Effective immediately, new labels will have to be put on flea collars sold in California warning that the collars may contain a cancer causing chemical.
The NRDC says the chemicals can penetrate the skin of pets, get on people's hands and is especially dangerous for children.
"There are much safer ways to treat fleas on your pets that don't involve any chemicals at all. Regular bathing with a normal shampoo, vacuuming and keeping the pet's area clean. All of these are non-chemical safe ways to keep your pets safe," says Miriam Rotkin-Ellman, a scientist from the NRDC.
Petco tells 7 On Your Side retailers and manufacturers disagree on this, saying the collars' chemicals are not in high enough levels to pose a health risk to either humans or pets.