Pyrethroid use-malaria control and individual applications by households for other pests and home garden use

Presence of pyrethroid insecticides in human breast milk and in thatch wall material of dwellings from Southern Africa subtropical area (Manhiça, Mozambique) was investigated to assess potential pyrethroid route of human exposure. Human breast milk samples were collected during 2002 when pyrethroids were widely used as insecticides for mosquito bed nets in Mozambique for malaria control. The median concentration value of total pyrethroids ranged between 87 and 1200 ng/g lw, with λ-cyhalothrin being the most predominant pyrethroid in human breast milk contributing for 35% of the total amount. Moreover, and for the first time, an isomer-specific enrichment was found in human breast milk, showing a selective isomeric accumulation or metabolism in the human body. Based on the calculated pyrethroid concentrations in human breast milk, the daily ingestion rate of pyrethroid was estimated. The nursing infant dietary intake ranged from 0.67 to 9.0 μg (kg of body weight)^− 1 day^− 1. In addition, thatch materials collected after the reintegration of dichlorodiphenyltrichloroethene (DDT) as insecticide residual spraying (IRS) in Mozambique, showed the presence of pyrethroids with concentration values ranging between 6.9 and 700 ng/g dw. In thatch material as well as in human breast milk, pyrethroid contamination was mainly attributed to the agriculture usage of this insecticide knowing that agriculture represent the 80% of the economy in Mozambique. However, a possible usage of this insecticide as IRS in Mozambique cannot be excluded despite their low efficiency for malaria control. The continued use of these compounds (both for agriculture and malaria prevention) and the ingestion rates calculated from the breast milk concentrations indicate that these insecticides cannot be overlooked for the assessment of the lactation risks of breastfeeding infants from the Manhiça region.     

Pyrethroids: A new threat to marine mammals?

The present study constitutes the first investigation to demonstrate pyrethroid bioaccumulation in marine mammals, despite the assumption that these insecticides are converted to non-toxic metabolites by hydrolysis in mammals. Twelve pyrethroids were determined in liver samples from 23 male franciscana dolphins from Brazil. The median concentration values for total pyrethroids were 7.04 and 68.4 ng/g lw in adults and calves, respectively. Permethrin was the predominant compound, contributing for 55% of the total pyrethroids. Results showed a distinct metabolic balance of pyrethroids through dolphin life. High loads are received at the beginning of their lives and, when they reach sexual maturity, these mammals seem to degrade/metabolize pyrethroids. Maternal transfer of these compounds was also evaluated through the analysis of breast milk and placenta samples. Pyrethroids were detected in both matrices, with values between 2.53–4.77 ng/g lw and 331–1812 ng/g lw, respectively. Therefore, for the first time, a study shows mother-to-calf transfer of pyrethroids by both gestational and lactation pathways in dolphins.     

Measurement of estrogenic activity in sediments from Haihe and Dagu River, China

Sediments from two rivers in China, the Haihe and Dagu Rivers, were examined for estrogenic activity using an estrogen receptor (ER)-mediated in vitro bioassay system. ER-active compounds were isolated from sediments by Soxhlet extraction, and the crude extracts were fractionated using a florisil column into three fractions. The estrogenic activity of each extract was detected by measuring luciferase activity in the human breast cancer cell line MCF-7 transfected with a luciferase receptor gene. Significant estrogenic activity was observed in each total extract. The 17beta-estradiol equivalents (E2-EQs) ranged from 8.24 to 95.28 ng E2 g(-1) dw. As a result, the relative estrogenic potencies of three fractions in this study descended in the order of Fraction 3>Fraction 2>Fraction 1. The results of the bioassay analysis indicated the heavy pollution status of these sites with estrogenic contaminants. In this study, five selected chemicals, the natural estrogens 17beta-estradiol (E2) and estrone (E1), and the xeno-estrogens 4-octylphenol (OP), 4-nonylphenol (NP), and Bisphenol A (BPA) were also analyzed using the in vitro bioassay. The estrogenic activity of these chemicals were E2>E1>NP>OP>BPA.     

