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PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for Cyanide. 

It is one in a series of Public Health Statements 

about hazardous substances and their health effects. 

A shorter version, the ToxFAQsTM, is also 

available. This information is important because 

this substance may harm you. The effects of 

exposure to any hazardous substance depend on the 

dose, the duration, how you are exposed, personal 

traits and habits, and whether other chemicals are 

present. For more information, call the ATSDR 

Information Center at 1-888-422-8737. 

This public health statement tells you about cyanide 

and the effects of exposure to it. 

The Environmental Protection Agency (EPA) 

identifies the most serious hazardous waste sites in 

the nation. These sites are then placed on the 

National Priorities List (NPL) and are targeted for 

long-term federal clean-up activities. Cyanide has 

been found in at least 471 of the 1,662 current or 

former NPL sites. Although the total number of 

NPL sites evaluated for this substance is not known, 

the possibility exists that the number of sites at 

which cyanide is found may increase in the future 

as more sites are evaluated. This information is 

important because these sites may be sources of 

exposure and exposure to this substance may harm 

you. 

When a substance is released either from a large 

area, such as an industrial plant, or from a container, 

such as a drum or bottle, it enters the environment. 

Such a release does not always lead to exposure. 

You can be exposed to a substance only when you 

come in contact with it. You may be exposed by 

breathing, eating, or drinking the substance, or by 

skin contact. 

If you are exposed to cyanide, many factors will 

determine whether you will be harmed. These 

factors include the dose (how much), the duration 

(how long), and how you come in contact with it. 

You must also consider any other chemicals you are 

exposed to and your age, sex, diet, family traits, 

lifestyle, and state of health. 

1.1 WHAT IS CYANIDE? 

Cyanide is a chemical group consisting of one atom 

of carbon connected to one atom of nitrogen by 

three molecular bonds (C≡N) and cyanides are 

compounds (substances formed by the joining of 

two or more atoms) that contain a cyanide group 

(typically shown as CN). Cyanides can both occur 

naturally or be man-made and many are powerful 

and rapid-acting poisons. Hydrogen cyanide 

(HCN), which is a gas, and the simple cyanide salts 

(sodium cyanide and potassium cyanide) are 

common examples of cyanide compounds. Certain 

bacteria, fungi, and algae can produce cyanide, and 

cyanide is found in a number of foods and plants. 

In certain plant foods, including almonds, millet 

sprouts, lima beans, soy, spinach, bamboo shoots, 

and cassava roots (which are a major source of food 

in tropical countries), cyanides occur naturally as 

part of sugars or other naturally-occurring 

compounds. However, the edible parts of plants 

that are eaten in the United States, including tapioca 

which is made from cassava roots, contain relatively 

low amounts of cyanide. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

Many of the cyanides in soil and water come from 

industrial processes. The major sources of cyanides 

in water are discharges from some metal mining 

processes, organic chemical industries, iron and 

steel plants or manufacturers, and publicly owned 

wastewater treatment facilities. Other cyanide 

sources include vehicle exhaust, releases from 

certain chemical industries, burning of municipal 

waste, and use of cyanide-containing pesticides. 

Much smaller amounts of cyanide may enter water 

through storm water runoff where road salts are 

used that contain cyanide. Cyanide in landfills can 

contaminate underground water. Hydrogen 

cyanide, sodium cyanide, and potassium cyanide are 

the forms of cyanide most likely to be in the 

environment as a result of industrial activities. 

Hydrogen cyanide is a colorless gas with a faint, 

bitter, almond-like odor. Sodium cyanide and 

potassium cyanide are both white solids with a 

slight, bitter, almond-like odor in damp air. 

Cyanide salts and hydrogen cyanide are used in 

electroplating, metallurgy, organic chemicals 

production, photographic developing, manufacture 

of plastics, fumigation of ships, and some mining 

processes. Hydrogen cyanide has also been used in 

gas-chamber executions and as a war gas. 

Chlorination of water contaminated with cyanide 

produces the compound cyanogen chloride. Four 

incidents of cyanide in soil resulted from disposal of 

cyanide-containing wastes in landfills and use of 

cyanide-containing road salts. 

Thiocyanates are a group of compounds formed 

from a combination of sulfur, carbon, and nitrogen. 

Thiocyanates are found in various foods and plants; 

they are produced primarily from the reaction of 

free cyanide with sulfur. This reaction occurs in the 

environment (for example, in industrial waste 

streams that contain cyanide) and in the human 

body after cyanide is swallowed or absorbed. 

