Use Of DDT Research Articles

Persistent organic pesticide residues in sediments of Vasai Creek near Mumbai: Assessment of sources and potential ecological risk

Thirteen persistent organic pesticides were investigated in the sediments of Vasai Creek near Mumbai to evaluate their pollution levels and potential risks. It was observed that ΣOCPs level was in the range of 597–1538ng/g dw, with an average value of 1115.25ng/g dw. The level of ΣOPPs was in the range of 492–1034ng/g dw, with an average value of 798.15ng/g dw. The values o,p′-DDT/p,p′-DDT ratio gives an indication of use of technical DDT as the prime source of DDT, while the α/γ-BHC ratio indicate that BHCs in study area might have been received from fresh lindane. The results of an ecological risk assessment showed that sediment bound organic pesticides are of more ecotoxicological concern as they might create adverse ecological risk to the marine breeding habitats. These pesticides residues may get remobilize and released to overlying waters creating adverse effects on terrestrial and aquatic organisms.

Courting Disaster: Environmental Justice and the US Court System

In the summer of 1967, 10 young lawyers and scientists in Stony Brook, New York, challenged the widespread use of DDT, the insecticide that had gained wide notoriety following the publication of Rachel Carson’s Silent Spring.1 Frustrated by the slow pace of legislative action at the state and federal levels, they decided to sue cities, states, and chemical companies in an effort to halt the pollution of the nation’s land, streams, and lakes.

Sexual conflict maintains variation at an insecticide resistance locus.

BackgroundThe maintenance of genetic variation through sexually antagonistic selection is controversial, partly because specific sexually-antagonistic alleles have not been identified. The Drosophila DDT resistance allele (DDT-R) is an exception. This allele increases female fitness, but simultaneously decreases male fitness, and it has been suggested that this sexual antagonism could explain why polymorphism was maintained at the locus prior to DDT use. We tested this possibility using a genetic model and then used evolving fly populations to test model predictions.ResultsTheory predicted that sexual antagonism is able to maintain genetic variation at this locus, hence explaining why DDT-R did not fix prior to DDT use despite increasing female fitness, and experimentally evolving fly populations verified theoretical predictions.ConclusionsThis demonstrates that sexually antagonistic selection can maintain genetic variation and explains the DDT-R frequencies observed in nature.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0143-3) contains supplementary material, which is available to authorized users.

DDT-based indoor residual spraying suboptimal for visceral leishmaniasis elimination in India

Indoor residual spraying (IRS) is used to control visceral leishmaniasis (VL) in India, but it is poorly quality assured. Quality assurance was performed in eight VL endemic districts in Bihar State, India, in 2014. Residual dichlorodiphenyltrichloroethane (DDT) was sampled from walls using Bostik tape discs, and DDT concentrations [grams of active ingredient per square meter (g ai/m(2))] were determined using HPLC. Pre-IRS surveys were performed in three districts, and post-IRS surveys were performed in eight districts. A 20% threshold above and below the target spray of 1.0 g ai/m(2) was defined as "in range." The entomological assessments were made in four districts in IRS and non-IRS villages. Vector densities were measured: pre-IRS and 1 and 3 mo post-IRS. Insecticide susceptibility to 4% DDT and 0.05% deltamethrin WHO-impregnated papers was determined with wild-caught sand flies. The majority (329 of 360, 91.3%) of pre-IRS samples had residual DDT concentrations of <0.1 g ai/m(2). The mean residual concentration of DDT post-IRS was 0.37 g ai/m(2); 84.9% of walls were undersprayed, 7.4% were sprayed in range, and 7.6% were oversprayed. The abundance of sand flies in IRS and non-IRS villages was significantly different at 1 mo post-IRS only. Sand flies were highly resistant to DDT but susceptible to deltamethrin. The Stockholm Convention, ratified by India in 2006, calls for the complete phasing out of DDT as soon as practical, with limited use in the interim where no viable IRS alternatives exist. Given the poor quality of the DDT-based IRS, ready availability of pyrethroids, and susceptibility profile of Indian sand flies, the continued use of DDT in this IRS program is questionable.

