Elimite
A Comparison of the Toxicity of Synergized and Technical Formulations of Permethrin, Sumithrin, and Resmethrin to Trout.

Paul EA, Simonin HA, Tomajer TM.

New York State Department of Environmental Conservation, Rome Field Station, Rome, NY, 13440, USA, eapaul gw.dec.state.ny.us.

Synthetic pyrethroids often have synergists added to improve effectiveness, yet decisions regarding the use of these pesticides are often based upon toxicity tests using technical material without the synergist, piperonyl butoxide. We conducted toxicity tests with brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) to compare the toxicity of synergized and technical formulations of permethrin, sumithrin, and resmethrin. We found a significant increase in toxicity in the synergized permethrin formulation using traditional 24, 48, and 96-h tests, relative to tests with the technical formulation. However, there was little difference in toxicity between synergized and technical sumithrin until 48 h had elapsed. Many test fish were strongly intoxicated by either formulation of permethrin or sumithrin, but the synergized formulations of both chemicals affected fish at lower concentrations. Intoxication was potentially severe enough to reduce the survival of these fish in the wild. Following short (6-h) exposures, we also found a larger difference in the number of fish that died or became intoxicated between the synergized and technical formulations of permethrin and sumithrin. Finally, we tested the ability of exposed fish to swim against a current. Fish exposed for 6 h to synergized permethrin and resmethrin had far less swimming stamina than those exposed to technical formulations. We found no difference in the effect on swimming between the synergized and technical formulation of sumithrin. In general, the synergized formulations of these chemicals appeared to cause a faster response than the technical formulations. This response increases the lethal and sublethal impacts of the insecticides. We also found that sumithrin was the least toxic of the three pyrethroids. Since the maximum application rate of sumithrin is half that of the other two pyrethroids, the potential risk to wild trout in streams may be reduced.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15696349&dopt=Abstract permethrin Elimite



Elimite
Diffusion of the synthetic pyrethroid permethrin into bed-sediments.

Allan IJ, House WA, Parker A, Carter JE.

Centre for Ecology and Hydrology Dorset, Winfrith Technology Centre, Dorchester, UK. ian.allan port.ac.uk

Bed-sediments are a sink for many micro-organic contaminants in aquatic environments. The impact of toxic contaminants on benthic fauna often depends on their spatial distribution, and the fate of the parent compounds and their metabolites. The distribution of a synthetic pyrethroid, permethrin, a compound known to be toxic to aquatic invertebrates, was studied using river bed-sediments in lotic flume channels. trans/cis-Permethrin diagnostic ratios were used to quantify the photoisomerization of the trans isomer in water. Rates were affected by the presence of sediment particles and colloids when compared to distilled water alone. Two experiments in dark/light conditions with replicate channels were undertaken using natural sediment, previously contaminated with permethrin, to examine the effect of the growth of an algal biofilm at the sediment-water interface on diffusive fluxes of permethrin into the sediment. After 42 days, the bulk water was removed, allowing a fine sectioning of the sediment bed (i.e., every mm down to 5 mm and then 5-10 mm, then every 10 mm down to 50 mm). Permethrin was detected in all cases down to a depth of 5-10 mm, in agreement with estimates by the Millington and Quirk model, and measurements of concentrations in pore water produced a distribution coefficient (Kd) for each section. High Kd's were observed for the top layers, mainly as a result of high organic matter and specific surface area. Concentrations in the algal biofilm measured at the end of the experiment under light conditions, and increases in concentration in the top 1 mm of the sediment, demonstrated that algal/ bacterial biofilm material was responsible for high Kd's at the sediment surface, and for the retardation of permethrin diffusion. This specific partition of permethrin to fine sediment particles and algae may enhance its threat to benthic invertebrates. In addition,the analysis of trans/cis-permethrin isomer ratios in sediment showed greater losses of trans-permethrin in the experiment under light conditions, which may have also resulted from enhanced biological activity at the sediment surface.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15707052&dopt=Abstract permethrin Elimite



Elimite
Pregnancy outcome following exposure to permethrin and use of teratogen information.

Kennedy D, Hurst V, Konradsdottir E, Einarson A.

MotherSafe, Royal Hospital for Women and University of NSW, Randwick, Australia.

