Toxicity assessment of binary mixtures of BP3 with 4-MBC (UV-filters), and BP3 with DEET (insect repellent) using the aquatic midge Chironomus riparius.

Personal care products have various organic ultraviolet filters (UV filters) in their composition to increase protection against ultraviolet radiation. Some of these products also contain insect repellents in their formulations. Consequently, these compounds reach freshwater ecosystems, exposing aquatic organisms to a cocktail of anthropogenic contaminants. In this study, the joint effects of two most frequently detected UV filters (Benzophenone - 3 (BP3) and Enzacamene (4-MBC)) and joint effects of BP3 combined with an insect repellent (N, N diethyl-3-methylbenzamide - DEET) were evaluated using life-history traits of the aquatic midge Chironomus riparius such as emergence rate, time to emergence and imagoes body weight. The results showed synergistic effects between BP3 and 4-MBC for C. riparius emergence rate. Regarding the effects of BP3 and DEET mixture, our analysis suggests synergism in the case of males but antagonism in the case of females' time to emergence. Our results imply that the effects of UV filters present in sediments within chemical mixtures are complex and that the evaluation of effects using different life-history traits can yield different patterns of responses. This study demonstrates the importance of assessing the combined effects of pollutants used/found concomitantly in aquatic systems for a more accurate risk assessment, as individual chemical testing can underestimate the toxicity of organic UV filters.

Bioassay-Guided Isolation of Iridoid Glucosides from Stenaria nigricans, Their Biting Deterrence against Aedes aegypti (Diptera: Culicidae), and Repellency Assessment against Imported Fire Ants (Hymenoptera: Formicidae).

In our natural product screening program, we screened natural products for their repellency and toxicity against insect vectors. Methanolic extract of aerial parts of Stenaria nigricans (Lam.), with no published chemistry, was tested for repellency against mosquitoes and imported hybrid fire ants. Methanolic extracts showed biting deterrence similar to DEET (N,N-diethyl-3-methylbenzamide) against Aedes aegypti L. Based on this activity, the crude extract was fractionated into chloroform, ethyl acetate, and methanol subfractions. The active methanolic subfraction was further fractionated into 13 subfractions. These fractions were tested for their biting deterrence against Ae. Aegypti. Active subfractions were further characterized to identify the compounds responsible for this activity. Four undescribed iridoid glucosides (1-4) and three previously reported compounds (5-7) were isolated from active subfractions and tested for their biting deterrent activity. Based on BDI values, compounds 2, 3, 6, and 7, with biting deterrence similar to DEET, showed the potential to be used as repellents against mosquitoes. In an in vitro digging bioassay, none of these compounds showed any repellency against hybrid imported fire ants at a dose of 125 µg/g. This is the first report of biting deterrence and repellency of S. nigricans extract and its pure compounds, iridoid glucosides against mosquitoes and imported fire ants. Further studies will be conducted to explore the repellent potential of these compounds in different formulations under field conditions.

Molecular insights on ar-turmerone as a structural, functional and pharmacophoric analogue of synthetic mosquito repellent DEET by comprehensive computational assessment.

Mosquitoes are vectors for a variety of infectious illnesses, and chemical synthetic insecticides have made it possible to control them effectively. Mosquito repellents are a typical means of keeping mosquitos at bay. Because of its main effectiveness of skin permeability, N,N-Diethyl-meta-toluamide (DEET) is one of the most extensively used mosquito repellents but a dangerous synthetic chemical. DEET was identified about a decade ago to inhibit mosquito's Odorant Binding Protein 1 (OBP1), impairing the mosquito's ability to recognise the host body odour. OBP1 has been identified as a possible target for the development of new mosquito repellents since its discovery. Essential oils from different plants, on the other hand, have been used to repel mosquitos since antiquity. One essential oil from the Curcuma longa (Zingiberales: Zingiberaceae) rhizome display mosquito repellent properties, according to the literature. Furthermore, one of the phytochemicals found in abundance in C. longa essential oil, ar-turmerone, exhibits mosquito repellency as comparable to synthetic DEET. Till date studies on in-silico interaction of natural ar-turmerone with OBP1, which we depict in our current work are scarce. Further, there exist no published reports demonstrating the literary evidence on detailed insights of interaction of DEET with OBP1 along with Molecular Dynamics (MD) simulation studies. We further performed detailed molecular investigations using pharmacophore analysis of ar-turmerone and compared it with DEET, where our findings in the current manuscript unveils for the first time that ar-turmerone is a functional, structural and pharmacophoric analogue of DEET.

