Pyrethroids: How They Affect Human and Animal Health? (original) (raw)

Current Research on the Safety of Pyrethroids Used as Insecticides

Medicina

Pyrethroids are synthetic derivatives of natural pyrethrins extracted from Chrysanthemum cinerariaefolium. They are 2250 times more toxic to insects than to vertebrates due to insects’ smaller size, lower body temperature and more sensitive sodium channels. In particular, three pyrethroid compounds, namely deltamethrin, permethrin, and alpha-cypermethrin, are commonly used as insecticides and are recommended for in-home insect control because they are considered to be relatively non-toxic to humans in all stages of life. However, recent data show that they are not completely harmless to human health as they may enter the body through skin contact, by inhalation and food or water, and absorption level depending on the type of food. Permethrin seems to have an adverse effect on fertility, the immune system, cardiovascular and hepatic metabolism as well as enzymatic activity. Deltamethrin induces inflammation, nephro- and hepatotoxicity and influences the activity of antioxidant enzyme...

Relative Potencies for Acute Effects of Pyrethroids on Motor Function in Rats

Toxicological Sciences, 2005

The prevalence of pyrethroids in insecticide formulations has increased in the last decade. A common mode-of-action has been proposed for pyrethroids based on in vitro studies, which includes alterations in sodium channel dynamics in nervous system tissues, consequent disturbance of membrane polarization, and abnormal discharge in targeted neurons. The objective of this work was to characterize individual dose-response curves for in vivo motor function and calculate relative potencies for eleven commonly used pyrethroids. Acute oral dose-response functions were determined in adult male Long Evans rats for five Type I (bifenthrin, S-bioallethrin, permethrin, resmethrin, tefluthrin), five Type II (bcyfluthrin, l-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate) and one mixed Type I/II (fenpropathrin) pyrethroids (n = 8-18 per dose; 6-11 dose levels per chemical, vehicle = corn oil, at 1 ml/kg). Motor function was measured using figure-8 mazes. Animals were tested for 1 h during the period of peak effects. All pyrethroids, regardless of structural class, produced dosedependent decreases in motor activity. Relative potencies were calculated based on the computed ED30s. Deltamethrin, with an ED30 of 2.51 mg/kg, was chosen as the index chemical. Relative potency ratios ranged from 0.009 (resmethrin) to 2.092 (esfenvalerate). Additional work with environmentally-based mixtures is needed to test the hypothesis of dose-additivity of pyrethroids.

Comparative toxicology of the pyrethroid insecticides

Reviews of environmental contamination and toxicology, 1989

The toxic effects elicited by synthetic pyrethroids in animals are varied in degree and nature. Their relative safety to birds and mammals contrasts sharply with their acute effects on fish and arthropods. Explantation of their differences in toxicity depends on examination of all factors of their comparative toxicology. Routes of exposure are important, as are metabolism and elimination rates, especially for mammals and birds with their considerable capabilities for biotransformation. Significant differences in sensitivity at the sites of toxic action may also play a role in differential responses to these insecticides. Finally, physical properties that influence the environmental disposition and subsequently affect bioavailability of the compounds in water, soil, air, produce, and nontarget species are also instrumental in determining the impact of current and future synthetic pyrethroid insecticides.

Evidence for a separate mechanism of toxicity for the Type I and the Type II pyrethroid insecticides

NeuroToxicology, 2009

Neurotoxicity and mechanistic data were collected for six a-cyano pyrethroids (b-cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin and l-cyhalothrin) and up to six non-cyano containing pyrethroids (bifenthrin, S-bioallethrin [or allethrin], permethrin, pyrethrins, resmethrin [or its cis-isomer, cismethrin] and tefluthrin under standard conditions. Factor analysis and multivariate dissimilarity analysis were employed to evaluate four independent data sets comprised of (1) fifty-six behavioral and physiological parameters from an acute neurotoxicity functional observatory battery (FOB), (2) eight electrophysiological parameters from voltage clamp experiments conducted on the Na v 1.8 sodium channel expressed in Xenopus oocytes, (3) indices of efficacy, potency and binding calculated for calcium ion influx across neuronal membranes, membrane depolarization and glutamate released from rat brain synaptosomes and (4) changes in chloride channel open state probability using a patch voltage clamp technique for membranes isolated from mouse neuroblastoma cells.

Insecticidal Activity, Toxicity, Resistance and Metabolism of Pyrethroids: a Review

Science and Technology Indonesia

Pyrethroids are synthetic or man-made versions of natural pyrethrins discovered in the flowers of a plant species of the Compositae family called "Chrysanthemum cinerariaefolium". The plant was transported into Europe and America after it was discovered in the Near East. Commercial insecticides such as pyrethrin and synthetic pyrethroid are available. These are used to control agricultural pests as well as non-agricultural insects. They are also commercially used in personal care items such as shampoo and as a scent in insect repellent to boost efficacy and persistence in the environment, these insecticides are frequently combined with additional chemicals in diverse formulations, known as synergists. Nerve toxins, known as pyrethroids, although their chemical mechanism of action is unknown. Pyrethroids are neurotoxins, which interfere with the messages sent along nerves by maintaining sodium and chloride channels in an open position. This review presents perspectives, com...

Systematic review on pyrethroid toxicity with special reference to deltamethrin

Pyrethroids are synthetic organic compounds synthesized from chrysanthemum flowers that are used extensively as household and commercial insecticides. The keto-alocoholic esters of chrysanthemic and pyrethroic acid being lipophilic are responsible for its insecticidal properties. Pyrethroids are broadly classified into first and second generation pyrethroids. The first generation (Type 1) pyrethroids are less toxic to mammals than the second generation (Type II) pyrethroids. Mainly Type II pyrethroids cause paresthesia, which is characterized by transient burning/tingling/itching sensation of the exposed skin. Also, it has been suggested that some pyrethroids cause developmental neurotoxicity, but available evidence has been judged to be insufficient. While some pyrethroids have been shown to cause tumors in rodent models, the tumor induction does not appear to reflect a common carcinogenic endpoint for this particular subset of compounds. Deltamethrin is an alpha-cyano pyrethroid insecticide used extensively in pest control. Although initially thought to be least toxic, a number of recent reports showed its toxicity in mammalian and non-mammalian laboratory and wildlife animal species. The article sheds light on deltamethrin induced various toxicities during acute and chronic exposure in different species.