How reliable are drinking water quality tests?

Published on 06/07/2022 Last updated on 23/10/2023

According to reports by the Human Environment and Transport Inspectorate (ILT), drinking water companies and the National Institute for Public Health and the Environment (RIVM) , tap water in the Netherlands is high quality. But what tests do they use, and how reliable are they?

PFAS – A problem in our tap water

Do you know Bucky Bailey? The 41 year old American actor is hard to forget. By the time he was seven years old, he had had 30 operations. For years, nobody understood why he had been born with a deformed face. Now, we know that this was due to the nature of his mother’s work. Sue Bailey worked at the DuPont chemical plant in Parkersburg and was exposed to poly and perfluoroalkyl substances (PFAS) for years. PFAS contaminated the local water supply and nearby residents experienced an increase in illnesses such as kidney and testicular cancer as well as reproductive disorders.

Bucky has been the face of the PFAS drama in Parkersburg since 2017, when DuPont employees and local residents sued the chemical giant. Their story was made into the movie Dark Waters, which describes the scandal that led to DuPont having to pay 671 million dollars to settle more than 3,500 lawsuits.

You might think PFAS is not a problem in Europe, but this chemical is found in our tap water too. Even in the Netherlands.

Dutch tap water is bound by strict quality standards set out in the Drinking Water Decree. The ILT reports annually in order to check and guarantee water cleanliness and quality. The checks apply to drinking water facilites that supply over 1,000 cubic meters of water per day, and that are used by over 5,000 people per day. The ten drinking water companies in the Netherlands are Vitens, Dunea, Evides, PWN Waterleidingbedrijf Noord-Holland, Oasen, Brabant Water, Waterleiding Maatschappij Limburg (WML), Waterbedrijf Groningen (WBG), Waternet and WMD Drinkwater.

Water testing program

These companies extract water from ground and/or surface water, purify it, and send it to our taps via a network of water pipes. In 2020, they extracted and supplied 1,159 billion cubic meters of drinking water.

Each year, water companies propose a program for measuring and testing the water. This programme sets out which substances will be measured, where they will be measured, and how often. The ILT then approves the program, and laboratories that have been approved by the Minister of Infrastructure and Water Management (IenW) carry out sampling and analyzing.  

These laboratories are:

  • Aqualab Zuid BV te Werkendam
  • Het Waterlaboratorium NV te Haarlem
  • Laboratorium van KWR Watercycle Research Institute
  • Laboratorium van RIVM Centrum voor Inspectie-, Milieu- en Gezondheidsadvisering te Bilthoven
  • Vitens Laboratorium te Leeuwarden
  • Waterlaboratorium Noord te Glimmen

The tests check the quality of drinking water after treatment (at the pumping station) and once it reaches the customer (at the tap). If the water does not meet standards, the company must immediately inform the ILT, which assesses all reports. In 2020, 492,327 measurements were taken and tested. This was much less than in 2019, when 616,000 measurements were taken, because corona measures made home visits more difficult.

Several parameters are monitored by these tests:

  • Microbiological parameters

Pathogenic bacteria, such as E.coli bacteria.

[note: removed lactic acid bacteria and intestine bacteria and replaced with e.coli because this is on the list of parameters and easily recognised by readers as a toxic bacteria]

  • Chemical parameters

A total of 29 chemicals that have been found to affect human health in cases of long-term exposure or high doses. These include lead, copper, nitrates, pesticides and vinyl chloride.

  • Indicators

These include various operational and aesthetic parameters, such as the water’s hardness, temperature, color, pH and flavor.

  • Radioactivity

To test the water’s radioactivity, levels of radon and tritium are measured.

Random Daytime Samples

These parameters are checked using a protocol called Random Daytime (RDT) sampling. This means samples are taken at taps across the water network, at random days and random times. Drinking water companies tend to choose the tap that is used most often (the kitchen tap). Unfortunately, this method can deliver inaccurate results, especially for contaminants such as lead. Lead residues in water are not often found, even though lead pipes are still present in some buildings; that’s because water has to be in contact with the pipes for a little time for residues to register. RDT samples are not as suitable for detecting lead in water.

The chemicals that are tested can also offer a distorted image of water quality. When it comes to chromium, for example, only the total amount is measured. But there are different forms of chromium, such as the highly toxic chromium-6. This means that the results might give an indication that water quality is good, when in fact it contains unhealthy chemicals.

In December 2020, the European Parliament decided to revise the EU Drinking Water Directive in order to tighten legislation and add new rules to include endocrine disrupting chemicals like microplastics and new problem substances like PFAS. According to Article 13 of the updated directive, these substances will be added to the monitoring parameters by January 2024 . In the meantime, these chemicals are not included in the water quality tests carried out by Dutch drinking water companies.

Man-made pollutants

These revisions are urgently needed because there is currently no legal standard established for PFAS. All we have is a Tolerable Weekly Intake (TWI) value established by the European Food Safety Authority (EFSA) of 4.4 nanograms per kilogram of body weight per week. Meanwhile, a growing number of alarming reports are being published with information about PFASs and other man-made pollutants contaminating our drinking water. Some of the chemicals that have been found in our tap water include chlorate (present in disinfectants), melamine (a type of plastic found in reusable utensils) , naphthalene (an aromatic hydrocarbon found in coat tar, crude oil and plastics), sucralose (an artificial sweetener) and sulfamic acid (used as a bleach and industrial cleaner).

Because of the extra pollution present in water sources, water companies are finding it increasingly difficult and expensive to remove contaminants. Vewin chairman Peter Van de Velden warns that water quality is under pressure and argues for stronger protection of water sources. “The discharge of chemicals, microplastics, pesticides and fertilizers is still tolerated. We close our eyes to the long-term consequences. We’ve been talking about it for years but the problem is only increasing. The question is: how long will we continue to discuss the dossier on polluting substances before taking action?”

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