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Water Disinfectants & disinfectant by-products

 

Glossary over Water Disinfectants

Agency for Toxic Substances and Disease Registry

The Agency for Toxic Substances and Disease Registry (ATSDR) is an agency of the U.S. Department of Health and Human Services (HHS). As mandated by the federal superfund law, the agency assesses health risks from hazardous waste sites on the EPA's National Priorities List. ATSDR determines if additional health studies are needed at these sites, provides health advisories and publishes toxicological profiles on chemicals found at hazardous waste sites.

ATSDR also maintains exposure registries of people exposed to certain substances. (Source: ATSDR website  )

Aldehyde(s)

A class of organic compounds which have a -CH=O group at the end of a carbon chain (in contrast to ketones which have the group elsewhere). Aldehydes are highly reactive chemical compounds. They are formed from alcohols and can be made both synthetically or by natural processes. Health effects caused by aldehydes vary depending on the length of the chain and the presence of a carbon (aromatic) ring. (Source: GreenFacts )

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Bias

Deviation of results or inferences from the truth, or processes leading to such systematic deviation. Any trend in the collection, analysis, interpretation, publication, or review of data that can lead to conclusions that are systematically different from the truth. (Source: CDC Glossary of Epidemiologic Terms  )

Biocide(s)

According to the Biocides Directive (98/8/EC), biocidal products are those that are intended to destroy, render harmless, prevent the action of, or otherwise exert a controlling effect on any harmful organism by chemical or biological means. Examples include disinfectants, preservatives, antiseptics, pesticides, herbicides, fungicides and insecticides.

Biocidal products mentioned in the Biocides Directive are listed in the following table: (Source: GreenFacts, based on the Biocides Directive (98/8/EC)  )

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Biologic intake

The process by which a substance crosses the outer boundary of an organism without passing an absorption barrier, e.g. through ingestion or inhalation. (Source: US EPA glossary )

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Bromate

BrO3-. An inorganic anion, bromate is tasteless and colourless, with a low volatility. As a moderately strong oxidant, bromate is reactive. (Source: GreenFacts )

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Bromide

Br-. An inorganic bromide anion. Also used to describe any compound (usually a bromide salt) that contains the Br- ion, such as sodium bromide (NaBr). (Source: GreenFacts)

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Cancer

Any one of a group of diseases that occur when cells in the body become abnormal and have the potential to spread and establish growth in nearby tissues and other parts of the body (malignancy). (Source: GreenFacts )

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Carcinogen

A substance, factor or situation that causes or induces cancer. (Source: GreenFacts )

Chloral hydrate

CCl3CH(OH)2. Chloral hydrate is a haloaldehyde, an organic compound. (Source: For more information on the chlorate ion: WHO Guidelines for drinking water quality  )

Chloramination

The treatment of drinking water with a chloramine disinfectant. Both chlorine and small amounts of ammonia are added to the water one at a time which react together to form chloramine (also called combined chlorine), a long lasting disinfectant. As such, chloramine disinfection is sometimes used in large distribution systems. Chloraminated water is toxic to fish and must not be used for kidney dialysis. (Source: GreenFacts)

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Chlorate

ClO3-. A very reactive inorganic anion. The term chlorate can also be used to describe any compound containing the chlorate ion, normally chlorate salts (e.g. potassium chlorate, KClO3). The chlorate ion is a natural breakdown product of chlorine dioxide (e.g. by sunlight or in water). (Source: GreenFacts)

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Chlorine

Chlorine (Cl2) is produced in large amounts and widely used both industrially and domestically as a disinfectant and bleach. In particular, it is widely used in the disinfection of swimming pools and is the most commonly used disinfectant and oxidant for drinking-water treatment. In water, chlorine reacts to form hypochlorous acid and hypochlorites. (Source: WHO  Guidelines for drinking water quality )

Chlorine Chemistry Council

"The Chlorine Chemistry Council (CCC), a business council of the American Chemistry Council, is a national trade association based in Arlington, representing the manufacturers and users of chlorine and chlorine-related products.