First report of pyrethroid bioaccumulation in wild river fish: A case study in Iberian river basins (Spain)

For the first time, this work described pyrethroid bioaccumulation in edible river fish samples. We analyzed 42 whole fish samples collected in 4 different Iberian rivers. All samples were positive to these insecticides. Levels of concentration ranged from 12 to 4938 ng g^− 1 lipid weight (lw). Moreover, isomeric characterization was carried out. Our results remarked a general preference of cis isomers in bioaccumulation. Finally, the enantiomeric evaluation showed that there was an enantioselective bioaccumulation of some pyrethroids, depending on the studied species. Pyrethroid concentrations were compared with levels obtained for other common pollutants, such as flame retardants, personal care products, hormones and pharmaceuticals. The highest values corresponded to pyrethroid insecticides, even though, pyrethroid levels are safe for human consumption taken into account the current regulations.     

EPA's SHEDS-multimedia model: Children's cumulative pyrethroid exposure estimates and evaluation against NHANES biomarker data

The U.S. EPA's SHEDS-Multimedia model was applied to enhance the understanding of children's exposures and doses to multiple pyrethroid pesticides, including major contributing chemicals and pathways. This paper presents combined dietary and residential exposure estimates and cumulative doses for seven commonly used pyrethroids, and comparisons of model evaluation results with NHANES biomarker data for 3-PBA and DCCA metabolites. Model input distributions were fit to publicly available pesticide usage survey data, NHANES, and other studies, then SHEDS-Multimedia was applied to estimate total pyrethroid exposures and doses for 3–5 year olds for one year variability simulations. For dose estimations we used a pharmacokinetic model and two approaches for simulating dermal absorption. SHEDS-Multimedia predictions compared well to NHANES biomarker data: ratios of 3-PBA observed data to SHEDS-Multimedia modeled results were 0.88, 0.51, 0.54 and 1.02 for mean, median, 95th, and 99th percentiles, respectively; for DCCA, the ratios were 0.82, 0.53, 0.56, and 0.94. Modeled time-averaged cumulative absorbed dose of the seven pyrethroids was 3.1 nmol/day (versus 8.4 nmol/day for adults) in the general population (residential pyrethroid use and non-use homes) and 6.7 nmol/day (versus 10.5 nmol/day for adults) in the simulated residential pyrethroid use population. For the general population, contributions to modeled cumulative dose by chemical were permethrin (60%), cypermethrin (22%), and cyfluthrin (16%); for residential use homes, contributions were cypermethrin (49%), permethrin (29%), and cyfluthrin (17%). The primary exposure route for 3–5 year olds in the simulated residential use population was non-dietary ingestion exposure; whereas for the simulated general population, dietary exposure was the primary exposure route. Below the 95th percentile, the major exposure pathway was dietary for the general population; non-dietary ingestion was the major pathway starting below the 70th percentile for the residential use population. The new dermal absorption methodology considering surface loading had some impact, but did not change the order of key pathways.     

Estrogenic activity in extracts and exudates of cyanobacteria and green algae

Here is presented some of the first information on interactions of compounds produced by cyanobacteria and green algae with estrogen receptor signaling. Estrogenic potency of aqueous extracts and exudates (culture spent media with extracellular products) of seven species of cyanobacteria (10 different laboratory strains) and two algal species were assessed by use of in vitro trans-activation assays. Compounds produced by cyanobacteria and algae, and in particular those excreted from the cells, were estrogenic. Most exudates were estrogenic with potencies expressed at 50% of the maximum response under control of the estrogen receptor ranging from 0.2 to 7.2 ng 17β-estradiol (E₂) equivalents (EEQ)/L. The greatest estrogenic potency was observed for exudates of Microcystis aerigunosa, a common species that forms water blooms. Aqueous extracts of both green algae, but only one species of cyanobacteria (Aphanizomenon gracile) elicited significant estrogenicity with EEQ ranging from 15 to 280 ng 17β-estradiol (E₂)/g dry weight. Scenedesmus quadricauda exudates and extracts of Aphanizomenon flos-aquae were antagonistic to the ER when coexposed to E₂. The EEQ potency was not correlated with concentrations of cyanotoxins, such as microcystin and cylindrospermopsin, which suggests that the EEQ was comprised of other compounds. The study demonstrates some differences between the estrogenic potency of aqueous extracts prepared from the same species, but of different origin, while the effects of exudates were comparable within species. The observed estrogenic potencies are important namely in relation to the possible mass expansion of cyanobacteria and release of the active compounds into surrounding water.     

