Mixture Of Cypermethrin Research Articles

A novel wood preservative with plant extracts in a cypermethrin mixture protects envelope-treated tropical kempas hardwood against Coptotermes termites when exposed to an above-ground indoor situation after evaporative ageing

In keeping with sustainability initiatives in the commercial wood protection sector to develop cost-effective, environmentally acceptable wood treatment alternatives to traditional biocides, this paper reports on an above-ground test for protection against subterranean termite damage to blocks of termite-susceptible heartwood of tropical (Malaysian) kempas hardwood (Koompassia malaccensis). The blocks were envelope-treated (brush-on) with a novel wood preservative based on plant extracts in a cypermethrin mixture (Biocide 1: 0.16% cypermethrin, 0.08% tebuconazole, 2% vegetal extracts). A commercial permethrin-based LOSP (Biocide 2: 0.2% permethrin, 1.8% tributyltin naphthenate, 0.1% dichlorofluanid) applied in 3-minute dips served as the control treatment. The air-dried kempas blocks were H2-weathered under a rigorous laboratory volatilization regime (representing long-term evaporative ageing of treated wood for above-ground indoor use in prolonged H2-hazard class situations). The blocks were then exposed for 6 months above ground, inside a containerised test design targeting subterranean Coptotermes curvignathus termites, at a humid forest site (representing a severe H2-hazard class situation with treated wood isolated from wetting, soil contact, and weather). The results showed irrefutably that untreated kempas heartwood was severely attacked by C. curvignathus (mean mass loss: 70.4% and 20,416 mg) with a low mean visual termite rating (2.4). However, the treated kempas wood was well protected at very low surface retention of Biocide 1 (mean negligible mass loss: 0.66% and 207 mg) and very low surface retention of the control Biocide 2 (mean negligible mass loss: 1.01% and 306 mg), with both treatments similarly yielding the highest mean visual termite rating for all replicate kempas specimens (rating 10). The performances of the two biocides were similar but varied significantly (P < 0.05) from the attacks against their untreated counterparts. Biocide 1 therefore has considerable anti-termite potential and could replace conventional LOSP Biocide 2 treatments to protect wood exposed to a long-term H2-hazard class environment.

Risk of control failure to insecticides malathion, profenophos + cypermethrin mixture, and fipronil in boll weevil (Coleoptera: Curculionidae) populations from Bahia, Brazil

BackgroundTo control the boll weevil Anthonomus grandis grandis (Coleoptera: Curculionidae), a key pest of cotton in the Americas, insecticides have been intensively used to manage their populations, increasing selection pressure for resistant populations. Thus, this study aimed to detect insecticide resistance and assess insecticide control failure likelihood of boll weevil populations exposed to malathion, profenophos + cypermethrin, and fipronil insecticides.ResultsTwelve populations of the boll weevil were collected from commercial cotton fileds of the state of Bahia, northeastern Brazil. These populations were exposed to malathion, profenophos + cypermethrin mixture, and fipronil, at their respective maximum label dose for field applications. Three replicates of 10 adult beetles were exposed to the insecticides and mortality was recorded after 24 h treatment. The control failure likelihood was determined after 48 h. Highest median lethal times (LT50) were observed for malathion and the profenophos + cypermethrin mixture. Resistance to at least one insecticide was detected in 11 populations; three populations were resistant to malathion and profenophos + cypermethrin; seven were resistant to all insecticides tested. The resistance levels were low (< 10-fold) for the three insecticides. Among 12 populations tested, 58% of them exhibited significant risk of control failure for the insecticides malathion and profenophos + cypermethrin. The insecticide fipronil was efficient for the control of the boll weevil in 83% of the populations.ConclusionsThe results confirm the significant risk of insecticide control failure in the boll weevil populations to the main compounds used in the region. Thus, proper insecticide resistance management plans are necessary for the boll weevil in the region, particularly for malathion and profenophos + cypermethrin insecticides.