To fulfill this mission, CCC:

  • Serves as a credible source of information and expertise on chlorine and chlorine-based product.
  • Promotes the use of sound science and comparative risk assessment in public policies affecting chlorine chemistry.
  • Sponsors and conducts research into the potential health and environmental effects of chlorine and the products of chlorine chemistry.
  • Creates better understanding of chlorine's health and safety benefits among customers, policy-makers and the public."
Chlorine dioxide

ClO2: Chlorine dioxide is a strong oxidizing agent that is added to water as a disinfectant and to control taste and odour. Chlorine dioxide rapidly decomposes into chlorite, chloride, and chlorate. (Source: WHO Guidelines for drinking water quality  )

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Chlorite

(ClO-) Chlorite is an inorganic anion; it is colorless, odorless, tasteless, and dissolves easily in water. Chlorite is fairly stable unless it comes in contact with other chemicals such as free chlorine.

In water treatment, chlorite is one of the chemicals involved in the process of generating chlorine dioxide. Chlorite is also the byproduct of disinfection with chlorine dioxide, with about 70% of the chlorine dioxide converted to chlorite and about 30% converted to chlorate (ClO3-) and chloride (Cl-). Though chlorine dioxide is consider to be a powerful disinfectant, chlorite is a weak bactericidal agent.

Another source of chlorite in the environment is the bleaching of wood pulp by paper mills. (Source: GreenFacts)

Chloroacetaldehyde

C2H3ClO. In the organic class of haloaldehydes. A colorless liquid with an acrid, penetrating odor. (Source: GreenFacts)

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Chloroform

CHCl3: Chloroform is an organic compound part of the trihalomethane. It is colorless and has a pleasant, nonirritating odor with a slightly sweet taste. Chloroform evaporates easily into the air and dissolves easily in water. It is derived primarily from various industrial and chemical processes, or as a by-product of disinfecting water with chlorine. Chloroform is largely present in drinking water. Although it is both a man-made and a naturally occurring compound, human activity is responsible for most of the chloroform found in the environment. (Source: GreenFacts)

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Chromosome

One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers. (Source: NHGRI Talking Glossary of Genetic Terms  )

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Chronic exposure

Contact with a substance that occurs over a long time (more than 1 year [for humans]). (Source: ATSDR Glossary of Terms  )

Circulatory system

The system that contains the heart and the blood vessels and moves blood throughout the body. This system helps tissues get enough oxygen and nutrients, and it helps them get rid of waste products. The lymph system, which connects with the blood system, is often considered part of the circulatory system. (Source: NCI Dictionary of cancer terms  )

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Coagulation

The clumping together of very fine particles to form larger particles; caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles and cause destabilization of the particles. The clumping together makes it easier to separate the solids from the water by settling, skimming, draining or filtering. (Source: US EPA Drinking Water Glossary  )

Compound(s)

A material made up of two or more elements combined in a fixed ratio. (Source: CoRIS glossary  )

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Concentration

The amount of a chemical or substance present in a particular quantity of soil, water, air, food, blood, hair, urine, breath, or any other media. (Source: GreenFacts)

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Contaminant(s)

A substance that is either present in an environment where it does not belong or is present at levels that might cause harmful effects to humans or the environment. (Source: GreenFacts)

Cyanogen chloride

ClCN. Cyanogen chloride is an inorganic compound. It is a gas with a pungent pepper odor.

Cyanogen Chloride is formed as a water disinfectant byproduct when chlorine is used to oxidize water impurities such as cyanide. Once in the body, it is metabolized to cyanide. (Source: GreenFacts)

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Dibromochloromethane

CHBr2Cl. An organic compound, of the trihalomethane group. Dibromochloromethane is a colorless to yellow heavy, nonflammable, liquid with a sweet odor. Dibromochloromethane is slightly soluble in water and readily evaporates to air. (Source: GreenFacts)

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Dichloroacetic acid

CHCl2COOH. A haloacetic acid (organic). A colourless liquid with a pungent odour. Dichloroacetic acid is an irritant and corrosive to the eyes, skin and respiratory tract. Inhalation of the vapour may lead to a sore throat and cause fluid to fill the lungs (pulmonary oedema). Dichloroacetic acid is also corrosive on ingestion. Exposure to large amounts may result in death. (Source: GreenFacts)

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Disinfectant(s)

A chemical or physical process that kills or inactivates microorganisms such as bacteria, viruses, and protozoa. (Source: US EPA US EPA Drinking Water Glossary  )

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DNA

DNA constitutes the molecules inside cells that carry genetic information and pass it from one generation to the next. (Source: NCI cancer.gov dictionary  )

