One possible reason is the growing use of a pyrethroid called cypermethrin, which both the SEPA and the Environment Agency believe is more toxic. (newscientist.com)
Consumers can identify pyrethroids in products by checking labels for compounds that end in «thrin,» such as bifenthrin, permethrin and cypermethrin. (scientificamerican.com)
Common chemical names include permethrin, cypermethrin, cyphenothrin, bifenthrin, etc.. (petpoisonhelpline.com)