Thiocyanate is the major product formed from 

cyanide that passes into the body as the body 

attempts to rid itself of cyanide. Although 

thiocyanates are less harmful than cyanide in 

humans, they are known to affect the thyroid 

glands, reducing the ability of the gland to produce 

hormones that are necessary for the normal function 

of the body. 

Ammonium thiocyanate is used in antibiotic 

preparations, pesticides, liquid rocket fuels, 

adhesives, and matches. It also is used in 

photographic processes, to improve the strength of 

silks, and as a weed killer. 

Thiocyanates are present in water primarily because 

of discharges from coal processing, extraction of 

gold and silver, and mining industries. 

Thiocyanates in soil result from direct application 

of herbicides (weed killers), insecticides, and 

rodenticides and from disposal of byproducts from 

industrial processes. Less important sources 

include release from damaged or decaying tissues of 

certain plants, such as mustard, kale, and cabbage. 

1.2 WHAT HAPPENS TO CYANIDE WHEN 

IT ENTERS THE ENVIRONMENT? 

Cyanide enters air, water, and soil from both natural 

processes and industrial activities. Airborne 

cyanide is generally far below levels that would 

cause concern. In air, cyanide is present mainly as 

gaseous hydrogen cyanide. A small amount of 

cyanide in air is present as fine dust particles. This 

dust eventually settles over land and water. Rain 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

and snow help remove cyanide particles from air. 

The gaseous hydrogen cyanide is not easily 

removed from the air by settling, rain, or snow. The 

half-life (the time needed for half of the material to 

be removed) of hydrogen cyanide in the atmosphere 

is about 1–3 years. Most cyanide in surface water 

will form hydrogen cyanide and evaporate. 

However, the amount of hydrogen cyanide formed 

is generally not enough to be harmful to humans. 

Some cyanide in water will be transformed into less 

harmful chemicals by microorganisms (plants and 

animals of very small size), or will form a complex 

with metals, such as iron. The half-life of cyanide 

in water is not known. Cyanide in water does not 

build up in the bodies of fish. 

Cyanides are fairly mobile in soil. Once in soils, 

cyanide can be removed through several processes. 

Some cyanide compounds in soil can form 

hydrogen cyanide and evaporate, whereas some 

cyanide compounds will be transformed into other 

chemical forms by microorganisms in soil. 

Consequently, cyanides usually do not seep into 

underground water. However, cyanide has been 

detected in underground waters of a few landfills 

and industrial waste disposal sites. At the high 

concentrations found in some landfill leachates 

(water that seeps through landfill soil) and in the 

wastes stored in some disposal sites, cyanide 

becomes toxic to soil microorganisms. Because 

these microorganisms can no longer change cyanide 

to other chemical forms, cyanide is able to passes 

through soil into underground water. 

Less is known about what happens to thiocyanate 

when it enters the environment. In soil and water, 

thiocyanate is changed into other chemical forms by 

microorganisms. This occurs in soil mainly at 

temperatures up to 86 °F (30 °C). At these 

temperatures, thiocyanate in soil does not undergo 

much evaporation or sorption (binding to soil). 

1.3 HOW MIGHT I BE EXPOSED TO 

CYANIDE? 

You can be exposed to cyanides by breathing air 

and drinking water, touching soil or water 

containing cyanide, or eating foods that contain 

cyanide. Many plant materials, such as cassava 

roots, lima beans, and almonds, naturally contain 

low-to-moderate levels of cyanide. The 

concentration of hydrogen cyanide in unpolluted air 

is less than 0.2 parts of hydrogen cyanide per 

million (ppm; 1 ppm is equivalent to 1 part by 

volume of hydrogen cyanide in a million parts by 

volume of air). The concentration of cyanide in 

drinking water ranges from 0.001 to 0.011 ppm 

(1 ppm is equivalent to 1 part by weight in 1 million 

parts by volume of water) in the United States and 

Canada. Cyanogen chloride, which can be formed 

in the process of water chlorination, has been found 

at concentrations ranging from 0.00045 to 

0.0008 ppm in drinking water from 35 U.S. cities. 

We do not know how many people in the general 

population of the United States are exposed to 

significant amounts of cyanide from eating foods 

that naturally contain it. Smoking is probably one 

of the major sources of cyanide exposure for people 

who do not work in cyanide-related industries. 

