For the testing plants assessed task we had to look up contact details of information points on poisoning.
I found the Nationaal Vergiftigingen Informatie Centrum (https://nvic.umcutrecht.nl/nvic/nl/contact). But the practice is that in case of poisoning you contact your general practicioner and if necessary they call the NVIC for information.
There is also the gifwijzer, who have mainly information on chemicals in for example cleaning materials, but also some n plants. https://www.gifwijzer.nl/