Frequently asked questions follow-up study dinoterb 2025

What was investigated (four studies)? 

In 2024, Deltares conducted a source and cause investigation into dinoterb on behalf of HHNK. This was in response to high dinoterb readings in surface water measurements. The investigation did not identify any source or cause for the presence of dinoterb in surface water measurements. Since then, four different additional and in-depth studies have been conducted: 

  1. The Deltares source and cause investigation from 2024 prompted Waterproef to look further into possible contamination and so-called false positive measurements indinoterb analyses. Waterproef commissioned Deltares to conduct a new investigation into this (2024/25).
  2. Waterproef also asked Deltares to investigate whether the results of the contamination study could also apply to the more than 200 crop protection products (CPPs) that Waterproef measures on behalf of HHNK.
  3. In addition, the Deltares study from 2024 prompted HHNK to conduct additional sampling to investigate the release of dinoterb into the waterbed and
  4. Perform additional sampling in the wastewater from the WWTPs. 

What came of it?

Deltares' in-depth investigation into the measurement data and analysis method for dinoterb at Waterproef concludes that the concentration of dinoterb cannot always be measured reliably and that Waterproef performs the measurements in accordance with the accreditation rules for laboratories (NEN). These findings apply specifically to dinoterb and not to other crop protection products. In addition, the extra samples taken by HHNK from the waterbed and from wastewater samples show no evidence of dinoterb.   

Is there or is there not dinoterb in the surface water? 

Since last year (2024), a lot of new research has been conducted and new knowledge and insights have been gained. With this knowledge (as it stands today), HHNK concludes that there is no dinoterb in the surface water.   

What will HHNK do now? 

  1. HHNK will immediately stop monitoring dinoterb.  
  2. HHNK is withdrawing all published dinoterb data from 2020 to the present.
  3. HHNK will discontinue sampling for post-delivery from the waterbed through dredging and at the WWTPs.
  4. HHNK will continue to monitor water quality and crop protection products, while maintaining its focus on four specific GBMs that have been designated as substances of concern by Deltares.
  5. HHNK remains fully committed to improving water quality in collaboration with others.