Breathing smoke-filled air during fires also may be 

a major source of cyanide exposure. People who 

live near hazardous waste sites that contain cyanide 

may be exposed to higher amounts of cyanide than 

the general population. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

Cyanide is used or produced in various occupational 

settings where activities include electroplating, 

some metal mining processes, metallurgy, metal 

cleaning, certain pesticide applications, tanning, 

photography and photoengraving, firefighting, and 

gas works operations. Cyanide also is used in some 

dye and pharmaceutical industries. The National 

Occupational Exposure Survey (NOES) has 

estimated the numbers of workers potentially 

exposed to the following cyanides: 4,005 to 

hydrogen cyanide; 66,493 to sodium cyanide; 

64,244 to potassium cyanide; 3,215 to potassium 

silver cyanide; 3,606 to calcium cyanide; 22,339 to 

copper (I) cyanide; and 1,393 to cyanogen chloride. 

You can be exposed to thiocyanate in the same 

ways that you can be exposed to cyanide. Exposure 

to cyanide will expose you to thiocyanate because 

your body changes toxic cyanide to the much less 

toxic thiocyanate. Many foods (plants, dairy 

products, meat) contain thiocyanate. People who 

work in cyanide-related industries, such as the 

manufacture of electronic computing equipment, 

commercial printing, photographic processes, 

hospitals, production of adhesives, and construction 

and furniture manufacture, may be exposed to 

thiocyanate. No information is available about the 

concentrations of thiocyanate in unpolluted air or 

drinking water. We do not know how many people 

in the general U.S. population are exposed to 

significant amounts of thiocyanate from eating 

foods that contain thiocyanate. People who smoke 

or breathe tobacco smoke in the environment can be 

exposed to high levels of thiocyanate. People who 

live near hazardous waste sites that contain 

thiocyanate potentially can be exposed to higher 

amounts of thiocyanate compared with nonsmokers 

in the general population. The National 

Occupational Exposure Survey (NOES) estimates 

that 90,599 workers potentially are exposed to 

ammonium thiocyanate. 

1.4 HOW CAN CYANIDE ENTER AND 

LEAVE MY BODY? 

Cyanide can enter your body if you breathe air, eat 

food, or drink water that contains it. Cyanide can 

enter your body through the skin, but this may occur 

only in people who work in cyanide-related 

industries without adequate protective gear. You 

can be exposed to contaminated water, air, or soil at 

hazardous waste sites. Once it is in your lungs or 

stomach, cyanide can quickly enter the bloodstream. 

Some of the cyanide is changed to thiocyanate, 

which is less harmful and leaves the body in the 

urine. A small amount of cyanide is converted in 

the body to carbon dioxide, which leaves the body 

in the breath. At low levels of exposure to cyanide 

compounds, most of the cyanide and its products 

leave the body within the first 24 hours after 

exposure. The way cyanide enters and leaves the 

body is similar in people and animals. 

1.5 HOW CAN CYANIDE AFFECT MY 

HEALTH? 

Scientists use many tests to protect the public from 

harmful effects of toxic chemicals and to find ways 

for treating persons who have been harmed. 

One way to learn whether a chemical will harm 

people is to determine how the body absorbs, uses, 

and releases the chemical. For some chemicals, 

animal testing may be necessary. Animal testing 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

may also help identify health effects such as cancer 

or birth defects. Without laboratory animals, 

scientists would lose a basic method for getting 

information needed to make wise decisions that 

protect public health. Scientists have the 

responsibility to treat research animals with care 

and compassion. Scientists must comply with strict 

animal care guidelines because laws today protect 

the welfare of research animals. 

Exposure to small amounts of cyanide can be 

deadly regardless of the route of exposure. The 

severity of the harmful effects depends in part on 

the form of cyanide, such as hydrogen cyanide gas 

or cyanide salts. Exposure to high levels of cyanide 

for a short time harms the brain and heart and can 

even cause coma and death. Cyanide produces 

toxic effects at levels of 0.05 milligrams of cyanide 

per deciliter of blood (mg/dL) or higher, and deaths 

have occurred at levels of 0.3 mg/dL and higher (a 

deciliter equals 100 milliliters). People who 

breathed 546 ppm of hydrogen cyanide have died 

after a 10-minute exposure; 110 ppm of hydrogen 

cyanide was life-threatening after a 1-hour 

exposure. People who eat small amounts of cyanide 

compounds in a short time may die unless they 

quickly receive antidote therapy. 

Some of the first indications of cyanide poisoning 

are rapid, deep breathing and shortness of breath, 

followed by convulsions (seizures) and loss of 

consciousness. These symptoms can occur rapidly, 

depending on the amount eaten. The health effects 

of large amounts of cyanide are similar, whether 

you eat, drink, or breathe it; cyanide uptake into the 

body through the skin is slower than these other 

types of exposure. Skin contact with hydrogen 

cyanide or cyanide salts can irritate and produce 

sores. Workers who breathed in amounts of 

hydrogen cyanide as low as 6–10 ppm over a period 

of time developed breathing difficulties, chest pain, 

vomiting, blood changes, headaches, and 

enlargement of the thyroid gland. 

