Dinoterb

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

Resource Survey 2024 

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

Follow-up surveys 2025 

As recommended in the 2024 source survey, HHNK and water board laboratory Waterproef commissioned four follow-up surveys, which are detailed below. After these new surveys, HHNK concludes that there is no dinoterb in the surface water. Although the method of measurement is correct and all accreditation rules for laboratories are met, research shows that with the current measurement method dinoterb cannot always be reliably measured. HHNK therefore stops measuring dinoterb and also withdraws all reported dinoterb readings for the period 2020-present. 

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

Explanation of follow-up surveys 2025 

  1. Deltares was commissioned by the Waterproef laboratory to investigate possible contamination in dinoterb analyses. Deltares concludes that Waterproef performs the analysis of plant protection products (GBM) according to the applicable standards and accreditation requirements, but that the concentration of dinoterb cannot always be reliably measured. There may be so-called false positive measurement results. This means that the measurement indicates that dinoterb is present, while in reality this does not have to be the case. The actual source cannot be determined, despite in-depth research.
  2. It was also investigated whether the conclusions of the contamination study could also apply to the more than 200 other crop protection agents (GBM) measured by Waterproef on behalf of HHNK.Deltares concluded that these findings apply very specifically only to dinoterb and not to other crop protection agents.
  3. HHNK conducted additional sampling to determine whether dinoterb stored in the water bottom in the past may be released by stirring (e.g., during dredging operations). No dinoterb was detected during this additional sampling.
  4. HHNK also conducted additional sampling to determine whether dinoterb from industrial or human use inflows into the sewage treatment plant.No dinoterb was detected in this additional sampling either.

Attachments 

Announcement dinoterb