Risk assessment: A Toxicological Approach

A tremendous amount of chemicals such as personal care products, medicines, plant protection products and industrial chemicals are used in daily life. By various emission sources, natural or anthropogenic chemicals enter the environment and eventually can reach the drinking water. For example, chemicals can enter the sewage treatment plants in the Rhine, Meuse and IJsselmeer, which serve as a source of drinking water.

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Through screening techniques, increased amounts of emerging contaminants are discovered. Besides, compounds can be found in high concentrations, for example due to a discharge or other calamities. Sufficient knowledge about the possible effects of emerging contaminants on human health and the environment is very important to prevent potential risks from ingestion via drinking water. Therefore, at Het Waterlaboratorium, toxicological assessments for these substances are performed.

The human health toxicological assessments are based on studies performed in mammals. From experimental studies, specific toxicological endpoints on which a chemical has an effect can be derived. Examples of endpoints are effects on reproduction or tumor formation. Besides, experimental studies tests chemicals in different concentrations, in order to determine at which concentration an effect is observed. Consequently, limit values can be derived for human toxicity.

For many groups of chemicals, such as food additives or plant protection products, limit values are derived in the legal authorization procedure. For industrial compounds, limit values are established in the REACH registration dossiers. The health-based limit value ​​can be converted into a so-called provisional drinking water guideline value: this is the safe risk limit for a substance in drinking water where no effect on health is expected with a lifelong intake. The RIVM and WHO already derived indicative drinking water guideline values ​​for a number of relevant drinking water substances.

Het Waterlaboratorium has the toxicological expertise to derive provisional drinking water guidelines, based on available toxicological data. By comparing guidelines ​​with measured concentrations, the risk and impact of a substance for the water sector can be better estimated. This is important for making decisions in the case of a calamity and for determining which contaminant has more priority based on its health effects. Factsheets of many relevant substances made by Het Waterlaboratorium for Dunea, PWN and Waternet contain a toxicological evaluation. Also, as part of risk-based monitoring, an annual toxicological evaluation is carried out for emerging contaminants discovered by screening techniques.