Use of cassava roots as a primary food source has 

led to high blood cyanide levels in some people in 

tropical countries. Some of them suffered harmful 

effects to the nervous system, including weakness 

of the fingers and toes, difficulty walking, dimness 

of vision, and deafness, but chemicals other than 

cyanide also could have contributed to these effects. 

Cyanide exposure from cassava was linked to poor 

functioning and later enlargement of the thyroid 

gland; this is because in the body, cyanide is 

converted to thiocyanate, which is toxic to the 

thyroid gland. These effects have not been seen at 

levels of cyanide usually found in foods in the 

United States. Cyanide has not been reported to 

directly cause reproductive problems in people. 

Harmful effects on the reproductive system 

occurred in rats and mice that drank water 

containing sodium cyanide. Other cyanide effects 

in animal studies were similar to those observed in 

people. Cyanide has not been reported to cause 

cancer in people or animals. EPA has determined 

that cyanide is not classifiable as to its human 

carcinogenicity (ability to cause cancer in humans). 

Vitamin B12, a natural chemical containing cyanide, 

is beneficial to your body because it prevents 

anemia (iron-poor blood). The cyanide binds in 

vitamin B12 so that it does not serve as a source of 

cyanide exposure and cannot harm you. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

1.6 HOW CAN CYANIDE AFFECT 

CHILDREN? 

This section discusses potential health effects in 

humans from exposures during the period from 

conception to maturity at 18 years of age. 

Like adults, children can be exposed to cyanide by 

breathing air, drinking water, touching soil or water, 

or eating foods that contain cyanide, but the 

amounts are usually low. Breathing second-hand 

tobacco smoke is a more important source of 

cyanide exposure for children. Serious exposures 

can occur when children accidentally eat certain 

fruit pits, such as apricot kernels, containing a 

cyanide-releasing substance. A high blood level of 

thiocyanate is a sign of cyanide exposure in 

children, as well as adults. If a pregnant mother is 

exposed to cyanide, for example, by exposure to 

tobacco smoke, the fetus will be exposed to both 

cyanide and thiocyanate crossing the placenta. 

Animal studies show that cyanide and thiocyanate 

can be transferred into milk and pass to nursing 

baby animals, and suggest that this may also occur 

in humans. 

Effects reported in exposed children are like those 

seen in exposed adults. Children who ate large 

quantities of apricot pits, which naturally contain 

cyanide as part of complex sugars, had rapid 

breathing, low blood pressure, headaches, and 

coma, and some died. Cyanide has not been 

reported to directly cause birth defects in people. 

However, among people in the tropics who eat 

cassava root, children have been born with thyroid 

disease because of the mothers' exposure to cyanide 

and thiocyanate during pregnancy. Birth defects 

occurred in rats that ate cassava root diets, and 

harmful effects on the reproductive system occurred 

in rats and mice that drank water containing sodium 

cyanide. 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO CYANIDE? 

If your doctor finds that you have been exposed to 

cyanide, ask whether your children might also have 

been exposed. Your doctor might need to ask your 

state health department to investigate. 

Families can reduce their exposure to cyanide by 

not breathing in tobacco smoke, which is the most 

common source of cyanide exposure for the general 

population. In the event of a building fire, families 

should evacuate the building immediately, because 

smoke from burning plastics contains cyanide (and 

carbon monoxide). Breathing this smoke can lead 

to unconsciousness or death. Cyanide in smoke can 

arise from the combustion of certain plastics (e.g., 

polyacryl-amines, polyacrylics, polyurethane, etc.). 

Compounds that release cyanide are naturally 

present in plants. The amounts are usually low in 

the edible portion but are higher in cassava. Pits 

and seeds of common fruits, such as apricots, 

apples, and peaches, may have substantial amounts 

of cyanide-releasing chemicals, so people should 

avoid eating these pits and seeds to prevent 

accidental cyanide poisoning. Parents should teach 

their children not eat fruit pits and seeds. People 

should be aware that taking high levels of vitamin C 

may increase the danger of cyanide poisoning from 

fruit pits, because more cyanide is released from the 

pits. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

Studies have shown that the effects of cyanide are 

worse in humans and animals with poor nutrition. 

Diets containing adequate amounts of protein 

should improve recovery from cyanide exposure 

incidents. 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO CYANIDE? 