Screening of hormone-like activities in bottled waters available in Southern Spain using receptor-specific bioassays

Bottled water consumption is a putative source of human exposure to endocrine-disrupting chemicals (EDCs). Research has been conducted on the presence of chemicals with estrogen-like activity in bottled waters and on their estrogenicity, but few data are available on the presence of hormonal activities associated with other nuclear receptors (NRs). The aim of this study was to determine the presence of endocrine activities dependent on the activation of human estrogen receptor alpha (hERa) and/or androgen receptor (hAR) in water in glass or plastic bottles sold to consumers in Southern Spain. Hormone-like activities were evaluated in 29 bottled waters using receptor-specific bioassays based on reporter gene expression in PALM cells [(anti-)androgenicity] and cell proliferation assessment in MCF-7 cells [(anti-)estrogenicity] after optimized solid phase extraction (SPE). All of the water samples analyzed showed hormonal activity. This was estrogenic in 79.3% and anti-estrogenic in 37.9% of samples and was androgenic in 27.5% and anti-androgenic in 41.3%, with mean concentrations per liter of 0.113 pM 17β-estradiol (E₂) equivalent units (E₂Eq), 11.01 pM anti-estrogen (ICI 182780) equivalent units (ICI 182780Eq), 0.33 pM methyltrienolone (R1881) equivalent units (R1881Eq), and 0.18 nM procymidone equivalent units (ProcEq). Bottled water consumption contributes to EDC exposure. Hormone-like activities observed in waters from both plastic and glass bottles suggest that plastic packaging is not the sole source of contamination and that the source of the water and bottling process may play a role, among other factors. Further research is warranted on the cumulative effects of long-term exposure to low doses of EDCs.     

Dietary exposure to cadmium and risk of breast cancer in postmenopausal women: A systematic review and meta-analysis

BackgroundWith tobacco smoking, diet is the main source of cadmium (Cd) exposure in the general population. The carcinogenic and estrogenic activities of Cd make it a contaminant of potential concern for hormone-dependent cancers including breast cancer. Postmenopausal women represent the most appropriate population to investigate the possible impact of exogenous factors with potential estrogenic activity on breast cancer as, after menopause, their estrogenic influence is predominant.ObjectivesWe systematically reviewed available studies on the association between dietary exposure to Cd and breast cancer focusing on postmenopausal women. A meta-analysis combining the risk estimators was performed and potential sources of between studies heterogeneity were traced.MethodsStudies were searched from MEDLINE through 31 January 2015 and from the reference lists of relevant publications. Six eligible studies published between 2012 and 2014 were identified and relative risk estimates were extracted. Meta-rate ratio estimates (mRR) were calculated according to fixed and random-effect models. Meta-analyses were performed on the whole set of data and separate analyses were conducted after stratification for study design, geographic location, use of hormone replacement therapy (HRT), tumor estrogen receptor status (ER + or ER −), progesterone receptor status (PGR + or PGR −), body mass index (BMI), smoker status, zinc or iron intake.ResultsNo statistically significant increased risk of breast cancer was observed when all studies were combined (mRR = 1.03; 95% confidence interval [CI]: 0.89–1.19). Several sources of heterogeneity and inconsistency were identified, including smoker status, HRT use, BMI, zinc and iron intake. Inconsistency was also strongly reduced when only considering ER −, PGR −, tumors subgroups from USA and from Japan. The risks were, however, not substantially modified after stratifications. No evidence of publication bias was found.ConclusionThe present study does not provide support for the hypothesis that dietary exposure to Cd increases the risk of breast cancer in postmenopausal women. Misclassification in dietary Cd assessment in primary studies could have biased the results towards a finding of no association.     

