Asbestos in drinking water and in old asbestos cement water pipes

In Germany, asbestos in water almost always comes from one source: old drinking water pipes made of asbestos cement. Around 6.7% of the German pipe network still consists of this material. The danger of asbestos is well documented. However, it comes from inhaling the fibres. For exposure via drinking water, the World Health Organization (WHO) and German authorities assess the data differently. This guide separates the two and shows when an asbestos cement pipe becomes a problem.

The main source of asbestos in drinking water is asbestos cement pipes in the water supplier's network. This is what the WHO states in its fact sheet on asbestos in drinking water (as of 2021). The WHO also names three other routes: the weathering of asbestos-bearing minerals and ores, industrial wastewater and air pollution.

A fourth route concerns rainwater. If rainwater is collected from poorly sealed asbestos cement roofs, it can contain asbestos fibres. This applies to rainwater tanks and cisterns, not to the public drinking water supply.

To give an idea of the scale: according to the WHO, levels in drinking water are usually below 1 million fibres per litre. More than 10 million fibres per litre are rare. The WHO reports higher levels where asbestos cement pipes are in use. At the same time, it points out that data on occurrence are sparse.

Around 6.7% of drinking water pipes in Germany are made of asbestos cement. This figure comes from the pipe network statistics of the Deutscher Verein des Gas- und Wasserfaches (DVGW, German Technical and Scientific Association for Gas and Water). The pipes were laid mainly in the 1950s and 1960s. Estimates put the total at around 30,000 kilometres. There is a particular concentration in Schleswig-Holstein.

Since 1 January 1995, no new asbestos cement pipes may be laid. Old pipes may remain in service. The DVGW justifies this on the grounds that contact with drinking water poses no risk to consumers' health.

The pipes are ageing nonetheless. Manufacturers state a service life of 60 to 70 years. On this basis, all asbestos cement pipes would, in theory, have to be replaced by 2050. The DVGW research project W 201721 therefore developed a method for this: water suppliers chemically test the condition of pipe samples that have been removed and estimate the remaining service life.

Eternit is a brand name, not the name of a material. The Austrian industrialist Ludwig Hatschek filed a patent application for the process in 1900. In 1903, he had Eternit protected as a word mark. The name comes from the Latin “aeternus”, meaning eternal. The material behind it is called fibre cement.

Until the early 1990s, the fibre in this fibre cement was asbestos. The Eternit water pipes that still lie in the ground today date from this period. AZ stands for Asbestzement (asbestos cement). AZ-Rohr and AZ-Leitung (AZ pipe, AZ main) are the abbreviations that water suppliers use in their network plans.

Important for context: today's Eternit contains no asbestos. Since the ban in 1993, fibre cement products sold under this brand name have been made with plastic or cellulose fibres. An Eternit product from a DIY store is therefore no indication of asbestos. An Eternit pipe from the 1960s, on the other hand, certainly is.

An asbestos cement pipe becomes a problem in 2 cases: when lime-dissolving water attacks the cement, or when someone damages the pipe mechanically. As long as the water is in lime-carbonic acid equilibrium, a protective layer forms on the cement surface. The fibres then remain bound.

Very soft water in particular dissolves lime. Soft water is low in lime and can leach lime out of the cement. Hard water tends to deposit lime instead. This is why water hardness in the supply area is an important factor for asbestos cement pipes.

This is exactly where the Drinking Water Ordinance (TrinkwV) comes in. Under Annex 3, the calculated calcite dissolution capacity at the waterworks outlet must not exceed 5 mg/l CaCO₃. This is considered to be met if the pH value at the waterworks outlet is at least 7.7. Downstream of points where water from several waterworks is mixed, a maximum value of 10 mg/l applies in the network. The permissible pH range for drinking water is between 6.5 and 9.5.

The WHO explicitly names one limitation: if a pipe is already damaged, late corrosion control will no longer stop fibres from being released. The WHO therefore advises water suppliers to map asbestos cement pipes, check their condition and replace severely damaged pipes with asbestos-free ones.

There is no limit value for asbestos in drinking water in Germany or the EU. The WHO has not set a guideline value either. The USA, on the other hand, has regulated asbestos with a fixed maximum level since 1992. Germany instead regulates it indirectly via the calcite dissolution capacity.

The EPA sets its target value (MCLG) at the same level as the fixed maximum level, i.e. also 7 million fibres per litre. The EU occupational exposure limit is included in the table for contrast. In 2023, the EU lowered it from 0.1 to 0.01 fibres per cubic centimetre of air. It concerns inhaled fibres, not water that is drunk.

The WHO sees no reliable evidence that ingested asbestos harms health. This is precisely its reason for not setting a guideline value for asbestos in drinking water. In its fact sheet (as of 2021), the WHO puts forward 2 arguments.

First, studies on the link between asbestos in drinking water and cancer of the stomach and gastrointestinal tract are inconsistent. Some show a weak positive correlation, others find none at all. Second, in large animal studies, asbestos did not clearly increase the number of tumours in the gastrointestinal tract. According to the WHO, the two types of study taken together do not support the hypothesis that oral intake of asbestos increases the risk of cancer.

The WHO assessment is not an all-clear. Proof of safety is lacking, just as reliable proof of harm is. The USA assesses the same data more cautiously and has set a maximum level.

In Germany, a 1983 drinking water study by the Fraunhofer Institute was hotly debated. It reportedly found up to 1.57 million freely dissolved asbestos fibres per litre. As early as 1989, a Fraunhofer employee disputed this interpretation in the newspaper taz. According to him, no one had even checked which pipes the water had flowed through. What had been measured was the total content of mineral fibres, not asbestos specifically.

The real asbestos risk is working on the pipe, not drinking the water. The WHO identifies the main problem with asbestos cement in drinking water as the people who work on the outside of the pipes, for example when cutting them. This creates dust, and they breathe that dust in.

The same rule applies in the home. If an asbestos cement drainpipe or water pipe is blocked or damaged or needs to be shortened, the work should be left to a specialist company. The Gefahrstoffverordnung (German Hazardous Substances Ordinance) and the Technical Rules for Hazardous Substances (TRGS) 519 apply here. The DVGW has revised its worksheet W 396 on the renewal and repair of asbestos cement pipes. In it, the DVGW recognises a low-emission tapping method.

Disposal is also regulated. Material containing asbestos is hazardous waste and may only be disposed of by licensed companies. Moistening binds the dust and is standard practice in asbestos work, but it is no substitute for protective equipment or a specialist company.

The local water supplier can provide information about asbestos cement pipes in the network. It keeps network plans showing the pipe material for each section. There, asbestos cement pipes are listed as AZ pipes or AZ mains. Asking the supplier is the quickest way to get a reliable answer.

For the pipe on your own property, the year of construction provides a first clue. If it was built before 1995, asbestos cement is possible. Only a material analysis by a specialist company provides certainty, not a layperson's inspection. Owners and companies can find recommendations from the DVGW on handling drinking water pipes made of asbestos cement.

Besides asbestos, other substances in tap water also play a role. The guide to heavy metals in tap water explains which pollutants these are and where they come from. For particles in the nanometre range, the article on the microplastics filter for drinking water is worth reading.