Alzheimer’s- and Multiple Sclerosis-Like Features on Key Brain Centres of Wistar Rats Exposed to Cypermethrin and Dichlorvos

Insecticides are suspected environmental factors in the aetiology of Alzheimer’s and multiple sclerosis diseases. Several studies have reported long-term exposure to insecticides in the development of plaques, neurofibrillary tangles, and demyelination. However, there is no literature on the impact of short-term combined insecticide exposure on specific neurological conditions. This investigation assessed the role of short-term exposure to the mixture of cypermethrin and dichlorvos on Alzheimer’s- and multiple sclerosis-like features. Thirty-two male adult Wistar rats were divided into four groups: the control group was exposed to normal atmospheric air, and the test groups were exposed to a combined cypermethrin and dichlorvos at 2, 3, and 4 h/day [LC50 of 5 mm-1 (4.4 ppm) of dichlorvos and 10 mm-1 (8.7 ppm) of cypermethrin] for four weeks. In the last three days of exposure, neurobehavioural tests were conducted. Twenty-four hours after the last exposure, the animals were anesthetized using chloroform vapour. The brains were harvested by making an occipitofrontal incision for biochemical and histological assessment. The fixation was done in 10% neutral buffered formalin for 48 h following the brain mapping to isolate the brain tissue of interest. The insecticide-exposed rats showed significant (p&lt;=0.05) progressive behavioural deficits and oxidative stress when compared to the control group. Neurofibrillary tangles, senile plaques, and demyelination of the neurons were observed in the brains of the insecticide-exposed rats. This study indicates that the mixture of cypermethrin and dichlorvos can induce the development of Alzheimer’s and multiple sclerosis within a short time

In vivo mutagenic effects and oxidative stress parameters evaluation of cypermethrin and benzoate of emamectin and their mixtures in female mice

We evaluated the biological effects of ingestion by gavage, for 28 days, of the pesticides cypermethrin (CP) and emamectin benzoate (EB) and their mixtures in female Swiss mice. The groups were Control (water); CP; EB and three distinct concentrations of CP and EB mixture expressed in mg/kg/day. The biological effects were analyzed in the complete blood count and plasma (alkaline phosphatase (ALP), alanine aminotransferase (ALT) and creatinine); the biochemical parameters of oxidative stress (substances reactive to thiobarbituric acid (TBARS); reduced glutathione (GSH); catalase (CAT), superoxide dismutase (SOD) and glutathione-S-transferase (GST)), and bone marrow cells obtained from the femur for the micronucleus (MN) test. In the heart, there was a reduction in GSH in the groups (0.5 + 0.67 and 2.5 + 3.37), although in the brain this effect appeared for the other groups, except EB. Brain TBARS increased in CP and in the group (2.5 + 3.37) and platelets increased in the group (12.5 + 16.87). Genotoxic/mutagenic effects, showing a consistent increase dose-dependent effect on micronucleus counting for in the female mice. After 28 days of treatment, we can observe that the pesticide mixtures promoted genotoxic damage and oxidative brain damage in female mice, which can damage the health of these animals and possibly their future offspring.

Impacts of changes in temperature and exposure time on the median lethal concentrations (LC50) of a combination of organophosphate and pyrethroid in the control of Culex quinquefasciatus, say (Diptera: Culicidae)

Climate change factors such as rainfall, heat waves, rising temperatures and flooding have positively impacted insect vector population. This scenario poses considerable demand on chemical control. This study was carried out with the specific aim to examine the influence of changes in temperature and exposure time of C. quinquefasciatus to toxicities of pyrethroid (Cypermethrin), organophosphate (2, 2- dichlorovinyl dimethyl phosphate) and their mixtures. Eggs of C. quinquefasciatus were collected at the Federal University of Technology, Akure, Nigeria, in an area far from residential and cultivated zones, with a remote chance of the mosquitoes being exposed to insecticides. The eggs were allowed to hatch into larvae/pupae in the field at 27–29 °C temperature, 70–85% RH, 14:10 (L: D) photoperiod. F3 adult generation reared were transferred to the Entomology Laboratory and exposed to different concentrations of Cypermethrin and DDVP applied singly and in mixtures at varying temperatures and exposure time with mortality recorded. The median lethal concentration (LC50) values for the insecticides were higher when the insecticides were applied singly than when applied as mixtures. Therefore, mixtures of cypermethrin and DDVP have enhanced toxicity. Again, temperature changes also affect insecticide toxicity and because climate change has a characteristic temperature variability, it poses a barrier to insecticide toxicity. Hence, it is expedient to have a climate change adaptation policy in synergy with modality of chemical applications. Further study of toxico-kinetic of the insecticides in mosquito control is also recommended.

