This is a fact sheet about a chemical that may be found in some public or
private drinking water supplies. It may cause health problems if found
in amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What is 1,2,4-Trichlorobenzene and how is it used?
1,2,4-Trichlorobenzene (1,2,4-TCB) is an aromatic, colorless organic
liquid. The greatest use of 1,2,4-trichlorobenzene is primarily as a dye
carrier. It is also used to make herbicides and other organic chemicals;
as a solvent; in wood preservatives; in abrasives. It was once used as a
soil treatment for termite control.
The list of trade names given below may help you find out whether you are using this chemical at home or work.
Trade Names and Synonyms:
Why is 1,2,4-Trichlorobenzene being regulated?
In 1974, Congress passed the Safe Drinking Water Act. This law requires
EPA to determine safe levels of chemicals in drinking water which do or
may cause health problems. These non-enforceable levels, based solely on
possible health risks and exposure, are called Maximum Contaminant Level
The MCLG for 1,2,4-trichlorobenzene has been set at 0.07 parts per
million (ppm) because EPA believes this level of protection would not
cause any of the potential health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a
Maximum Contaminant Level (MCL). MCLs are set as close to the MCLGs as
possible, considering the ability of public water systems to detect and
remove contaminants using suitable treatment technologies.
The MCL has also been set at 0.07 ppm because EPA believes, given
present technology and resources, this is the lowest level to which
water systems can reasonably be required to remove this contaminant
should it occur in drinking water.
These drinking water standards and the regulations for ensuring
these standards are met, are called National Primary Drinking Water
Regulations. All public water supplies must abide by these regulations.
What are the health effects?
Short-term: EPA has found 1,2,4-trichlorobenzene to potentially cause the
following health effects when people are exposed to it at levels above
the MCL for relatively short periods of time: changes in liver, kidneys
and adrenal glands.
Long-term: 1,2,4-Trichlorobenzene has the
potential to cause the following effects from a lifetime exposure at
levels above the MCL: increased adrenal gland weights.
How much 1,2,4-Trichlorobenzene is produced and released to the
Current production figures on 1,2,4-trichlorobenzene are not available.
EPA estimated 1983 production to be in the range of 3 to 8 million lbs.,
with imports over 3 million lbs. Major environmental releases of
1,2,4-trichlorobenzene are due to its manufacture and use as a dye
From 1987 to 1993, according to EPA's Toxic Chemical Release
Inventory, 1,2,4-trichlorobenzene releases to land and water totalled
over 180,000 lbs. These releases were primarily from textile finishing
industries. The largest releases occurred in North Carolina and
What happens to 1,2,4-Trichlorobenzene when it is released to the
1,2,4-Trichlorobenzene (1,2,4-TCB) binds well to the soil and therefore
will not leach appreciably to the groundwater when released to land.
However, 1,2,4-TCB has been detected in some groundwater samples which
indicates that it can be transported there by some process. If released
to water it will largely evaporate within a few hours. It has some
potential to accumulate in fish.
How will 1,2,4-Trichlorobenzene be detected in and removed from my
The regulation for 1,2,4-trichlorobenzene became effective in 1994.
Between 1993 and 1995, EPA required your water supplier to collect water
samples every 3 months for one year and analyze them to find out if
1,2,4-trichlorobenzene is present above 0.5 ppb. If it is present above
this level, the system must continue to monitor this contaminant.
If contaminant levels are found to be consistently above the MCL,
your water supplier must take steps to reduce the amount of
1,2,4-trichlorobenzene so that it is consistently below that level. The
following treatment methods have been approved by EPA for removing
1,2,4-trichlorobenzene: Granular activated charcoal in combination with
Packed Tower Aeration.
How will I know if 1,2,4-Trichlorobenzene is in my drinking water?
If the levels of 1,2,4-trichlorobenzene exceed the MCL, 0.07 ppm, the
system must notify the public via newspapers, radio, TV and other means.
Additional actions, such as providing alternative drinking water
supplies, may be required to prevent serious risks to public health.
This is a factsheet about a chemical that may be found in some
public or private drinking water supplies. It may cause health problems
if found in amounts greater than the health standard set by the United
States Environmental Protection Agency (EPA).
Drinking Water Standards:
|Mclg: 0.07 ppm (parts per million)
Mcl: 0.07 ppm
1,2,4-Trichlorobenzene Releases to Water and Land, 1987 to 1993 (in
|TOTALS (in pounds)
Top Five States*|
Finishing plants, misc
Finishing plants, synth.
Weaving, finishing mills
Knitting mills, misc
Knit outerwear mills
* Water/Land totals only include facilities with releases greater than 100 lbs.
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water