Fiprinol has I believe, been banned in Switzerland now. Apparently it's more deadly when released into water. A vet on Exmoor has done extensive research and was responsible for the Swiss ban.The issue of pesticide residues entering water courses has long been blamed on agriculture, but recent studies have identified that a major source of the problem is treatments given to household pets, which in urban areas are present in extremely high densities.
On that basis alone, some degree of control over their usage ought to be maintained.