DDT Exposure in Utero and Breast Cancer.

Currently no direct evidence links in utero dichlorodiphenyltrichloroethane (DDT) exposure to human breast cancer. However, in utero exposure to another xenoestrogen, diethylstilbestrol, predicts an increased breast cancer risk. If this finding extends to DDT, it could have far-reaching consequences. Many women were heavily exposed in utero during widespread DDT use in the 1960s. They are now reaching the age of heightened breast cancer risk. DDT exposure persists and use continues in Africa and Asia without clear knowledge of the consequences for the next generation. In utero exposure to DDT is associated with an increased risk of breast cancer. This was a case-control study nested in a prospective 54-year follow-up of 9300 daughters in the Child Health and Development Studies pregnancy cohort (n = 118 breast cancer cases, diagnosed by age 52 y and 354 controls matched on birth year). Kaiser Foundation Health Plan members who received obstetric care in Alameda County, California, from 1959 to 1967, and their adult daughters participated in the study. Daughters' breast cancer diagnosed by age 52 years as of 2012 was measured. Maternal o,p'-DDT predicted daughters' breast cancer (odds ratio fourth quartile vs first = 3.7, 95% confidence interval 1.5-9.0). Mothers' lipids, weight, race, age, and breast cancer history did not explain the findings. This prospective human study links measured DDT exposure in utero to risk of breast cancer. Experimental studies are essential to confirm results and discover causal mechanisms. Findings support classification of DDT as an endocrine disruptor, a predictor of breast cancer, and a marker of high risk.

The Invisible and Indeterminable Value of Ecology: From Malaria Control to Ecological Research in the American South.

This essay tells the story of the Emory University Field Station, a malaria research station in southwest Georgia that operated from 1939 to 1958. Using the tools of environmental history and the history of science, it examines the station's founding, its fieldwork, and its place within the broader history of malaria control, eradication, and research. A joint effort of Emory University, the U.S. Public Health Service, and the Communicable Disease Center (CDC), this station was closely aligned with a broader movement of ideas about tropical diseases across the globe, but it also offers a case study of how science in the field can veer from mainstream thinking and official policy. As the CDC and other disease-fighting organizations were moving toward a global strategy of malaria eradication through the use of DDT, the Emory Field Station developed a postsanitarian approach to malaria. Drawing on resistance among American conservationists to environmental transformation in the name of malaria control, the station's staff embraced the science and worldview of ecology in an effort to lighten public health's hand on the land and to link human health to the environment in innovative, if sometimes opaque, ways. This essay, then, argues that the Emory Field Station represents an early confluence of ecology with the biomedical sciences, something very similar to what is now the important discipline of disease ecology.

Enantiomeric fraction and isomeric composition to assess sources of DDT residues in soils

Chiral pesticides such as o,p′-DDT can undergo enantioselective microbial degradation in soil. Hence, the enantiomeric fraction (EF) of o,p′-DDT was used as an approach to assess potential recent inputs of DDT in the lower part of the Ebro River basin (NE Spain), a region heavily impacted by agricultural and industrial activities, including a dicofol production and a chloro-alkali plants. The EFs of five out of nineteen soils were not different from the racemic value (0.505±0.010), confirming that the Ebro River and some of its tributaries, Segre and Cinca rivers, transported fresh DDT residues despite its ban in Spain during the 90s. o,p′-DDT/p,p′-DDT ratios in soils suggest that recent use of technical DDT and/or DDT-contaminated dicofol may be responsible for the fresh DDT inputs in the Segre River, while in the Ebro River, they indicate a dominant contribution of technical DDT, likely related to the residues accumulated by the chloro-alkali plant discharges.