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Dose

The amount of a substance to which a person is exposed over some time period. Dose is a measurement of exposure. Dose is often expressed as milligram (amount) per kilogram (a measure of body weight) per day (a measure of time) when people eat or drink contaminated water, food, or soil. In general, the greater the dose, the greater the likelihood of an effect. An "exposure dose" is how much of a substance is encountered in the environment. An "absorbed dose" is the amount of a substance that actually got into the body through the eyes, skin, stomach, intestines, or lungs. (Source: ATSDR Glossary of Terms  )

Dose-response relationship

The relationship between the amount of exposure [dose] to a substance and the resulting changes in body function or health (response). (Source: ATSDR Glossary of Terms  )

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Epidemiological studies

Studies on human populations, which attempt to link human health effects (e.g. cancer) to a cause (e.g. exposure to a specific chemical). (Source: GreenFacts)

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Exposure

Contact of the cells of an organism with a substance, micro-organism or radiation. In the case of humans, this may involve contact with a substance or agent by swallowing, breathing, or through the skin or eyes. Exposure may be short-term [acute exposure], of intermediate duration, or long-term [chronic exposure].

Exposure can be divided into external and internal.

External exposure refers to the whole dose to which an organism is exposed.

Internal exposure refers only to that fraction of the initial chemical dose that is absorbed and distributed throughout the body via systemic circulation. (Source: GreenFacts)

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Exposure assessment(s)

Quantitative or qualitative evaluation of the contact of a chemical [or a physical factor] with the outer boundary of the human body, which includes consideration of the intensity, frequency and duration of contact, the route of exposure (e.g. dermal, oral or respiratory), rates (chemical intake or uptake rates), the resulting amount that actually crosses the boundary (dose), and the amount absorbed (internal dose) (WHO 1999). (Source: EMCOM Glossary  )

Genotoxic

Toxic (damaging) to DNA. Substances that are genotoxic may bind directly to DNA or act indirectly leading to DNA damage by affecting enzymes involved in DNA replication, thereby causing mutations which may or may not lead to cancer or birth defects (inheritable damage). Genotoxic substances are not necessarily carcinogenic. (Source: GreenFacts)

Granular activated carbon

A highly porous adsorbent material, produced by heating organic matter, such as coal, wood and coconut shell, in the absence of air, which is then crushed into granules. Activated carbon is positively charged and therefore able to remove negative ions from the water such as ozone, chlorine, fluorides and dissolved organic solutes by absorption onto the activated carbon. The activated carbon must be replaced periodically as it may become saturated and unable to absorb. Activated carbon is not effective in removing heavy metals. (Source: GreenFacts )

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Haloacetic acids

A family of organic compounds based on the acetic acid molecule (CH3COOH) where one or more hydrogen atoms attached to carbon atoms are replaced by a halogen (chlorine, bromine, fluorine and/or iodine). There are nine species of HAAs including monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), and dibromoacetic acid (DBAA). HAAs are colourless, have a low volatility, dissolve easily in water and are fairly stable. (Source: GreenFacts)

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Haloacetonitriles

Organic compounds in which a methyl group (CH3+) is attached to a CN- ion, where one or more of the hydrogen atoms are substituted by halogens (chlorine, bromine, fluorine and/or iodine). Examples of haloacetonitriles are bromochloroacetonitrile, chloroacetonitrile and dibromoacetonitrile.

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Haloaldehydes

Organic compounds whose carbon chain molecules contain the C=O (carbonyl) functional group at the end of a carbon chain (aldehydes), with one or more hydrogen atoms substituted by halogens (chlorine, bromine, fluorine, and/or iodine). Chloral hydrate and chloroacetaldehyde are haloaldehydes. Although some toxicity data is available for chloral hydrate, little is known of the potential health effects of other haloaldehydes. (Source: GreenFacts)

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Halogenated hydroxyfuranone

A class of organic compounds, hydroxyfuranones, where one or more hydrogen atoms attached to carbon atoms have been replaced by halogens (chlorine, bromine, fluorine, and/or iodine). Examples include brominated hydroxyfuranone, chlorinated hydroxyfuranone and MX (3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone)which are water disinfectant by-product. (Source: GreenFacts )

Haloketones

A class of organic compounds. Ketones are carbon chain compounds whose molecules contain the C=O (carbonyl) functional group between two other carbon atoms. In haloketones, one or more hydrogen atoms have been substituted by halogens (chlorine, bromine, fluorine, and/or iodine). Examples of haloketones are 1,1-dichloropropanone 1,1,1-trichloropropanone. (Source: GreenFacts)

In vitro

In an artificial environment outside a living organism or body. For example, some toxicity testing is done on cell cultures or slices of tissue grown in the laboratory, rather than on a living animal. (Source: ATSDR Glossary of Terms  )

Ingestion

The act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way. (Source: ATSDR Glossary of Terms  )

Inhalation

The act of breathing.