Alteration of steroidogenesis in H295R cells by organic sediment contaminants and relationships to other endocrine disrupting effects

A novel bioassay with the human adrenocortical carcinoma cell line H295R can be used to screen for endocrine disrupting chemicals that affect the expression of genes important in steroidogenesis. This assay was employed to study the effects of organic contaminants associated with the freshwater pond sediments collected in the Ostrava-Karvina region, Czech Republic. The modulation of ten major genes involved in the synthesis of steroid hormones (CYP11A, CYP11B2, CYP17, CYP19, 17betaHSD1, 17betaHSD4, CYP21, 3betaHSD2, HMGR, StAR) after exposure of H295R cells to sediment extracts was investigated using quantitative real-time polymerase chain reaction (PCR). Crude sediment extracts, containing high concentrations of polycyclic aromatic hydrocarbons (PAHs) and moderate amounts of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) significantly stimulated expression of the CYP11B2 gene (up to 10-fold induction), and suppressed expression of 3betaHSD2 and CYP21 genes. A similar pattern was observed with the extracts after treatment with concentrated sulfuric acid to remove labile chemicals (including PAHs) leaving only persistent PCBs, OCPs and potentially PCDD/Fs. Comparison of the results with other mechanistically based bioassays (arylhydrocarbon receptor, AhR, mediated responses in H4IIE-luc cells, and estrogen receptor mediated effects in MVLN cells) revealed significant endocrine disrupting potencies of organic contaminants present in the sediments (most likely antiestrogenicity). Pronounced effects were observed particularly in sediment extracts from the Pilnok Pond which harbors an unusual intersexual population of the narrow-cawed crayfish Pontastacus leptodactylus (Decapoda, Crustacea). This pilot study provided the first experimental evidence of the wider application of the H295R bioassay for screening complex environmental samples, and the results support the hypothesis of chemical-induced endocrine disruption in intersexual crayfish.     

A review of botanical phytochemicals with mosquitocidal potential

Identification of novel effective mosquitocidal compounds is essential to combat increasing resistance rates, concern for the environment and food safety, the unacceptability of many organophosphates and organochlorines and the high cost of synthetic pyrethroids. An increasing number of researchers are reconsidering botanicals containing active phytochemicals in their efforts to address some of these problems. To be highly competitive and effective, the ideal phytochemical should possess a combination of toxic effects and residual capacity. Acute toxicity is required at doses comparable to some commercial synthetic insecticides while chronic or sub-chronic toxicity is required to produce growth inhibition, developmental toxicity and generational effects. In this article, we review the current state of knowledge on larvicidal plant species, extraction processes, growth and reproduction inhibiting phytochemicals, botanical ovicides, synergistic, additive and antagonistic joint action effects of mixtures, residual capacity, effects on non-target organisms, resistance, screening methodologies, and discuss promising advances made in phytochemical research.     

Estrogenic and androgenic activities in total plasma measured with reporter-gene bioassays: relevant exposure measures for endocrine disruptors in epidemiologic studies?

Measurements of estrogenic and androgenic activities in total plasma with Chemically Activated LUciferase gene eXpression (CALUX?) bioassays could provide biologically relevant measures for exposure to endocrine disruptors in epidemiologic studies. The objective of this study was to explore the effects of a variety of sources of potential endocrine disruptors on estrogenic and androgenic activities in total plasma measured by CALUX?. Plasma samples and interview data on sources of potential endocrine disruptors were collected from 108 men with different exposures profiles. CALUX? measurements (BioDetection Services) involved human U2-OS cell lines controlled by the estrogen receptor alpha and the androgen receptor. Mean differences (beta) in 17β-estradiol equivalents (EEQs) and dihydrotestosterone equivalents (AEQs) between exposure groups were estimated using general linear models. Mean plasma AEQs and EEQs were 9.1×10(-1)ng/ml and 12.0pg/ml, respectively. Elevated AEQs were found in smokers (beta 1.9 (95%CI 0.1-3.6)×10(-1)ng/ml) and heavy drinkers (1.4 (0.2-3.1)×10(-1)ng/ml), and in men occupationally exposed to disinfectants (1.6 (0.3-3.5)×10(-1)ng/ml) or welding/soldering fumes (1.4 (-0.2-2.9)×10(-1)ng/ml). Occupational exposure to pesticides, disinfectants, and exhaust fumes seemed to be associated with increased plasma EEQs: 1.5 (-0.2-3.2)pg/ml, 2.1 (0.2-3.9)pg/ml, and 2.9 (0.6-5.2)pg/ml, respectively. Moderate to high plasma dioxin levels, measured in a subgroup by the dioxin-responsive CALUX?, were accompanied by a 20% increase in AEQs. This is the first study in which CALUX? was used to assess hormone activities in total plasma. Although the results are not yet readily interpretable, they indicate that these measurements can be valuable for epidemiologic studies on endocrine disruptors and give direction for further research.     

