Use Of Pyrethroids Research Articles

Preliminary Evidence that Copper and Zinc Inhibits the Dissipation of Synthetic Pyrethroid in Red Soil

Extensive use of synthetic pyrethroids has resulted in concerns regarding their potential effects on human health and ecosystems. In the present study, we evaluated the influence of coexisting Cu2+, Zn2+, soil water contents (15%, 25%, 40% by weight and waterlogged) and temperature levels (15°C, 25°C, 35°C, and 45°C) on the dissipation of cypermethrin, fenvalerate and deltamethrin in red soil. To further clarify the influence of Cu2+ and Zn2+ on biological and chemical dissipation processes, serial concentrations of the synthetic pyrethroids containing Cu2+ (21.3, 50, 100, and 400 mg kg−1) and Zn2+ (35.8, 100, 250, and 500 mg kg−1) were used to spike the soil and then incubated at 25°C in the dark at 25% moisture. The results revealed a very severe inhibitory effect on the dissipation rates with increasing Cu2+ and Zn2+ levels. Conversely, there were no significant decreases in dissipation rates in response to exposure to 50 mg kg−1 Cu2+ or 100 mg kg−1 Zn2+, and the dissipation rates decreased significantly (p < 0.05) when the Cu2+ and Zn2+ concentration increased to 100 and 250 mg kg−1, respectively, which were the respective maximum field recommended rates. When compared with unsterilized batch treatments, the t 1/2 in sterilized (chemical dissipation) batch treatments increased by 1.0–4.8-fold. Additionally, there was a highly significant difference in the dissipation of pyrethroids in the 15% water content treatments and waterlogged treatments (p < 0.05). Finally, the difference in the dissipation rates at 15°C and 25°C was significant (p < 0.05).

Pesticide Use and Thyroid Disease Among Women in the Agricultural Health Study

Thyroid disease is common, and evidence of an association between organochlorine exposure and thyroid disease is increasing. The authors examined the cross-sectional association between ever use of organochlorines and risk of hypothyroidism and hyperthyroidism among female spouses (n = 16,529) in Iowa and North Carolina enrolled in the Agricultural Health Study in 1993-1997. They also assessed risk of thyroid disease in relation to ever use of herbicides, insecticides, fungicides, and fumigants. Prevalence of self-reported clinically diagnosed thyroid disease was 12.5%, and prevalence of hypothyroidism and hyperthyroidism was 6.9% and 2.1%, respectively. There was an increased odds of hypothyroidism with ever use of organochlorine insecticides (adjusted odds ratio (OR(adj)) = 1.2 (95% confidence interval (CI): 1.0, 1.6) and fungicides (OR(adj) = 1.4 (95% CI: 1.1, 1.8) but no association with ever use of herbicides, fumigants, organophosphates, pyrethroids, or carbamates. Specifically, ever use of the organochlorine chlordane (OR(adj) = 1.3 (95% CI: 0.99, 1.7), the fungicides benomyl (OR(adj) = 3.1 (95% CI: 1.9, 5.1) and maneb/mancozeb (OR(adj) = 2.2 (95% CI: 1.5, 3.3), and the herbicide paraquat (OR(adj) = 1.8 (95% CI: 1.1, 2.8) was significantly associated with hypothyroidism. Maneb/mancozeb was the only pesticide associated with both hyperthyroidism (OR(adj) = 2.3 (95% CI: 1.2, 4.4) and hypothyroidism. These data support a role of organochlorines, in addition to fungicides, in the etiology of thyroid disease among female spouses enrolled in the Agricultural Health Study.

