It causes moderate eye irritation. Prolonged or frequently repeated skin contact may cause allergic reactions in some individuals. Skin exposure may result in a transient sensation described as a tingling, itching, burning, or prickly feeling. Onset may occur immediately to four hours after exposure and may last 2–30 hours, without apparent skin damage. First aid measures are included with the label information. Metabolism The mammalian LD50 is 21.8 mg/kg (rats, oral). Phase I metabolism of tefluthrin proceeds via both oxidation and hydrolysis. Initial targets for oxidation are its methyl groups. Those on the cyclopropane ring and on the tetrafluorobenzene ring are oxidized to alcohol groups which can be further oxidized into carboxylic acids. Hydrolysis of tefluthrin occurs at the ester bond which results in cyhalothrin acid and 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol, which can be further oxidized into the corresponding carboxylic acid. In phase II metabolism, the phase I metabolites are glucuronidated on any available alcohol groups to facilitate membrane transport and eventually excretion. Environmental effects Tefluthrin is very highly toxic to freshwater and estuarine fish and invertebrates. Its properties and effects on the environment have been summarized in several publications. Ultimately it is the regulatory authorities in each country who must weigh up the benefits to end users and balance these against the compound's inherent hazards and consequent risks to consumers and the wider environment. These authorities stipulate the conditions under which tefluthrin may be used. Resistance management Species have the ability to evolve and develop resistance to pyrethroids (and, indeed, almost all pesticides). This potential can be mitigated by careful management. Reports of individual pest species becoming resistant to tefluthrin are monitored by manufacturers, regulatory bodies such as the EPA and the Insecticide Resistance Action Committee (IRAC). In some cases, the risks of resistance developing can be reduced by using a mixture of two or more insecticides which each have activity on relevant pests but with unrelated mechanisms of action. IRAC assigns insecticides into classes so as to facilitate this. References Further reading External links PPDB pesticides properties database of tefluthrin MSDS of tefluthrin from Sigma-Aldrich Tefluthrin on Pubchem International Chemical safety information (2,3,5,6-tetrafluorophenyl)methyl 3-ethenyl-2,2-dimethylcyclopropane-1-carboxylates Trifluoromethyl compounds