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Resmethrin, a pyrethroid pesticide used to control insects, is toxic to non-target organisms and other mammals. However, little is known about the reproductive toxicity of resmethrin in the testes, or its mechanism of toxicity. In this study, we investigated the testicular toxicity of resmethrin on mouse Leydig (TM3) and Sertoli (TM4) cells, focusing on the mitochondria and endoplasmic reticulum (ER). We found that resmethrin inhibited proliferation and cell cycle progression and disrupted mitochondrial membrane potential (MMP; ΔΨ) in TM3 and TM4 cells. In particular, resmethrin exposure significantly reduced the expression of mitochondria-associated membranes (MAMs) proteins, such as Vapb, Vdac, and Grp75, in both cell lines. Resmethrin also disrupts calcium homeostasis in the mitochondrial matrix and cytoplasm. In addition, resmethrin activates oxidative stress-mediated ER stress signals. Finally, we confirmed that 4-PBA, an ER stress inhibitor, restored the growth of TM3 and TM4 cells, which was decreased by resmethrin. Therefore, we confirmed that resmethrin hampered MAMs and activated ER stress, thus suppressing TM3 and TM4 cell proliferation. [Display omitted] • Resmethrin inhibits the proliferation of Leydig and Sertoli cells in mice. • Resmethrin impairs mitochondria and calcium homeostasis in mouse testis cells. • Resmethrin disrupts mitochondria-associated ER membranes in mouse testis cells. • Resmethrin activates oxidative stress-mediated ER stress signals in mouse testis cells. • Resmethrin-induced ER stress suppresses the proliferation of mouse testis cells. [ABSTRACT FROM AUTHOR]

The use of pesticides provides benefits such as growing food products necessary for life, sustainability of production efficiency and prevention of diseases caused by pests. However, these benefits can turn into negative effects for humans and other living organisms with the use of pesticides in inappropriate doses and application methods. In this study, it was aimed to determine resmethrin, which belongs to the insecticide class, by gas chromatography-flame ionization detector (GC-FID) method. Hence, a suitable temperature program was utilized to determine resmethrin at a certain retention time. Limit of detection (LOD) and limit of quantification (LOQ) values were recorded as 0.02 and 0.08 mg/L under the proposed conditions, respectively. After corn silk sample was extracted using acetonitrile, analytical measurements were carried out to investigate the presence of resmethrin. There was no analytical signal detected that belonged to resmethrin in the analyzed sample. Recovery experiments were performed using external calibration method with spiked samples at three different concentrations and good percent recovery results were obtained between 93 and 97%. [ABSTRACT FROM AUTHOR]