Cytotoxicity of lambda-cyhalothrin on the macrophage cell line RAW 264.7

The wide use and wide-spectrum toxicity of synthetic pyrethroids (SPs) insecticides make them an emerging ecotoxicological concern. Some previous studies showed that SPs possessed cytotoxicity in some immune cells such as human lymphocytes and rat bone marrow. However, the cytotoxicity of SPs to macrophages, which are crucial to innate immunity, has not been explored. In the present report, we investigated a new pyrethroid insecticide, lambda-cyhalothrin (LCT), which may increase the generation of reactive oxygen species (ROS) and DNA damage levels and cause cytotoxicity in RAW 264.7 cells in dose- and time-dependent manners. The results for the first time implicated increased endogenous ROS and DNA damage as co-mediators of LCT-induced cytotoxicity in macrophages. Our results also suggested that macrophages were involved in synthetic pyrethroid-induced adverse immune effects. Considering the ubiquitous environmental presence of SPs, this study provided new information relative to the potential long-term physiological and immunological effects associated with chronic exposure to SPs. Hence, the potential immunotoxicity of SPs should be considered in assessing the safety of these compounds in sensitive environmental compartments.

Developmental Neurotoxicity of Pyrethroid Insecticides in Zebrafish Embryos

Pyrethroid insecticides are one of the most commonly used residential and agricultural insecticides. Based on the increased use of pyrethroids and recent studies showing that pregnant women and children are exposed to pyrethroids, there are concerns over the potential for developmental neurotoxicity. However, there have been relatively few studies on the developmental neurotoxicity of pyrethroids. In this study, we sought to investigate the developmental toxicity of six common pyrethroids, three type I compounds (permethrin, resmethrin, and bifenthrin) and three type II compounds (deltamethrin, cypermethrin, and lambda-cyhalothrin), and to determine whether zebrafish embryos may be an appropriate model for studying the developmental neurotoxicity of pyrethroids. Exposure of zebrafish embryos to pyrethroids caused a dose-dependent increase in mortality and pericardial edema, with type II compounds being the most potent. At doses approaching the LC(50), permethrin and deltamethrin caused craniofacial abnormalities. These findings are consistent with mammalian studies demonstrating that pyrethroids are mildly teratogenic at very high doses. However, at lower doses, body axis curvature and spasms were observed, which were reminiscent of the classic syndromes observed with pyrethroid toxicity. Treatment with diazepam ameliorated the spasms, while treatment with the sodium channel antagonist MS-222 ameliorated both spasms and body curvature, suggesting that pyrethroid-induced neurotoxicity is similar in zebrafish and mammals. Taken in concert, these data suggest that zebrafish may be an appropriate alternative model to study the mechanism(s) responsible for the developmental neurotoxicity of pyrethroid insecticides and aid in identification of compounds that should be further tested in mammalian systems.

Widespread distribution of a newly found point mutation in voltage-gated sodium channel in pyrethroid-resistant Aedes aegypti populations in Vietnam.

BackgroundResistance of Aedes aegypti to photostable pyrethroid insecticides is a major problem for disease-vector control programs. Pyrethroids target the voltage-gated sodium channel on the insects' neurons. Single amino acid substitutions in this channel associated with pyrethroid resistance are one of the main factors that cause knockdown resistance in insects. Although kdr has been observed in several mosquito species, point mutations in the para gene have not been fully characterized in Ae. aegypti populations in Vietnam. The aim of this study was to determine the types and frequencies of mutations in the para gene in Ae. aegypti collected from used tires in Vietnam.Methods and FindingsSeveral point mutations were examined that cause insensitivity of the voltage-gated sodium channel in the insect nervous system due to the replacement of the amino acids L1014F, the most commonly found point mutation in several mosquitoes; I1011M (or V) and V1016G (or I), which have been reported to be associated to knockdown resistance in Ae. aegypti located in segment 6, domain II; and a recently found amino acid replacement in F1269 in Ae. aegypti, located in segment 6, domain III. Among 756 larvae from 70 locations, no I1011M or I1011V nor L1014F mutations were found, and only two heterozygous V1016G mosquitoes were detected. However, F1269C mutations on domain III were distributed widely and with high frequency in 269 individuals among 757 larvae (53 collection sites among 70 locations surveyed). F1269C frequencies were low in the middle to north part of Vietnam but were high in the areas neighboring big cities and in the south of Vietnam, with the exception of the southern mountainous areas located at an elevation of 500–1000 m.ConclusionsThe overall percentage of homozygous F1269C seems to remain low (7.4%) in the present situation. However, extensive and uncontrolled frequent use of photostable pyrethroids might be a strong selection pressure for this mutation to cause serious problems in the control of dengue fever in Vietnam.