A hazardous substance can enter the body by inhaling an airborne substance or contaminant in the form of gas, fumes mists, vapors, dusts, or aerosols. Once inhaled, contaminants can be deposited in the lungs and/or transported into the blood. (Source: GreenFacts)

Inorganic

Not organic. Inorganic compounds are generally structured by ionic bonds and do not contain carbon chemically bound to hydrogen (hydrocarbons) or any of their derivatives. Examples of inorganic compounds include sodium chloride (NaCl) and calcium carbonate (CaCO3) and pure elements (e.g. elemental mercury, elemental lead). (Source: GreenFacts)

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International Programme on Chemical Safety

The International Programme on Chemical Safety (IPCS) was established in 1980 by the WHO, the UNEP and the ILO (International Labour Organisation) "for the early warning and prevention of harmful effects of chemicals to which humans were being increasingly exposed, and for the assessment of the potential risks to human health."

It has collaborated to and published many highly recognized scientific publications.

Most publications are availaible from the INCHEM website www.inchem.org, "a means of rapid access to internationally peer reviewed information on chemicals commonly used throughout the world, which may also occur as contaminants in the environment and food." Publications include:

Ion(s)

An ion is an atom or molecule that is not electrically neutral, but instead carries a positive or negative electrical charge, which is due to the loss or gain of one or more electrons.

An anion is a ion with a negative electrical charge, e.g. chloride (CI-), as opposed to a cation which is an ion with a positive electrical charge, e.g. sodium (Na+). (Source: GreenFacts)

Lipophilic

Lipophilic or 'lipid-loving' molecules are attracted to lipids. A substance is lipophilic if it is able to dissolve much more easily in lipid (a class of oily organic compounds) than in water. (Source: GreenFacts )

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Lowest Observed Adverse Effect Level

The lowest tested dose of a substance that has been reported to cause harmful (adverse) health effects on people or animals. (Source: ATSDR glossary  )

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Membrane filtration

Water under high pressure is forced through a membrane, a thin material with very small pores, stopping small particles (including bacteria). (Source: GreenFacts )

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Metabolism

The conversion or breakdown of a substance from one form to another by an enzyme. (Source: GreenFacts, based on ATSDR Glossary of Terms )

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Model

Mathematical representation or simulation of an actual situation. (Source: GreenFacts)

Mutagen

A substance or physical agent that causes mutations, i.e. permanently alters the DNA of a cell. (Source: GreenFacts)

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MX

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is a member of the halogenated hydroxyfuranone class. It is a water disinfection by product when drinking water is chlorinated, formed by the reaction of chlorine with complex organic matter in water. MX has been identified in chlorinated effluents of pulp mills. (Source: GreenFacts)

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Natural organic matter

Organic matter originating from plants and animals present in natural (untreated or raw) waters, for example, in lakes, rivers and reservoirs. (Source: GreenFacts)

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Neurobehavioural

Having to do with the way the brain affects emotion, behavior, and learning. (Source: NCI cancer.gov dictionary   )

Neurological effects

Effects to nervous system especially regarding structure, functions, and abnormalities. (Source: GreenFacts)

Nitrate & Nitrite

Nitrate [NO3-]and nitrite [NO2-] are naturally occurring ions that are part of the nitrogen cycle. Nitrate is used mainly in inorganic fertilizers, and sodium nitrite is used as a food preservative, especially in cured meats. The nitrate concentration in groundwater and surface water is normally low but can reach high levels as a result of agricultural [activity and] runoff, refuse dump runoff, or contamination with human or animal wastes. (Source: Safe Water for International Travelers Water Quality Standards; Nitrate )

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No Observed Adverse Effect Level

The highest tested dose of a substance that has been reported to have no harmful (adverse) health effects on people or animals. (Source: ATSDR Glossary of Terms   )

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Organic

The term organic has different meanings (depending on the context):

In chemistry, "organic" refers to a chemical compound based on a hydrocarbon, i.e. a chain or a ring of carbon atoms onto which hydrogen atoms are bonded.

