Piperonyl butoxide potentiates the synaptosome ATPase inhibiting effect of pyrethrin

Avoidance behaviour toxicity tests should account for animal gregariousness: a case study on the terrestrial isopod Porcellioscaber

Avoidance behaviour enables woodlice to escape suboptimal environmental conditions and to mitigate harmful effects of pollutants. However, several studies have shown that at least in some woodlice species the tendency to aggregate can lead to suboptimal responses as the between-conspecific attraction can outweigh the aversive stimuli. The present study evaluated the influence of gregariousness on the behaviour of Porcellioscaber in a heterogeneously polluted environment. The hypothesis was that the tendency for aggregation outweighs the tendency for exploratory activity, therefore animals in groups will be less active. Consequently, this will affect their avoidance of polluted environmental patches. To test this hypothesis, isolated individuals or pairs of individuals were monitored in free-choice arenas where animals could select between uncontaminated and pyrethrin-contaminated soils. Animals were video recorded for 3 h in darkness using infrared light and analysed for avoidance behaviour and locomotor activity. In general, isolated animals were more locomotory active and avoided the contaminated soil more than paired animals. It can be concluded that aggregation behaviour suppresses exploratory behaviour and consequently also the avoidance of polluted environments. This should be accounted for when interpreting results of avoidance tests with groups of gregarious animals, which may underestimate the effect of pollutants.

Piperonyl butoxide, a synergist of pesticides can elicit male-mediated reproductive toxicity

A semi-synthetic methylenedioxyphenyl compound piperonyl butoxide (PBO) has been used as a ubiquitous synergist to increase the insecticidal effect of pesticides for agricultural and household use. Despite previously demonstrated effects of PBO, the detailed mechanism of PBO in spermatozoa and reproductive toxic effects on male germ cells have not been fully elucidated. Therefore, this study evaluated the effects of PBO on various sperm functions during capacitation and clarified the mechanisms of reproductive toxic effects on male fertility at different concentrations of PBO (0.1, 1, 10, and 100 μM). Sperm motility and kinematics were assessed using computer-assisted sperm analysis and the status of capacitation was evaluated using combined H33258/chlortetracycline (CTC) staining. Intracellular adenosine triphosphate (ATP) and cell viability levels were also measured. In addition, protein kinase A (PKA) activity and protein tyrosine phosphorylation were evaluated. In addition, in vitro fertilization was performed to determine the effects of PBO on cleavage and blastocyst formation rates. We found that PBO significantly decreased sperm motility, kinematics, and acrosome-reacted and capacitated spermatozoa. In addition, PBO suppressed the intracellular ATP levels and directly affected cell viability. Moreover, PBO detrimentally decreased the activation of PKA and altered the levels of tyrosine-phosphorylated proteins. Consequently, cleavage and blastocyst formation rates were significantly reduced in a dose-dependent manner. In line with our observations, the synergist of pesticides PBO may directly and/or indirectly cause disorder in male fertility. Hence, we suggest that careful attention is made to consider reproductive toxicity when using PBO as a synergist.

Sulfoxaflor and Natural Pyrethrin with Piperonyl Butoxide Are Effective Alternatives to Neonicotinoids against Juveniles of Philaenus spumarius, the European Vector of Xylella fastidiosa

The threat imposed by the bacterial pathogen Xylella fastidiosa to crops of utter importance to European agriculture such as olive, stone fruit and grapevine calls for immediate research against the meadow spittlebug, Philaenus spumarius (L.), the main European vector. Management tools should consider reducing juveniles of vector populations growing on weeds or cover crops during spring as nymphs have limited movement and do not contribute to disease spread. We examined a wide range of insecticides with different modes of action against P. spumarius nymphs in laboratory and semi-field glasshouse conditions. Pyrethroids (delthamethrin and λ-cyhalothrin) and natural pyrethrin (Pirecris^®) + piperonyl butoxide (PBO) efficacy surpassed 86% after 24 h of exposure, without significant differences in the PBO amount tested. The inclusion of PBO caused a 3-fold increase in the mortality of P. spumarius nymphs compared to pyrethrin alone. Sulfoxaflor (Closer^®) exhibited similar efficacy at 48 and 72 h but it was slow acting and mortality only reached 60% at 24 h. The LC₉₀ was 34 ppm at 72 h. Pymetrozine, spirotetramat, azadirachtin and kaolin were not effective against nymphs (mortality <33%) although in azadirachtin-treated plants, mortality had a 3-fold increase from 24 to 72 h. Our results will help decision-making policy bodies to set up a sustainable integrated pest management of P. spumarius in areas where X. fastidiosa becomes a problem.

