Definitions for Arsenic Terminology

Words about Arsenic Science

Arsenobetaine: Arsenobetaine (AB) is an organic arsenic compound that is the main source of arsenic found in fish. Unlike inorganic arsenic compounds and other organic arsenic compounds, arsenobetaine is considered non-toxic to humans.

Inorganic arsenic: The most toxic form of arsenic. Inorganic arsenic occurs naturally in soils and groundwater used as drinking water in certain parts of the world. It is also found in certain foods.

Microgram: One millionth of a gram. This very small unit is often used to measure arsenic since it is found in such small amounts in food and water.

Organic arsenic: Chemical forms of arsenic where the arsenic is attached to a carbon atom. Organic arsenic is found in food, some forms of which are less toxic than inorganic arsenic. Arsenic also occurs in various organic forms in the environment. Scientists are still learning more about the health effects of different organic arsenic compounds.

Parts per billion (ppb): The number of units of mass of a contaminant per 1000 million units of total mass. Also µg/L or micrograms per liter. Ppb is used to measure the concentration of a contaminant in water, soils and sediments.

Total arsenic: A measure of all the arsenic present in food, water or other types of substances (both organic and inorganic arsenic). Fish have high total arsenic levels but they are not toxic because almost all of the arsenic is an organic compound called arsenobetaine that is not harmful.

Words about Arsenic Health Effects

Absorb: For a person or an animal, absorbing is the process of a substance getting into the body through the eyes, skin, stomach, intestines, or lungs.

Acute exposure: Contact with a substance that occurs once or for only a short time and which can cause adverse health effects.

Carginogen: Something that causes cancer.

Chronic low-dose exposure: Regularly taking in a small amount of a harmful substance over a long period of time.

Concentration: Amount or level of.

Development: Growth or progress.

Exposure: To come into contact with by touching, eating, or breathing.

Ingest: To swallow or take in through your mouth. Most arsenic exposure happens from eating food or drinking water.

Methylation: A chemical process that adds a methyl group (a carbon atom and three hydrogen atoms) and changes a chemical’s form. This process happens to arsenic in lots of organisms, including humans. Scientists are still learning more about how and why methylation happens, and how it affects health.

Poison: Something that can harm or kill a person if it is swallowed or breathed in or absorbed through the skin at a high enough dose.

Risk: A chance of getting hurt or sick. The risk of arsenic-related health effects goes down with steps you take to avoid arsenic in your food or water or from other sources.

Symptom: A sign of illness, such as a headache or a fever. Arsenic does not cause obvious symptoms even at levels that might increase your risk of cancer or other health effects.

Words about arsenic regulation

Action level: The concentration of inorganic arsenic that the U.S. Food and Drug Administration considers, in addition to other factors, when considering whether to bring enforcement action to food producers in a particular case.

Monitoring and enforcement: How arsenic regulations are implemented by government agencies. Arsenic regulations must be enforced to reduce public exposure to arsenic.

Risk assessment: A systematic process of evaluating the potential risks that may be involved in a projected activity or undertaking.


CDC/ATSDR: The Centers for Disease Control and the Agency for Toxic Substances and Disease Registry. CDC and ATSDR research the health effects of toxic metals like arsenic and communicate health risks to the public.

EPA: The U.S. Environmental Protection Agency. The EPA regulates arsenic in public water systems but not in private wells.

FDA: The U.S. Food and Drug Administration. The FDA monitors arsenic in food and is responsible for regulating toxins such as arsenic in food supplies.

SRP: Superfund Research Program. SRPs are programs at universities that conduct interdisciplinary research on environmental health issues. Several SRPs research arsenic and have made important discoveries about how people are exposed to arsenic and arsenic’s health effects. SRPs also work with communities and policymakers to help people understand the health risks of arsenic and provide recommendations to reduce arsenic exposure.

Superfund Site: Any land in the United States that has been contaminated by hazardous waste and identified by the EPA as a candidate for cleanup because it poses a risk to human health and/or the environment.

USGS: United States Geological Survey. Along with many other metals, the USGS looks at arsenic in groundwater and soil across the country to identify high arsenic regions.

Words about Water Testing and Treatment

Accredited: A laboratory that meets state criteria for testing well water for drinking water contaminants. Every state has a list of accredited laboratories; to test your well for arsenic, you should pick one from this list to be sure they will give you accurate information about how much arsenic is in your well.

Arsenic 3 and Arsenic 5: Different chemical forms of arsenic in groundwater. If you have arsenic in your water, the amount of arsenic 3 (III) and 5 (V) will affect the type of system you choose and the maintenance the system requires.

Maximum Contaminant Level (MCL): Standards that are set by the U.S. Environmental Protection Agency (EPA) for drinking water quality. An MCL is the legal threshold limit on the amount of a substance that is allowed in public water systems under the Safe Drinking Water Act.

Maximum Contaminant Level Goal (MCLG):  A non-enforceable concentration of a drinking water contaminant, set at the level at which no known or anticipated adverse effects on human health occur and which allows an adequate safety margin. The MCLG is usually the starting point for determining the regulated Maximum Contaminant Level.

Point of Entry: Point-of-Entry water treatment systems are installed on the water line as it enters the home and treat all the water in the house.

Point of Use: Point-of-use (POU) water treatment systems are designed to treat small amounts of drinking water for use in the home. These devices can sit on the counter, attach to the faucet, or be installed under the sink. They do not treat all the water in the home.

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