Resmethrin, a type I pyrethroid insecticide, is frequently used globally in residential and farmland areas to control pests. Owing to the repeated administration of resmethrin, and particularly because of its lipophilic nature, residues have been detected in various environments, crops, and livestock. Previous studies have shown the adverse effects of resmethrin, including neurotoxicity and hepatotoxicity. However, the toxic effects of resmethrin on the female reproductive system have rarely been investigated. In the present study, we used two cell types, porcine trophectoderm (pTr) and porcine uterine luminal epithelial (pLE) cells, to examine the toxic effects of resmethrin on implantation and its mechanisms. Our study showed that resmethrin exposure induced apoptosis and inhibited cell cycle progression, thereby reducing the viability of both cell types. In addition, calcium homeostasis was disrupted following resmethrin treatment, and disrupted calcium homeostasis impaired the mitochondrial membrane potential and mitochondrial respiration. In addition to mitochondrial dysfunction, GRP75 and ER stress-related proteins were upregulated. Furthermore, the AKT and MAPK cascades were altered, and reactive oxygen species production and inflammation occurred after resmethrin treatment. Ultimately, through various mechanisms, resmethrin decreased the migratory abilities, and it could diminish the crosstalk between the two cell lines and lower the probability of successful implantation. Overall, we demonstrated that resmethrin interfered with the implantation process by triggering various toxic mechanisms. This study presents, for the first time, evidence regarding the mechanisms through which resmethrin exerts toxic effects on the female reproductive system, thereby raising awareness regarding the potential implications of its widespread use., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Purpose: The quantification of parent molecules of pyrethroids tetramethrin and resmethrin in human specimens by a mass spectrometry (MS) technique has not been reported yet. A woman in her 60s was found dead in a wasteland. At the scene, an empty beer can and a spray for insecticides containing tetramethrin and resmethrin were found. Therefore, the concentrations of tetramethrin and resmethrin in postmortem specimens and the methanol solution used for rinsing the inside of the beer can were determined using liquid chromatography (LC)–tandem mass spectrometry (MS/MS). Methods: The quantification method by LC–MS/MS for intact parent molecules of tetramethrin and resmethrin in whole blood and urine has been devised and validated in this work. The method was applied to the quantification of tetramethrin and resmethrin in whole blood, urine and stomach contents obtained from a cadaver at autopsy. Results: The limits of detection of tetramethrin and resmethrin were 0.06 and 0.03 ng/mL; limits of quantification were 0.2 and 0.1 ng/mL in blood and urine, respectively. The concentrations of tetramethrin of the deceased were 11.1 ± 1.2 and 0.425 ± 0.017 ng/mL for stomach contents and urine, respectively; the concentration of resmethrin in stomach contents was 1.77 ± 0.18 ng/mL. The tetramethrin and resmethrin were unstable in blood and urine at room temperature; they should be kept at not higher than 4 ℃. Conclusions: To our knowledge, this is the first report for quantification of unchanged tetramethrin and resmethrin in human specimens obtained in a fatal case. [ABSTRACT FROM AUTHOR]

Resmethrin is a widely used pyrethroid insecticide, which causes low toxicity in mammals. However, its toxicity in testes has not been fully investigated. Therefore, we evaluated the toxicity of resmethrin in mouse testes using an in vitro organ culture. Mouse testicular fragments (MTFs) derived from neonates were cultured in medium containing resmethrin for 30 days. Effects on spermatogenesis in the cultured testes were investigated as functions of both time and dose. Resmethrin significantly downregulated the transcription levels of marker genes for spermatogonia and the number of spermatogenic germ cells relative to those of the controls, according to quantitative PCR and immunostaining. In addition, spermatocyte was observed in the control, but not in 50 μM resmethrin-exposed cultures. Levels of the SYCP3 meiotic marker and phosphorylated H2AX decreased by resmethrin treatment, as observed by Western blotting. Toxic or apoptotic effects of resmethrin in Sertoli and Leydig cells from MTFs were not observed by immunostaining and Tunnel assay. No changes in the expression of steroidogenic enzymes were noted. Apoptosis was only detected in the germ cells of resmethrin-treated MTFs. Thus, the highest dose of resmethrin tested (50 μM) completely inhibited spermatogenesis, because of apoptosis of germ cells and spermatocytes. Although the in vivo toxicity of resmethrin has not yet been studied in detail, significant evidence for cytotoxicity was observed in our organ cultures. This methodological approach is useful for the study of reproductive toxicity before proceeding to animal models, as it greatly reduces the use of laboratory animals. [ABSTRACT FROM AUTHOR]