The effect of suspended particles coated by humic acid on the toxicity of pharmaceuticals, estrogens, and phenolic compounds

The sorption characteristics of 10 organic chemicals, categorized as pharmaceuticals, estrogens and phenols, onto synthetic suspended particle (i.e., alumina) coated with humic acid were investigated according to their octanol-water partition coefficient (K(ow)). Chemical analyses were performed with gas chromatography and mass spectrometry (GC/MS) and high performance liquid chromatography (HPLC). The effects of particles on the toxicity reduction were evaluated using bioassay tests, using Daphnia magna and Vibrio fisheri for phenols and pharmaceuticals, and the human breast cancer cell MCF-7 for estrogens. Sorption studies revealed that 22 and 38% of octylphenol and pentachlorophenol, respectively, were removed by suspended particle, whereas 2,4-dichlorophenol was not removed, which was directly proportional to the logK(ow) value. Similar to the sorption tests, suspended particles significantly reduced the acute toxicities of octylphenol and pentachlorophenol to D. magna and V. fisheri (p<0.01), but there was no significant difference in the toxicity of 2,4-dichlorophenol to D. magna (p=0.8374). Pharmaceuticals, such as ibuprofen, gemfibrozil and tolfenamic acid, showed no discernible sorption to the suspended particle, with the exception of diclofenac, which revealed 11% sorption. For estrogens, such as estrone, 17beta-estradiol and 17alpha-ethynylestradiol, the results indicated no reduction in the sorption test. This may be attributed to the polar interaction by functional groups in sorption between pharmaceuticals and estrogens and suspended particles. In the bioassays, presence of suspended particles did not significantly modify the toxicity of pharmaceuticals (regardless of their K(ow) values) to D. magna, V. fisheri or E-screen.     

Bacillus thuringiensis, nucleopolyhedrosis virus,and pheromones: Environmental considerations and uncertainties in large-scale insect control

The mode of action, extent of use, and the current knowledge on environmental fate and toxicity of three biological insecticides [Bacillus thuringiensis (B.t.), nucleopolyhedrosis virus (NPV), and pheromones] are reviewed. Data gaps, environmental uncertainties in any large-scale use, and proposed registration guidelines which may lead to more extensive use are discussed. B.t. disappears rapidly from plant foliage on exposure to sunlight and/or moisture, although it may persist in dry soil for several months or years. Foliar-applied NPVs are also inactivated by sunlight; the halflife on cotton leaves is 20–25 h. In the soil, NPVs may remain active for several years. Pheromones volatilize readily and do not persist in plant or in soil. Limited available data indicate that B.t. and pheromones do not persist in aquatic environments; quantitative data are unavailable for NPVs. Based on bioassay data, the three insecticides exhibit undetectable to low toxicity to nontarget organisms; there are also no reports of human disease or injury due to exposure to these pesticides and no bioaccumulation is expected with normal application. Except for B.t. which has been used in a limited large-scale applications, pest control uses of NPVs and pheromones are still in experimental stages. Areas of uncertainties requiring research and development include potential adverse health and ecological impacts in any large-scale and widespread use and efficacy and cost relative to synthetic chemical pesticides.     

Assessment of the endocrine-disrupting effects of short-chain chlorinated paraffins in in vitro models