Susceptibility status of &lt;i&gt;Anopheles gambiae&lt;/i&gt; s.l. (Diptera: Culicidae) from cabbage growing areas associated with pyrethroid and organophosphate use in Accra, Ghana

Resistance in malaria vectors is likely to be caused by the massive use of insecticides in agriculture. Anopheles gambiae s.l. collected from breeding grounds in two cabbage growing areas within Accra were assessed for levels of resistance to 0.75% permethrin, 0.05% deltamethrin, 5% malathion and 4% DDT using standard WHO susceptibility test kits. Pyrethroid and organophosphate residue levels in soil and run-off water from these cabbage farms were determined and possible association between resistance and residue levels were established. Compared to the susceptible ‘Kisumu’ strain, both Korle-Bu and Airport populations were highly resistant to DDT and gave resistance levels which were over nine-fold for permethrin and over 2.5-fold for deltamethrin. Both wild and susceptible populations showed full susceptibility to malathion. The S and M forms of A. gambiae s.s. were found to occur in sympatry in the two study sites with a higher frequency of S form in the Airport area. Toxicity testing of extracts of soil and run-off water from these cabbage farms, using brine shrimp lethality tests, showed high level of toxicity, indicative of the presence of residues of insecticides. Differential fractionation of these extracts using solid phase extractor (SPE) suggests that the bulk of residues in these extracts may be pyrethroids and organophosphates. No correlation was observed between either residue levels or residual bioactivity in soil and run-off water, and resistance levels in A. gambiae s.l. populations, collected from breeding grounds within the farms under investigation. It is proposed that resistance in A. gambiae larvae in these breeding sites contaminated with agricultural insecticides may have occurred over time due to continuous exposure to sub-lethal doses.

Evaluation of the benefits of an insecticide resistance management programme in Punjab in India

In India, many IPM programmes have been implemented, but they have not achieved the desired level of success in reducing insecticide use and increasing adoption of IPM practices. This inter-disciplinary study evaluated an Insecticide Resistance Management-based Integrated Pest Management (IRM-IPM) programme in cotton and compared it with non-IRM production for a range of IPM and economic measures. The IRM-IPM programme has been implemented in 28 districts of 10 states of India since 2002 to help rationalize and reduce the use of insecticides and to overcome the development of resistance in cotton pests, especially Helicoverpa armigera. The IRM-IPM strategy includes applying insecticides only when pests exceed economic threshold levels, using selective insecticides that are compatible with biological control, and rotating between different insecticide classes. The IRM-IPM programme we evaluated resulted in a reduction in insecticide consumption (technical grade material) by 30%, and it reduced the number of sprays by 15%; however, it did not result in a significant change in productivity. The majority of IRM farmers avoided using highly toxic insecticides such as monocrotophos, avoided use of synthetic pyrethroids beyond 140 days after sowing to avoid resurgence of Bemisia tabaci, and rotated the insecticide compounds/groups to delay the development of resistance and ensured effective management of H. armigera. On average, the IRM-IPM programme resulted in a return of US $24.05 ha−1 (at 2005 rates: US $1 = 45 Indian rupees), by saving on insecticide costs. While the farmers gained significantly in knowledge of IPM practices, the level of adoption of IPM techniques was low. Further studies based on impact evaluation methodology, employing a with/without and before/after quasi-experimental design, would provide feedback to help in the formulation of future IPM strategies.

