Complex sentence: Metal salt-based molluscicides are not toxic to higher animals while metaldehyde-based and especially acetylcholinesterase inhibitor-based products are highly toxic and have resulted in many deaths of pets and humans.
Split into simpler sentences: Metal salt-based molluscicides are not toxic to higher animals. However, metaldehyde-based and especially acetylcholinesterase inhibitor-based products are highly toxic, and have resulted in many deaths of pets and humans.