Short-chain chlorinated paraffins (SCCPs), which are candidate persistent organic pollutants (POPs) according to the Stockholm Convention, are of great concern because of their persistent bioaccumulation, long-range transport and potential adverse health effects. However, data on the endocrine-disrupting effects of SCCPs remain scarce. In this study, we first adopted two in vitro models (reporter gene assays and H295R cell line) to investigate the endocrine-disrupting effects of three SCCPs (C10-40.40%, C10-66.10% and C11-43.20%) via receptor mediated and non-receptor mediated pathway. The dual-luciferase reporter gene assay revealed that all test chemicals significantly induced estrogenic effects, which were mediated by estrogen receptor α (ERα), in the following order: C11-43.20% > C10-66.10% > C10-40.40%. Notably, C10-40.40% and C10-66.10% also demonstrated remarkable anti-estrogenic activities. Only C11-43.20% showed glucocorticoid receptor-mediated (GR) antagonistic activity, with a RIC₂₀ value of 2.6 × 10^− 8 mol/L. None of the SCCPs showed any agonistic or antagonistic activities against thyroid receptor β (TRβ). Meanwhile, all test SCCPs stimulated the secretion of 17β-estradiol (E₂). Both C10-66.10% and C11-43.20% increased the production of cortisol at a high level in H295R cell lines. In order to explore the possible mechanism underlying the endocrine-disrupting effects of SCCPs through the non-receptor pathway, the mRNA levels of 9 steroidogenic genes were measured by real-time polymerase chain reaction (RT-PCR). StAR, 17βHSD, CYP11A1, CYP11B1, CYP19 and CYP21 were upregulated in a concentration-dependent manner by all chemicals. The data provided here emphasized that comprehensive assessments of the health and ecological risks of emerging contaminants, such as SCCPs, are of great concern and should be investigated further.     

Effect of bisphenol A with or without enzyme treatment on the proliferation and viability of MCF-7 cells

Recently, aqueous solutions polluted by BPA have been bioremediated by us using laccase immobilized on hydrophobic membranes in non-isothermal bioreactors. BPA degradation was checked using analytical methods. To assess in vitro the occurred bioremediation, the proliferation and viability indexes of MCF-7 cells incubated in the presence of aqueous solutions of BPA, or of enzyme-treated BPA solutions, have been measured as a function of the initial BPA concentration. The results demonstrated that: i) at each initial BPA concentration used, both the proliferation and viability indexes are a function of the duration of enzyme treatment; ii) proliferation and viability are uncoupled biological processes with respect to BPA enzyme treatment. Non-isothermal bioreactors are a useful tool for the bioremediation of aqueous solutions polluted by BPA, which is an example of an endocrine disruptor that belongs to the alkyl phenol family.     

Organic compounds in tire particle induce reactive oxygen species and heat-shock proteins in the human alveolar cell line A549

Debris produced from the attrition of tires of motor vehicles constitutes 5-7% of the atmospheric particulate matter (PM10). Debris particles are indeed small enough to enter human lung and thus morphological and chemical characterization has been performed. We demonstrated that the organic fraction of tire debris induces a dose-dependent increase in cell mortality, DNA damage, as well as a significant modification of cell morphology at the dose of 60 microg/ml, which may correspond to the quantity present in the air humans inhale daily. The present research aims at investigating if reactive oxygen species (ROS) production and Hsp70 expression are involved in the cascade of toxic effects produced on the A549 cell line, as it has been suggested for the ultrafine atmospheric particles and diesel exhaust. To this end, cells were exposed at the doses of 10, 50, 60, 75 microg/ml of TD organic extract (TDOE) and analyzed at different exposure time. ROS were detected by the oxidation of 2'7'-dichlorodihydrofluorescein diacetate to dichlorofluorescein, and fluorescence was measured by flow cytometry. Hsp70 protein expression was determined by immunochemical analysis, and protein expression quantification performed by optical densitometry. ROS production was analysed after 2 h of treatment. A statistically significant increase in fluorescence was observed and the intensity of the stress response was parallel to the increasing concentrations used. An evident increase of Hsp70 expression at lower doses (10, 50 microg/ml) and at longer exposure times (72 h) was observed, during the time that our previous studies showed that cell viability, plasma membrane integrity, and DNA molecules were not affected. Thus it can be deduced that the increase in Hsp70 expression protected the cells from those damages, which became evident at the higher doses, and that this parameter might be used as a sensitive indicator of exposure. These data suggest that ROS production may be the first event caused by A549 exposure to TDOE and this result is in line with other evidences provided for the role of ROS generation in ultrafine PM toxicity. It can be suggested that this event induces an overexpression of Hsp70 only at the lower doses and longer exposure time, when cells still appear unaffected. Subsequently when ROS generation reaches high levels, a general inhibition of protein synthesis probably occurs, culminating in cell toxicity.     