Reproductive and Pup Parameters of Female Wistar Rats (Rattusnorvegicus) Mated by Males Treated with Date Fruit Extract and Cypermethrin

The work was designed to study the effect on fertility and pup parameters of female Wistar rats mated to male Wistar rats that were treated with Date fruit extract and Cypermethrin. A total of 48 mature Wistar rats (Rattusnorvegicus) comprising of 24 males and 24 females were randomly distributed into four groups (I, II, III, and IV) of 12 animals per group of which six were males and six were females. The six males in groups I, II, III and IV received distilled water; Cypermethrin at 60mg/kg body weight; Date fruit extract (DFE) at 250 mg/kg body weight; and a mixture of Cypermethrin (60 mg/kg body weight) and DFE (250mg/kg body weight) respectively. Treatment was given once weekly per os for eight weeks after which treated males were mated with the females at a ratio of 1: 1. Conception and pregnancy rates; gestation length; litter size; litter weights at birth, day‐5, day‐10, day‐15 and day‐21 post‐partum; anogenital distance at day‐10; sex ratio and age of pup at hair growth were measured. Results showed that there were no significant differences (p&gt;0.05) in all parameters measured except sex ratio. More female than male offsprings were born to the Date fruit treated male groups. It was concluded that Cypermethrin at 60 mg/kg body weight did not alter the fertility of male Wistar rats while Date fruit extract at 250 mg/kg body weight favored the birth of more female off springs. Further investigation is required to unravel the potential of Date fruit extract in sex selection.

Resistance profile and molecular characterization of pyrethroid resistance in a Rhipicephalus microplus strain from Colombia.

Intensive use of chemical acaricides for the control of cattle ticks (Rhipicephalus microplus) has led to the development of multiple acaricide resistance in Colombia. The present study aimed to characterize, using toxicological bioassays and molecular biology techniques, the resistance profile of a tick strain isolated from the Arauca state, Northeast Colombia. Commercial acaricides were used in adult immersion tests to determine its in vitro efficacies. Deltamethrin showed very low activity (4-7.3%), a mixture of cypermethrin and chlorpyrifos had intermediate efficacy (64-75.2%), and ethion presented the highest activity (88.5-100%). A colony (Arauquita strain) was established and larval immersion tests confirmed high resistance level to deltamethrin (241-fold) and susceptibility to ivermectin. A quantitative polymerase chain reaction-high resolution melt technique was used to identify single nucleotide polymorphisms (SNPs) in the para-sodium channel gene. All of the genotyped individuals were mutant, presenting one (n= 7), two (n= 7) or three (n= 9) SNPs previously associated with pyrethroid resistance. Sequencing revealed a novel mutation (F712L), that was found for the first time in R. microplus ticks from South America. This is the first description of mutations associated with pyrethroid resistance in R. microplus from Colombia. The acaricide resistance pattern found in the Arauquita strain is similar to other parts of Colombia.

MECHANISM OF HOUSE FLY RESISTANCE: II- BINARY MIXTURES OF CYPERMETHRIN, IMIDACLOPRID AND SPINOSAD AND THEIR IMPACT TO BREAK DOWN THE LABORATORY DEVELOPED RESISTANCE.

The present study indicated that the repeated exposure of thelaboratory strain of the house fly, Musca domestica (Linnaeus) toCypermethrin, Imidacloprid and Spinosad lead to developing resistanceagainst these insecticides. The resistance level of the selected strainsreached after 30th generation to 24.8, 15.53 and 9.56 folds forCypermethrin, Imidacloprid and Spinosad compared with the laboratorystrain.This study also showed the breakdown of resistance usinginsecticide binary mixtures, where the mixture of Cypermethrin+Imidacloprid exhibited potentiation at the ratio of 1:1 and 1:2 against allthe resistant strains. Also, the combination of Cypermethrin withSpinosad gave potentiation at the ratios of 1:1, 1:2 and 2:1 againstImidacloprid and Spinosad resistant strains.