Screening of pesticides and emerging contaminants in eighteen Greek lakes by using target and non-target HRMS approaches: Occurrence and ecological risk assessment.

Lakes, albeit ecosystems of vital importance, are insufficiently investigated with respect to the degradation of water quality due to the organic micropollutants load. As regards Greece, screening of lake waters is scarce and concerns a limited number of contaminants. However, understanding the occurrence of contaminants of emerging concern (CECs) and other micropollutants in lakes is essential to appraise their potential ecotoxicological effects. The aim of this study was to deploy a multiresidue screening approach based on liquid chromatography-high-resolution mass spectrometry (HRMS) to get a first snapshot for >470 target CECs, including pesticides, pharmaceuticals, personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), as well as organophosphate flame retardants (OPFRs) in eighteen Greek lakes in Central, Northern and West Northern Greece. The omnipresent compounds were DEET (N,N-diethyl-meta-toluamide), caffeine and TCPP (tris (1-chloro-2-propyl) phosphate). Maximum concentrations varied among the different classes. DEET was detected at a maximum average concentration of >1000 ng/L in Lake Orestiada, while its mean concentration was estimated at 233 ng/L. The maximum total concentrations for pesticides, PPCPs, PFASs, and OPFRs were 5807, 2669, 33.1, and 1214 ng/L, respectively, indicating that Greek lakes are still threatened by the intense agricultural activity. Besides, HRMS enabled a non-target screening by exploiting the rich content of the full-scan raw data, allowing the 'discovery' of tentative candidates, such as surfactants, pharmaceuticals, and preservatives among others, without reference standards. The potential ecotoxicity was assessed by both the risk quotient method and ECOSAR (Ecological Structure Activity Relationships) revealing low risk for most of the compounds.

[Contamination Characteristics and Ecological Risk Assessment of Pharmaceuticals and Personal Care Products (PPCPs) in the Third Drain of Ningxia].

To investigate the contamination characteristics and potential ecological risks of pharmaceuticals and personal care products (PPCPs) in the Third Drain of Ningxia, 14 PPCPs were detected and analyzed using solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry. The results showed that these 14 PPCPs were detected in the Third Drain and its confluent streams, with total concentrations of 117.74-1947.64 ng·L-1 and 63.94-4509.39 ng·L-1, respectively. Detection ratios of gemfibrozil (GEM), caffeine (CAF), avobenzone (BM-DBM), benzophenone-3 (BP-3), 3-(4-methylbenzylidene)-camphor (4-MBC), and diethyltoluamide (DEET) were 100% in the drain. The highest-concentration pharmaceutical was GEM (7.78-721.84 ng·L-1), followed by CAF (41.74-246.86 ng·L-1), and the highest-concentration personal care product was DEET (3.17-219.91 ng·L-1), followed by BP-3 (56.92-150.14 ng·L-1). Concentrations of PPCPs at different sampling points exhibited spatial differences. The total PPCPs concentration increased dramatically and reached a maximum value after flowing through Pingluo County, then showed a decreasing trend downstream. Correlation analysis showed that 4-MBC was significantly positively correlated with COD (P<0.01). IBU, XMTD, TCC, and TCS were significantly correlated with NH4+-N (P<0.05). DIC, BF, CBZ, and DEET were significantly correlated with TN (P<0.05). The results indicated that concentrations of PPCPs were closely related to water quality indexes. Risk assessment showed that DIC, IBU, GEM, CBZ, CAF, and BP-3 had high risks, whereas BM-DBM, TCC, and TCS had moderate risks.

The Potential of a Site-Specific Delivery of Thiamine Hydrochloride as a Novel Insect Repellent Exerting Long-Term Protection on Human Skin: In-vitro, Ex-vivo Study and Clinical Assessment.

