Metaldehyde is used in slug pellets. It’s use is widespread.
Authorisation of Metaldehyde-containing products is regulated by EU law EC Regulation 1107/2009 (Plant Protection Products). This document is a retained law in Britain.
DEFRA announced in September 2020 it would not renew current authorisations for the outdoor use of mollusc-killer in the UK, where Metaldehyde is the active ingredient.
The details are here.
The effect of this decision is from 1st April 2022 Metaldehyde slug pellets should not be used outdoors.