Like predators, contaminant stressors such as pesticides may have large and interacting effects on natural communities by removing species or altering behaviors and species interactions. Yet, few studies in estuarine systems have evaluated the effects of a single, low-dose exposure to pesticides on key predators. Here, we investigated the effects of a common pyrethroid (resmethrin) + synergist (piperonyl butoxide; PBO) mixture used for mosquito abatement on two life stages (adult and juvenile) of an important invertebrate estuarine predator, prey, and fishery species: the blue crab (Callinectes sapidus). The effects of resmethrin with PBO (Res-PBO) were assessed using behavioral and mesocosm experiments to link effects on individuals with changes in predator-prey interactions: (1) In static non-renewal exposures, crabs exposed to 1:3, 10:30, or 100:300 µg l−1 Res-PBO or PBO-alone had increased mortality and reduced locomotor ability within 1-12 h, with higher effects in adults than juveniles. (2) In mesocosms, sublethal exposure to 1:3 µg l−1 Res-PBO altered abult and juvnile foraging ability by  lowering the ability of adult crabs to cannibalize juvenile crabs but increasing juvenile crab foraging rates. Juvenile crabs were also more vulnerable to predation following pesticide exposure. Thus, a single, sublethal exposure to low, environmentally occurring pesticide concentrations reduced blue crab survivorship and locomotor functioning, and altered predator-prey interactions by changing foraging rates and increasing vulnerability to predators. Pesticide stressors may therefore play an important but underestimated role in shaping coastal ecosystems in which invertebrate predators are important and may contribute to U.S. blue crab population declines. [ABSTRACT FROM AUTHOR]

Few studies have examined the impact of mosquito adulticides on honey bees under conditions that reflect actual field exposure. Whereas several studies have evaluated the toxicity of mosquito control products on honey bees, most have been laboratory based and have focused solely on acute mortality as a measure of impact. The goal of this study was to determine effects of routine applications of truck-based ultra-low volume (ULV) mosquito adulticides (i.e., Scourge, Duet, and Deltagard) on honey bees in a suburban setting. The mosquito adulticides used in this study were pyrethroids with active ingredients resmethrin (Scourge), prallethrin and sumithrin (Duet), and deltamethrin (Deltagard), in which resmethrin, prallethrin, and sumithrin were synergized with piperonyl butoxide. We measured and compared mortality and detoxification enzyme activities (esterase and glutathione S-transferase) from sentinel beehives within and outside of mosquito control areas. Concurrently, colony health (i.e., number of adult bees, brood quantity and brood quality) was compared throughout the study period. No significant differences were observed in honey bee mortality, colony health or detoxification enzyme activities between treated (five sprayed areas each received one to three insecticide treatment) and control sites (four unsprayed areas that did not receive insecticide treatment) over the seven week study period. However, our laboratory study showed that exposure to resmethrin, the active ingredient in Scourge, caused significant inhibition of esterase activity compared with the control group. Our findings suggest that proper application of truck based insecticides for mosquito control results in little or no exposure and therefore minimal effects on domestic honey bees. [ABSTRACT FROM AUTHOR]

Three insecticides commonly used for mosquito and sand fly control were applied 30 min to 3 h after sunset during June and July 2010, at Camp Buehring, Kuwait, to determine the relative quantity of pesticides to height and distance traveled in a hot desert environment. A BVA dilution oil was used for the control. Oil-based adulticides were sprayed using a truck-mounted Curtis DynaFog Maxi-Pro 4 ultra-low volume (ULV) sprayer. Malathion (Fyfanon ULV, 96% active ingredient [AI]), resmethrin (Scourge 4 + 12, 4% AI), pyrethrins (ULD BP-300, 3% AI), and BVA Spray 13 (100% refined petroleum distillate) were mixed with Uvitex optical brightener fluorescent dye and applied at 2 speeds on evenings when wind speed was less than 16.1 km/h (10 mph). Collection targets using biodegradable cotton ribbons (1 m × 2.5 cm) were later read with a fluorometer to quantify the amount of insecticide deposited on targets set at heights of 15.2, 76.2, and 152.4 cm (6, 30, and 60 in.) and distances of 1.5, 6.1, 15.2, 30.5, 61.0, and 91.4 m (5, 20, 50, 100, 200, and 300 ft). Mean insecticide deposition across all distances was 31% on 76.2-cm targets and 49% on 152.4-cm targets, while 15.2-cm targets typically collected <20% of test spray. Mean ground temperatures were typically within 5°C of air temperatures at 152.4 cm and within 1 to 5°C of air at 15.2 cm or 76.2 cm. Collectively, mean insecticide deposition was 80% at or above 76.2 cm for all insecticides. This finding may explain in part why control of low-flying phlebotomine sand flies with ULV insecticides has been met with less than optimal success by US military forces deployed in the Middle East. [ABSTRACT FROM AUTHOR]