Biological risk, source and pollution history of organochlorine pesticides (OCPs) in the sediment in Nansha mangrove, South China

In the last century, organochlorine pesticides (OCPs) have been extensively used, especially in South China, to promote crop yield. In view of their toxicity, persistence and bioavailability, however, the Chinese government has attempted to regulate their production and use. We aimed to examine the biological risk, source and pollution history of OCPs in the sediment in Nansha mangrove which is located in the industrial region in South China. Results showed that HCHs and DDTs, mainly originating from lindane and technical DDT respectively, were the dominant OCPs, but their concentrations were too low to cause adverse effects on biota. In the last decade, the total concentration of HCHs showed a decreasing trend, whereas DDTs remained stable, despite their limited input. This suggests that management of HCHs was effective, while more management efforts should be put on DDTs, especially the use of dicofol and technical DDT, in future.

Banned: a history of pesticides and the science of toxicology

Rachel Carson's eloquent book Silent Spring stands as one of the most important books of the twentieth century and inspired important and long-lasting changes in environmental science and government policy. Frederick Rowe Davis thoughtfully sets Carson's study in the context of the twentieth century, reconsiders her achievement, and analyzes its legacy in light of toxic chemical use and regulation today. Davis examines the history of pesticide development alongside the evolution of the science of toxicology and tracks legislation governing exposure to chemicals across the twentieth century. He affirms the brilliance of Carson's careful scientific interpretations drawing on data from university and government toxicologists. Although Silent Spring instigated legislation that successfully terminated DDT use, other warnings were ignored. Ironically, we replaced one poison with even more toxic ones. Davis concludes that we urgently need new thinking about how we evaluate and regulate pesticides in accounting for their ecological and human toll.

Male fertility following occupational exposure to dichlorodiphenyltrichloroethane (DDT)

BackgroundThe inconsistent epidemiological results of the endocrine disrupting effects of DDT fuel a harsh debate on its global ban. ObjectivesWe tested the hypothesis that occupational exposure to dichloro-diphenyl-trichloroethane (DDT) causes impairment in male fertility in a cohort of DDT exposed workers, in Sardinia, Italy. MethodsWe accessed official records on date of marriage and date of birth of the first child to estimate time to pregnancy (TTP) in the spouses of 1223 workers employed in a 1946–1950 anti-malarial campaign. The TTP calculation was censored at the 13th month after date of marriage. We used a modified Cox's proportional hazard model to calculate the fecundability ratio (FR) by job, by cumulative exposure to DDT, and by time window in relation to the anti-malarial operations, adjusting by paternal age at marriage. ResultsAmong the spouses of DDT applicators, fecundability did not vary during DDT use (FR=1.22, 95% CI 0.84–1.77) nor in the following decade (FR=1.01, 95% CI 0.67–1.50) with reference to the prior years. A significant increase occurred among the unexposed and the less exposed sub-cohorts, which generated a non-significantly reduced FR among the DDT applicator sub-cohort with reference to the unexposed following exposure. ConclusionWe did not find evidence of an impairment in male fertility following heavy occupational exposure to DDT. However, although fecundability was highest among the spouses of the DDT applicators in the years prior to the anti-malarial campaign, we cannot exclude that DDT exposure prevented an increase parallel to that observed among the unexposed and the less exposed sub-cohorts.

Historical deposition behaviors of organochlorine pesticides (OCPs) in the sediments of a shallow eutrophic lake in Eastern China: Roles of the sources and sedimentological conditions