MECHANISM OF HOUSE FLY RESISTANCE: I- Toxicity of Cypermethrin, Imidacoloprid and Spinosad to Larvae and Adults of the Laboratory Strain

The house fly, Musca domestica L., is a vector for more than100 human and animal diseases and has the ability to developeresistance to different insecticides. This study evaluated toxicity ofCypermethrin, Imidacloprid and Spinosad, in addition to, their mixturesunder laboratory conditions against larvae and adults of M. domesticafor laboratory strain. The LC50s of the three tested insecticides were579.30, 415.46 and 16.32ppm, respectively, against larvae 48h posttreatment. The toxic effect of these insecticides against M. domesticaadults was assessed 24h post treatment. The LC50s of Cypermethrin,Imidacloprid and Spinosad were 208.75, 238.3 and 86.05 ppm,respectively, against the laboratory strain. This study also showedefficacy of the binary mixtures of these insecticides, where the mixtureof Cypermethrin+Imidacloprid and Cypermethrin+Spinosad showedpotentiation at ratios 1:1, 1:2 and 2:1. On other hand, the mixture ofImidaclporid+Spinosad showed an additive effect at all mixing ratios.

Effects of cypermethrin (pyrethroid), glyphosate and chlorpyrifos (organophosphorus) on the endocrine and immune system of Salvator merianae (Argentine tegu)

Several geographical areas where Salvator merianae is distributed in Argentina are included in regions with agricultural activity and exposed to pesticide formulations. Some pesticides could affect defense mechanisms being able alter structures of some components of immune and endocrine systems. To assess the potential effects of pesticides in this reptile under seminatural conditions, on the immune system and endocrine responses in S. merianae we analyzed several blood parameters. Total (TWBCC), differential (DWBCC) white blood cells count, heterophils/lymphocytes index (H/L), lobularity index (LI), natural antibodies (NAbs) titres, complement system (CS), and corticosterone concentration were analyzed in animals exposed to a mixture of cypermethrin (25%), glyphosate (66.2%) and chlorpyrifos (48%) formulations. In addition, body size was considered in these analyzes. TWBCC and NAbs revealed lower values in organisms exposed to pesticides respect to a control indicating a possible immunosuppression effect. Besides, the LI showed a greater number of lobes in organism exposed demonstrating symptoms of chronic infection. In addition, we observed a reduced growth in these animals possibly related to a less energy investment in body mass to maintain an active defense against pesticides. Finally, we found high levels of plasma corticosterone in animals exposed to mix formulation that could demonstrate neuroendocrine axis activation. Other parameters like DWBCC, H/L index and activity of CS showed no differences in treated animals respect to control group, which could indicate low sensibility of these parameters to the concentration of pesticides used. Our results provide evidence of the toxic effects of pesticides on different immune system parameters, but also a trade-off among these parameters, corticosterone levels and growth. In this way, we can conclude that the formulated pesticides applied widely and constantly in the areas occupied by S. merianae, would be affecting its immune and endocrine systems and therefore its ability to defend against external agents. This kind of studies is of great interest to know the possible responses of wild species to anthropogenic disturbances such as pesticide contamination.

Potential of pyrethroid-synergised pyrethrum on stored product insects and implications for use as prophylactic sprays.

The study was conducted to evaluate the synergistic effects of 2% pyrethrum extract with synthetic pyrethroids on the mortality of stored product insects. Contact toxicity was performed at variable concentrations observing mortality at 12, 24 and 48h durations. The results of the present study indicated that, pyrethrum + deltamethrin combination (25:1 ratio) was effective on the adults of Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). On the other hand, pyrethrum + cypermethrin combination proved effective against Sitophilus oryzae (L.). The efficacy of the tested combination showed reasonable increase in mortality response in treated insects over increasing exposures. At 48h, 450ppm pyrethrum + deltamethrin combination induced 25, 90 and 97% mortalities in S. oryzae, T. castaneum and R. dominica adults; while, pyrethrum-cypermethrin combination recorded 75, 45 and 75% mortalities respectively. On the other hand, it was observed that, among the pyrethrum alone treatments i.e. at 300, 450 and 600ppm concentrations, maximum mortality (62.5%) was observed in S. oryzae exposed to 600ppm pyrethrum for 48h. The effective LC50 concentrations for pyrethrum (600ppm) + deltamethrin combination was estimated to be as 0.1987 and 0.7039µl/cm2 for R. dominica and T. castaneum adults respectively. Contrastingly, for treatments with S. oryzae, a LC50 value of 0.8673µl/cm2 was recorded for pyrethrum (600ppm) + cypermethrin mixture. This investigation strengthens the fact that pyrethrum along with pyrethroids is effective against storage insect pests which can be promisingly a safer insecticidal combination.

