TOXICOLOGICAL PROFILE FOR CYANIDE

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 cyaniderelated 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. You can find more information about the movement of cyanide in the body in Chapter 3. 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 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 CYANIDE 7 1. PUBLIC HEALTH STATEMENT 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 lifethreatening 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 CYANIDE 8 1. PUBLIC HEALTH STATEMENT a source of cyanide exposure and cannot harm you. You can find more information about the harmful effects of cyanide in Chapter 3. 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 secondhand 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. More information on the effects of cyanide exposure in children can be found in Section 3.7. 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. CYANIDE 9 1. PUBLIC HEALTH STATEMENT 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., polyacrylamines, 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. 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.