Phenothrin, also called sumithrin and d-phenothrin, a synthetic pyrethroid compound, is widely used to control agricultural and household insects, as well as to eliminate human louse infestation, but studies conducted in Paris, France and the United Kingdom have shown widespread resistance to phenothrin. Synthetic pyrethroids, including phenothrin, have a similar mode of action as organochlorines. They act on the membrane of nerve cells of insects blocking the closure of the ion gates of the sodium channel during re-polarization. This strongly disrupts the transmission of nervous impulses. At low concentrations insects suffer from hyperactivity. At high concentrations they are paralyzed and die. The EPA has not assessed its effect on cancer in humans. However, one study performed by the Mt. Sinai School of Medicine links sumithrin with breast cancer; the link made by sumithrin's effect on increasing the expression of a gene responsible for mammary tissue proliferation.