Oxidative effects of the acute exposure to a pesticide mixture of cypermethrin and chlorpyrifos on carp and zebrafish – A comparative study

The use of commercial pesticides combinations increases the risk of intoxication in non-target aquatic organisms. Here, we investigate the potential of a commercial pesticide formulation containing (CYP) plus chlorpyrifos (CPF) to induce oxidative damage on two fish species (common carp and zebrafish). Carp and zebrafish were exposed for 96 h under laboratory conditions. Fish were divided in three different groups: CTL, 0.3 μg L−1 or 0.6 μg L−1 of CYP and 0.5 or 1 μg L−1 of CPF in commercial formulation. Both carp and zebrafish showed an increase in lipid peroxidation (LPO) and glutathione-S-transferase (GST) activity when compared to control group. Other oxidative parameters responded differently to exposure in carp and zebrafish. There were an increase in ascorbic acid (ASA) levels and decrease in catalase (CAT) activity and non-protein thiols (NPSH) levels in treated groups of carps. In the other hand, zebrafish showed significant decrease in ASA and increase in CAT activity and NPSH levels. Overall, we demonstrate noxious effects on redox parameters in two fish experimental models and different effects were observe in each fish species exposed to commercial pesticide formulation. This difference responses observed can be related with specific mechanisms of detoxification and antioxidant defense system of each species.

Efficacy of commercial synthetic pyrethroids and organophosphates associations used to control Rhipicephalus (Boophilus) microplus in Southern Brazil.

This study evaluated the acaricidal efficiency of synthetic pyrethroids (SP) associated with organophosphates (OP) against Rhipicephalus (Boophilus) microplus populations in the state of Rio Grande do Sul, Southern Brazil. Ticks were collected in 54 cattle farms and tested using in vitro adult immersion test against four commercially available acaricide mixtures of SP and OP. Only one of four acaricides, comprising a mixture of cypermethrin, chlorpyrifos, and fenthion, had a mean efficiency higher than 95%, and was effective in 94.44% (51/54) of the cattle farms tested. The acaricide with a mixture of cypermethrin, chlorpyrifos, and citronelall had the lowest mean efficiency (62.11%), and was effective in 29.62% (16/54) of cattle farms tested. Furthermore, R. (B.) microplus in Southern Brazil exhibited differing degrees of resistance to SP and OP mixtures. The results suggest that the presence of fenthion contributes to the higher efficiency of the formulation with this active principle. This is possibly due to its recent commercial availability, as tick populations have been lower challenged with this product. Monitoring the resistance of ticks to carrapaticides is essential to maximize the efficiency of these products in the control of R. (B.) microplus.

COMPARATIVE STUDY OF CERTAIN INSECTICIDES AND THE MIXTURES OF SOME PLANT OILS AGAINST COTTON LEAFWORM Spodoptera littoralis (BOISD)

Laboratory experiments were conducted under controlled conditions to test the insecticidal activity of two insecticides i.e. Cypermethrin (25% E.C) a synthetic pyrethroid and Chlorpyrifos (48% E.C) an organophosphate insecticide. Also five plant oils were used in a ratio (1:1) i.e (v/v) and they were as in following: Menth piperita L., Syzygium aromaticum L., Cinnamomum camphora L., Allium sativum L. and Anethum graveolens L. The 4th instar larvae was used in bioassay of these insecticides and oils alone and the mixture of (insecticide: oil). The acute toxicity (LC50) of each treatment recorded after 120 hr. Also the toxicity index (T.I) and relative potency (R.P) were calculated. The results showed that cypermethrin is more toxic than chlorpyrifos, also the Allium sativum L. was the most toxic oil and the lowest one was oil Syzygium aromaticum L. Finally the most toxic mixture was with cypermethrin, especially the mixture of cypermethrin and Allium sativum L. (1:1).

