The pesticides from pet flea and tick treatments get into our freshwater habitats via these main routes:
Via the wastewater system
Everytime you stroke your pet, some of the pesticide can be transferred to your hands. Everytime you wash your hands the pesticide is then going down the plughole.
Everytime you wash your dog, some of the pesticide is washed off and down the plughole.
Everytime you wash your pet’s bedding, or anything they have slept on (like your favourite jumper), the pesticide is washed away via your washing machine.
All water that leaves your house via the plughole or the washing machine goes into the sewer > The sewer goes to the wastewater treatment works > The treated effluent from the WWTW is discharged into the river or sea > along with some of the pesticide.
References:
Dogs swimming in ponds & rivers
If you use a Spot-On treatment and your dog swims in a pond or river 5 days after spot-on treatment has been administered:
10% of the active ingredient will be washed off your pet and into the water if the product contains Imidacloprid
4% of the active ingredient will be washed off your pet and into the water if the product contains Fiprolnil
After 28 days some of the product will be washed off by swimming, so if your pet is treated monthly it will always be potentially polluting any water which it swims in.
References: