Historical Document
This document is provided by the National Center for Environmental Health ONLY as an historical reference for the public health community. It is no longer being maintained and the data it contains may no longer be current and/or accurate.
For current information about cancer clusters, please visit
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What are trichlorophenols?
Trichlorophenols are part of a group of human-made chemicals called chlorophenols that are produced by adding chlorines to phenol. Trichlorophenols do not occur naturally. Most trichlorophenols are no longer produced in the United States but are still available in other countries. In the past, they were used mostly as disinfectants and pesticides such as fungicides and herbicides. They also were used to preserve wood, glue, and leather.
The human body can change other chemicals to trichlorophenols. When you are exposed to hexachlorobenzene, pentachlorophenol, and hexachlorocyclohexane, your body forms trichlorophenols. Two different trichlorophenols were measured in your urine sample: 2,4,5-trichlorophenol and 2,4,6-trichlorophenol.
Hexachlorocyclohexane has several forms: alpha, beta, gamma, and delta. The gamma form is usually called lindane. It is a persistent pesticide once used in agriculture and still used to treat scabies and lice on people. The other forms were once used as fungicides or to make other chemicals. Although in the United States lindane was banned from production in the late 1970s, other countries still produce it.
How do trichlorophenols enter the environment?
Trichlorophenols can enter the environment when they are being made, when they are used as pesticides or disinfectants, and when they are produced from the breakdown of other chemicals. Most trichlorophenols released to the environment go into water and soil.
2,4,5- trichlorophenol can be released into the environment from the chlorination of phenol-containing wastewater or drinking water and from the bleaching process in pulp and paper mills.
Trichlorophenols stick to soil and sediments at the bottom of lakes, streams, and rivers. Microorganisms break down and remove low levels of trichlorophenols from water, soil, or sediment in a few days to weeks.
Fish and shellfish from areas near sewage releases or industries that use trichlorophenols can accumulate trichlorophenols in their tissues.
How can people be exposed to trichlorophenols?
- By breathing air contaminated with trichlorophenols. This is likely only if you are exposed to air near places where these chemicals are made, around hazardous waste sites, or during forest fires.
- Drinking contaminated water, eating food contaminated with trichlorophenols or chemicals that are metabolized to trichlorophenols.
- By absorbing trichlorophenols through the skin after an exposure.
People who make trichlorophenols or use them as pesticides or disinfectants are most likely to have high exposure to these chemicals.
Can exposure to trichlorophenols make people sick?
Yes. Trichlorophenols can cause irritation of the skin, eyes, nose, throat, and lungs. We need more studies to know whether trichlorophenols can cause other problems.
Workers who make pesticides from chlorophenols and were exposed to chlorophenols as well as other chemicals through breathing and through the skin can have acne and mild injury to their livers.
Can trichlorophenols cause any types of cancer, including leukemia?
Long-term use of high doses of 2,4,6-trichlorophenol in food caused leukemia in lab rats and liver cancer in mice. Human exposure to 2,4,6-trichlorophenol has not been linked with any cancers including leukemia.
Can trichlorophenol cause reproductive or developmental problems?
In lab animals, 2,4,6-trichlorophenol has caused lower birth weight in newborns and fewer offspring. In humans, we do not know whether exposure to trichlorophenols causes reproductive or developmental problems.
