Dinoterb

To determine the state of water quality in our management area, we regularly take measurements at various locations in surface water. We monitor water quality for the use of crop protection products and substances that fall under the Water Framework Directive (WFD). In 2022, the plant protection product dinoterb, which has been banned since 1998, was occasionally found at several locations in our area.  

Source research 2024 

In response to this finding, we commissioned the independent knowledge institute Deltares to conduct a source investigation in 2024. Deltares found no identifiable source for the presence of dinoterb, nor any indications that the substance is still in use. 

Follow-up studies 2025 

As recommended in the 2024 source investigation, HHNK and the Waterproef water board laboratory commissioned four follow-up studies, which are explained below. Following these new studies, HHNK concluded that there is no dinoterb in surface water. Although the measurement method is correct and all accreditation rules for laboratories have been complied with, research shows that dinoterb cannot always be measured reliably using the current measurement method. HHNK will therefore stop measuring dinoterb and will also withdraw all reported dinoterb measurements for the period 2020 to the present. 

Portfolio holder Jos Beemsterboer: "The results of these four follow-up studies clearly show that there is no dinoterb in surface water anywhere. The results are clear and definitive. As far as we are concerned, this concludes the research into dinoterb. HHNK will stop measuring dinoterb and will also remove all dinoterb measurement data published since 2020. We remain fully committed to working together to improve water quality." 

Explanation of follow-up studies 2025 

  1. Deltares was commissioned by the Waterproef laboratory to investigate possible contamination in dinoterb analyses. Deltares concluded that Waterproef performs the analysis of crop protection products (CPP) in accordance with the applicable standards and accreditation requirements, but that the concentration of dinoterb cannot always be measured reliably. There may be false positive measurement results. This means that the measurement indicates that dinoterb is present, while in reality this may not be the case. Despite in-depth research, the actual source cannot be determined.
  2. In addition, research was conducted to determine whether the conclusions of the contamination study could also apply to the more than 200 other crop protection products (CPPs) that Waterproef measures on behalf of HHNK. Deltares concluded that these findings apply specifically to dinoterb and not to other crop protection products.
  3. HHNK conducted additional sampling to determine whether dinoterb stored in the waterbed in the past could be released as a result of disturbance (e.g., during dredging work). No dinoterb was found during this additional sampling.
  4. HHNK also conducted additional sampling to determine whether dinoterb from industrial or human use enters the sewage treatment plant. No dinoterb was found in this additional sampling either.

Appendices 

Reporting dinoterb