In agriculture, "organic" refers to a production system that excludes or limits the use of chemicals

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Ozone

Ozone is a form of oxygen having the molecular form of O3. It is a bluish, unstable gas with a pungent odour, found in two parts of the atmosphere: the stratosphere and the troposphere.

The ozone layer: The stratosphere contains a layer in which the concentration of ozone is greatest, the so called ozone layer. The layer extends from about 12 to 40 km. It shields the Earth from ultraviolet radiation's harmful health effects on humans and the environment. This layer is being depleted by human emissions of chlorine- and bromine-containing compounds.

Ground-level ozone: At ground level (in the troposphere), ozone is considered an air pollutant that can seriously affect the human respiratory system. It is a chemical oxidant and a major component of photochemical smog. (Source: GreenFacts)

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Peritoneum

The tissue that lines the abdominal wall and covers most of the organs in the abdomen. (Source: NCI NCI cancer.gov dictionary  )

pH

pH is a measure of the concentration of protons (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S.P.L. Sørensen in 1909. The p stands for the German "Potenz", meaning power or concentration, and the H for the hydrogen ion (H+). In layman's terms , the "pH" value is an approximate number between 0 and 14 that indicates whether a solution is acidic (pH < 7), basic (pH > 7) or neither (pH = 7) [neutral]. (Source: GreenFacts )

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Population

A group or number of people living within a specified area or sharing similar characteristics (such as occupation or age). (Source: ATSDR Glossary of Terms  )

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Precursor(s)

A precursor is a chemical which precedes and is the source of another. (Source: GreenFacts)

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Pregnancy outcomes

Results of conception and ensuing pregnancy, such as sex ratio, birth weight, spontaneous abortion, congenital malformations, lower birth weight, preterm delivery or stillbirth. (Source: GreenFacts)

Respiratory irritant(s)

Any substance which can cause inflammation or other adverse reactions in the respiratory system (lungs, nose, mouth, larynx and trachea). Examples of respiratory irritants include tobacco smoke, ozone, sulphur dioxide or nitrogen oxides. (Source: GreenFacts)

Risk

The probability that something will cause injury or harm. (Source: ATSDR Glossary of Terms  )

Soluble

A substance is soluble if it dissolves in certain fluids. The fluid [gas or liquid] (present in excess) is called the solvent and the substance dissolved in it is called the solute which together form a solution. The process of dissolving is called solvation. A solution that can not hold any more solute is said to be saturated. (Source: GreenFacts )

Surface water

Water on the surface of the Earth, such as in lakes, rivers, streams, ponds, and springs. (Source: ATSDR Glossary of Terms   )

Thyroid gland

The thyroid gland consists of two bodies like small walnuts; they are connected by an isthmus beside the larynx (voice box). The thyroid gland produces thyroid hormones T3 and T4 which regulate the metabolism of all cells in the body. Disorders of the thyroid gland are characterized by the inability to produce or release sufficient thyroid hormones (hypothyroidism) or the overactivity of the thyroid gland (hyperthyroidism). (Source: EMCOM Endocrine Disruptors Glossary  )

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Tissue

A group of cells joined to perform a set of functions. (Source: GreenFacts)

Tolerable Daily Intake

A TDI is an estimate of the amount of a substance in air, food or drinking water that can be taken in daily over a lifetime without appreciable health risk. TDIs are calculated on the basis of laboratory toxicity data to which uncertainty factors are applied.