Blood and urine levels of cyanide and thiocyanate 

can be measured, and small amounts of these 

compounds are always detectable in blood and urine 

because of natural processes. After cyanide 

poisoning, increased blood levels of cyanide and 

thiocyanate are detectable. Harmful effects can 

occur when blood levels of cyanide are higher than 

0.05 parts per million (ppm), but some effects can 

occur at lower levels. Tissue levels of cyanide can 

be measured if cyanide poisoning is suspected. 

However, cyanide and thiocyanate are cleared 

rapidly from the body in urine or exhaled breath; for 

that reason, blood measurements are only useful for 

detecting recent exposure. A bitter, almond-like 

odor in the breath may alert a physician that a 

person was exposed to cyanide, but this is not 

always found. In general, if cyanide exposure is 

suspected, treatment should be started immediately 

without waiting for the results of blood cyanide 

measurements. 

1.9 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and 

recommendations to protect public health. 

Regulations can be enforced by law. The EPA, the 

Occupational Safety and Health Administration 

(OSHA), and the Food and Drug Administration 

(FDA) are some federal agencies that develop 

regulations for toxic substances. Recommendations 

provide valuable guidelines to protect public health, 

but cannot be enforced by law. The Agency for 

Toxic Substances and Disease Registry (ATSDR) 

and the National Institute for Occupational Safety 

and Health (NIOSH) are two federal organizations 

that develop recommendations for toxic substances. 

Regulations and recommendations can be expressed 

as “not-to-exceed” levels, that is, levels of a toxic 

substance in air, water, soil, or food that do not 

exceed a critical value that is usually based on 

levels that affect animals; they are then adjusted to 

levels that will help protect humans. Sometimes 

these not-to-exceed levels differ among federal 

organizations because they used different exposure 

times (an 8-hour workday or a 24-hour day), 

different animal studies, or other factors. 

Recommendations and regulations are also updated 

periodically as more information becomes available. 

For the most current information, check with the 

federal agency or organization that provides it. 

Some regulations and recommendations for cyanide 

include the following: 

EPA sets regulations for the amount of cyanide 

allowed in drinking water. The highest amount 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

__________________________________________________________________________________________ 

 

PUBLIC HEALTH STATEMENT 

Cyanide 

CAS#: 74-90-8, 143-33-9, 151-50-8, 592-01-8, 

544-92-3, 506-61-6, 460-19-5, 506-77-4 

Division of Toxicology and Environmental Medicine July 2006 

allowed is 200 micrograms of cyanide per liter of 

water (μg/L or 0.2 ppm). EPA also sets limits for 

amounts of hydrogen cyanide in stored foods that 

have been treated with cyanide to control pests. 

The maximum amount allowed on citrus fruits is 

50 ppm. EPA also requires industries to report 

spills of 1 pound or more of potassium silver 

cyanide and 10 pounds or more of hydrogen 

cyanide, potassium cyanide, sodium cyanide, 

calcium cyanide, or copper cyanide. 

OSHA sets levels of cyanide that are allowable in 

workplace air. The permissible exposure limit for 

hydrogen cyanide (HCN) and most cyanide salts is 

10 ppm or 11 milligrams of cyanide per cubic meter 

of air (mg/m3

) averaged over an 8-hour workday 

and 40-hour workweek. NIOSH sets guidelines 

(recommended exposure limits or RELs) for 

chemicals in workplace air. The short-term REL 

for hydrogen cyanide is 4.7 ppm or 5 mg/m3, 

averaged over 15 minutes and not to be exceeded at 

any time in the workday. There is a 10-minute 

ceiling limit for most cyanide salts of 4.7 ppm or 

5 mg/m3. NIOSH also determines levels that are 

immediately dangerous to life and health (IDLH) if 

a worker is exposed for more than half an hour. 

IDLH levels are 50 ppm for hydrogen cyanide or 

25 mg/m3 as cyanide for most cyanide salts. 

1.10 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, please 

contact your community or state health or 

environmental quality department, or contact 

ATSDR at the address and phone number below. 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses that result from exposure to 

hazardous substances. 

Toxicological profiles are also available on-line at 

www.atsdr.cdc.gov and on CD-ROM. You may 

request a copy of the ATSDR ToxProfilesTM CDROM by calling the toll-free information and 

technical assistance number at 1-888-42ATSDR 

(1-888-422-8737), by e-mail at atsdric@cdc.gov, or 

by writing to: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology and Environmental 

Medicine 

1600 Clifton Road NE 

Mailstop F-32 

Atlanta, GA 30333 

Fax: 1-770-488-4178 

Organizations for-profit may request copies of final 

Toxicological Profiles from the following: 

National Technical Information Service (NTIS) 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 1-800-553-6847 or 1-703-605-6000 

Web site: http://www.ntis.gov/ 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov