Preservatives pyrethroids

The acute effects of high oral or intravenous doses of the pyrethrins and most noncyano pyrethroids closely resemble those of DDT (which acts similarly on the sodium channel). They are characterized by fine continuous tremor, which may be severe enough to cause hyperthermia, and by marked reflex hyperexcitability. Consciousness is preserved up to the point... 

Figure 1. Examples of Phase I and Phase II metabolites of the carbamate insecticide carbanolate, the synthetic pyrethroid insecticide permethrin, and the wood preservative pentachlorophenol...

Some pyrethroids are especially useful for wood preservation due to their physico-chemical parameters, e.g. very low vapor pressure, high UV-resistance and very low water solubility, resulting in a long-term protection of technical material. Today the active ingredients Permethrin, Cypermethrin, Cyfluthrin, Deltamethrin and Bifenthrin (Figure 18 and 19) are used in wood protection. Due to their long-term protection and their fast action these compounds can be used in preservative and curative applications. Table 7 summarizes the efficacy in tests according to European standards EN 21 and EN 47. 

Gruning, R., Pospischil, R., Cymorek, S. and Metzner, W., 1986. Pyrethroids Isomerism and Efficacy. International Research Group on Wood Preservation and Wood Protection Chemicals, Section 3, 1986 (IRG/WP 1284/1986). 

Pyrethroids. More accurately described as the synthetic pyrethroids, this group of compounds has been used extensively in wood preservation for control of both beetles and termites. Activity, cost and performance characteristics vary depending upon the specific compound but most readily accepted for use in wood preservative formulations are permethrin, cypermethrin, deltamethrin, bifenthrin and cyfluthrin. In terms of activity against wood boring beetles, cyfluthrin is estimated to be 20 times more effective than permethrin, 10 times as effective as cypermethrin and twice as effective as deltamethrin when compared in laboratory evaluative procedures. However, in practice other factors need to be considered, particularly the relative vapour pressures (and therefore evaporative loss) and, in wood in soil contact, the rate of biotransformation by colonising bacteria. The pyrethroids are effective as neurotoxins, and are axonic poisons. 

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