Nationwide Investigation of the Pyrethroid Susceptibility of Mosquito Larvae Collected from Used Tires in Vietnam

Pyrethroid resistance is envisioned to be a major problem for the vector control program since, at present, there are no suitable chemical substitutes for pyrethroids. Cross-resistance to knockdown agents, which are mainly used in mosquito coils and related products as spatial repellents, is the most serious concern. Since cross-resistance is a global phenomenon, we have started to monitor the distribution of mosquito resistance to pyrethroids. The first pilot study was carried out in Vietnam. We periodically drove along the national road from the north end to the Mekong Delta in Vietnam and collected mosquito larvae from used tires. Simplified susceptibility tests were performed using the fourth instar larvae of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus. Compared with the other species, Ae. aegypti demonstrated the most prominent reduction in susceptibility. For Ae. aegypti, significant increases in the susceptibility indices with a decrease in the latitude of collection points were observed, indicating that the susceptibility of Ae. aegypti against d-allethrin was lower in the southern part, including mountainous areas, as compared to that in the northern part of Vietnam. There was a significant correlation between the susceptibility indices in Ae. aegypti and the sum of annual pyrethroid use for malaria control (1998–2002). This might explain that the use of pyrethroids as residual treatment inside houses and pyrethroid-impregnated bed nets for malaria control is attributable to low pyrethroid susceptibility in Ae. aegypti. Such insecticide treatment appeared to have been intensively administered in the interior and along the periphery of human habitation areas where, incidentally, the breeding and resting sites of Ae. aegypti are located. This might account for the strong selection pressure toward Ae. aegypti and not Ae. albopictus.

EVALUATING PYRETHROID ALTERNATIVES FOR THE MANAGEMENT OF COTTON BOLLWORMS AND RESISTANCE IN CAMEROON

SUMMARYIn sub-Saharan Africa, the bollworm complex, including Helicoverpa armigera, Diparopsis watersi and Earias spp., threatens the continued success of cotton production. Pyrethroid resistance in H. armigera led to serious crop losses while endosulfan, a suitable alternative to pyrethroids, was banned for cotton pest management. Five candidates with no cross-resistance to pyrethroids were evaluated in both on-station and on-farm trials from 2002 to 2006. Two applications were made at the early peak of H. armigera infestation in September, the period when pyrethroid use should be restricted for resistance management purposes. Results showed that, as expected, bollworm infestation consistently peaked from mid-September to mid-October. Spinosad, thiodicarb and emamectin-benzoate were the most suitable alternatives to reduce damage, regardless of the cotton bollworm species. Indoxacarb and lufenuron were less effective in controlling D. watersi. On-farm experiments confirmed the suitability of spinosad for control of pyrethroid-resistant H. armigera, particularly on late sown fields. These new chemistries offer control of bollworms which justify their relevance for pyrethroid resistance management in Cameroon and sub-Saharan Africa.

Chronic toxicity and cytotoxicity of synthetic pyrethroid insecticide cis-bifenthrin

With the increasing use of synthetic pyrethroids (SPs), the significance of ecological safety and health risk is an emerging concern. In this study, we evaluated the chronic aquatic toxicity of cis-bifenthrin (cis-BF) in Daphnia magna and its cytotoxicity in Chinese hamster ovary (CHO) cells as well as human cervical carcinoma (Hela) cells. Chronic aquatic toxicity tests showed that cis-BF could significantly affect the reproduction of D. magna. The lowest observed effective concentration and the non-observed effective concentration of cis-BF to D. magna were 0.02 and 0.01 microg/L, respectively, and the chronic value was 0.014 microg/L. The intrinsic rate of natural increase was significantly decreased (p < 0.05) to 0.02 microg/L. The cytotoxicity assay demonstrated that cis-BF decreased cell viability in CHO and Hela cells in a concentration- and time-dependent manner. The IC50 values for Hela and CHO cells were 4.0 x 10(-5) and 3.2 x 10(-5) mol/L, respectively. Together, these results indicated that cis-BF induced chronic toxicity in both aquatic invertebrate animals and mammalian cells. These findings assist in understanding the impact of SPs on health and environmental safety. Considering the wide spectrum of SPs, a more comprehensive understanding of the negative effects is indispensible for planning future application and regulation of these pesticides.

