Chemical substances can have adverse effects on people, depending on the nature of the chemical, its concentration, the nature and duration of the exposure and individual susceptibility.
A Threshold Limit Value (TLV) for a chemical is the maximum amount of airborne chemical which people may be exposed to repeatedly without causing adverse effect.
Category
Description
ceiling
This is the amount of chemical that should not be exceeded at any time.
short-term exposure limit (STEL)
This is the concentration of a compound which a person may be exposed to for a short period of time (15 minutes) without tissue damage, irritation or other adverse effect.
time-weighted average (TWA)
This is the concentration of chemical that a person can be repeatedly exposed to over a long period without adverse effect, based on a time-weighted average concentration for the average work week of 40 hours as five 8 hour days.
These are developed in populations.
An individual may differ from the population because of:
(1) hypersensitivity or tolerance to the chemical
(2) concurrent disease making a person more susceptible to drug toxicity
(3) interactions with other chemicals or drugs, including multiple exposures to a chemical at different times and locations, which may contribute to cumulative toxicity
(4) genetic variation in metabolic pathways
To read more or access our algorithms and calculators, please log in or register.