Organochlorine pesticides (OCPs) were quantified in sediments from Lake Chaohu, a shallow eutrophic lake in Eastern China, to investigate their historical deposition behaviors and to reconstruct their use history. The OCP concentrations ranged from 2.17 to 18.61ngg−1 in the surface sediments in the lake region and from .28 to 86.27ngg−1 in the inflowing river. The highest values of the aforementioned variables were attributed to urban-industrial pollution sources in the west lake region and decreased with distance from the river inlets. Historically, OCP contamination displayed three stages in Lake Chaohu: an initial increase before the 1930s, a sharp increase until the 1980s, and a decrease due the implementation of policies banning their use in the 1980s. During the second stage, the OCP concentrations increased rapidly from .69, .58, 1.95 and .02ngg−1 in the C4, C5, C6 and C10 samples in the 1930s to 8.68, 61.89, 24.14 and 3.53ngg−1, respectively, in the early 1980s. This temporal trend of OCP concentrations corresponded with historically intense anthropogenic activities, indicating that contamination by OCPs was accompanied by industrialization and civilization prior to their prohibition. In addition, dichlorodiphenyltrichloroethane (DDT) contamination was derived from the historical use of technical DDTs, whereas hexachlorocyclohexane (BHC) contamination was attributed to the historical use of technical BHCs with Lindane and new inputs of illegal DDTs. Strong positive relationships between the OCP concentrations and the total organic carbon (TOC) concentrations, sediment grain sizes (<4μm), nutrient contents and heavy metal contents indicated that the sedimentary conditions and human activities affected the depositional characteristics of the OCPs. The DDT residues and their metabolites, particularly those in the inlet rivers, should be of concern because they result in an ecotoxicological risk in the catchment of Lake Chaohu.

Chlorinated, brominated and fluorinated organic pollutants in African Penguin eggs: 30 years since the previous assessment

The African Penguin population has drastically declined over the last 100years. Changes in food availability due to over-fishing and other oceanographic changes seem to be major causes. However, it has also been 30years since organic pollutants as a potential factor have been assessed. We analysed penguin eggs collected in 2011 and 2012 from two breeding colonies 640km apart: Robben Island near Cape Town on the Atlantic Ocean coast, and Bird Island near Port Elizabeth on the Indian Ocean coast of South Africa. We quantified organochlorine pesticides, brominated flame retardants, and perfluorinated compounds (PFCs). Compared to 30years ago, concentrations of ΣDDT have remained about the same or slightly lower, while ΣPCBs declined almost four-fold. The use of DDT in malaria control is unlikely to have contributed. PFCs were detected in all eggs. Indications (non-significant) of eggshell thinning associated with ΣDDT and ΣPCB was found. It seems therefore that the concentrations of measured organic pollutants the African Penguin eggs are not contributing directly to its current demise, but concerns remain about thinner shells and desiccation. Effects of combinations of compounds and newer compounds cannot be excluded, as well as more subtle effects on reproduction, development, and behaviour.

RNAi validation of resistance genes and their interactions in the highly DDT-resistant 91-R strain of Drosophila melanogaster

4,4'-dichlorodiphenyltrichloroethane (DDT) has been re-recommended by the World Health Organization for malaria mosquito control. Previous DDT use has resulted in resistance, and with continued use resistance will increase in terms of level and extent. Drosophila melanogaster is a model dipteran that has many available genetic tools, numerous studies done on insecticide resistance mechanisms, and is related to malaria mosquitoes allowing for extrapolation. The 91-R strain of D. melanogaster is highly resistant to DDT (>1500-fold), however, there is no mechanistic scheme that accounts for this level of resistance. Recently, reduced penetration, increased detoxification, and direct excretion have been identified as resistance mechanisms in the 91-R strain. Their interactions, however, remain unclear. Use of UAS-RNAi transgenic lines of D. melanogaster allowed for the targeted knockdown of genes putatively involved in DDT resistance and has validated the role of several cuticular proteins (Cyp4g1 and Lcp1), cytochrome P450 monooxygenases (Cyp6g1 and Cyp12d1), and ATP binding cassette transporters (Mdr50, Mdr65, and Mrp1) involved in DDT resistance. Further, increased sensitivity to DDT in the 91-R strain after intra-abdominal dsRNA injection for Mdr50, Mdr65, and Mrp1 was determined by a DDT contact bioassay, directly implicating these genes in DDT efflux and resistance.

Association between lung function in adults and plasma DDT and DDE levels: results from the Canadian Health Measures Survey.

