United States
Environmental Protection
Agency
Office of Water
4601
EPA.811-F-95-003 I-C
October 1995
vvEPA National Primary Drinking
Water Regulations
Dioxin (2,3,7,8-TCDD)
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: ZERO
MCL: 0.03 PPB
WHAT is .
DIOXIN
AND HOW IS IT USED?
Dioxin is an organic solid of white crystalline needles. Dioxin is not produced or
used commercially in the US. It is a contaminant formed in the production of some
chlorinated organic compounds, including a few herbicides such as silvex. It may
also be formed during combustion of a variety of chlorinated organic compounds.
The list of trade names given below may help you find out whether you are using
this chemical at home or work.
WHYIS DIOXIN
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 Goals.
The MCLG for dioxin has been set at zero 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
Eotntaminant 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.
f he MCL has been set at 0.03 parts per billion (ppb) because EPA believes,
BftSen present technology and resources, this is the lowest level to which water
systems can reasonably be required to remove this contaminant should it occur
jn drinking water.
These drinking water standards and the regulations for ensuring these stan-
dards are met, are called National Primary Drinking Water Regulations. All public
water supplies must abide by these regulations..' v
WHAT ARE THE
HEALTH EFFECTS?
October 1995
Short-term: EPA has found dioxin to potentially cause the
following health effects when people are exposed to it at levels
above the MCL for relatively short periods of time: liver damage,
weight loss, wasting of glands important to the body's immune
system. <
Long-term: Dioxin has the potential to cause the following
effects from a lifetime exposure at levels above the MCL: a variety
of reproductive effects, from reduced fertility to birth defects;
TRADE NAMES AND
SYNONYMS:
DIOXIN
TETRADIOXIN
Consumer Version
Printed on Recycled Paper
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cancer.
Dioxin is released to the environment in emissions from the incineration of
municipal refuse and certain chemical wastes, in exhaust from automobiles
powered. by leaded gasOline, in er iôns from wood burning in the presence of
chlorine, in accidental fires involv . transformers containing PCBS and chlori
nated benzenes and from the improper disposal of certain chlorinated chemical
wastes. It has been released to the environment as a lOw level impurity in various
pesticides.
Dioxin is one of the most toxic and environmentally stable tricyclic aromatic
compounds of its structural class.
Due to its very low water solubility, most of the dioxin occurring in water will
adhere to sediments and suspended silts. Similarly, it tends to adhere to soil if
released to land, and is not likely to leach to ground water. Two processes which
may be able to remove dioxin from water and soil are evaporation and breakdown
• by sunlight. Dioxin is generally resistant to microbial breakdown. Dioxin has a very
great tendency to accumulate in aquatic life, from algae to fish.
• The regulation for dioxin 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 fin,d out if dioxin is present above 5 parts per trillion. If
it is present. above this level, the system must continue to monitor this contami-
nant. . .
If contaminant levels are found to be consistently above the MCL, your water
supplier must take steps to reduce the amount of dioxin so that it is consistently
below that level. The. following treatment methods have been approved by EPA
for removing dioxin: Granular activated charcoal.
If the levels of dioxin exceed the MCL, 0.03 ppb, 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.
How MUCH DIOXIN
IS PRODUCED AND
RELEASED TO THE
ENVIRONMENT?
WHAT HAPPENS TO
DIOXIN
WHEN IT IS RELEASED TO
THE ENVIRONMENT?
How Vv1LL
DioxiN
BE DETECTED.IN AND
REMOVED FROM
M DRINKING WATER?
How WILL.. IKNOwIF
DIoXIN IS IN MY DRINKING
WATER?
Learn more about your drinking water!
EPA strongly encourages people to learn more Your state Department of Health/Environment is also a
about theirdrinking water, andtosupportlocalefforts valuable source of information.
to proteOt and upgrade the supply of safe drinking
water. Your water bill .or telephone book’s govern-U
ment listings are a good starting point.
Your Ioáal water supplier can give you a list of the
chemicals they test for in your water, as well as how
your water is treated.
For help in locating these agencies or for information on
drinking water in general, call:
EPA’s Safe Drinking Water Hotline: (800) 426 4791.
For additional information on the uses and releases of
chemicals in your state, contact the:
Community Right-to-Know Hotline: (800) 535-0202.
October 1995 Consumer Version
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