Environmental and Health Effects of Cyanide

Cyanide is produced naturally in over 1,000 plant species and the human body (International Cyanide Management Institute, 2006). Cyanogenic plants such as cassava, young bamboo shoots, coffee beans, lima beans, soy, and chickpeas naturally contain low concentrations of cyanide, which occurs as part of sugars or other compounds. Certain bacteria, fungi, and algae also produce cyanide (Agency for Toxic Substances and Disease Registry, 2006). Cyanide is acutely toxic to humans and wildlife; fish and invertebrates are particularly susceptible to cyanide poisoning (International Cyanide Management Institute, 2006). Cyanide does not bioaccumulate, so chronic exposure to very low concentrations does not result in acute toxicity. However, incidences of chronic cyanide poisoning have been documented in people who consistently eat a diet containing large quantities of cyanogenic plants such as cassava (International Cyanide Management Institute, 2006). In Fiji and other tropical climates across the globe, cassava is a staple source of carbohydrates. However, the inner portion of the tuber contains the lowest concentrations of cyanide and traditional preparation methods can reduce cyanide concentrations even further (Agency for Toxic Substances and Disease Registry, 2006; Keeler & Tu, 1983).

Hydrogen cyanide gas (HCN) is colorless and has a faint, bitter, almond-like odor. Sodium cyanide and potassium cyanide are white solids which also have a bitter almond-like odor in damp air (Agency for Toxic Substances and Disease Registry, 2006).

Humans may be exposed to cyanide by breathing in HCN gas, breathing tobacco smoke or smoke from burning buildings or plastics, through contaminated drinking water, eating foods containing cyanides, or by touching soil contaminated with cyanide. In surface waters, the majority of cyanide will evaporate as HCN gas under most natural conditions. Exposure to large concentrations of cyanide over a short period of time may result in acute cyanide poisoning. The first indications that a person may be experiencing cyanide poisoning include shortness of breath, deep and rapid breathing, seizures, or loss of consciousness (Agency for Toxic Substances and Disease Registry, 2006). Similar health effects of acute toxicity are exhibited by both adults and children.

Environmental and Health Effects of Arsenic

Arsenic is naturally found in all soils in varying quantities. The geological origins of a soil and its past uses determine the amount of arsenic present, and areas with volcanic activity are known to contain particularly high levels of arsenic (Aalbersberg, 2007; Agency for Toxic Substances and Disease Registry, 2007). Use of arsenic containing pesticides, coal-fired power plants, and incinerators are also environmental sources of arsenic, which may enter the water, soil, or air. Many common arsenic compounds can dissolve in water, so they may enter lakes, rivers, and streams. Unlike mercury and lead, which are most toxic in their organic forms, inorganic arsenic is the most toxic form of arsenic to humans (Agency for Toxic Substances and Disease Registry, 2007). A person may be exposed to arsenic through drinking water or air, but food consumption is the largest source of arsenic. Children may also be exposed to arsenic if they consume soil during play (Agency for Toxic Substances and Disease Registry, 2007).

Inorganic arsenic is toxic to humans and may cause death in large doses (above 60,000 ppb in water). Inorganic arsenic is recognized as a human carcinogen (cancer-causing chemical) by the following agencies: the Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC) and the Environmental Protection Agency (Agency for Toxic Substances and Disease Registry, 2007). Symptoms of acute exposure to inorganic arsenic include nausea, vomiting, fatigue, impaired nerve function. Long-term exposure to lower doses causes patches of darkened skin and the appearance of small "corns" or "warts" on the palms, soles, and torso, associated with changes in the blood vessels (Agency for Toxic Substances and Disease Registry, 2007). Breathing in low does of inorganic arsenic may cause a sore throat and lung irritation. Skin, liver, bladder, and lung cancer are also associated with exposure to inorganic arsenic (Agency for Toxic Substances and Disease Registry, 2007). Organic arsenic is much less toxic, and is usually excreted in urine within several days of exposure.