Thiamine hydrochloride (TH) was thought to exert a good insect repellent activity. The purpose of this work was to develop a formulation that releases TH in sustained regimen on human skin. Long lasting protection against mosquito bites was achieved. Pullulan acetate (PA) was used to prepare TH nanospheres. Optimal system was incorporated in Pluronic® hydrogel. Formulae were tested for in-vitro release and ex-vivo permeation. Complete protection time (CPT) was done adopting Kaplan-Meier survival function for the synthetic repellent (DEET), TH solution and nanospheres in hydrogel. Release profile of TH solution, nanospheres and nanosphere-loaded hydrogel (DG) demonstrated an added effect of DG, where t 1/2 was 11.2 ± 1.4 h. SEM for DG showed homogenous dispersion of nanospheres inside the matrix of the gel. Ex-vivo permeation showed only 0.761 ± 0.04% of TH in hydrogel permeated the skin after 12 h, while 44.98 ± 3.2% permeated when TH solution was applied. Clinical study revealed a significant difference in CPT between TH solution with either DEET or (DG) (p<0.05), and no significant difference between DEET and DG with CPT 400 ± 31 and 360 ± 18 min, respectively (P > 0.05). The high efficacy of TH-loaded hydrogel rendered it a successful alternative for DEET, offering long protection against mosquito bites.

In vitro skin irritation assessment using EpiDerm™: applicability for updating toxicity information of oxybenzone and N,N-diethyl-m-toluamide.

A skin irritation test using in vitro reconstructed human epidermis (RhE) models was established for hazard identification of irritant chemicals in accordance with UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS) category. In this study, EpiDerm™ was used to assess skin irritation by oxybenzone and N,N-diethyl-m-toluamide (DEET), which are widely used sunscreen and insect repellent components, respectively. EpiDerm™ was applied with oxybenzone and DEET, combined and sequentially with each single dose. Epidermal morphology and differentiation/proliferation were examined microscopically. Oxybenzone and sequential administration groups were determined as nonirritant with cell viability >50% and the morphology was comparable to the human epidermis. Contrastingly, the DEET and coadministration groups exhibited cell viability <50% and poor epidermal morphology. Interleukin (IL)-1α release from substance-treated EpiDerm™ increased inversely to cell viability, suggesting the pro-inflammatory reaction was initiated by DEET. CK-10, E-cadherin, Ki-67, laminin, and ceramide were identified as relevant markers to assess oxybenzone- or DEET-induced epidermal injury. In conclusion, these results may indicate to be aware of the possible skin irritation by indiscriminate use of oxybenzone and DEET without animal testing.

Aquatic life criteria derivation and ecological risk assessment of DEET in China.

N,N-diethyl-meta-toluamide (DEET) is the most widely used active ingredient in commercial insect repellents. In addition to its adverse effects in insects, DEET can affect non-target organisms in surface water systems. Nevertheless, the aquatic life criteria of DEET are not available. This study conducted both acute and chronic toxicity tests on DEET in native Chinese aquatic species, and derived its criterion maximum concentration (CMC) and criterion continuous concentration (CCC). The determined CMC and CCC of DEET were 21.53 and 0.52 mg/L, respectively. The toxicity data indicated that DEET exposure posed a higher toxicity to some algae than other aquatic species. Compared with other insect repellents, DEET exposure posed a moderate toxicity to aquatic species. Therefore, the exposure concentration of DEET in Chinese surface water was collected to assess the potential ecological risk. The preliminary ecological risk assessment showed that DEET posed negligible risk to aquatic ecosystems in China. However, considering its toxic effects on the growth and reproduction to aquatic organisms, the ecological risk posed by DEET is worth further concern.

Critical assessment of the ubiquitous occurrence and fate of the insect repellent N,N-diethyl-m-toluamide in water.

