Trichloroethane (TCA) Pollution

Synonyms: methyl chloroform, methyltrichloromethane, trichloromethylmethane, alpha trichloroethane

1,1,1-TCA is an organic chemical introduced in the environment by human activity. Although, in theory, its natural formation cannot be excluded, so far it was not reported. Thus, 1,1,1-TCA presence in the environment (water, air, soil) is associated with spills and leaks from facilities using this chemical or from consumer products containing it.

Until recently, 1,1,1-TCA was a widely used solvent in degreasing operations, as well as a solvent in household products such as cleaners, paints, and glues. It is also found in building materials.

1,1,1-TCA is less toxic compared to other chlorinated solvents (such as PCE, TCE, or carbon tetrachloride). However, 1,1,1-TCA was proven to affect the ozone layer, which is why its production has declined and it is no more manufactured for domestic use in the United States. Despite its lower toxicity compared to other chemicals in its class, 1,1,1-TCA can create adverse health effects when exposure to high amounts occurs.

The Environmental Protection Agency has established a Maximum Contaminant Level (MCL) for 1,1,1-TCA in water of 0.2 parts per million (or milligrams per Liter), which is equivalent to 200 parts per billion (ppb or micrograms per Liter). This is higher than the 5 ppb which is the MCL for PCE and also for TCE in water. The limit in air (above which health risk is assumed) is at 350 ppm.

Where Is 1,1,1-TCA Used/Found?

General Description/Properties

1,1,1-TCA is a halogenated organic compound composed of 2 atoms of carbon and 3 atoms of chlorine (all chlorine atoms are bound to one carbon atom, while hydrogen is bound to the other carbon atom). The two carbons are bound to each other by a single chemical bond (covalent bond).

1,1,1-TCA is a colorless liquid with a sweet sharp odor. It is little flammable under normal temperature and pressure and it is part of a class of chemicals also known as halogenated volatile organic compounds (HVOCs). This means that it evaporates (part of it goes from liquid into gaseous form when in contact with air).

1,1,1-TCA is also a member of the class of chemicals generically referred to as “chlorinated solvents”. Due to the presence of one or more chlorine atoms in their structure chlorinated solvents are heavier than water. They are also not miscible with water. Thus, chlorinated solvents are also referred to as Dense Non-Aqueous Phase Liquids (DNAPLs).

Environment Fate and Transport

Basically, when spilled into the environment, part of the spilled 1,1,1-TCA will evaporate, while another part will infiltrate through the ground into the subsurface. Thus, 1,1,1-TCA spilled in the environment is found in the following media:

The transport of 1,1,1-TCA in the environment is governed by the physical-chemical characteristics of this chemical, which dictates how much of it will partition into air, water, and soil respectively. Also, its characteristics will determine how much of it will sorb to soil particles, thus retarding its subsurface transport. The degradation (bio- and chemical degradation) of 1,1,1-TCA in the environment is also a function of its structure and characteristics. Without getting into details on physical-chemical characteristics of this compound (largely available from textbooks, MSDS sheets, etc), a summary of 1,1,1-TCA fate and transport in the environment is given below:

How Can You Be Exposed to 1,1,1-TCA?

Through inhalation by the breathing of:

Through skin absorption while:

Through ingestion by consuming:

Health Effects

Non-Cancer Effects

Exposure to high amounts of 1,1,1-TCA for short times may cause a series of health issues which will disappear when the exposure ceases:

Much higher amounts of 1,1,1-TCA may cause more serious effects:

Exposure to low levels of 1,1,1-TCA is more difficult to evaluate due to the lack of long-term observations which cannot be tested in the lab.

Cancer Effects – 1,1,1-TCA is not classified as a human carcinogen