Dinoterb update
In response to the presence of dinoterb in surface water in 2022, HHNK started a cause and source investigation. It is unknown when, how and why this substance entered the surface water. We first analyzed the measurement data in more detail. One part of that analysis is the validation of the data used. A second part is a comprehensive sources and causes investigation that will be conducted in the coming months.
Data validated
Validation shows that the measurement data are correct. All reported analytical results for dinoterb meet the set quality requirements and are correctly reported. Moreover, comparisons between laboratories (so-called interlaboratory comparisons) show that the laboratory scores well for this method, including specifically the component dinoterb. This conclusion was also shared with NVWA and RIVM.
Surface water standard
Dinoterb has an MTR (maximum allowable risk) standard. This standard is based on the adverse effects of a substance on animals and plants upon long-term exposure in the aquatic ecosystem. Thus, this standard says nothing about possible effects on humans. To determine whether a substance meets the standard, the annual average concentration is calculated. If the substance exceeds the set standard on average (for dinoterb this is 30 ng/liter), the substance is harmful to nature. Individual measurements are therefore not used to determine whether a standard has been exceeded. The results of the annual measuring network for crop protection are calculated and tested against the standard. These results are presented on the website Atlas of pesticides in surface water.
Presence of dinoterb Zwanenwater below standard
Review of the 2022 measurement data for dinoterb in the Zwanenwater shows that dinoterb does not test above the surface water standard. Further analysis of the 2022 measurement data of dinoterb for the Zwanenwater shows that there is a single elevated measurement. This measurement occurred on September 1, 2022. To determine whether the surface water standard is exceeded, multiple measurements are used which are then tested. This testing shows that dinoterb does not test above the standard in 2022 in the Zwanenwater.
Multiple locations above standard
Dinoterb was found at several locations in HHNK's management area in 2022. In contrast to the Zwanenwater, dinoterb was measured above the surface water standard at the locations below in 2022:
- Krassekeet pumping station, Texel
- Drieban polder pumping station
- Oosterpolder pumping station, Hoorn
- Pieter Engelgemaal, Assendelft
- Western Randweg, Beverwijk
- Slootgaardweg, Waarland
- Pumping station het Hoekje, Zijpe
- King William II road, 't Zand
- 't Zand, along the N9
- De Stolpen, along the N9
- Sint Maartensvlotbrug, along the N9
- Westerduinweg, Petten