The insect repellent diethyltoluamide (DEET) is among the most frequently detected organic chemical contaminants in water across a wide range of geographies from around the world. These observations are raising critical questions and increasing concerns regarding potential environmental relevance, particularly when the emergence of severe neurological conditions attributed to the Zika virus has increased the use of insect repellents. After dermal application, DEET is washed from the skin when bathing and enters the municipal sewer system before discharge into the environment. Mainly measured by gas chromatography or liquid chromatography coupled to mass spectrometry (GC-MS or LC-MS), more than 200 peer-reviewed publications have already reported concentrations of DEET ranging ng/L to mg/L in several water matrices from North America, Europe, Asia, Oceania, and more recently Africa and South America. While conventional wastewater treatment technology has limited capacity of removal, advanced technologies are capable of better attenuation and could lower the environmental discharge of organic contaminants, including DEET. For instance, adsorption on activated carbon, desalinating membrane processes (nanofiltration and reverse osmosis), ozonation, and advanced oxidation processes can achieve 50% to essentially 100% DEET attenuation. Despite the abundant literature on the topic, the ubiquity of DEET in the environment still raises questions due to the apparent lack of obvious spatio-temporal trends in concentrations measured in surface water, which does not fit the expected usage pattern of insect repellents. Moreover, two recent studies showed discrepancies between the concentrations obtained by GC-MS and LC-MS analyses. While the occurrence of DEET in the environment is well established, the concentrations reported should be interpreted cautiously, considering the disparities in methodologies applied and occurrence patterns observed. Therefore, this manuscript provides a critical overview of the origin of DEET in the environment, the relevant analytical methods, the occurrence reported in peer-reviewed literature, and the attenuation efficacy of water treatment processes.

iSTREEM(®) : An approach for broad-scale in-stream exposure assessment of "down-the-drain" chemicals.

The "in-stream exposure model" iSTREEM(®) , a Web-based model made freely available to the public by the American Cleaning Institute, provides a means to estimate concentrations of "down-the-drain" chemicals in effluent, receiving waters, and drinking water intakes across national and regional scales under mean annual and low-flow conditions. We provide an overview of the evolution and utility of the iSTREEM model as a screening-level risk assessment tool relevant for down-the-drain products. The spatial nature of the model, integrating point locations of facilities along a hydrologic network, provides a powerful framework to assess environmental exposure and risk in a spatial context. A case study compared national distributions of modeled concentrations of the fragrance 1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8,-hexamethylcyclopenta-γ-2-benzopyran (HHCB) and the insect repellent N,N-Diethyl-m-toluamide (DEET) to available monitoring data at comparable flow conditions. The iSTREEM low-flow model results yielded a conservative distribution of values, whereas the mean-flow model results more closely resembled the concentration distribution of monitoring data. We demonstrate how model results can be used to construct a conservative estimation of the distribution of chemical concentrations for effluents and streams leading to the derivation of a predicted environmental concentration (PEC) using the high end of the concentration distribution (e.g., 90th percentile). Data requirements, assumptions, and applications of iSTREEM are discussed in the context of other down-the-drain modeling approaches to enhance understanding of comparative advantages and uncertainties for prospective users interested in exposure modeling for ecological risk assessment. Integr Environ Assess Manag 2016;12:782-792. © 2016 SETAC.

Acute toxicity assessment of N,N-diethyl-m-toluamide (DEET) on the oxygen flux of the dinoflagellate Gymnodinium instriatum.

Despite the ubiquitous occurrence of N,N-diethyl-m-toluamide (DEET) in aquatic systems, assessments evaluating the toxicity of DEET on phytoplankton species are summed to a single study on a unicellular green alga. In particular, the toxicological effects of DEET in dinoflagellates are unknown. In this study, we employed the mixotrophic dinoflagellate Gymnodinium instriatum as a study system to evaluate acute effects of DEET on the oxygen flux of laboratory cultures. This study reports an inhibitory reaction model of DEET described by the equation y = 4.99x(0.54), where y represents the percent inhibition of oxygen flux and x represents DEET concentration in mg L(−1) (r(2) = 0.98). Based on this model, the effective concentration of DEET needed to reduce O2 flux by 50% (EC50) for this species was found to be at 72.9 mg L(−1). The reported EC50 is more than five times lower than the EC50 reported previously for the unicellular green algae Chlorella protothecoides. This study raises the question of the potential toxicological effects of DEET in dinoflagellates, in particular those populations inhabiting systems characterized by low water circulation such as enclosed bays and lagoons.