ROS-dependent genotoxicity, cell cycle perturbations and apoptosis in mouse bone marrow cells exposed to formulated mixture of cypermethrin and chlorpyrifos.

Swiss albino mice were exposed to formulated cypermethrin (CMR) and/or or chlorpyrifos (CPF) through oral gavages for 60 days. Test doses of CMR (0.69, 1.38 or 2.76mg/kg/day) or CPF (0.5, 1.0 or 2.0mg/kg/day) or CMR + CPF (0.69 + 0.5, 1.38 + 1.0 or 2.76 + 2.0mg/kg/day) were based on the acute oral median lethal doses of CMR or CPF. Chromosome aberrations (CA), micronucleus (MN) induction, cell cycle perturbations, apoptosis and reactive oxygen species (ROS) generation were analysed in bone marrow cells. To explore the involvement of ROS induction, HaCat cells were exposed in vitro to arbitrary concentrations of CMR and/or CPF. Exposure of CMR (2.76mg/kg/day) induced significant inhibition of mitotic index. Significant (P < 0.01) frequencies of CA and MN were observed with the CMR at 1.38mg/kg/day, whereas CPF or its mixture CMR + CPF showed at highest doses. Chromosome/chromatid breaks and fragments were found to be major aberrations in all the treatment groups. Highest doses of CMR or CMR + CPF revealed significant (P < 0.01 or 0.001) elevation of G0/G1 peak, while CPF-exposed cells revealed significant (P < 0.01) declined in G1 phase. Decline in S phase was observed with highest dose of CMR only. Apoptosis induction measured by gating cell population beside G1 peak showed 3- to 4-fold increase in apoptotic cells in CPF-exposed mice as compared to control or CMR or CMR + CPF-treated mice. Further, all the treatment groups in vivo as well as in vitro revealed significant generation of ROS in comparison with the control group. Present results, together with the earlier reports, which substantiate ROS generation may be major cause of genotoxicity, cell cycle perturbations and apoptosis, nonetheless co-exposure of low doses of CMR and CPF mixture does not potentiate genotoxicity.

REPRODUCTIVE TOXICITY AND ENDOCRINE DISRUPTION OF ORAL AND DERMAL EXPOSURE TO PESTICIDE MIXTURE IN MALE RATS

The current study was performed to assess the risk and hazards of oral & dermal exposure to chlorpyrifos & cypermethrin mixture based on some reproductive & endocrine impaired parameters as well as histopathological alterations & histomorphometric study. Eighty-five Wister male rats (weighing 130-150g) were randomly classified into four groups (a, b, c and d). Each of group (a) and (b) were further subdivided into 5 subgroups used for determination of the oral and dermal LD50. While group (c) and (d) were classified into 3 subgroups which were used for oral and dermal treatments respectively. The first subgroups of (c) and (d) were considered as control. Rats of two subgroups (c) treated orally by 2 doses 4.26 mg/kg (1/20 LD50) and 2.84 mg/kg(1/30 LD50). Rats of two subgroups (d) treated by dermal application of 2 doses70.85mg/kg (1/30 LD50) and 42.51 mg/kg (1/50 LD50). The experiment was conducted for 65 consecutive days. The results revealed that, the tested pesticides mixture caused a significant reduction in reproductive organs weights, sperm count, sperm motility percent, alive sperm percent, pseudocholinesterase and serum testosterone levels in all treated groups especially the dermally treated groups (P≤0.05), moreover there was azoospermia in most of the group of rats treated with high dermal dose. The treated groups showed a significant increase in sperm abnormalities and composite score which represent sperm DNA fragmentation. Moderate to severe histopatholoical alterations were detected in testis and epididymis of treated rats in a dose and route dependant manner in the form of germ cell desquamation, multinucleated giant cells formation and leydig cell vacuolization with disturbance in spermatogenesis. Moreover the histomorphometric parameters analysis detected significant (P≤0.05) reduction of diameter, thickness, endothelium height & lumen of seminiferous tubules and also significant reduction of sertoli cell population. There was significant increase of blood vessel wall thickness. These results indicated that the tested formulation had synergistic effects and induced significant harmful effects on male reproductive system which were more pronounced with dermal exposure.