The ability of Anopheles gambiae mosquitoes to bite through a permethrin-treated net and the consequences for their fitness

Insecticide-treated bed-nets (ITNs) control malaria by keeping mosquitoes from reaching people sleeping under a net and by killing mosquitoes. Most tests of ITNs consider their overall epidemiological outcome without considering the different behaviors underlying their effects. Here we consider one of these behaviors: that mosquitoes can bite through the net if its user is touching it. We assayed the ability of an insecticide-sensitive strain of the mosquito Anopheles gambiae to bite through a permethrin-treated or an untreated net, and their subsequent survival and fecundity. Despite the irritancy of permethrin, 71% of the mosquitoes took blood through the ITN (vs. 99% through the untreated net). The ITN reduced the time spent biting, the blood-meal size and the fecundity, and it killed about 15% of the mosquitoes within 24 hours of feeding (vs. 5% on the untreated net). However, the mosquito's survival was much higher than what we found in WHO cone assays, suggesting that the bloodmeal increased the mosquito's resistance to the insecticide. Thus, our results suggest that the irritancy and the toxicity of ITNs are reduced when mosquitoes contact and feed on their host, which will affect our understanding of the personal and community protection offered by the ITNs.

In vitro bioassays reveal that additives are significant contributors to the toxicity of commercial household pesticides

Pesticides commonly used around households can contain additives of unknown concentrations and toxicity. Given the likelihood of these chemicals washing into urban waterways, it is important to understand the effects that these additives may have on aquatic organisms. The aim of this study was to compare the toxicity of commercially available household pesticides to that of the active ingredient(s) alone. The toxicity of five household pesticides (three herbicides and two insecticides) was investigated using a bacterial cytotoxicity bioassay and an algal photosynthesis bioassay. The commercial products were up to an order of magnitude more toxic than the active ingredient(s) alone. In addition, two commercial products with the same listed active ingredients in the same ratio had a 600× difference in potency. These results clearly demonstrate that additives in commercial formulations are significant contributors to the toxicity of household pesticides. The toxicity of pesticides in aquatic systems is therefore likely underestimated by conventional chemical monitoring and risk assessment when only the active ingredients are considered. Regulators and customers should require more clarity from pesticide manufacturers about the nature and concentrations of not only the active ingredients, but also additives used in commercial formulations. In addition, monitoring programmes and chemical risk assessments schemes should develop a structured approach to assessing the toxic effects of commercial formulations, including additives, rather than simply those of the listed active ingredients.

Assessment of genotoxicity of pyrethrin in cultured human lymphocytes

Pyrethrin is an insecticide that is obtained from the Chrysanthemum flower (Pyrethrum). In this study, we examined the genotoxic effects of pyrethrin on cultured human lymphocytes using sister chromatid exchanges (SCEs) and 8-hydroxy deoxyguanosine (8-OHdG) assays. Cultures were treated with different concentrations of pyrethrin (25, 50, and 100 μg/mL), which was dissolved in in dimethyl sulfoxide (DMSO). The results showed that treatment of cultured lymphocytes with pyrethrin at 50 μg/mL and 100 μg/mL induced significant elevation in SCEs (p < 0.05). In addition, the 100 μg/mL concentration significantly affected both mitotic and proliferative indices (p < 0.05). Finally, pyrethrin induced significant elevation in the oxidative stress marker 8-OHdG in a dose-dependent manner (p < 0.001). In conclusion, the results suggest that pyrethrin is genotoxic as measured by two independent assays on genetic toxicity.

The efficacy of long-lasting nets with declining physical integrity may be compromised in areas with high levels of pyrethroid resistance

BACKGROUND

Long-lasting insecticide-treated mosquito nets (LLINs) are a primary malaria prevention strategy in sub-Saharan Africa. However, emergence of insecticide resistance threatens the effectiveness of LLINs.