The discovery of resmethrin almost five decades ago was the seminal event in the development of pyrethroid insecticides as important pest management tools, the value of which endures to this day. This brief review considers the development of pyrethroids from the perspective of the discovery of resmethrin. I describe the pathway to the discovery of resmethrin and the unique properties that differentiated it from the pyrethrins and earlier synthetic pyrethroids is described. I also summarize information on metabolic fate and mechanisms of selective toxicity, first elucidated with resmethrin, that have shaped our understanding of pyrethroid toxicology since that time. Finally, I review the discovery pathway that led from resmethrin to the development of the first photostable, agriculturally useful pyrethroids that established the importance of this insecticide class. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Resmethrin (RES) is a synthetic pyrethroid insecticide widely used to control pests in agriculture, but it may cause potential hazards to human health. The characteristics of the binding of RES with calf thymus DNA (ctDNA) were investigated in a physiological buffer (pH 7.4) by multiple spectroscopic methods combined with ctDNA melting and viscosity measurements, multivariate curve resolution-alternating least-squares (MCR-ALS) chemometrics and the molecular docking technique. The concentration profiles and the pure spectra for the reactive species (RES, ctDNA and RES–ctDNA complex), obtained through decomposing the augmented UV-vis spectral data matrix by the MCR-ALS approach, indicated that RES could bind to ctDNA and the reaction process could be quantitatively monitored. The RES molecules bound to ctDNA by groove binding, as evidenced by the negligible changes in the ctDNA melting temperature, viscosity and iodide quenching effect and the increase in the single-stranded DNA quenching effect. Fluorescence titration data indicated that the complexation of RES with ctDNA was mainly driven by hydrogen bonds and van der Waals forces, and had strong affinity. The changes in the Fourier transform infrared spectra of ctDNA suggested that RES molecules preferentially bound to the G–C region of ctDNA, which was consistent with the prediction of the molecular docking. The circular dichroism spectral analysis indicated that RES induced a decrease in the right-handed helicity of ctDNA. The DNA cleavage assay showed that RES did not cleave the pUC18 plasmid DNA. This study offers a comprehensive picture of RES–ctDNA interaction, which may provide insights into the toxicological effect of the insecticide. [ABSTRACT FROM AUTHOR]

Advances in the synthesis and utilization of new chemical compounds have led to improvements in our daily lives. However, new chemicals may be both beneficial and toxic. Thus, exposure to these new compounds should be restricted in an attempt to limit their potential toxicities. We predicted the safety of three biocides (p-cresol, diazinon and resmethrin) by comparing their skin permeability coefficients and desquamation rate (the counter flux of permeability coefficient for chemical compounds induced by skin turnover) following skin exposure. In vitro skin permeation experiments revealed that the permeability coefficients of diazinon and resmethrin were smaller than the desquamation rate; therefore, these biocides could not permeate the skin, which resulted in very low skin concentrations of these compounds. On the other hand, the skin concentration of p-cresol was high because of its higher permeability coefficient than the desquamation rate. Furthermore, low in vitro cell viability was reported for skin exposed to p-cresol. These results in the present study indicate that the method described herein is useful for predicting the toxicities of chemicals following their topical exposure. [ABSTRACT FROM AUTHOR]