Assessment of dermal absorption of DEET-containing insect repellent and oxybenzone-containing sunscreen using human urinary metabolites.

Mutual enhancement of dermal absorption of N,N-diethyl-m-toluamide (DEET) and oxybenzone (OBZ) has been reported recently with DEET and OBZ being active ingredients of insect repellent and sunscreen, respectively. To assess the reported enhancing effect directly, we used human urinary metabolites as biomarkers; besides, we also sought to determine the best way for concurrent use of these two products without extra absorption of either. Four dermal application methods were used: DEET only (S1), OBZ only (S2), DEET on top of OBZ (S3), and OBZ on top of DEET (S4). Among the study methods, there was a significant difference (p = 0.013), which was attributed to the difference between S1 and S4, suggesting that applying OBZ over DEET on the skin lead to significantly higher absorption of DEET. Using both products in reverse order, (S3) did not result in extra DEET absorption significantly. As for OBZ permeation, no significant difference was observed among the methods. In summary, the enhancement of DEET absorption is confirmed for OBZ being applied over DEET on the skin; should concurrent use of both be necessary, applying sunscreen (OBZ) first and then insect repellent (DEET) with a 15-min interval is recommended.

Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET).

N,N-diethyl-m-toluamide (DEET) has been registered for commercial use as an insect repellent for over five decades, and is used widely across the world. Concerns over the safety of DEET first emerged during the 1980s after reports of encephalopathy following DEET exposure, particularly in children. However, the role of DEET in either the illness or deaths was and remains purely speculative. In response to these cases a number of reviews and investigations of DEET safety were carried out. Here we examine the methods used and information available to determine the safety of DEET in humans. Animal testing, observational studies and intervention trials have found no evidence of severe adverse events associated with recommended DEET use. Minor adverse effects noted in animal trials were associated with very large doses and were not replicated between different test species. The safety surveillance from extensive humans use reveals no association with severe adverse events. This review compares the toxicity assessment using three different models to define the risk assessment and safety threshold for DEET use in humans and discusses the clinical consequences of the thresholds derived from the models.The theoretical risks associated with wearing an insect repellent should be weighed against the reduction or prevention of the risk of fatal or debilitating diseases including malaria, dengue, yellow fever and filariasis. With over 48 million European residents travelling to regions where vector borne diseases are a threat in 2009, restricting the concentration of DEET containing repellents to 15% or less, as modelled in the 2010 EU directive, is likely to result in extensive sub-therapeutic activity where repellents are infrequently applied. Future European travellers, as a consequence of inadequate personal protection, could potentially be at increased risk of vector borne diseases. Risk assessments of repellents should take these factors into account when setting safe limits.

Do topical repellents divert mosquitoes within a community? Health equity implications of topical repellents as a mosquito bite prevention tool.

OBJECTIVES: Repellents do not kill mosquitoes--they simply reduce human-vector contact. Thus it is possible that individuals who do not use repellents but dwell close to repellent users experience more bites than otherwise. The objective of this study was to measure if diversion occurs from households that use repellents to those that do not use repellents. METHODS: The study was performed in three Tanzanian villages using 15%-DEET and placebo lotions. All households were given LLINs. Three coverage scenarios were investigated: complete coverage (all households were given 15%-DEET), incomplete coverage (80% of households were given 15%-DEET and 20% placebo) and no coverage (all households were given placebo). A crossover study design was used and coverage scenarios were rotated weekly over a period of ten weeks. The placebo lotion was randomly allocated to households in the incomplete coverage scenario. The level of compliance was reported to be close to 100%. Mosquito densities were measured through aspiration of resting mosquitoes. Data were analysed using negative binomial regression models. FINDINGS: Repellent-users had consistently fewer mosquitoes in their dwellings. In villages where everybody had been given 15%-DEET, resting mosquito densities were fewer than half that of households in the no coverage scenario (Incidence Rate Ratio [IRR]=0.39 (95% confidence interval [CI]: 0.25-0.60); p<0.001). Placebo-users living in a village where 80% of the households used 15%-DEET were likely to have over four-times more mosquitoes (IRR=4.17; 95% CI: 3.08-5.65; p<0.001) resting in their dwellings in comparison to households in a village where nobody uses repellent. CONCLUSIONS: There is evidence that high coverage of repellent use could significantly reduce man-vector contact but with incomplete coverage evidence suggests that mosquitoes are diverted from households that use repellent to those that do not. Therefore, if repellents are to be considered for vector control, strategies to maximise coverage are required.

