1,2,3-Trichloropropane (TCP) is an
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...
with the formula CHCl(CH
2Cl)
2. It is a colorless liquid that is used as a solvent and in other specialty applications.
[
]
Production
1,2,3-Trichloropropane is produced the addition of chlorine to allyl chloride
Allyl chloride is the organic compound with the formula C H2=CHCH2 Cl. This colorless liquid is insoluble in water but soluble in common organic solvents. It is mainly converted to epichlorohydrin, used in the production of plastics. It is a chl ...
. TCP also may be produced as a by-product also is produced in significant quantities as an unwanted by-product of the production of other chlorinated compounds such as epichlorohydrin and dichloropropene.
Uses
Historically, TCP has been used as a paint or varnish remover, a cleaning
Cleaning is the process of removing unwanted substances, such as dirt, infectious agents, and other impurities, from an object or environment. Cleaning is often performed for aesthetic, hygienic, functional, environmental, or safety purposes ...
and degreasing agent, and a solvent.[ It is also used as an intermediate in the production of ]hexafluoropropylene
Hexafluoropropylene is the fluoroalkene with the formula CF3CF=CF2. It is the perfluorocarbon counterpart to the hydrocarbon propylene. It is mainly used to produce copolymers with tetrafluoroethylene. Hexafluoropropylene is used as a chemical ...
. It is a crosslinking agent
In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
for polysulfide
Polysulfides are a class of chemical compounds containing chains of sulfur atoms. There are two main classes of polysulfides: inorganic and organic. Among the inorganic polysulfides, there are ones which contain anions, which have the general formu ...
polymers and sealants.
Effects of exposure
Humans can be exposed to TCP by inhaling its fumes or through skin contact and ingestion. TCP is recognized in California as a human carcinogen
A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...
, and extensive animal studies have shown that it causes cancer. Short term exposure to TCP can cause throat and eye irritation and can affect muscle coordination and concentration. Long term exposure can affect body weight and kidney function.[
]
Regulation
United States
Proposed federal regulation
TCP was not regulated as a contaminant by the federal government, but research shows that it could have severe health effects; only the state of California had significant regulation of this compound.
In a drinking water project proposed by the United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...
(EPA), TCP was one of sixteen suspected human carcinogens being considered for regulation in 2011.
State regulation
Pre-1980s, agricultural use of chloropropane-containing soil fumigants for use as pesticides and nematicides was prevalent in the United States. Some soil fumigants, which contained a mixture of primarily 1,3-dichloropropene and 1,2-dichloropropane, and in which 1,2,3-TCP was a minor component, e.g., trade name of D-D, were marketed for the cultivation of various crops including citrus fruits, pineapples, soy beans, cotton, tomatoes, and potatoes. D-D was first marketed in 1943, but is no longer available in the United States, and has been replaced with Telone II, which was first available in 1956. Telone II reportedly contains as much as 99 percent 1,3-dichloropropene and up to 0.17 percent by weight 1,2,3-TCP (Zebarth et al., 1998). Before 1978, approximately 55 million pounds/year of 1,3-dichloropropene were produced annually in the United States, and approximately 20 million pounds/year of 1,2-dichloropropane and 1,2,3-TCP were produced as by-products in the production of 1,3-dichloropropene. Over 2 million pounds of pesticides containing 1,3-dichloropropene were used in California alone in 1978. Telone II is still used for vegetables, field crops, fruit and nut trees, grapes, nursery crops, and cotton.
The California State Water Resources Control Board's Division of Drinking Water established an enforceable Maximum Contaminant Level (MCL) of 5 ng/L (parts per trillion). The state of Alaska has promulgated standards establishing cleanup levels for 1,2,3-trichloropropane contamination in soils and groundwater. The state of California considers 1,2,3-trichloropropane to be a regulated contaminant that must be monitored. The state of Colorado has also promulgated a groundwater standard although there is no drinking water standard. Although there is not much regulation on this substance, it has proved that TCP is a carcinogen in laboratory mice, and most likely a human carcinogen as well. On a federal scale, there is no MCL for this contaminant. The Permissible Exposure Limit (PEL) in occupational setting for air is 50 ppm or 300 mg/m. The concentration in air at which TCP becomes an Immediate Danger to Life and Health (IDLH) is at 100 ppm. These regulations were reviewed in 2009.
TCP as an emerging contaminant
TCP does not contaminate soil. Instead, it leaks down into groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...
and settles at the bottom of the reservoir because TCP is more dense
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematically ...
than water. This makes TCP in its pure form a DNAPL ( Dense Nonaqueous Phase Liquid) and it is, therefore, harder to remove it from groundwater. There is no evidence that TCP can naturally decompose
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...
, but it might in favorable conditions. Groundwater remediation of TCP can occur through in situ chemical oxidation
In situ chemical oxidation (ISCO), a form of advanced oxidation process, is an environmental remediation technique used for soil and/or groundwater remediation to lower the concentrations of targeted environmental contaminants to acceptable leve ...
, permeable reactive barriers, and other remediation techniques. Several TCP remediation strategies have been studied and/or applied with varying degrees of success. These include extraction with granular activated carbon, in situ chemical oxidation, and in situ chemical reduction. Recent studies suggest that reduction with zerovalent metals, particularly zerovalent zinc, may be particularly effective in TCP remediation. Bioremediation
Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...
may also be a promising clean-up technique.
References
External links
California Department of Public Health
{{DEFAULTSORT:Trichloropropane, 1, 2, 3-
Chloroalkanes
Halogenated solvents
IARC Group 2A carcinogens