Abstract: Resmethrin, phenothrin, and fenvalerate are the synthetic pyrethroids that have been used widely against groundling or flying insect pests both indoors and outdoors. In this study, the heterogeneous reactions of the three pyrethroid particles with NO3 radicals are investigated with a mixed-phase relative rate method. The reactions are performed in a reaction chamber equipped with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS) and an atmospheric gas analysis mass spectrometer. The uptake coefficients of NO3 radicals on resmethrin, phenothrin, and fenvalerate particles are ∼0.20, 0.04, and 0.03 respectively, calculated with a spherical shell model. And the atmospheric lifetimes of the three pyrethroid particles toward NO3 radicals are estimated to be ∼2.6, 7.5, and 9.3h, respectively. The molecular structures of reaction products and the reaction pathways are suggested based on the measurements of VUV-ATOFMS and off-line GC–MS. [Copyright &y& Elsevier]

The southern house mosquito, Culex quinquefasciatus Say, is a competent vector of human disease and an important target of mosquito abatement programs. However, these management programs have been compromised by development of insecticide resistance. In the current study, susceptibilities to naled and resmethrin, two adulticides used in mosquito abatement, were monitored using a topical and contact bioassay, respectively, in five field- collected populations of C. quinquefasciatus (MARC, HOOD1, HOOD2, MINLOVE, and THffi). Frequencies of resistance, measured as survival after treatment with discriminating concentrations (i.e., sufficient to kill >90% of a reference susceptible strain) were high (88.0-96.8%) in all field collections treated with naled, but were variable (3.3-94.2%) with resmethrin. In addition, esterase activities in mosquitoes from these collections were quantified using a-naphthyl acetate and ranged from 1.08 to 3.39 µmol α-naphthol produced min-1 mg prot-1. Heightened activities were associated with decreased insecticide susceptibility in HOOD1, THIB, and MINLOVE but not HOOD2. Esterases were visualized using native polyacrylamide gel electrophoresis, and intra- and interstrain differences in banding patterns were detected. In addition, esterases from MINLOVE mosquitoes were more numerous and intensely staining when compared with those from a laboratory-susceptible strain. Finally, naled synergized the toxicity of resmethrin in populations with decreased insecticide susceptibility and increased esterase activity by 2.5-(MINLOVE) to three-fold (THIB). Results from this study will allow management strategies for populations of C. quinquefasciatus to be optimized, and provide a foundation for further studies exploring use of esterase inhibitors as synergists of pyrethroid toxicity. [ABSTRACT FROM AUTHOR]

The article presents the discoveries of scientist Michel Elliott in insecticide chemistry which focused on safe and effective pest control. It states that Elliot's discoveries of resmethrin, cypermethrin, permethrin and deltamethrin in England with David Pulman and Norman Janes provide crop protection and malaria control for millions of people. It also states his achievements in the research on lipophilic amide, dithiane and stereochemically pure crystalline compound.

Abstract: Public health agencies utilize aerial insecticides to interrupt an active West Nile virus (WNV) transmission cycle, which may expose WNV-infected birds to these agents. Although resmethrin has been considered benign to birds, no studies have evaluated whether the environmentally employed form of resmethrin with PBO synergist (synergized resmethrin (SR)) can suppress avian immunity to WNV infection and enhance a bird''s host competence. Recognizing that wild birds confront toxicological stressors in the context of various physiological states, we exposed four groups (n =9–11) of 9-week-old chickens (Gallus domesticus) to drinking water with either SR (three alternate days at 50μg/l resmethrin+150μg/l piperonyl butoxide), CORT (10 days at 20mg/l to induce subacute stress), the combination of SR and CORT, or 0.10% ethanol vehicle coincident with WNV infection. Compared to controls, SR treatment did not magnify but extended viremia by 1 day, and depressed IgG; CORT treatment elevated (mean, 4.26log10 PFU/ml) and extended viremia by 2 days, enhanced IgM and IgG, and increased oral virus. The combination of SR and CORT increased the number of chickens that shed oral virus compared to those treated with CORT alone. None of the chickens developed a readily infectious viremia to mosquitoes (none ≥5log10 PFU/ml), but viremia in a CORT-exposed chicken was up to 4.95log10 PFU/ml. Given that SR is utilized during WNV outbreaks, continued work toward a complete risk assessment of the potential immunotoxic effects of SR is warranted. This would include parameterization of SR exposures with immunological consequences in wild birds using both replicating (in the laboratory) and non-replicating (in the field) antigens. As a start, this study indicates that SR can alter some immunological parameters, but with limited consequences to primary WNV infection outcome, and that elevated CORT mildly enhances SRs immunotoxicity in chickens. [Copyright &y& Elsevier]