Assessment of the environmental fate and ecotoxicity of N,N-diethyl-m-toluamide (DEET).

N,N-diethyl-m-toluamide (DEET) is a key active ingredient in many insect repellents available commercially throughout the world. Owing to its popularity among consumers for nearly 30 years, considerable work conducted in the past has demonstrated-and continues to demonstrate-that human exposure to DEET poses no significant health risk to the general population. The results of several studies reported in this paper describe more recent work to understand the environmental fate of DEET, particularly in surface waters and soil, and the potential hazards to aquatic and terrestrial organisms. In summary, DEET enters the environment through several pathways: directly into air during spray application; to surface water from overspray and indirectly via wastewater treatment plant (WTTP) discharges (as a result of washing of skin and laundering of clothing); or to soil via overspray and application of treated sewage as an amendment. Multimedia environmental fate modeling predicts that DEET entering the environment is retained either in receiving waters (∼79%) or in soil (∼21%). Based on its physicochemical properties, DEET is expected to be moderately mobile in the soil column. In surface waters and soil, DEET degrades at a moderate to rapid rate (its half-life is measured in days to weeks). The small amounts of DEET retained in air are subject to rapid photo-oxidation via hydroxyl radical-mediated degradation or, if in droplet form, gravitational settling to soil or water. DEET does not interfere with ozone formation in the upper atmosphere. The bioaccumulation potential of DEET is low; it is neither a persistent, bioaccumulative toxicant nor a persistent organic pollutant. Among aquatic species, acute effect concentrations range between 4 and 388 mg/L. The chronic no-observed effect concentrations (NOEC) for daphnids and green algae range from approximately 0.5 to 24 mg/L. Measured concentrations of DEET in surface waters are several hundreds to thousands of times lower than the lowest NOEC measured, and thus the probability for adverse effects to environmental species is low. A separate paper by Aronson et al. (this issue) supports this conclusion by quantitatively exploring the risks to the aquatic environment using a combination of monitoring data and exposure modeling.

Assessment of groundwater pollution in Tokyo using PPCPs as sewage markers.

While the occurrence of pharmaceuticals and personal care products (PPCPs) in groundwater has typically been reported in bank filtration sites, irrigated fields, septic tanks, and sewage disposal practices, fewer studies have been conducted in highly urbanized areas, where infiltration of treated or untreated sewage is not supposed to be a source of groundwater recharge. Furthermore, little is known about the occurrence of various kinds of PPCPs in relation to microbial indicators in groundwater from different types of aquifers. Thus, we examined the city-wide occurrence of selected PPCPs (diethyltoluamide, crotamiton, ethenzamide, propyphenazone, carbamazepine, and caffeine) and E. coli in 50 groundwaters from unconfined aquifers (<30 m in depth) and confined aquifers (up to 500 m in depth) in Tokyo, where unintended groundwater contamination could take place due to decrepit sewer networks. PPCPs were detected in unconfined aquifers and springs (23/34 samples, 68%), and in confined aquifers (7/16 samples, 44%). Compared with published results for sewage influents, concentrations of PPCPs, excluding caffeine, were generally 1-2 orders of magnitude lower, while in some samples concentrations were quite comparable. The high occurrence rate of PPCPs, even in confined aquifers, indicated that such aquifers are not always protected from pollution by sewage near the land surface. Among the PPCPs analyzed, carbamazepine and crotamiton were most frequently detected, which would appear to be owing to their high persistence, combined with the high concentration of crotamiton in sewage. Crotamiton was detected in all four E. coli-positive groundwaters, and thus may potentially serve as a precautionary indicator of E. coli contamination. Using carbamazepine as a sewage marker, we estimated that 0.8%-1.7% of the dry-weather flow of sewage was leaking out into the unconfined aquifers.

Assessment of plant-driven removal of emerging organic pollutants by duckweed.