TDIs are used for substances that do not have a reason to be found in food (as opposed to substances that do, such as additives, pesticide residues or veterinary drugs in foods- see ADI). (Source: GreenFacts)

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Toxic

Able to poison or harm an organism. Toxic substances can cause adverse health effects. (Source: GreenFacts)

Toxicity

The capacity or property of a substance to cause adverse effects. (Source: GreenFacts)

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Toxicology

The study of the harmful effects of substances on humans or animals. (Source: ATSDR Glossary of Terms  )

Trichloroacetic acid

CCl3COOH. A haloacetic acid (organic). A colourless to white, crystalline solid with a sharp, pungent odor and very soluble in water. Trichloroacetic acid is an irritant and corrosive. Inhalation of trichloroacetic acid vapour may lead to a sore throat and cause fluid to fill the lungs (pulmonary oedema). Trichloroacetic acid can burn the skin and eyes. Blurred vision and permanent eye damage can occur. Long term exposures may lead to a chronic cough and bronchial pneumonia may also occur. Teeth may erode. Trichloroacetic acid is also corrosive on ingestion. (Source: GreenFacts)

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Trihalomethanes

A class of organic compounds, based on the methane molecule (CH4) where the hydrogen atoms normally present are replaced by three halogen atoms (chlorine, bromine, fluorine and/or iodine). Examples include chloroform and dibromochloromethane. (Source: GreenFacts)

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Tumour

An abnormal mass of tissue resulting from uncontrolled and excessive cell division.

Tumours can be either benign (localised, without the invasion of other tissues) or malignant (showing progressive invasion of other tissues). (Source: GreenFacts)

Uncertainty factor

A number (equal or greater than 1) used to divide NOAEL or LOAEL values derived from measurements in animals or small groups of humans, in order to estimate a NOAEL or LOAEL value for the whole human population; also called margin-of-safety. (Source: IPCS )

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US Center for Disease Control and Prevention

"As the Center for Disease Control and Prevention (CDC) is recognized as the lead federal agency for protecting the health and safety of people - at home and abroad, providing credible information to enhance health decisions, and promoting health through strong partnerships. CDC serves as the national focus for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States."

"CDC, located in Atlanta, Georgia, USA, is an agency of the Department of Health and Human Services." (Source: CDC website )

US Environment Protection Agency

The Environment Protection Agency's of the USA was founded in 1970. It's "mission is to protect human health and to safeguard the natural environment — air, water, and land — upon which life depends."

The EPA enforces federal environmental protection laws. It registers and regulates pesticides, enforces laws covering outdoor air and drinking water quality and regulates the disposal of hazardous and solid wastes.

It has now grown into a big and powerful administration: "18,000 people in Headquarters program offices, 10 regional offices, and 17 labs across the country, EPA employs a highly educated, technically trained staff, more than half of whom are engineers, scientists, and environmental protection specialists. A large number of employees are legal, public affairs, financial, and computer specialists."

U.S. EPA's scientific publications are widely recognized as reference materials. (Source: US EPA website  )

US National Institute of Environmental Health Sciences

The US National Institute of Environmental Health Sciences (NIEHS) is one of 27 Institutes and Centers  of the National Institute of Health (NIH) , which is a component of the Department of Health and Human Services (DHHS) .

The National Institute of Environmental Health Sciences tries to reduce human illness from environmental causes by understanding environmental factors, individual susceptibility and age.

It conducts biomedical research programs, prevention and intervention efforts, and education.

It has collaborated to and published many highly recognized scientific publication. (Source: NIEHS website )

Volatile

Able to readily evaporate at normal temperatures and pressures. (Source: GreenFacts)

Water disinfection by-product(s)

A chemical compound formed by the reaction of a water disinfectant (e.g. chlorine) with a precursor (e.g. natural organic matter) in a water supply. (Source: GreenFacts)

World Health Organization

"The World Health Organization  (WHO) is the directing and coordinating authority on international health within the United Nations’ system. WHO experts produce health guidelines and standards, and help countries to address public health issues. WHO also supports and promotes health research. Through WHO, governments can jointly tackle global health problems and improve people’s well-being.

193 countries and two associate members are WHO’s membership. They meet every year at the World Health Assembly in Geneva to set policy for the Organization, approve the Organization’s budget, and every five years, to appoint the Director-General. Their work is supported by the 34-member Executive Board, which is elected by the Health Assembly. Six regional committees focus on health matters of a regional nature."

WHO's scientific publications are widely recognized as a reference source.

The WHO has a number of regional offices which address the specific issues of those regions.

WHO World Regional Offices
  WHO African Region  (46 countries)
  WHO European Region  (53 countries)
  WHO Eastern Mediterranean Region  (21 countries)
  WHO Region of the Americas  (35 countries)
  WHO South-East Asia Region  (11 countries)
  WHO Western Pacific Region  (27 countries)

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