Glossary

Glossary

Learn more about the phrases, terms and abbreviations used on this website to discuss perchlorate and the issues related to the compound.

Perchlorate Science

• Iodide
  A substance (a particular state of iodine) the thyroid gland uses in the manufacture of hormones. Most Americans eat a diet with at least twice the recommended daily allowance of iodide, much of which comes from common table salt (i.e., "iodized" salt). The thyroid gland keeps a substantial reserve of iodide to compensate for times when the amount of iodide in the body fluctuates.
• Iodide Uptake
  The process by which the thyroid gland absorbs iodide from the blood stream
• "No Effect" Level
  The dosage below which a compound has no measurable effect on human health
• Parts per billion (ppb)
  A measurement expression used to describe the concentration of a substance in air, water or soil. In water, one part per billion is roughly equal to one half teaspoon of liquid in an Olympic-sized pool (660,000 gallons).
• Perchlorate
  A salt-like substance made up of chlorine and oxygen. It is found in nature and it can be man-made. It is widely used today by the military, NASA and the commercial space industry as an ingredient in solid rocket fuels and explosives. It's also used in safety flares, fireworks, auto air bag inflators, lubricating oils and aluminum refining. Perchlorate also is naturally present in some fertilizers, typically used in organic farming. Perchlorate also has a long history of use as a medicine for certain thyroid gland disorders.
• Thyroid gland
  A gland at the base of the neck that produces various hormones, which the body uses for normal growth, development and metabolism

Perchlorate Regulation

• Action Level
  The level set by a regulatory agency at which water system operators are required to notify local government agencies about the presence of a compound in drinking water.
• Maximum Contaminant Level (MCL)
  The national and state drinking water standards for any regulated contaminant. The Maximum Contaminant Level must be set as close to the Reference Dose (national) or Public Health Goal (California) as possible but must take into account several other factors, including the economic and technological feasibility of meeting that standard and the accuracy and limits of detection of analysis methodology.
• Public Health Goal (PHG)
  A level set by a regulatory agency to be protective of human health. Specifically, public health goals are levels of contaminants in drinking water that would not be expected to pose a significant health risk to individuals consuming an average of two liters a day of that water over a 70-year lifetime.
• Reference Dose (RfD)
  The amount of perchlorate in drinking water that the U.S. Environmental Protection Agency (U.S. EPA considers "safe" if consumed every day for a lifetime of exposure. This is essentially a goal the U.S. EPA sets before establishing a national drinking water standard (see Maximum Contaminant Level).

Substances Commonly Found in Food

• Nitrates
  Salt-like substances composed of nitrogen and oxygen that have essentially the same effect on the thyroid as perchlorate, in that they can block the uptake of iodide. Nitrates occur at some level in most drinking water, as well as in processed meats and garden vegetables like carrots and celery. Much like perchlorate, nitrates can occur naturally or be manufactured. Nitrates are an essential component of fertilizers.
• Thiocyanate
  A salt-like substance composed of sulfur, carbon and nitrogen that is found in foods such as milk, cabbage, broccoli, cauliflower, and Brussels sprouts. It has essentially the same effect on the thyroid as perchlorate, in that it can block the uptake of iodide.

Treatment Technologies

• Biological Treatment
  Biological treatment is a process that uses microorganisms to break down perchlorate into other components. Contaminated water and carbon sources such as alcohol or corn syrum are placed in a tank or underground, where microorganisms break down the perchlorate and carbon into two primary components, carbon dioxide and chloride.
• Ion Exchange
  Ion exchange technology uses a resin to absorb perchlorate and remove it from water. Contaminated water is pumped through a system of resin "beds," which are up to six feet in diameter and up to six feet high. As negatively charged perchlorate is captured on the positively charged resin, it releases chloride, a component of table salt, in its place.