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 Cyanide and how is it used?
Cyanide is a carbon-nitrogen chemical unit which combines with many
organic and inorganic compounds. The most commonly used form, hydrogen
cyanide, is mainly used to make the compounds needed to make nylon and
other synthetic fibers and resins. Other cyanides are used as
Why is Cyanide 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 cyanide has been set at 0.2 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 0.2 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 cyanide to potentially cause the following
health effects when people are exposed to it at levels above the MCL for
relatively short periods of time: rapid breathing, tremors and other
Long-term: Cyanide has the potential to cause the following
effects from a lifetime exposure at levels above the MCL: weight loss,
thyroid effects, nerve damage.
How much Cyanide is produced and released to the environment?
Production of the most common cyanides was roughly 5 billion pounds a year
in the late 1980s and early 1990s. The major cyanide releases to water
are discharges from metal finishing industries, iron and steel mills,
and organic chemical industries. Releases to soil appear to be primarily
from disposal of cyanide wastes in landfills and the use of
cyanide-containing road salts. Chlorination treatment of some
wastewaters can produce cyanides as a by-product.
From 1987 to 1993, according to the Toxics Release Inventory
cyanide compound releases to land and water totaled about 1.5 million
lbs. These releases were primarily from steel mills and metal heat
treating industries. The largest releases occurred in California and
What happens to Cyanide when it is released to the environment?
Cyanides are generally not persistent when released to water or soil, and
are not likely to accumulate in aquatic life. They rapidly evaporate and
are broken down by microbes. They do not bind to soils and may leach to
How will Cyanide be detected in and removed from my drinking water?
The regulation for cyanide became effective in 1992. Between 1993 and
1995, EPA required your water supplier to collect water samples once and
analyze them to find out if cyanide is present above 0.2 ppm. If it is
present above this level, the system must continue to monitor this
contaminant every 3 months.
If contaminant levels are found to be consistently above the MCL,
your water supplier must take steps to reduce the amount of cyanide so
that it is consistently below that level. The following treatment
methods have been approved by EPA for removing cyanide: Ion Exchange,
Reverse Osmosis, Chlorine.
How will I know if Cyanide is in my drinking water?
If the levels of cyanide exceed the MCL, 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: 0.2 ppm (parts per million)
MCL: 0.2 ppm
Cyanide Releases to Water and Land, 1987 to 1993 (in pounds):
Top Ten States|
Blast furnaces + steel
Metal heat treating
Ind organic chems
Plating + polishing
* Water/Land totals only include facilities with releases greater
than a certain amount - usually 1000 to 10,000 lbs.
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water