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Adverse effect

Change in the morphology, physiology, growth, development, reproduction or life span of an organism, system or (sub) population that results in an impairment of functional capacity, an impairment of the capacity to compensate for additional stress or an increase in susceptibility to other influences.

Active pharmaceutical ingredient (API)

Any substance or mixture of substances used in a pharmaceutical product with the intention to provide pharmacological activity or to otherwise have direct effect in the diagnosis, cure, mitigation, treatment or prevention of disease, or to have direct effect in restoring, correcting or modifying physiological functions in human beings and animals.


Any physical, chemical, biological, or radiological substance or matter that is not naturally present in water, or is present at concentrations greater than would naturally occur.

Contaminants of emerging concern (CECs)

A vast array of contaminants that have only recently appeared in water, or that are of recent concern because they have been detected at concentrations significantly higher than expected, and/or their risk to human and environmental health may not be fully understood. Examples include pharmaceuticals, industrial and household chemicals, personal care products, pesticides, manufactured nanomaterials, microplastics, and their transformation products. Also commonly known as micropollutants or emerging pollutants.

Environmental quality norm (EQN)

The maximum allowable concentration of a substance in water. Also commonly known as environmental quality standards.


Molecules resulting from changes of the chemical structure within the body, or on the skin, of humans and treated animals. Metabolites may be formed by biological and/or non-biological processes. They may also result from the activity of metabolic pathways of humans and treated animals, as well as from changes performed by other organisms living within or on the body of humans and treated animals, and from non-biotic processes occurring there (Kümmerer, 2009[1]).

Mixture effect

Temporal co-exposure to any combination of two or more compounds that may jointly contribute to actual or potential effects in a receptor population.

Predicted no effect concentration (PNEC)

The concentration of a chemical which marks the limit below which no unacceptable adverse effects on an ecosystem are expected.

No observed adverse effect level (NOAEL)

Highest concentration or amount of a substance, found by experiment or observation, that causes no adverse alteration of morphology, functional capacity, growth, development or lifespan of the target organism distinguishable from those observed in normal (control) organisms of the same species and strain under the same defined conditions of exposure.


Under the EU Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), ‘substance’ is defined as a chemical element and its compounds in the natural state or obtained by any production process, including any additive necessary to preserve its stability and any impurity deriving from the process used, but excluding any solvent which may be separated without affecting the stability of the substance or changing its composition (European Commission, 2006[2]).


Inherent property of an agent to cause an adverse biological effect.

Transformation product

Molecules resulting from changes of the chemical structure after the excretion of parent compounds and metabolites into the environment. Transformation processes can be those such as hydrolysis and photo-oxidation, or biotic ones. They may occur as a result of chemical reactions in wastewater or drinking treatment facilities, or bio-transformed by bacteria and fungi in the environment (Kümmerer, 2009[1]).

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