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 used by the thyroid gland in the manufacture of hormones. Most Americans eat a diet with at least twice the recommended daily allowance of iodide, much of it coming 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. In the human body at high doses, perchlorate can compete with iodine, which the thyroid gland uses to make hormones. This effect is called iodide uptake inhibition, or IUI, and this effect is not adverse. Notably, in its 2005 report, the National Research Council of the National Academies of Science (NAS) in the United States confirmed that IUI is not an adverse health effect, and that adverse effects of perchlorate exposure are only theoretical and have not been demonstrated in humans.

NOEL "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 substance made up of chlorine and oxygen. It is found in nature and can also be produced artificially. It is widely used today by the military, NASA and the commercial space industry as an ingredient in solid rocket propellant (not "rocket fuel") 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 safe 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 also 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 maximum amount of a substance 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).

Other Substances Commonly Found in Food That Act Like Perchlorate and Inhibit Iodide Uptake

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 syrup are placed in a tank or underground, where microorganisms break down the perchlorate and carbon into three primary components: carbon dioxide, chloride, and nonhazardous biomass which naturally degrades.

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.

Rocket Fuel vs. Rocket Propellant

Rocket Propellant

Typically (but not always) a chemical composition (solid or liquid) that burns in a controlled manner to produce thrust. In solid form, this is typically comprised primarily of a fuel (such as powdered aluminum) that produces heat and energy, an oxidizer (such as ammonium perchlorate) that provides oxygen for the fuel to burn, and in the case of solid propellants, a binder (such as polybutadiene acrylonitrile) that binds the fuel and oxidizer together.

Rocket Fuel

This is solely the fuel component of a rocket propellant that is combined with other materials to burn and produce thrust.