Organophosphate-pyrethroid combination pesticides may be associated with increased toxicity in human poisoning compared to either pesticide alone

Background. Organophosphate (OP) poisoning results in significant toxicity while pyrethroid poisoning is associated with extremely low fatality. OPs can inhibit the detoxification of pyrethroid and increase the toxicity of the combination. We assessed whether mixed OP-pyrethroid poisoning impacted outcome in human poisoning. Methods. Patients were identified from a prospectively collected institutional poisoning database that incorporates demographic and outcome data of patients presenting with poisoning. Results. Of the 1177 poisoned patients admitted over 2 years, 32 presented with OP-pyrethroid (50% chlorpyrifos-5% cypermethrin mixture) poisoning (Group 1), 26 consumed 20% chlorpyrifos (Group 2), and 32 took 15% cypermethrin (Group 3). Seizures occurred in 15.6% (n = 5) with chlorpyrifos-cypermethrin poisoning, 18.8% (n = 6) with cypermethrin poisoning, and 3.9% (n = 1) with chlorpyrifos poisoning. Ventilatory requirements were 53.5% (17/32), 42.3% (11/26), and 15.7% (5/32) in Groups 1–3, respectively. Ventilator-free days (Mean ± SD) was significantly lower (p < 0.006) in Group 1 (20.9 ± 9.3 days) than those in Group 2 (26.1 ± 4.4 days) or 3 (27.8 ± 0.6). The median (inter-quartile range) hospital stay was 5.5 (4–19.5), 5 (5–6), and 1 (0.65–1.5) days, respectively, in the three groups. Four patients died in Group 1 (13%). None died in the other groups. Conclusion. Although confounded by the varying quantity of chlorpyrifos and cypermethrin in the different formulations, patients with mixed poisoning appear to have shorter ventilator-free days than patients poisoned by either of the pesticides alone. Further studies are required comparing patients poisoned by formulations with similar quantities of OP and pyrethroid or with analysis of blood pesticide concentration on admission.

Ionoregulatory Impairment in African Catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) Exposed to Combined Stressors of Lead and Cypermethrin

The contamination of aquatic ecosystem with heavy metals and pesticides has increased dramatically over the years, and this has generated a lot of attention by environmental experts. There are reports on impacts of different single toxicants on aquatic organisms but not much has been done to investigate the impacts of mixtures of toxicants on aquatic life. In this study we investigated the effects of multiple stressors of Pb and cypermethrin on ionoregulation in the African catfish (Clarias gariepinus). Adults C. gariepinus were exposed to either borehole water (control), 2 mg/L Pb, 0.5 μg/L cypermetrin or a mixture of 2 mg/L Pb and 0.5 μg/L cypermethrin for 96 h, after which the levels of plasma Na+, Cl- and K+ were determined as a measure of branchial ionoregulatory disturbance. The exposure of C. gariepinus to 0.5 μg/L cypermethrin resulted in a significant reduction in plasma Na+ (43% decrease) and Cl- (31% decrease) but a 2-fold increase in plasma K+ concentrations. Exposure to a mixture of cypermethrin and Pb resulted in 53% decrease in plasma Na+, 40% decrease in plasma Cl- and a 3- fold increase in plasma K+. There was no significant difference between the control and those exposed to just only 2 mg/L Pb for all the parameters measured. The results of this study indicated that exposure of aquatic organisms to combined stressors of heavy metals pollution as well as pesticide contamination could have a serious effect on the physiology especially on ionic regulation in the exposed fish.