Current status of insecticide resistance in Q biotype Bemisia tabaci populations from Crete

A major problem of crop protection in Crete, Greece, is the control of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) with chemical insecticides owing to the rapid development of resistance. The aim of this study was to investigate the establishment of resistance and the underlying mechanisms to major insecticide classes with classical bioassays and known biochemical resistance markers. During a 2005-2007 survey, 53 Q biotype populations were collected. Application history records showed extensive use of neonicotinoids, organophosphates, carbamates and pyrethroids. High resistance levels were identified in the majority of populations (>80%) for imidacloprid (RF: 38-1958x) and alpha-cypermethrin (RF: 30-600x). Low resistance levels (RF < 12) were observed for pirimiphos-methyl. A strong correlation between resistance to imidacloprid and the number of applications with neonicotinoids was observed. Significant correlations were observed between COE and P450-dependent monoxygenase activity with resistance to alpha-cypermethrin and imidacloprid respectively. A propoxur-based AChE diagnostic test indicated that iAChE was widespread in most populations. Resistance levels for alpha-cypermethrin were increased when compared with a previous survey (2002-2003). Differentiation of LC(50) values between localities was observed for imidacloprid only. Bemisia tabaci resistance evolved differently in each of the three insecticides studied. Imidacloprid resistance seems less established and less persistent than alpha-cypermethrin resistance. The low resistance levels for pirimiphos-methyl suggest absence of cross-resistance with other organophosphates or carbamates used.

Efficacy of transgenic cotton plant containing the Cry1Ac and Cry2Ab genes of Bacillus thuringiensis against Helicoverpa armigera and Syllepte derogata in cotton cultivation in Burkina Faso

As part of the research into alternatives to pyrethroids, to which lepidopteran cotton pests have begun to develop resistance, transgenic cotton expressing two endotoxins (Cry1Ac and Cry2Ab) of Bacillus thuringiensis Berliner ( Bt), in the U.S. germplasms DP50 and Coker 312, was tested under field conditions in Burkina Faso in two contained areas. An untreated (no lepidopteran insecticidal sprays) conventional (non-transgenic) U.S. variety (Coker 312 in 2003; DP50 in 2004 & 2005) and two conventional local varieties (untreated and treated) were utilized in each test as comparators. The experiments conducted in 2003, 2004 and 2005 showed that the transgenic cotton plant significantly reduced larval populations of the cotton bollworm, Helicoverpa armigera, and the cotton leafroller, Syllepte derogata compared to untreated varieties. Plant damage analyses upon maturity revealed significantly higher levels of sound bolls in transgenic cotton plants. Seed cotton yields and lint quality were also higher for the transgenic cotton than for untreated convention varieties. The transgenic variety was always statistically equivalent or superior to the treated conventional one. The transgenic cotton plant expressing two endotoxins (Cry1Ac and Cry2Ab) of B. thuringiensis Berliner ( Bt) can therefore be an alternative to the use of pyrethroids and endosulfan in cotton cultivation in Burkina Faso. This will have dual advantage of significantly reducing the quantities of pesticides sprayed in the cotton fields while protecting yields and quality of lint.

Distribution and Management of Citrus in California: Implications for Management of Glassy-Winged Sharpshooter