BackgroundAlthough DDT [1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane] has been banned in many countries since the 1970s, it may still pose a risk to human respiratory health. In agriculture, DDT exposures have been associated with asthma and chronic bronchitis. However, little is known about the effect of DDT on lung function.MethodsWe used data on 1,696 participants 20–79 years of age from the Canadian Health Measures Survey (CHMS) and conducted multiple regression analysis to estimate associations between plasma p,p´-DDT/DDE and lung function.ResultsAlmost all participants (> 99.0%) had detectable concentrations of plasma p,p´-DDE, but only 10.0% had detectable p,p´-DDT. Participants with detectable p,p´-DDT had significantly lower mean FVC (difference = 311 mL; 95% CI: –492, –130; p = 0.003) and FEV1 (difference = 232 mL; 95% CI: –408, –55; p = 0.015) than those without. A 100-ng/g lipid increase in plasma p,p´-DDE was associated with an 18.8-mL decrease in mean FVC (95% CI: –29, –9) and an 11.8-mL decrease in mean FEV1 (95% CI: –21, –3). Neither exposure was associated with FEV1/FVC ratio or FEF25%–75%.ConclusionsDDT exposures, which may have occurred decades ago, were still detectable among Canadians. Plasma DDT and DDE were negatively associated with lung function parameters. Additional research on the potential effects of DDT use on lung function is warranted.CitationYe M, Beach J, Martin JW, Senthilselvan A. 2015. Association between lung function in adults and plasma DDT and DDE levels: results from the Canadian Health Measures Survey. Environ Health Perspect 123:422–427; http://dx.doi.org/10.1289/ehp.1408217

Post-DDT Recovery of Osprey (Pandion haliaetus) Populations in Southern New England and Long Island, New York, 1970–2013

The Osprey (Pandion haliaetus) population nesting between New York City and Boston, Massachusetts, collapsed from approximately 1000 pairs in 1940 to 109 in the early 1970s. In the 1970s, within five or six years of the cessation of DDT use in the region, the Osprey population began recovering. The recovery was asynchronous across the region. Current (2013) distribution and numbers differ dramatically from those of the pre-DDT period. Colonies on Narragansett and Mount Hope bays in Rhode Island, the Connecticut River estuary, and on Gardiners Island, New York, failed to recover their former remarkable densities. Osprey populations expanded from eastern to western Long Island, New York. In Connecticut, Ospreys now occupy the entire coastline and are nesting inland. A new concentration of Ospreys has become established in southeastern Massachusetts on the Westport River, the islands of Martha's Vineyard and Nantucket, and most recently, on Cape Cod. From this area, the species' range has gradually expanded northward. The population in Massachusetts is now contiguous with the New Hampshire population, and pairs are nesting west of the Connecticut River. The current population in southern New England easily exceeds 1200 pairs and is predominantly (ca. 95%) nesting on human-made structures either erected as nest platforms or co-opted by Ospreys as nest support structures.La población de Pandion haliaetus nidificando entre la ciudad de Nueva York y Boston, Massachusetts, colapsó de aproximadamente 1000 pares en 1940 a 109 a comienzos de la década de 1970. En dicha década, en cinco o seis años de cese en el uso de DDT en la región, las poblaciones de P. haliaetus comenzaron a recuperarse. La recuperación fue asincrónica a lo largo de la región. La distribución y los números actuales (2013) difieren dramáticamente de aquellos del periodo pre-DDT. Las colonias de las bahías de Narragansett y Mount Hope en Rhode Island, el estuario del Río Connecticut y en Gardiners Island, Nueva York, no pudieron recuperar sus notables densidades pasadas. Las poblaciones de P. haliaetus se expandieron desde el este hacia el oeste de Long Island, Nueva York. En Connecticut, P. haliaetus ahora ocupa la línea de costa completa y está nidificando tierra adentro. Una nueva concentración de individuos de P. haliaetus se ha establecido en el sudeste de Massachusetts en el Río Westport, las islas de Martha's Vineyard y Nantucket y más recientemente en Cape Cod. Desde esta área la distribución de la especie se ha expandido gradualmente hacia el norte. La población en Massachusetts ahora es contigua con la población de New Hampshire y las parejas están nidificando al oeste del Río Connecticut. La población actual al sur de Nueva Inglaterra fácilmente supera las 1200 parejas y nidifica predominantemente (ca. 95%) en estructuras hechas por el hombre, tanto las construidas como plataformas para nidos como aquellas que P. haliaetus utiliza como estructuras de soporte para sus nidos.