Constructed treatment wetlands have the potential to reclaim wastewaters through removal of trace concentrations of emerging organic pollutants, including pharmaceuticals, personal care products, and pesticides. Flask-scale assessments incorporating active and inactivated duckweed were used to screen for plant-associated removal of emerging organic pollutants in aquatic plant systems. Removals of four of eight pollutants, specifically atrazine, meta-N,N-diethyl toluamide (DEET), picloram, and clofibric acid, were negligible in all experimental systems, while duckweed actively increased aqueous depletion of fluoxetine, ibuprofen, 2,4-dichlorophenoxyacetic acid, and triclosan. Active plant processes affecting depletion of experimental pollutants included enhancement of microbial degradation of ibuprofen, uptake of fluoxetine, and uptake of degradation products of triclosan and 2,4-dichlorophenoxyacetic acid. Passive plant processes, particularly sorption, also contributed to aqueous depletion of fluoxetine and triclosan. Overall, studies demonstrated that aquatic plants contribute directly and indirectly to the aqueous depletion of emerging organic pollutants in wetland systems through both active and passive processes.

A low-cost repellent for malaria vectors in the Americas: results of two field trials in Guatemala and Peru.

BACKGROUND: The cost of mosquito repellents in Latin America has discouraged their wider use among the poor. To address this problem, a low-cost repellent was developed that reduces the level of expensive repellent actives by combining them with inexpensive fixatives that appear to slow repellent evaporation. The chosen actives were a mixture of para-menthane-diol (PMD) and lemongrass oil (LG). METHODS: To test the efficacy of the repellent, field trials were staged in Guatemala and Peru. Repellent efficacy was determined by human-landing catches on volunteers who wore the experimental repellents, control, or 15% DEET. The studies were conducted using a balanced Latin Square design with volunteers, treatments, and locations rotated each night. RESULTS: In Guatemala, collections were performed for two hours, commencing three hours after repellent application. The repellent provided >98% protection for five hours after application, with a biting pressure of >100 landings per person/hour. The 15% DEET control provided lower protection at 92% (p < 0.0001). In Peru, collections were performed for four hours, commencing two hours after repellent application. The PMD/LG repellent provided 95% protection for six hours after application with a biting pressure of >46 landings per person/hour. The 20% DEET control provided significantly lower protection at 64% (p < 0.0001). CONCLUSION: In both locations, the PMD/LG repellent provided excellent protection up to six hours after application against a wide range of disease vectors including Anopheles darlingi. The addition of fixatives to the repellent extended its longevity while enhancing efficacy and significantly reducing its cost to malaria-endemic communities.

Traditional use of indigenous mosquito-repellents to protect humans against mosquitoes and other insect bites in a rural community of Cameroon.

OBJECTIVE: To document and test the efficacy of indigenous traditional personal protection methods against mosquito bites and general nuisance. DESIGN: A prospective study based on a survey and field evaluation of selected plant-based personal protection methods against mosquito bites. SETTING: Bolifamba, a rural setting of the Mount Cameroon region. SUBJECTS: A structured questionnaire was administered to 179 respondents and two anti-mosquito measures were tested under field conditions. MAIN OUTCOME MEASURES: Identified traditional anti-mosquito methods used by indigenes of Bolifamba. Two plants tested under field conditions were found to be effective. RESULTS: Of the 179 respondents, 88 (49.16%) used traditional anti-mosquito methods; 57 (64.77%) used plant-based methods while 31 (35.2%) used various petroleum oils. The rest of the respondents, 91 (50.8%) used conventional personal protection methods. Reasons for using traditional methods were because they were available, affordable and lack of known more effective alternatives. The demerits of these methods were: labourious to implement, stain dresses, produce a lot of smoke/ repulsive odours when used; those of conventional methods were lack of adequate information about them, high cost and non-availability. When the two most frequently used plants, Saccharum officinarium and Ocimum basilicum were evaluated under field conditions, each gave a better protection than the control. CONCLUSION: Most plants used against mosquitoes in the area are known potent mosquito repellents but others identified in the study warrant further research. The two tested under field conditions were effective though less than the commonly used commercial diethyltoluamide.