The epidemiology of Pierce’s disease of grape (Vitis spp.) in California has changed over the past 10 yr due to the introduction of an exotic vector, Homalodisca vitripennis (Germar), the glassy-winged sharpshooter. Although this insect is highly polyphagous, citrus (Citrus spp.) is considered a preferred host and proximity to citrus has been implicated as a significant risk factor in recent epidemics of Pierce’s disease in southern California. Consequently, a detailed knowledge of the distribution and management of citrus in relation to grape is needed to improve insect and disease management. Analysis of data on the area planted to these two commodities indicates that only five counties in California concomitantly grow >1,000 ha of grape and >1,000 ha of citrus: Riverside, Kern, Tulare, Fresno, and Madera counties. Comparison of the distribution of grape and citrus within each of these counties indicates that the percentage of grape that is in proximity to citrus is greatest for Riverside County, but the total area of grape that is in proximity to citrus is greater for Fresno, Kern, and Tulare counties. The use of carbamates, neonicotinoids, organophosphates, and pyrethroids as part of the citrus pest management program for control of key insect pests was compared among the same five counties plus Ventura County from 1995 to 2006. Ventura County was included in this analysis as this county grows >10,000 ha of citrus and has established glassy-winged sharpshooter populations. The use of these broad-spectrum insecticides was lowest in Riverside and Ventura counties compared with the other four counties. Analysis of historical trapping data at the county scale indicates a negative association of broad-spectrum insecticide use with glassy-winged sharpshooter abundance. These results are used to retrospectively analyze the Pierce’s disease outbreaks in Kern and Riverside counties.

Distribution and Management of Citrus in California: Implications for Management of Glassy-Winged Sharpshooter

The epidemiology of Pierce's disease of grape (Vitis spp.) in California has changed over the past 10 yr due to the introduction of an exotic vector, Homalodisca vitripennis (Germar), the glassy-winged sharpshooter. Although this insect is highly polyphagous, citrus (Citrus spp.) is considered a preferred host and proximity to citrus has been implicated as a significant risk factor in recent epidemics of Pierce's disease in southern California. Consequently, a detailed knowledge of the distribution and management of citrus in relation to grape is needed to improve insect and disease management. Analysis of data on the area planted to these two commodities indicates that only five counties in California concomitantly grow >1,000 ha of grape and >1,000 ha of citrus: Riverside, Kern, Tulare, Fresno, and Madera counties. Comparison of the distribution of grape and citrus within each of these counties indicates that the percentage of grape that is in proximity to citrus is greatest for Riverside County, but the total area of grape that is in proximity to citrus is greater for Fresno, Kern, and Tulare counties. The use of carbamates, neonicotinoids, organophosphates, and pyrethroids as part of the citrus pest management program for control of key insect pests was compared among the same five counties plus Ventura County from 1995 to 2006. Ventura County was included in this analysis as this county grows >10,000 ha of citrus and has established glassy-winged sharpshooter populations. The use of these broad-spectrum insecticides was lowest in Riverside and Ventura counties compared with the other four counties. Analysis of historical trapping data at the county scale indicates a negative association of broad-spectrum insecticide use with glassy-winged sharpshooter abundance. These results are used to retrospectively analyze the Pierce's disease outbreaks in Kern and Riverside counties.

Tracking pyrethroid resistance in the polyphagous bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae), in the shifting landscape of a cotton-growing area

In cotton-growing areas of Central Africa, timing of host crops and pest management practices in annual rainfed cropping systems result in a shifting mosaic of habitats that influence the dynamics and resistance of Helicoverpa armigera (Hübner) populations on spatial scales, both within and across seasons. From 2002 to 2006, regional and local resistance was monitored among cotton fields and among the major host plants of the bollworm. From 2002, pyrethroid resistance increased within and across cotton-growing seasons to reach a worrying situation at the end of the 2005 growing season. Cotton crops played a fundamental role in the increase in seasonal resistance, even if the intensive use of insecticides on local tomato crops strongly concentrated resistance alleles in residual populations throughout the off-season. Due to the relative stability of resistance in H. armigera populations despite a long off-season, we believe that after the dispersal of the moths southwards at the end of the growing season, reverse migration mainly accounts for the reconstitution of populations at the onset of the following growing season. In addition, local resistance monitoring in 2005 and 2006 showed that it was possible to control the increase in resistance by temporarily stopping the use of pyrethroids during the period of peak infestation of cotton by H. armigera. On the other hand, the similar resistance frequency of populations sampled from sprayed and unsprayed synchronous hosts confirmed the absence of reproductive isolation between adults. As a result, diversity in cropping systems should be encouraged by planting alternative host plants to provide a mosaic of habitats, which in return would provide insecticide-free refuges. The implications for insecticide resistance management in annual cropping systems are discussed.

