Dutch water authorities call for stricter approach to diclofenac

The over-the-counter availability of certain self-care medicines is increasingly posing a challenge to water quality, according to the regional water authorities in the Netherlands. The Dutch Water Authorities call for a reassessment of the authorisation and distribution of environmentally harmful pharmaceuticals, particularly those containing diclofenac, in a letter to the Medicines Evaluation Board CBG. The water authorities warn that the widespread use of this substance is putting European water quality targets under pressure.

“We see that pharmaceutical residues are putting pressure on water quality and that it requires significant effort to purify that water,” the water authorities write in their letter. For some substances, complete removal is not even possible. A relatively large share of this pollution appears to originate from a limited number of medicines, including diclofenac, a widely used anti-inflammatory that is found in gels and creams. These products are often freely available at drugstores and supermarkets.

Diclofenac standards exceeded

Diclofenac stands out due to the scale of its environmental load and its impact on the aquatic environment. Research by the National Institute for Public Health and the Environment (RIVM) shows that the proposed European standard for diclofenac is exceeded at more than half of the monitoring locations in the Netherlands. Moreover, the substance is persistent and poorly biodegradable, with demonstrable harmful effects on aquatic organisms, such as tissue damage in fish. Notably, the majority of the pollution does not come from pills, but from topical use. “97–98 percent of diclofenac in surface water is caused by topical application,” according to the annex to the letter. When gels and creams are used, most of the active substance is washed off via the skin directly into the sewer system.

Unnecessary burden on the environment

Current treatment technologies are not designed to effectively remove these pharmaceutical substances. In conventional wastewater treatment plants (WWTPs), on average only around 10 percent of diclofenac is removed. Although advanced treatment techniques such as ozonation and activated carbon show better results, these are not yet widely implemented and involve high costs. In addition, sewer overflows also contribute to the direct discharge of polluted water into surface waters. The financial and environmental costs of this pollution ultimately fall on water authorities and society.

Reconsider over-the-counter availability

The water authorities therefore emphasize the importance of source-oriented measures. A first concrete step they propose is to reconsider the over-the-counter availability of diclofenac-containing self-care products. By making these medicines available only by prescription, they argue that ‘unnecessary pressure on the environment’ can be prevented.

In addition, the water authorities ask the Medicines Evaluation Board to jointly explore how environmental criteria can play a greater role in the authorisation and distribution of medicines. This could include stricter labeling, usage restrictions, or public awareness campaigns. They also advocate for better coordination with other government bodies, such as the Ministries of Health (VWS) and Infrastructure and Water Management (IenW).

Stricter European water quality requirements

The call fits within a broader policy context. European legislation, such as the Water Framework Directive and the revised Urban Wastewater Treatment Directive (UWWTD), is imposing increasingly strict requirements on water quality and the reduction of harmful substances. Diclofenac is also once again included on the list of priority substances for which Member States must take action.

This article was published first by the Dutch platform for water professionals H2O Magazine