METHODS

Cross-sectional surveys of LLINs were conducted in houses of seven and four villages in Gem and Bungoma Districts in western Kenya, respectively. Condition (number and area of holes in the nets), number and species of mosquitoes resting inside them, and insecticidal activity of nets were quantified. Mosquitoes collected inside nets were allowed to lay eggs and progeny tested for susceptibility to deltamethrin and permethrin, pyrethoids commonly deployed in LLINs in western Kenya.

RESULTS

In Gem, 83.3% of nets were less than three years old and 32.4% had at least one hole of any size; while in Bungoma, 92% were less than three years old and 48% had at least one hole. No anopheline and five Culex spp. mosquitoes were found resting inside nets in Gem regardless of the number and size of holes, while 552 Anopheles gambiae s.l., five Anopheles funestus s.l. and 137 Culex spp. were in nets in Bungoma. The number of mosquitoes resting inside nets increased with hole areas >50 cm in Bungoma. In WHO resistance assays, f1 offspring of samples collected in nets in Bungoma were 94 and 65% resistant to deltamethrin and permethrin, respectively. Nets from Bungoma retained strong activity against a susceptible laboratory strain, but not against f1 offspring of field-collected An. gambiae s.s. All An. gambiae s.s. samples collected in nets were homozygous for the kdr genotype L1014S.

CONCLUSIONS

In areas with pyrethroid resistant vectors, LLINs with modest hole areas permit mosquito entry and feeding, providing little protection against the vectors. LLIN formulations develop large holes within three years of use, diminishing their presupposed lifetime effectiveness.

Synthetic pyrethroid increases lipid and protein oxidation and induces glutathione depletion in the cerebellum of adult rats: ameliorative effect of vitamin C

The wide use and wide-spectrum toxicity of synthetic pyrethroid (SP) insecticides make them an emerging ecotoxicological concern. The objective of the current study was aimed to investigate the involvement of oxidative stress in lambda-cyhalothrin (LTC)-induced cerebellum damages in adult rats and to evaluate the possible protective effect of vitamin C (vit C) as antioxidant. Exposure of rats to LTC during 3 weeks caused a significant (p < 0.05) increase in the levels of lipid peroxidation (LPO), nitric oxide (NO) and protein carbonyls (PCO) along with a significant (p < 0.05) decrease in the levels of reduced glutathione (GSH) and the activities of acetylcholinesterase, superoxide dismutase, catalase, glutathione peroxidase and gluthione-S-transferase (p < 0.05) when compared with the control group. The oral administration of vit C (200 mg/kg per d) to LTC-treated rats significantly (p < 0.05) diminished the levels of LPO, NO and PCO and significantly (p < 0.05) increased the activities of GSH and antioxidant enzymes. Our results showed that the administration of vit C could ameliorate some of the oxidative damage in the cerebellum induced by SPs exposure, suggesting that the ascorbic acid could exhibit a potential antioxidant activity against neurotoxicity induced by pesticides exposure.

Pyrethroid and organophosphate pesticide-associated toxicity in two coastal watersheds (California, USA)

Portions of the Santa Maria River and Oso Flaco Creek watersheds in central California, USA, are listed as impaired under section 303(d) of the Clean Water Act and require development of total maximum daily load (TMDL) allocations. These listings are for general pesticide contamination, but are largely based on historic monitoring of sediment and fish tissue samples that showed contamination by organochlorine pesticides. Recent studies have shown that toxicity in these watersheds is caused by organophosphate pesticides (water and sediment) and pyrethroid pesticides (sediment). The present study was designed to provide information on the temporal and spatial variability of toxicity associated with these pesticides to better inform the TMDL process. Ten stations were sampled in four study areas, one with urban influences, and the remaining in agriculture production areas. Water toxicity was assessed with the water flea Ceriodaphnia dubia, and sediment toxicity was assessed with the amphipod Hyalella azteca. Stations in the lower Santa Maria River had the highest incidence of toxicity, followed by stations influenced by urban inputs. Toxicity identification evaluations and chemical analysis demonstrated that the majority of the observed water toxicity was attributed to organophosphate pesticides, particularly chlorpyrifos, and that sediment toxicity was caused by mixtures of pyrethroid pesticides. The results demonstrate that both agriculture and urban land uses are contributing toxic concentrations of these pesticides to adjacent watersheds, and regional water quality regulators are now using this information to develop management objectives.