Evaluation of water quality in an agricultural watershed as affected by almond pest management practices

In the last decade, the detection of organophosphate (OP) pesticides in the San Joaquin River watershed has raised concerns about water quality. This study examined the influences of almond pest management practices (PMPs) on water quality. The Soil and Water Assessment Tool (SWAT) model was employed to simulate pesticide concentration in water as affected by different PMPs. California Pesticide Use Reporting (PUR) data were used to investigate PMP use trends. Stepwise regression analysis was performed to test the correlation between specific PMP use and pesticide concentrations in surface water and sediment. Our results showed an increasing use of reduced risk pesticides and pyrethroids on almonds. SWAT simulation over the period of 1992–2005 showed decreases in OP concentrations in surface water. High OP and pyrethroid use in dormant sprays was associated with high pesticide concentrations in water and sediment. Almond pesticide use was proved to have significant impacts on the pesticide load in the San Joaquin River watershed. The PMP which combines the use of reduced risk pesticides with no dormant spray was recommended for almond orchard use. This paper presented a novel method of studying the environmental impacts of different agricultural PMPs. By combining pesticide use surveys with watershed modeling, we provided a quantitative foundation for the selection of PMPs to reduce pesticide pollution in surface water.

Human semen quality and sperm DNA damage in relation to urinary metabolites of pyrethroid insecticides

Exposure to synthetic pyrethroid insecticides is widespread, and is expected to increase among the general population due to the need to replace other common insecticides following regulatory use restrictions. On the basis of limited studies, there is animal and human evidence for altered reproductive or endocrine function following pyrethroid exposure. The present study measured urinary pyrethroid metabolites [3-phenoxybenzoic acid (3PBA) and cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (CDCCA and TDCCA)], semen quality, sperm motion parameters and sperm DNA damage with the neutral comet assay in 207 men recruited from an infertility clinic. In multivariate analysis, the highest 3PBA quartile was associated with a suggestive 20.2 million sperm/ml reduction (95% confidence interval -37.1 to + 2.6) in sperm concentration compared with men below the 3PBA median. There were significant inverse associations between TDCCA and sperm motility and sperm motion parameters when adjusting for CDCCA and other covariates. The highest TDCCA quartile was associated with a 15.5% decline (95% confidence interval -26.2 to -4.8) in sperm motility compared with men below the median. In multiple logistic analyses, there were dose-dependent increased odds for below reference sperm concentration, motility and morphology in relation to TDCCA. Among the comet assay measures, 3PBA and CDCCA were associated with increased sperm DNA damage, measured as percent DNA in the comet tail. We found evidence for reduced semen quality and increased sperm DNA damage in relation to urinary metabolites of pyrethroid insecticides. These findings may be of concern due to increased pyrethroid use and prevalent human exposure.

Identification of hotspots for potential pyrethroid runoff: a GIS modeling study in San Joaquin River Watershed of California, USA

This paper attempts to identify the high-risk areas for potential runoff of pyrethroid pesticides in the San Joaquin River Watershed. Pyrethroid pesticides have been detected in water and fluvial sediments in this watershed, creating concerns about potential negative impacts on water quality. However, little documentation exists regarding the distributions or the extent of the adverse effects caused by the use of pyrethroids. This study developed a geographic information systems (GIS) model to identify areas with high potential for pyrethroid runoff during the rainy season. The model was then validated using field-monitoring data. Nine factors were identified for the runoff risk assessment: amount of active ingredient used, soil erodibility factor, hydrologic group, surface layer depth, seasonal rainfall, seasonal number of rainy days, seasonal number of storm events, stream density, and land cover. The results indicated that high pyrethroid runoff risks were associated with basins such as the Stanislaus River Sub-basin, Newman Gustine Sub-basin and South Merced Sub-basin. This study demonstrated that the GIS model is capable of predicting high-risk areas of pyrethroid runoff at sub-basin scale. The model can be used to prioritize sites for water quality monitoring and guide implementations of best management practices.

