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 Ortho-dichlorobenzene and how is it used?
Ortho-dichlorobenzene, (o-DCB) is a colorless organic liquid with a
pleasant, aromatic odor. The greatest use of o-dichlorobenzene is as a
chemical intermediate for making agricultural chemicals, primarily
herbicides. Other present and past uses include: solvent for waxes,
gums, resins, wood preservatives, paints; insecticide for termites and
borers; in making dyes; as a coolant, deodorizer, degreaser.
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 Ortho-dichlorobenzene 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 o-DCB has been set at 0.6 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 been set at 0.6 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: o-DCB is not known to cause any health problems when people
are exposed to it at levels above the MCL for relatively short periods
Long-term: o-DCB has the potential to cause the following effects
from a lifetime exposure at levels above the MCL: damage to the nervous
system, liver, kidneys and blood cells.
How much Ortho-dichlorobenzene is produced and released to the environment?
Production of o-DCB was estimated at 43 million lbs. in 1991. Its use in
manufacturing and solvents may be significant sources of discharges into
water. Dichlorobenzenes also enter water systems from the use of o-DCB
as a deodorant in industrial wastewater treatment. Chemical waste dump
leachates and industrial wastewater are the major source of pollution of
dichlorobenzenes to Lake Ontario.
From 1987 to 1993, according to the Toxic Release Inventory, o-DCB
releases to land and water totalled 248 million lbs., mostly to land.
These releases were primarily form organic chemical manufacturing
industries. The largest releases occurred in New Jersey.
What happens to Ortho-dichlorobenzene when it is released to the environment?
If released to soil, o-DCB can bind to soil particles. However, its
detection in groundwater indicates that leaching can occur. It will
evaporate from soil or surface water and will be broken down by
microbes. o-DCB is likely to accumulate in fish and other aquatic life.
How will Ortho-dichlorobenzene be detected in and removed from my drinking water?
The regulation for o-DCB became effective in 1992. 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 o-DCB 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 o-DCB so
that it is consistently below that level. The following treatment
methods have been approved by EPA for removing o-DCB: Granular activated
charcoal in combination with Packed Tower Aeration.
How will I know if Ortho-dichlorobenzene is in my drinking water?
If the levels of o-DCB exceed the MCL, 0.6 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: 0.6 ppm (parts per million)
Mcl: 0.6 ppm
Ortho-dichlorobenzene Releases to Water and Land, 1987 to 1993 (in pounds):
|TOTALS (in pounds)
Top Five States*|
Cyclic crudes, dyes
Gum, wood chems.
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water
* Water/Land totals only include facilities with releases greater
than a certain amount - usually 1000 to 10,000 lbs.