Pyrethrins

Химические свойства

Pyrethrum , derived from extracts of the Chrysanthemum cinerariaefolinum plant, is a combination of six pyrethrin isomers, namely, pyrethrin 1, pyrethrin 2, cinerin 1, cinerin 2, jasmolin 1, and jasmolin 2. Pyrethroids are synthetically derived commercial compounds similar to pyrethrum. Pyrethrins and pyrethriods are insoluble in water and have a low vapor pressure. Pyrethrum is subject to photodegradation and is oxidized rapidly in the presence of air (U.S. EPA, 2006c; ATSDR, 2003).

Использование

Pyrethrins are used to kill a number of different flying and crawling insects and arthropods. First registered in the 1950s, currently over 1350 end-use products containing pyrethrins are available for agricultural, commercial, residential, and public health areas. They are used as household insecticides, as grain protectants, and to control pests on edible products just prior to harvest in a variety of locations, including residential, public, and commercial buildings, animal houses, warehouses, fields, and green houses. Pyrethrins are also extensively used in the field of veterinary medicine (U.S. EPA, 2006c; ATSDR, 2003).
Commercially available pyrethroids include allethrin, bifenthrin, bioresmethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, esfenvalerate (fenvalerate), flucythrinate, flumethrin, fluvalinate, fenpropathrin, permethrin, phenothrin, resmethrin, tefluthrin, tetramethrin, and tralomethrin.

Определение

Pyrethrolone ester of chrysanthemummonocarboxylic acid. Most potent insecticidal ingredient of pyrethrum flowers.

Показания

Pyrethrins, rapid-acting compounds, derived from chrysanthemum plants, are the leading over-the-counter louse remedy. These compounds interfere with neural transmission, leading to paralysis and death. Piperonyl butoxide (PBO) potentiates the pyrethrins by inhibiting the hydrolytic enzymes responsible for pyrethrin metabolism in arthropods.

Реакции воздуха и воды

Oxidize relatively rapidly in air. Water emulsifiable.

Профиль реактивности

PYRETHRINS decompose rapidly in base; may generate heat with caustic solutions. May also react with acids to liberate heat. Generate flammable hydrogen with alkali metals and hydrides.

Опасность

Toxic by ingestion and inhalation.

Угроза здоровью

Pyrethrum dust causes dermatitis and occasionally sensitization.The primary effect in humans from exposure to pyrethrum is dermatitis. The usual lesion is a mild erythematous dermatitis with vesicles, papules in moist areas, and intense pruritis; a bullous dermatitis may develop.
Some persons exhibit sensitivity similar to pollinosis, with sneezing, nasal discharge, and nasal stuffiness.2 A few cases of asthma due to pyrethrum mixtures have been reported; some of the people involved had a previous history of asthma with allergy to a wide spectrum of substances.

Пожароопасность

Some may burn but none ignite readily. Containers may explode when heated. Some may be transported hot.

Фармаколо?гия

The chrysanthemates (pyrethrin I, cinerin I, and jasmolin I) are generally more potent for insecticidal kill, whereas the pyrethrates (pyrethin II, cinerin II, and jasmolin II) cause more rapid knockdown. When combined with synergists, the pyrethrins are effective at low doses in causing knockdown and kill of a wide variety of pests. Pyrethrins exert their effects primarily by acting on sodium channels in nerves to disturb nerve conductance . Two distinct effects, referred to as type I and type II, have been defined for pyrethrins.

Клиническое использование

Because of the high cost and rapid degradation of the pyrethrins, they usually are combined with piperonyI butoxide, a synergist. PiperonyI butoxide has no insecticidal activity in it own right but is thought to inhibit the cytochrome P450 enzyme of the insect, thus preventing an oxidative inactivation of the pyrethrins by the parasite. The combination is used in a 10:1 ratio of . piperonyl butoxide to pyrethrins. The mixture is used for treatment of Pedicul us humanus capitis, Pediculus humanus corporis, and Phthir'us pubis. Various dosage forms are available, including a gel, shampoo, and topical solution.

Возможный контакт

Pyrethrins are used as an ingredient of various contact insecticides. Those engaged in the isolation, formulation, or application of these materials.

Экологическая судьба

If released to air, the relatively low vapor pressure indicates that the pyrethrins and pyrethroids will exist in both the vapor and particulate phases in the atmosphere. Vapor-phase compounds are rapidly degraded by direct photolysis and by reaction with photochemically produced hydroxyl radicals and ozone; the half-lives for these reactions in air are estimated to be 1.3 h and 17 min, respectively. Particulates may travel long distances and are removed from the atmosphere by wet or dry deposition (HSDB, 2013; ATSDR, 2003). Pyrethrins and pyrethroids are strongly adsorbed to the soil surfaces so they are not expected to be mobile. The compounds also strongly adsorb to suspended solids and sediment in the water column. Thus, partitioning to solids attenuates volatilization from soil and water surfaces. Pyrethrins and pyrethroids are often used indoors in sprays or aerosol bombs, and the volatilization rates from glass or floor surfaces may be significantly faster than from soils since these compounds are not likely to adsorb as strongly to these surfaces (ATSDR, 2003). These insecticides are readily biodegraded by microorganisms.
Pyrethrins and pyrethroids bioconcentrate in aquatic organisms, including fish, oysters, and insects. The bioconcentration factor for several commercial products in three species of fish ranged from 180 to 1200 depending on the amount of dissolved organic matter in the water column (ATSDR, 2003).

Перевозки

UN2902 Pesticides, liquid, toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.

Несовместимости

Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explo- sions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Compounds of the car- boxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water and a salt that may be harmful. Incompatible with arsenic com- pounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides (releasing heat, toxic and possibly flammable gases), thiosulfates and dithionites (releasing hydrogen sul- fate and oxides of sulfur).