Environmentally relevant mixing ratios in cumulative assessments: A study of the kinetics of pyrethroids and their ester cleavage metabolites in blood and brain; and the effect of a pyrethroid mixture on the motor activity of rats

National surveys of United States households and child care centers have demonstrated that pyrethroids are widely distributed in indoor habited dwellings and this suggests that co-exposure to multiple pyrethroids occurs in nonoccupational settings. The purpose of this research was to use an environmentally relevant mixture of pyrethroids to assess their cumulative effect on motor activity and develop kinetic profiles for these pyrethroids and their hydrolytic metabolites in brain and blood of rats. Rats were dosed orally at one of two levels (1.5× or 5.0× the calculated dose that decreases rat motor activity by 30%) with a mixture of cypermethrin, deltamethrin, esfenvalerate, cis-/trans-permethrin, and β-cyfluthrin in corn oil. At 1, 2, 4, 8, or 24h after dosing, the motor activity of each animal was assessed and the animals sacrificed. Concentrations of pyrethroids in brain and blood, and the following metabolites: cis-/trans-dichlorovinyl-dimethylcyclopropane-carboxylic acid, 3-phenoxybenzoic acid, 3-phenoxybenzyl alcohol, 4-fluoro-3-phenoxybenzoic acid, and cis-dibromovinyl-dimethylcyclopropane-carboxylic acid were determined using liquid chromatography tandem mass spectrometry (LC–MS/MS). Using this pyrethroid mixture in rats, the results suggest there is greater metabolism of trans-permethrin prior to entering the systemic circulatory system. All pyrethroids had tissue half-lives (t1/2) of less than 5h, excepting esfenvalerate in brain. At early time points, relative pyrethroid brain concentrations approximated their dose mixture proportions and a sigmoidal Emax model described the relationship between motor activity decrease and total pyrethroid brain concentration. In blood, the t1/2's of the cyclopropane metabolites were longer than the phenoxybenzoic metabolites. However, relative to their respective precursors, concentrations of the phenoxybenzoic acids were much higher than concentrations of the cyclopropane metabolites. Brain concentrations of all metabolites were low relative to blood concentrations. This implies limited metabolite penetration of the blood-brain barrier and little metabolite formation within the brain. In conclusion: toxicokinetic differences between the pyrethroids did not appear to be important determinants of their relative potency and their effect on motor activity was consistent with a pyrethroid dose additive model.

Joint toxicity of permethrin and cypermethrin at sublethal concentrations to the embryo-larval zebrafish

Pyrethroids, the widely used pesticides, are highly toxic to aquatic organisms. However, little information is so far available regarding the joint toxicity of type I and type II pyrethroids to fish. Zebrafish is a well-accepted aquatic vertebrate model for toxicity assessment due to small size, easy husbandry, high fecundity and transparent embryos. In this study, we utilized embryo-larval zebrafish to elucidate the combined effects of sublethal concentrations of permethrin (PM) and cypermethrin (CP), which are the most frequently used type I and type II pyrethroids, respectively. Fish were exposed from 3h postfertilization (hpf) to 144 hpf to binary mixtures of nominal concentrations of 100, 200, 300μgL−1 PM (PM100, PM200, PM300) and 10, 20, 30μgL−1 CP (CP10, CP20, CP30). Analytical data of the real concentrations of the chemicals showed a significant degradation of the pyrethroids but an obvious recovery after the renewal of the exposure solution. Defect rates of embryos exposed to these low concentrations of single PM or CP exhibited no statistically significant difference from the control,while the application of combination of PM and CP resulted in deleterious effects on zebrafish embryonic development. In all PM200 and PM300 exposure groups, increasing CP concentrations acted additively to the action of PM in terms of all sublethal endpoints. Co-treatment of embryos with the specific sodium channel blocker MS-222 and pyrethroids (individuals or the mixture) caused a decline in the incidences of body axis curvature and spasms compared to treatment of animals with pyrethroids alone, suggesting that the developmental toxicity of PM and CP to zebrafish was related to disruption of ion channels. We further revealed that mixture of the two pyrethroids caused greater down-regulation in the mRNA levels of proneural genes. The individual pesticides had no effect on the activity of superoxide dismutase (SOD), while the mixture exposure caused significant induction. Treatment with CP or the mixture increased the activity of catalase (CAT). Taken together, our data indicated that the mixture of PM and CP caused higher incidence of morphological defects, greater inhibition in proneural gene expression and more oxidative stress, compared to the single chemical at the corresponding doses. Our findings suggest that the combination of type I and type II pyrethroids poses a greater risk to fish in the water column.