Use of toxicity identification evaluations to determine the pesticide mitigation effectiveness of on-farm vegetated treatment systems

Evidence of ecological impacts from pesticide runoff has prompted installation of vegetated treatment systems (VTS) along the central coast of California, USA. During five surveys of two on-farm VTS ponds, 88% of inlet and outlet water samples were toxic to Ceriodaphnia dubia. Toxicity identification evaluations (TIEs) indicated water toxicity was caused by diazinon at VTS-1, and chlorpyrifos at VTS-2. Diazinon levels in VTS-1 were variable, but high pulse inflow concentrations were reduced through dilution. At VTS-2, chlorpyrifos concentrations averaged 52% lower at the VTS outlet than at the inlet. Water concentrations of most other pesticides averaged 20-90% lower at VTS outlets. All VTS sediment samples were toxic to amphipods (Hyalella azteca). Sediment TIEs indicated toxicity was caused by cypermethrin and lambda-cyhalothrin at VTS-1, and chlorpyrifos and permethrin at VTS-2. As with water, sediment concentrations were lower at VTS outlets, indicating substantial reductions in farm runoff pesticide concentrations.

Applications of carboxylesterase activity in environmental monitoring and toxicity identification evaluations (TIEs)

This review has examined a number of issues surrounding the use of carboxylesterase activity in environmental monitoring. It is clear that carboxylesterases are important enzymes that deserve increased study. This class of enzymes appears to have promise for employment in environmental monitoring with a number of organisms and testing scenarios, and it is appropriate for inclusion in standard monitoring assays. Given the ease of most activity assays, it is logical to report carboxylesterase activity levels as well as other esterases (e.g., acetylcholinesterase). Although it is still unclear as to whether acetylcholinesterase or carboxylesterase is the most "appropriate" biomarker, there are sufficient data to suggest that at the very least further studies should be performed with carboxylesterases. Most likely, data will show that it is optimal to measure activity for both enzymes whenever possible. Acetylcholinesterase has the distinct advantage of a clear biological function, whereas the endogenous role of carboxylesterases is still unclear. However, a combination of activity measurements for the two enzyme systems will provide a much more detailed picture of organism health and insecticide exposure. The main outstanding issues are the choice of substrate for activity assays and which tissues/organisms are most appropriate for monitoring studies. Substrate choice is very important, because carboxylesterase activity consists of multiple isozymes that most likely fluctuate on an organism- and tissue-specific basis. It is therefore difficult to compare work in one organism with a specific substrate with work performed in a different organism with a different substrate. An attempt should therefore be made to standardize the method. The most logical choice is PNPA (p-nitrophenyl acetate), as this substrate is commercially available, requires inexpensive optics for assay measurements, and has been used extensively in the literature. However, none of these beneficial properties indicates that the substrate is an appropriate surrogate for a specific compound, e.g., pyrethroid-hydrolyzing activity. It will most likely be necessary to have more specific surrogate substrates for use in assays that require information on the ability to detoxify/hydrolyze specific environmental contaminants. The use of carboxylesterase activity in TIE protocols appears to have excellent promise, but there are further technical issues that should be addressed to increase the utility of the method. The main concerns include the large amount of nonspecific protein added to the testing system, which can lead to undesirable side effects including nonspecific reductions in observed toxicity, decrease in dissolved oxygen content, and organism growth. It is probable that these issues can be resolved with further assay development. The ideal solution would be to have a commercial recombinant carboxylesterase that possessed elevated pyrethroid-hydrolysis activity and which was readily available, homogeneous, and inexpensive. The availability of such an enzyme would address nearly all the current method shortcomings. Such a preparation would be extremely useful for the aquatic toxicology community. Further work should focus on screening available esterases for stability, cost, and activity on pyrethroids, with specific focus on esterases capable of distinguishing type I from type II pyrethroids. It would also be beneficial to identify esterases that are not sensitive to OP insecticides. Many esterases and lipases are available as sets to test chemical reactions for green chemistry, enabling large-scale screening. Other potential approaches to increase the utility of the enzyme include derivatization with polyethylene glycol (PEG) or cyanuric acid chloride to increase stability and reduce microbial degradation. It is also possible that the enzyme could be formulated in a sol gel preparation to increase stability. It is likely that the use of carboxylesterase addition will increase for applications in sediment TIEs. Carboxylesterases are an interesting and useful enzyme family that deserves further study for applications in environmental monitoring as well as to increase our understanding of the fundamental biological role(s) of these enzymes. There are, of course, other enzymes that show high esterase activity on pyrethroids but are not technically carboxylesterases in the alpha/beta-hydrolase fold protein family. These enzymes should also be examined for use in TIE protocols and "esterase" arrays as well as for general applications in environmental monitoring. One can envision the creation of a standardized screen of enzymes with esterase activity to (1) identify environmental contaminants, (2) estimate the potential toxic effects of new compounds on a range of organisms, and (3) monitor organism exposure to agrochemicals (and potentially other contaminants). This approach would provide a multibiomarker integrative assessment of esterase-inhibiting potential of a compound or mixture. In conclusion, much is still unknown about this enzyme family, indicating that this area is still wide open to researchers interested in the applications of carboxylesterase activity as well as basic biological questions into the nature of enzyme activity and the endogenous role of the enzyme.