Identification of point mutations in a putative carboxylesterase and their association with acaricide resistance in Rhipicephalus ( Boophilus) microplus (Acari: Ixodidae)

Chemical control based on the use of pyrethroid and organophosphate compounds has selected resistant genotypes in populations of Rhipicephalus ( Boophilus) microplus. Point mutations in esterase-encoding genes represent one of the main resistance mechanisms in this species. In this study, the PCR-RFLP ( polymerase chain reaction-restriction fragment length polymorphism) technique was used to investigate the presence of mutations in a fragment of a putative carboxylesterase in a population of ticks with a history of resistance. The digestion of a fragment of 372 pb with EcoRI revealed three genotypes: W, H and M, observed in different frequencies. The homozygous wild-type genotype (W) was detected only in sensitive strains, with high frequency. The heterozygous genotype (H) was observed in all the strains, albeit with higher frequency in the strains with a moderate resistance, while the homozygous mutant genotype (M) was found only in the moderate resistant strain and resistant strains, with higher frequency in the resistant strains. A comparison of the sequences indicated the presence of other mutations, besides EcoRI polymorphism in the moderate resistant and resistant strains. Also found was the presence of stop codons generating truncated proteins in the sensitive and moderate resistant strains. A domain analysis revealed the presence of additional domains in the resistant strain. These findings suggest that different point mutations, as well as the influence of post-translational modification mechanisms, are altering the activity of the translated proteins and may be associated with resistance.

A Longitudinal Approach of Assessing Urban and Suburban Children’s Exposure to Pyrethroid Pesticides

P-448 Introduction: Although pyrethroids have been sold in the U.S. consumer market for more than 30 years with the estimated annual use ranging from several thousands to a million pounds, very few studies have been conducted to quantitatively assess human exposures to pyrethroids. Most of the relevant data were obtained from studies conducted in Germany or in occupational setting. Recently, the Center for Disease Control and Prevention reported urinary pyrethroid metabolites levels for the U.S. population aged 6–59 years in the National Health and Nutrition Examination Survey (NHANES) conducted in 2001–2002. All of these studies were conducted cross-sectionally, and therefore, the results only represent exposures over relatively short time periods. The primary objective of this study was to establish a temporal profile of pyrethroid exposure in a cohort of elementary school-aged children living in an urban/suburban community using urinary pyrethroid metabolites as exposure biomarkers. We also examined the relationship between pyrethroid exposure and children’s diets, self-reported residential pyrethroid use, and age. Methods: We conducted a longitudinal study to assess 23 elementary school-aged children’s exposure to pyrethroid pesticides using urinary pyrethroid metabolites as exposure biomarkers. We substituted most of children’s conventional diets with organic food items for 5 consecutive days, and collected two daily spot urine samples, first morning and before the bedtime voids, throughout the 15-day study period. Urine samples were analyzed for 5 common pyrethroid metabolites. Results: We found the association between self-reported pyrethroids use in the residential environment by the parents and the elevated pyrethroid metabolite levels found in their children’s urine. Children also expose to pyrethroids through their conventional diets, although the magnitude is smaller than the residential exposure. Children’s ages appear to be significantly associated with pyrethroids exposure, which is likely attributed by the use of pyrethroids around the premise or in the facilities where older age children engaged in the outdoor activities. Conclusion: We conclude that residential pesticide use represents the most important risk factor for children’s exposure to pyrethroid insecticides. Because of the wide use of pyrethroids in the U.S., the findings of this study are important from both the children’s pesticide exposure assessment and the environmental public health perspectives.