Characterisation of chlorinated,brominated and mixed halogenated dioxins,furans and biphenyls as potent and as partial agonists of the Aryl hydrocarbon receptor

The Aryl hydrocarbon receptor (AhR) binds a variety of chlorinated and brominated dioxins, furans and biphenyls. Mixed halogenated variants have been recently identified in food at significant levels but full characterisation requires potency data in order to gauge their impact on risk assessment. Rat H4IIE and human MCF-7 cells were treated with various mixed halogenated ligands. Antagonist properties were measured by treating cells with various concentrations of TCDD in the presence of EC₂₅ of the putative antagonist. Measurement of CYP1A1 RNA was used to quantify the potency of agonism and antagonism. The PXDDs were found to be slightly less potent than the corresponding fully chlorinated congeners with the exception of 2-B,3,7,8-TriCDD which was 2-fold more potent than TCDD. PXDFs and non-ortho-PXBs were found to be more potent than their chlorinated congeners whilst several mono-ortho-substituted PXBs were shown to have partial agonistic properties. REPs were produced for a range of mixed halogenated AhR-activating ligands providing a more accurate estimation of potency for risk assessment. Several environmentally abundant biphenyls were shown to be antagonists and reduce the ability of TCDD to induce CYP1A1. The demonstration of antagonism for AhR ligands represents a challenge for existing REP risk assessment schemes for AhR ligands.     

遥感降水产品在澜沧江流域径流模拟中的适用性研究

以澜沧江流域为研究区域,基于实测降水数据,从日尺度、月尺度到年尺度分别评价了TRMM 3B42 V7、CMORPH CRT、TRMM 3B42 RT、PERSIANN 4种遥感降水产品在格网尺度上的精度,并用实测降水数据和筛选出的精度较高的遥感降水产品驱动SWAT模型进行了径流模拟,以进一步探究遥感降水产品在澜沧江流域的适用性。结果表明：4种遥感降水产品在日尺度上精度都不高,与实测降水的相关系数都低于0.5。从整体看,TRMM 3B42 V7精度最高,月、年尺度下与实测降水的相关系数依次为0.95、0.90,CMORPH CRT精度稍低于TRMM 3B42 V7,其在月、年尺度下与实测降水的相关系数依次为0.89、0.77,TRMM 3B42 RT和PERSIANN精度较差,两者在不同时间尺度下与实测降水的相关系数都较低,基本都维持在0.5以下;径流模拟结果发现TRMM 3B42 V7和CMORPH CRT两种遥感降水产品对流域出口断面日、月径流模拟的能力均不如实测降水,但整体上三者都能够较好地反映出实测径流变化的趋势,三者径流模拟对应的纳西效率系数NS在0.65~0.94范围内;从纳西效率系数NS看,三者对应的数值相差幅度极小,从多年平均径流RE看,三者都表现出低估的情形,但与前两者（低估值在 -4%~-10% 范围内）相比,CMORPH CRT（低估值在 -10%~-20% 范围内）低估的幅度较大;TRMM 3B42 V7在整体上的径流模拟效果优于CMORPH CRT,在澜沧江流域具有更好的径流模拟适用性。     

21世纪三峡库区中雨以上日数的情景预估

利用用于IPCC AR4的全球气候模式产品，验证其对三峡库区极端降水指数中雨以上日数（R10）模拟能力的基础上，对模拟能力较好的模式进行组合，同时考虑模式的偏差，预估高（A2）、中(A1B)、低(B1)3种排放情景下未来21世纪三峡库区R10的变化。不同排放情景下未来三峡库区R10的变化存在差异。与目前气候（1980～1999年）相比，未来整个21世纪（2011～2100年），A2情景下三峡库区R10平均减少1.7 d，A1B情景下平均减少0.3 d，B1情景下平均增加0.2 d，3种情景平均将减少0.6 d。21世纪初期（2011～2040年）、中期（2041～2070年）和后期（2071～2100年），A2情景下三峡库区R10减少都最多，分别平均减少2.5、1.5和1.0 d；3种情景平均分别减少1.4、0.2和0.1 d。〖