The grass shrimp, Palaemonetes pugio, plays a large role in the marine ecosystem, serving as a vital link in the food web between many other species. Marine parasites such as the bopyrid isopod, Probopyrus pandalicola, reduce shrimp growth and reproductive output and may also cause P. pugio to be more vulnerable to the lethal effects of contaminants. The purpose of this study was to determine the toxicity of resmethrin and bifenthrin on the grass shrimp, P. pugio, infected with the bopyrid isopod, Probopyrus pandalicola. A 96-h static renewal test was conducted to determine the toxicity of the pyrethroid insecticides resmethrin and bifenthrin to grass shrimp, Palaemonetes pugio, parasitized with the bopyrid isopod, Probopyrus pandalicola. The results were then compared to similar tests utilizing unparasitized P. pugio. Parasitized P. pugio had lower 24-h LC50 (1.08 μg/L) and 96-h LC50 (0.43 μg/L) values for resmethrin than unparasitized P. pugio. However, LC50 ratio tests found that there was no significant difference between parasitized and unparasitized shrimp when affected by resmethrin (p = 0.1751 and 0.1108, respectively). In contrast, an LC10 ratio test indicated that there was a significant difference between parasitized and unparasitized P. pugio after 96 h (p < 0.0001). When subjected to bifenthrin, parasitized P. pugio had a higher 24-h LC50 (0.049 μg/L6) than unparasitized P. pugio. The LC50 ratio test established that the effects of bifenthrin on parasitized P. pugio when compared to unparasitized P. pugio were significantly different at 24 h (p = 0.0065). However, there were no significant differences between parasitized and unparasitized after 96 h (p = 0.4229). In conclusion, both resmethrin and bifenthrin are toxic to the grass shrimp, P. pugio, regardless of parasite presence, and parasitized shrimp may be more susceptible to lower doses of resmethrin (when exposed in the field). [ABSTRACT FROM AUTHOR]

We investigated the efficacy of various chemical injections against Cryptotermes brevis (Walker) (Isoptera: Kalotermitidae) in hardwood shipping pallets. We had three principle interests: efficacy in whole structures, relative efficacy of the active ingredients, and whether acoustic evidence augmented treatment site selection. Infested pallets were delineated into boards with four monitoring sites each. Six chemical treatments were compared: chlorpyrifos aerosol, aqueous disodium octaborate tetrahydrate (DOT), resmethrin aerosol, distilled water (control), and two treatments of spinosad SC (one treatment applied based upon visual and the other treatment upon acoustic [AE] evidence). Individual boards were split apart; efficacy was determined by percentage mortality and pre- and posttreatment AE counts. Injections were constrained to a single point per board with the greatest level of termite activity. In whole pallets, mean percentage mortality ranged from 53.3 to 58.7% for the visual and AE spinosad treatments, respectively, whereas water averaged 6.8%. Remaining treatment mortalities were 33.2, 30.4, and 18.1% for chlorpyrifos, DOT, and resmethrin, respectively. Analysis of whole-pallet data indicated that none of the insecticides produced commercially acceptable mortality; localized injections of insecticides were not comparable with whole-structure treatments. We delineated independent groups of board sections (sectional aggregates; SA) that were connected by galleries. When treated SA were analyzed, spinosad and DOT treatments were significantly different from controls, whereas remaining treatments were not different from controls or spinosad and DOT. AE readings and visual termite evidence were compared with presence or absence of termites in SA, and it was determined that both AE and visual evidence were effective predictors of termite presence. [ABSTRACT FROM AUTHOR]

