Cyanide in Drinking Water: Health Risks and Regulatory Standards

Understanding Cyanide Contamination in Drinking Water

Cyanide is a chemical compound that can be found in some public or private drinking water supplies, posing potential health risks if present in quantities exceeding the safety standards established by the United States Environmental Protection Agency (EPA). This comprehensive guide delves into the nature of cyanide, its uses, and the regulatory measures in place to ensure safe drinking water.

What is Cyanide and Its Applications?

Cyanide is a carbon-nitrogen chemical unit that forms various organic and inorganic compounds. Hydrogen cyanide, the most commonly used form, is primarily employed in the production of compounds essential for making nylon and other synthetic fibers and resins. Additionally, other types of cyanides serve as herbicides.

Regulatory Framework for Cyanide

The Safe Drinking Water Act of 1974 mandates the EPA to determine safe levels of chemicals in drinking water that could cause health issues. Based on potential health risks and exposure, the EPA sets non-enforceable levels known as Maximum Contaminant Level Goals (MCLGs). For cyanide, the MCLG is set at 0.2 parts per million (ppm) to prevent the health problems outlined below.

Enforceable Standards and Detection

The EPA has established an enforceable standard called the Maximum Contaminant Level (MCL), which is set as close to the MCLG as feasible, considering the capabilities of public water systems to detect and remove contaminants. The MCL for cyanide is also 0.2 ppm, reflecting the lowest level that water systems can reasonably be expected to achieve.

Health Implications of Cyanide Exposure

Short-term Effects

Exposure to cyanide above the MCL for short periods can lead to rapid breathing, tremors, and other neurological effects.

Long-term Effects

Prolonged exposure to cyanide levels above the MCL may result in weight loss, thyroid issues, and nerve damage.

Environmental Impact and Cyanide Production

In the late 1980s and early 1990s, the production of common cyanides reached approximately 5 billion pounds annually. The primary sources of cyanide releases into water include metal finishing industries, iron and steel mills, and organic chemical industries. Soil contamination mainly arises from the disposal of cyanide wastes in landfills and the use of cyanide-containing road salts. Chlorination treatment of some wastewaters can also 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 pounds, predominantly from steel mills and metal heat treating industries, with the largest releases occurring in California and Pennsylvania.

Behavior of Cyanide in the Environment

Cyanides are generally not persistent in water or soil and are unlikely to accumulate in aquatic life. They quickly evaporate and are broken down by microbes. They do not bind to soils and may leach into groundwater.

Detection and Removal of Cyanide from Drinking Water

The regulation for cyanide became effective in 1992. Between 1993 and 1995, the EPA required water suppliers to collect and analyze water samples to determine if cyanide levels exceeded 0.2 ppm. If detected above this threshold, continued monitoring every three months was mandatory.

Treatment Methods

Should cyanide levels consistently exceed the MCL, water suppliers must implement measures to reduce cyanide concentrations. The EPA has approved several treatment methods, including Ion Exchange, Reverse Osmosis, and Chlorine.

Public Notification and Alternative Water Supplies

If cyanide levels surpass the MCL, water suppliers are obligated to notify the public through newspapers, radio, TV, and other means. Additional measures, such as providing alternative drinking water supplies, may be necessary to mitigate serious public health risks.

Conclusion: Ensuring Safe Drinking Water

This factsheet provides critical information on cyanide contamination in drinking water, its potential health effects, and the regulatory measures in place to safeguard public health. By adhering to the National Primary Drinking Water Regulations, water suppliers can ensure that cyanide levels remain below the MCL, protecting consumers from potential health risks.

Drinking Water Standards:
– MCLG: 0.2 ppm
– MCL: 0.2 ppm

Cyanide Releases to Water and Land, 1987 to 1993 (in pounds):
– Water: 939,611
– Land: 641,082
– Total: 1,580,693

Top Ten States for Cyanide Releases:
– California: 430,886
– Pennsylvania: 208,239
– Indiana: 187,377
– Ohio: 160,203
– Texas: 54,379
– Maryland: 89,438

Major Industries Contributing to Cyanide Releases:
– Blastfurnaces and steel: 747,970
– Metal heat treating: 430,886
– Organic chemicals: 49,098
– Plating and polishing: 29,486

As part of the Drinking Water and Health pages, this fact sheet is part of a larger U.S. EPA publication: EPA National Primary Drinking Water Regulations.