NIX is a 1% permethrin creme rinse used for the treatment of head lice. There are no studies regarding human exposure during pregnancy. The primary objective of this study was to examine the safety of permethrin exposure during pregnancy. The secondary objective was to examine how teratogen information is perceived and used by women who requested information regarding this product. Women who had called the Motherisk and MotherSafe Programs to inquire about exposure to permethrin during pregnancy were followed-up to ascertain the outcome of their pregnancies. These women were compared with another group who had not been exposed to any known teratogenic drugs. Women who decided not to use permethrin were administered an additional questionnaire. We enrolled 147 women and completed outcomes on 113 pregnancies of women who had used permethrin some time during their pregnancy. There were 106 live births, six spontaneous abortions, one therapeutic abortion, and one major malformation in the women who used permethrin in the first trimester. The mean birthweight was 3540 +/- 492 g and the mean gestational age was 40 +/- 1 weeks. There were no statistically significant differences between the exposed and comparison groups in any of the pregnancy outcomes. Of the 34 women who chose not to use permethrin and who completed the additional questionaire, 18 (52%) did not use permethrin because they did not feel the information was sufficiently reassuring. The results of this study suggest that the use of permethrin products during pregnancy appears to be relatively safe because there was no increase in the rates of major malformations. We also found that some women will not use a product during pregnancy unless they can receive a 100% guarantee that it will not harm their baby.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15731987&dopt=Abstract permethrin Elimite



Elimite
Repression of activity-dependent c-fos and brain-derived neurotrophic factor mRNA expression by pyrethroid insecticides accompanying a decrease in Ca(2+) influx into neurons.

Imamura L, Hasegawa H, Kurashina K, Hamanishi A, Tabuchi A, Tsuda M.

Toyama Medical and Pharmaceutical University, Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Toyama, Japan.

Permethrin, a type I pyrethroid insecticide, is known to affect sodium channels of neurons and prolong sodium currents. On the other hand, the expression of brain-derived neurotrophic factor (BDNF) and c-fos genes is activated through Ca(2+) influx into neurons, in an activity-dependent manner. In this study, therefore, we investigated whether permethrin influenced the Ca(2+) signal-induced expression of these genes. In primary culture of mouse cerebellar granule cells (CGCs), stimulation with veratridine, a potent agonist for sodium channels, which causes membrane depolarization in neurons, induced c-fos and BDNF mRNA expression accompanying the Ca(2+) influx into neurons. Pretreatment with permethrin at doses nontoxic to CGCs repressed the induction of these genes dose dependently, with trans-permethrin more potent than cis-permethrin. Consistent with this, the increase in Ca(2+) influx caused by veratridine was repressed by permethrin. The membrane depolarization induced by elevating the potassium (K(+)) concentration in medium (high K(+)) caused the activation of c-fos and BDNF genes, which was also repressed by permethrin. Immunoblotting analysis of c-Fos and a gel-mobility assay of AP-1 DNA-binding activity supported the decrease in c-Fos synthesis in permethrin-treated CGCs. The type II pyrethroid cypermethrin also affected the expression of these genes but less effectively than permethrin. Thus, pyrethroids inhibit the activity-dependent gene expression in neurons.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11082455&dopt=Abstract permethrin Elimite



Elimite
Increased 8-hydroxy-2'-deoxyguanosine, a biomarker of oxidative DNA damage in rat urine following a single dermal dose of DEET (N, N-diethyl-m-toluamide), and permethrin, alone and in combination.

Abu-Qare A, Abou-Donia M.

Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.

Levels of the biomarker of DNA oxidative damage 8-hydroxy-2'-deoxyguanosine (8-OHdG) in rat urine following dermal exposure to DEET (N,N-diethyl-m-toluamide) and permethrin, alone and in combination have been determined. A group of five rats for each time point were treated with a single dermal dose of 400 mg/kg of DEET, 1.3 mg/kg of permethrin or their combination. Urine samples were collected 2,4,8,16,24,48, and 72 h following application. Control urine samples of rats treated with ethanol were also collected at the same time intervals. Solid phase extraction coupled with high performance liquid chromatography (HPLC) with UV detection at 254 nm was used for determination of 2'-deoxyguanosine, and (8-OHdG). The limits of detection (LOD) were 0.5 ng of both 2'-deoxyguanosine and 8-OHdG. Their average percentage recoveries from urine samples were between 70-85%. A single dermal dose of DEET or in combination with permethrin significantly induced levels of (8-OHdG) that are excreted in the urine over the time course of the study compared to control urine samples. Permethrin did not cause significant increase in the amount of 8-OHdG in the urine. Levels of 8-OHdG in urine excreted at 24 h were 1009+/-342, 1701+/-321, 1140+/-316, and 1897+/-231 ng following treatment with ethanol, DEET, permethrin, and DEET+permethrin, respectively. The results indicate that dermal administration of DEET could generate free radical species hence cause DNA oxidative damage in rats.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11087981&dopt=Abstract permethrin Elimite