Development of multifunctional metabolic synergists to suppress the evolution of resistance against pyrethroids in insects that blood feed on humans.

Pyrethroids are the insecticides of choice when exposure to humans is likely, such as occurs in vector and public-health-related control programs. Unfortunately, the pyrethroids share a common resistance mechanism with dichlorodiphenyltrichloroethane (DDT), knockdown resistance (kdr), and prior extensive use of DDT has predisposed the pyrethroids to cross-resistance via kdr. Given the widespread occurrence of kdr, the use of synergists with pyrethroids is considered to be prudent to guard against the selection of multiply resistant insects. 3-Phenoxybenzyl hexanoate (PBH) was synthesized as a multifunctional pyrethroid synergist that, besides being a surrogate substrate for sequestration/hydrolytic carboxylesterases, now also functions as a substrate for oxidative xenobiotic metabolism. The addition of PBH to permethrin-treated females of the ISOP450 strain of Culex pipiens quinquefasciatus resulted in a threefold increase in synergism, as judged by the synergistic ratio. Similarly, PBH synergized the action of deltamethrin sixfold on females of the common bed bug, Cimex lectularius, and was 2.8-fold more synergistic than piperonyl butoxide (PBO). PBH synergized the action of both type I and type II pyrethroids in a mosquito vector (Cx. p. quinquefasciatus) and in a public-health pest, C. lectularius, respectively, indicating a broad spectrum of action on blood-feeding insects. PBH appears to have residual properties similar to permethrin and is itself non-toxic, unlike PBO, and therefore should be compatible with existing pyrethroid formulations used for insecticide-treated nets and home/residential sprays.

Temporal trends in concentrations and total serum burdens of organochlorine compounds from birth until adolescence and the role of breastfeeding

Introduction: The aims of the present study are to assess the temporal trends of organochlorine compounds (OCs) concentrations and total serum burdens from birth until adolescence and the influence of breastfeeding in these temporal trends. Methods: In 1997 two birth cohort studies were set up in Ribera d'Ebre (N=102) and the island of Menorca (N=482), Spain. Concentrations (ng/mL) of OCs [pentachlorobenzene (PeCB), four isomers of hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (4,4′-DDT), dichlorodiphenyldichloroethylene (4,4′-DDE) and seven polychlorobiphenyl congeners (Σ7PCBs)] were measured in cord blood and at the age of 4 and 14years. The total serum burdens (ng) of these compounds were estimated based on the total blood volume (mL) of children at the different ages. We compared median concentrations and total serum burdens of these OCs at the different time-points of follow-up between children of Ribera d'Ebre and Menorca and between breastfed and non-breastfed children. Results: From birth until adolescence concentrations of all OCs drastically reduced. These reductions were mainly derived from the dilution of OCs, associated to an increase in total blood volume of children at the age of 4 and 14years. Despite the reduction in OCs concentrations, the total serum burdens of 4,4′-DDE and Σ7PCBs, were higher in adolescents than at birth. Increases in OCs total serum burden occurred both in breastfed and non-breastfed children, but were significantly higher in the first. Conclusions: Even after decades of banning OCs production and use, current young generations in westernized countries are still bioaccumulating these compounds. Given the potential health effects of OCs, especial attention should be paid in the control of secondary emissions in the environment and in the control of food production and contamination. In countries with endemic malaria it is important to work towards effective alternatives to the use of DDT.

Experimental hut and bioassay evaluation of the residual activity of a polymer-enhanced suspension concentrate (SC-PE) formulation of deltamethrin for IRS use in the control of Anopheles arabiensis.

