Environmental Health and Safety

MSDS Glossary

Target Organ Toxin
A toxic substance that attacks a specific organ of the body. For example, overexposure to carbon tetrachloride can cause liver damage.
TCL
Toxic concentration low, the lowest concentration of a gas or vapor capable of producing a defined toxic effect in a specified test species over a specified time.
TDL
Toxic dose low, lowest administered dose of a material capable of producing a defined toxic effect in a specified test species.
Temp
Temperature.
Ter
See Teratogen.
Teratogen
A substance or agent, exposure to which by a pregnant female can result in malformations in the fetus.
Tfx
Toxic effects(s).
TLV
Threshold Limit Value is a term used by ACGIH to express the airborne concentration of material to which nearly all persons can be exposed day after day without adverse effects. ACGIH expresses TLVs in three ways:
  • TLV-TWA: The allowable Time-Weighted Average concentration for a normal 8-hour workday or 40-hour workweek.
  • TLV-STEL: The Short-Term Exposure Limit, or maximum concentration for a continuous 15-minute exposure period (maximum of four such periods per day, with at least 60 minutes between exposure periods, and provided the daily TLV-TWA is not exceeded).
  • TLV-C: The Ceiling exposure limit. The concentration that should not be exceeded even instantaneously.
Torr
A unit of pressure, equal to 1/760 atmosphere.
Toxic
A chemical falling within any of the following categories:
  1. A chemical that has a median lethal dose (LD50) of more than 50 milligrams per kilogram but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
  2. A chemical that has a median lethal dose (LD50) of more than 200 milligrams per kilogram but not more than 1,000 milligrams 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 two and three kilograms each.
  3. A chemical that has a median lethal concentration (LC50) in air of more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor, or more than two milligrams per liter but not more than 20 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each. See also Highly Toxic.
Toxic Substance
Any substance that can cause acute or chronic injury to the human body, or which is suspected of being able to cause diseases or injury under some conditions.
Toxicity
The degree of poisoning that can occur from exposure to a chemical.
Trade name
The trademark name or commercial trade name for a material or product.
Transplacental
A chemical that is capable of causing physical defects in the developing embryo because it can easily cross the placental barrier between mother and fetus.
TSCA
Toxic Substances Control Act. Federal Environmental Legislation administered by EPA that regulates the manufacture, handling, and use of materials classified as "toxic substances."
TWA
Time-Weighted Average exposure is the airborne concentration of a material to which a person is exposed, averaged over the total exposure time-generally the total workday (8 hours). Also see TLV.

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