The effect of a synergistic concentration of a Piper nigrum extract used in conjunction with pyrethrum upon gene expression in Drosophila melanogaster

An ethyl acetate extract of Piper nigrum L. (Piperaceae) peppercorns was tested as a synergist for the botanical insecticide pyrethrum. A high synergist ratio of 11.6 against Drosophila melanogaster was obtained for the combination of pyrethrum supplemented with P. nigrum. The effect of this combination was investigated using cDNA microarray analysis of gene expression profiles in D. melanogaster. Treatment of D. melanogaster with pyrethrum alone resulted in a large number of differentially expressed genes, principally associated with stress responses. Seven genes were identified as being commonly expressed in D. melanogaster treated with at least two of the following treatments: P. nigrum, pyrethrum or P. nigrum plus pyrethrum. These are likely implicated in Drosophila defence responses to toxins.

Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, USA): relative effects of pesticides and suspended particles

Laboratory dose-response experiments with organophosphate and pyrethroid pesticides, and dose-response experiments with increasing particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previously observed in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midge Chironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides, including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrations of these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in the river. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River.

Oestradiol potentiates the effects of certain pyrethroid compounds in the MCF7 human breast carcinoma cell line

Pyrethroids are the most widely used insecticides for indoor pest control, so human exposure to them is common. The main target of pyrethroids is the nervous system, but their endocrine disrupting capabilities may also be of toxicological concern. In the present study, the proliferation of the breast cancer cell line, MCF7, was studied after a 7-day exposure to various concentrations of pyrethrin, permethrin and cypermethrin. The effects of oestradiol and the combined effects of oestradiol (0.10 nM) and pyrethroids (0.1-100 microM) on MCF7 cell proliferation were also evaluated. Proliferation and cell toxicity were studied by measuring the ATP content with a luminescence method, and mitochondrial metabolic enzyme activity with the WST-1 test. In the ATP test, low concentrations (0.1-1 microM) of pyrethroids in co-exposure with oestradiol caused a clear statistically significant increase in the proliferation of MCF7 cells. This was evident when compared to the proliferative effect caused by 0.1 nM oestradiol alone. High concentrations were cytotoxic, and the greatest cell toxicity was that of cypermethrin, which has a cyano group in its molecular structure.