Abstract: The acute toxicity of permethrin, resmethrin, and cypermethrin to four species of aquatic non-target invertebrate organisms, found in estuarine and freshwater ecosystems, was evaluated. Artemia franciscana and Brachionus plicatilis larvae, as estuarine organisms, and Brachionus calyciflorus and Thamnocephalus platyurus larvae, as freshwater organisms, were exposed for 24h to concentrations of these pyrethroids, and the LC50 values were compared. The freshwater organisms were more sensitive to these pyrethroids than estuarine organisms tested. A. franciscana larvae were more tolerant organisms than B. plicatilis larvae. The freshwater organisms tested have demonstrated to be a good alternative to the standard acute toxicity assays using Daphnia, although Brachionus plycatilis larvae were more sensitive to these pyrethroid insecticides than T. platyurus. Analysis of 24h LC50 values of these pyrethroids, determined by static bioassays, revealed that the rank order of toxicity was: permethrin&#60;resmethrin=cypermethrin for A. franciscana, B. calyciflorus, and T. platyurus, whereas with B. plicatilis larvae the order of toxicities was: resmethrin&#60;permethrin&#60;cypermethrin. [Copyright &y& Elsevier]

A comparative aquatic hazard assessment of resmethrin was conducted to investigate the need for its restricted use classification by the US. EPA as an adult mosquito control agent. This paper describes the environmental fate and aquatic toxicity of resmethrin. The following paper compares resmethrin to the alternative insecticides. Environmental fate studies indicate that resmethrin has a short photolytic half-life in water (< 1h). Furthermore, it is immobile in soil and biodegradable (half-life=36.5d) under aerobic conditions. Laboratory studies with constant 48- to 96-h exposures show it is acutely toxic to fish and invertebrates in the 0.22–15.0μg/L range. Daphnia magna, pink shrimp ( Penaeus duorarum) and rainbow trout ( Oncorhynchus mykiss) are the most sensitive and mollusks are the least sensitive species. Chronic laboratory studies indicate that the maximum acceptable toxicant concentrations (MATCs) for resmethrin and D. magna, Pimephales promelas, O. mykiss, and Cyprinodon variegatus are 0.58, 0.52, 0.43, and 10.3μg/L, respectively. The acute-to-chronic ratios (1.1–7.3) for all species studied indicate that chronic toxicity will not be an issue for resmethrin. Furthermore, the characteristics of acute exposures (48- to 96-h) used in the laboratory will not occur under field conditions because of the short half-life of resmethrin in fresh- and salt-water. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the association of synergized and non-synergized insecticides to trout. The study used toxicity testing and two resmethrin formulations to compare the synergized and non-synergized insecticides. Results show that the synergized formulation of insecticides undergoes greater intoxicating effect than non-synergized formulation to fish.

The article presents a study regarding the effect of synthetic pyrethroids and organophosphorus pesticides on tadpole shrimp Triops longicaudatus. The study used field tests of resmethrin and cypermethrin (emulsifiable concentrate) (EC), laboratory bioassays, and Mann-Whitney U statistics. Results showed that abundance of Triops was decreased by resmethrin while cypermethrin activity was enhanced against tadpole.

The article reports on the pyrethroid insecticides' public safety aspects which was used in West Nile virus-carrying (WNV) mosquito control. In the United States, WNV's outbreaks is increasing which cause many fatalities. The epidemic is reduced by controlling the mosquito vectors through the use of pyrethroid insecticides.Resmethrin and Pyrethrins, a pyrethroid, have been shown to cause tumors in an animal experimentation. An overview of the study is offered, which indicates that it is unlikely to be applicable to human. Even so, for resmethrin, the US Environmental Protection Agency (EPA) inferred that a risk of carcinogenicity in humans is present, thus requiring the manufacturers to provide more information to prove that it can be used safely in vector control.