The collars, which contain the chemical tetrachlorvinphos, make up more than half of flea and tick collars sold in the U.S., according to the EPA. They are much cheaper than many name brand collars and are largely aimed at low-income pet owners.
More than a decade ago, nonprofit Natural Resources Defense Council petitioned the EPA to ban the use of a pesticide called tetrachlorvinphos in pet products like flea and tick collars. The organization cited studies showing that the chemical, a possible carcinogen, had been linked to brain and nerv