Influence of pyrethroids and piperonyl butoxide on the Ca2+-ATPase activity of rat brain synaptosomes and leukocyte membranes

Pyrethroids are widely used insecticides of low acute toxicity in mammals but the consequences of long-term exposure are of concern. Their insecticidal action is related to neurotoxicity and, in addition, there are indications of mammalian immunotoxicity. In order to clarify structure-activity relationships of the membrane interactions of pyrethroids, the present study compared the influence of selected pyrethroids, i.e. permethrin and the more water soluble esbiol (S-bioallethrin), both type I, and cyfluthrin, type II, on the Ca(2+)-ATPase activity of rat brain synaptosomes and peritoneal leukocyte membranes. The pyrethroids were tested alone as well as mixed with the enhancing substance piperonyl butoxide (PBO) at concentration ratios of 1:5 and 1:10. At the highest concentration tested, permethrin (10 microM) alone inhibited the ATPase activity of leukocyte membranes by 20%, whereas the synaptosomes were affected less. Esbiol and cyfluthrin alone did not affect either membrane preparation significantly, whereas PBO (50 microM) alone caused 10-15% inhibition. Mixtures of either pyrethroid with PBO inhibited the ATPase activity of both types of membranes (up to 40% inhibition) in a synergistic manner, which always tended to be supra-additive. With esbiol a true potentiation took place. The synergistic interaction between pyrethroid and PBO was most apparent with mixtures of a concentration ratio of 1:5. The ATPase activity of leukocyte membranes tended to be more susceptible to inhibition than that of synaptosomes. The results are in accordance with the assumption that the mammalian toxicity of pyrethroids can be ascribed to a general disturbance of cell membrane function in neuronal tissue. The results indicate that it may also be the case in the immune apparatus.

The toxicity of pyrethroid compounds in neural cell cultures studied with total ATP, mitochondrial enzyme activity and microscopic photographing

Pyrethroids are important insecticides used largely because of their high activity as an insecticide and their low mammalian toxicity. Some studies have demonstrated that these products, especially compounds with an α-cyano group, show neurotoxic effects on the mammalian central nervous system (CNS). In this study, we investigate with different methods the cell toxic effects of commercial, chemically different pyrethroid compounds on neuronal cell line SH-SY5Y. Natural pyrethrin and permethrin (both with no α-cyano group) and cypermethrin (with an α-cyano group), were studied. For toxicity determinations, SH-SY5Y neuroblastoma cells were exposed to pyrethroids at 0.1-100μM concentrations for 1 day. The cell toxicity was evaluated by determining the total ATP with a luminescence method, the mitochondrial metabolic activity (WST-test) with a photometric method, and the morphological changes of the cell cultures with microscopic digital photographing at different dose levels of compounds. The results obtained with WST-1 method and with the measurement of total ATP were different. ATP measurement seemed to show cytotoxicity at lower concentrations than WST-1 method. There was induction of enzyme activities with WST-1 test with all pyrethroid compounds studied at low concentrations. With the ATP assay, exposure to 0.1-100μM of natural pyrethrin, as well as of permethrin and cypermethrin showed dose-dependent cytotoxicity. The most toxic pyrethroid was cypermethrin followed by permethrin and natural pyrethrin. Our study confirms that the cell toxicity was dependent on the chemical structure of pyrethroids and pyrethroids without an α-cyano group show the weakest physiological effect. Microscopic photographs of exposed cell cultures correlated to the toxic effects revealed by the metabolic tests.

The synaptosomal membrane bound ATPase as a target for the neurotoxic effects of pyrethroids, permethrin and cypermethrin

Pyrethroids are used widely as insecticides both in agriculture and in households. A cellular target of pyrethroids is the sodium channel in the membrane. In the present study, the activity of the membrane bound integral protein ATPase was studied as a biomarker for the membrane effect of the pyrethroids permethrin and cypermethrin. Male Sprague-Dawley rats were used for cerebral synaptosome preparation. The isolation of synaptosomes was performed with the Percoll gradient method. Both total ATPase and Mg(2+) activated ATPase were studied by determining inorganic phosphate liberated from the substrate ATP. One hour exposure to permethrin (Biokill) and cypermethrin (Ripcord) insecticide products affected ATPase activities. The activity of Na(+), K(+) ATPase decreased dose-dependently in 10-50 microM concentrations of permethrin, and Mg(2+) activated ATPase increased over twofold in the same concentrations of the active components. The effect of the cypermethrin compound Ripcord was not clearly dose-dependent. The activity of total ATPase was almost entirely lost in the concentrations of 100 microM of permethrin and cypermethrin. The results support the idea that membrane ATPases are one target of the neurotoxic effect of pyrethroid compounds.