BackgroundThe Stockholm Convention on Persistent Organic Pollutants (POPs) came into effect in 2004; the use of DDT for malaria control has been allowed to continue under exemption since then due to a perceived absence of equally effective and efficient alternatives. Alternative classes of insecticide for indoor residual spraying (IRS) have a relatively short residual duration of action (2-6 months according to WHO). In areas of year-round transmission multiple spray cycles are required, resulting in significantly higher costs for malaria control programs and user fatigue. This study evaluated performance of a new formulation of deltamethrin (pyrethroid) with polymer (SC-PE) to prolong the effective residual action to >6 months.MethodsDeltamethrin SC-PE was evaluated alongside an existing water dispersible granule (WG) formulation and DDT water dispersible powder (WP) in laboratory and hut bioassays on mud, concrete, palm thatch and plywood substrates. An experimental hut trial was conducted in Lower Moshi Rice Irrigation Zone, Tanzania from 2008-2009 against wild, free-flying, pyrethroid susceptible An. arabiensis. Performance was measured in terms of insecticide-induced mortality, and blood-feeding inhibition. Bioassays were carried out monthly on sprayed substrates to assess residual activity.ResultsBioassays in simple huts (designed for bioassay testing only) and experimental huts (designed for testing free flying mosquitoes) showed evidence that SC-PE improved longevity on mud and concrete over the WG formulation. Both deltamethrin SC-PE and WG outperformed DDT in bioassays on all substrates tested in the laboratory and simple huts. In experimental hut trials SC-PE, WG and DDT produced high levels of An. arabiensis mortality and the treatments were equivalent over nine months’ duration. Marked seasonal changes in mortality were recorded for DDT and deltamethrin treatments, and may have been partly influenced by outdoor temperature affecting indoor resting duration of mosquitoes on sprayed surfaces, although no clear correlation was demonstrated.ConclusionsThere is a limited range of alternative insecticides for IRS, and deltamethrin SC-PE is likely to have an important role as part of a rotation strategy with one or more different insecticide classes rotated annually, particularly in areas that currently have low levels of pyrethroid resistance or low LLIN coverage and year-round malaria transmission.

Determination of organochlorine pesticide residue levels in chewable parts of the khat (Catha edulis) plant.

In this study, the levels of DDT and its metabolite residues were determined in chewable parts of Catha edulis plants grown in the southern part of Ethiopia. The levels of p,p'-DDT and p,p'-DDE were found to be in the range of 10.8-19.7 and 3.5-18.6 μg/kg, respectively. These data revealed that the residue being detected is from recent applications. The estimated daily intake of total DDT from C. edulis consumption was calculated to be in the range between 0.0278 and 0.0747 μg/kg, which is significantly lower than the FAO/WHO guideline. However, this may not guarantee safety, as the application of DDT extends to vegetables as well. Even though the use of DDT was banned in Ethiopia for agriculture purposes, detectable levels are still being observed. The results of the study necessitate the need for awareness creation among the people in the community.

Sub-Lethal Pyrethroid Exposure at the Larval or Adult Life Stage and Selection for Resistance in the Major African Malaria VectorAnopheles funestus(Diptera: Culicidae)

Malaria vector control by indoor residual spraying (IRS) in South Africa currently relies on the use of DDT to control pyrethroid-resistant populations of the major malaria vector Anopheles funestus. Pyrethroid resistance in An. funestus in South Africa and Mozambique is primarily based on the over-production of monooxygenase P450 genes. Preliminary evidence suggests that the pyrethroid-resistant phenotype is primarily expressed in adults, raising questions as to how resistance was selected for in the field given that there was no malaria control targeting adults in southern Mozambique when this resistant phenotype was first discovered there. The aim of this study therefore was to select for pyrethroid resistance at the larval or adult stages in southern African An. funestus and then assay the pyrethroid susceptibility of subsequent life stages using samples of progeny from the pyrethroid-resistant selections. There was no significant variation between the lethal permethrin concentrations inducing 50% mor...