health hazard.

Hazardous Combustion Products

If a material emits a hazardous product while being burned, the products will be listed in this section of the MSDS.

Hazardous Decomposition Products

When chemicals burn, react with oxygen in the air or react with other workplace chemicals, they undergo various changes and may decompose to produce hazardous products.

Hazardous Warning Words, pictures, symbols, or combination thereof presented on a label or other appropriate form to inform of the presence of various materials.

Hazardous Ingredients

These are the chemical names of ingredients considered hazardous under WHMIS.

Hazardous Polymerixation

A reaction which can be extremely dangerous possibly causing fire or explosion.

HCS

Hazard Communication Standard is an OSHA regulation issued under 29 CFR Part 1910.1200.

Health Hazard

A chemical for which there is significant evidence, based on at least one study conducted in accordance with established scientific principles, that acute or chronic health effects may occur in exposed employees. The term "health hazard" includes chemicals that are carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents that act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.

Hematoma

A blood clot under the surface of the skin.

Hematopoietic System

The blood-forming mechanism of the human body.

Hematuria

The presence of blood in the urine.

Hemoglobin

An iron-containing conjugated protein or respiratory pigment occurring in the red blood cells of vertebrates.

Hepatotoxin

A substance that causes injury to the liver.

Highly toxic

A chemical in any of the following categories:

•	A chemical with a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
•	A chemical with a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
•	A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for 1 hour (or less if death occurs with in 1 hour) to albino rats weighing between 200 and 300 grams each.

Hormones

Act as chemical messengers to body organs.

Hyperplasia

Increase in volume of a tissue or organ caused by the growth of new cells.

IARC

International Agency for Research on Cancer. They publish a list of chemicals which may cause cancer in humans or animals.

Ignitable

Capable of being set afire.

Impervious

A material that does not allow another substance to pass through or penetrate it.

Incompatibility

Some chemicals may react violently when mixed together or may give off toxic vapors.