Action of pyrethrum-based formulations against grain weevils

Pyrethrum extract, containing six insecticidal esters, has a long history of successful application in the control of stored products. Its low environmental hazard makes it an ideal pesticide for outdoor pre-harvest treatment. However the disadvantage of its low light stability then becomes apparent. This drawback can be overcome by the complexation of pyrethrum extract with gamma-cyclodextrin. Primary object of the conducted studies was to investigate the effect of complexation upon the insecticidal action against the grain weevil, an important storage pest in temperate climates. To slow down the quick metabolism of pyrethrum by the insects' microsomal system synergistic substances are added. Additional to the already well-known piperonyl butoxide two natural synergists, sesamol and tocopherol acetate, were combined with pyrethrum extract to investigate their synergistic activity. A complex of pyrethrum with gamma-cyclodextrin, with piperonyl butoxide as synergist, has a slightly enhanced action compared to a commercial product, which contained pyrethrum in its free form. Sesamol and tocopherol acetate also display a synergistic action, but to a much smaller degree, even if applied in larger amounts. The optimal concentration of pyrethrum was found to be 0.3% combined with 3% piperonyl butoxide.

Integrated assessment of the impacts of agricultural drainwater in the Salinas River (California, USA)

The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California. Large areas of this watershed are cultivated year-round in row crops and previous laboratory studies have demonstrated that acute toxicity of agricultural drainwater to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. In the current study, we used a combination of ecotoxicologic tools to investigate incidence of chemical contamination and toxicity in waters and sediments in the river downstream of a previously uncharacterized agricultural drainage creek system. Water column toxicity was investigated using a cladoceran C. dubia while sediment toxicity was investigated using an amphipod Hyalella azteca. Ecological impacts of drainwater were investigated using bioassessments of macroinvertebrate community structure. The results indicated that Salinas River water downstream of the agricultural drain is acutely toxic to Ceriodaphnia, and toxicity to this species was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to H. azteca, which is a resident genus. Macroinvertebrate community structure was moderately impacted downstream of the agricultural drain input. While the lowest macroinvertebrate abundances were measured at the station demonstrating the greatest water column and sediment toxicity and the highest concentrations of pesticides, macroinvertebrate metrics were more significantly correlated with bank vegetation cover than any other variable. Results of this study suggest that pesticide pollution is the likely cause of laboratory-measured toxicity in the Salinas River samples and that this factor may interact with other factors to impact the macroinvertebrate community in the system.

Influence in the quality of life of the respiratory patients by environmental control and the acaricide Frontac®

The present prospective, open, observational study assessed the effect of the use of standard environmental control measures together with the application of an acaricide-containing aerosol of esbiol/benzyl benzoate/piperonyl butoxide/2-phenylphenol (Frontac) on several clinical and environmental parameters in patients suffering from perennial allergic rhinoconjunctivitis related to house dust mites (HDM). Fifty-five patients were enrolled and studied for one year. Both symptoms and the patients' quality of life (evaluated by the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ)) were assessed at several clinic visits. The amount of HDM antigen was semi-quantitatively estimated using the guanine test. We found a significant decrease (p < 0.001) in most nasal symptoms scores: sneezing, runny nose, stuffy nose and itching. The overall quality of life (QoL) score also showed a significant improvement during the study period; the mean score decrease found was 0.86 (CI 95 %, 0.54-1.17) (p < 0.001). Five of the seven domains included in the questionnaire decreased significantly: non-hayfever symptoms; practical problems; nasal symptoms; eye symptoms, and emotions. These QoL score decreases were found during the first 3 months and later remained stable at lower levels than at baseline. The content of guanine in dust samples decreased significantly from 2.17 0.75 to 1.43 0.68 (p < 0.001). No toxic adverse events were recorded. In conclusion, these results show an improvement in the quality of life and a clinical benefit of the long-term use of the new chemical acaricide tested, together with environmental measures, in the home of patients suffering from allergic respiratory pathology.