One of the Sergeant's products containing propoxur.

Flea Collar Makers Agree To Eventually Phase Out Collars Containing Toxic Chemical

Facing a lawsuit for allowing manufacturers to produce flea collars containing a pesticide that is a known neurotoxin and carcinogen, the folks at the Environmental Protection Agency, along with two major pet product companies, have agreed to phase out these controversial collars over the next few years. [More]

http://consumerist.com/2007/12/07/sergeants-sentrypro-xfc-flea-treatment/

Sergeants SentryPro XFC flea treatment gives pets Pyrethrin Toxicity, causing them to vomit and not be able to walk, and in one case, a dog died. Petco still has the stuff on its shelves. [Gibberish Is My Native Language]