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Last changed: 08/10/2010
Drinking water may contain numerous substances which were absorbed from the soil, from groundwater, or from surface waters during its treatment and distribution. It may also have traces of additives and their byproducts used during treatment or substances from materials it comes into contact with.
Prior to treatment drinking water comes into contact with the water in the environment as so-called raw water, and as waste water after treatment. Raw water always contains natural ingredients and micoorganisms. If sufficient appropriate barriers to protect against contamination (multibarrier principle) do not exist, it may contain other microorganisms or traces of pollutants that stem from harmful changes to the soil or contaminated water.
The Drinking water Ordinance (Trinkwasserverordnung - TrinkwV 2001) covers quality criteria as concerns health, aesthetics, and technology. It stipulates that ingredients, pollutants, and microorganisms must be removed by the water utility from raw water by means of drinking water treatment to the greatest extent possible, should raw water of better quality for the production of drinking water be unavailable. Residue that is generated during treatment must be disposed of, although some of the chemicals or chemical byproducts added during treatment unavoidably do remain in the drinking water.
Pollution of drinking water can also occur after distribution, perhaps as a result of contact with materials in the distribution channel somewhere along the way from the water utility to the household tap.
Drinking water may not contain concentrations of any substances that may be hazardous or at levels that might damage health. To this end, toxicologists assess the substances present in drinking water and identify maximum concentrations that are tolerable for health reasons. A distinction is made between life-long (health guidelines) and shorter term tolerability of contamination by a substance (action values). Precautionary health assessments take possible combined effects into account as well as at-risk groups, new types of effects, enrichment, persistent presence, extraordinary compounds and chemical formations of potentially hazardous substances, prevention of pollution and possibilities of clean-up during water treatment.
The German Federal Environment Agency (Umweltbundesamt) has delegates on national committees devoted to addressing matters of the toxicological classification of substances. Their approach is oriented towards the Hazardous Substance Ordinance and EU Directive 67/548/EEC. If necessary, their results are brought to bear in the sections of the Federal Soil Protection Act and the Federal Soil Protection and Contaminated Sites Ordinance pertaining to health.
The goal of assessment is to favor by regulatory means those substances which are of great benefit but either do not pollute the environment and drinking water at all, or only to the extent that maximum parameters of health, technology, and aesthetics are not exceeded. In so doing, it is possible to avoid a gradual increase to worrisome levels of undesirable substances in the water supply network.
Position paper by Drinking water Commission of the Federal Ministry for Health at the Federal Environment Agency: