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      SEDIMENT-ASSOCIATED PESTICIDES IN AN URBAN STREAM IN GUANGZHOU, CHINA: IMPLICATION OF A SHIFT IN PESTICIDE USE PATTERNS : Sediment-associated pesticides in an urban stream in China

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      Environmental Toxicology and Chemistry

      Wiley-Blackwell

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          Most cited references 24

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          How well can we predict the toxicity of pesticide mixtures to aquatic life?

          Results of publised pesticide mixure toxicity experiments conducted with aquatic organisms were compiled and evaluated to assess the accuracy of predictive mixture models. Three types of models were evaluated: Concentration addition (CA), independent action (IA), and simple interaction (SI). The CA model was the most often tested (207 experiments), followed by SI (59) and IA (37). The reviewed experiments are listed in the Supplemental material to provide a resource for future investigators. The predictive accuracy of each model was quantified for each experiment by the model deviation ratio (MDR), which was calculated by dividing the predicted toxicity by the observed toxicity. Eighty-eight percent of all experiments that evaluated the CA model had observed effective concentrations within a factor of 2 of predicted values (MDR values from 0.5-2.0). The median MDR was 1, about 5% of MDRs were less than 0.5, and about 5% were greater than 2, indicating unbiased estimates overall. The predictive accuracy of CA and IA models was influenced, however, by the different modes of action (MOA) of the pesticides. For experiments with pesticides with the same MOA, CA more accurately predicted effective concentrations for more experiments compared to IA, which tended to underpredict toxicity. The IA model was somewhat more accurate than the CA model for most mixtures with different MOAs, but in most cases there were relatively small differences between the models. Additionally, 80% of SI experiments had an MDR value below 2.0 despite a bias towards experiments that are likely to have an interaction. Thus, results indicate that the CA model may be used as a slightly conservative, but broadly applicable model with a relatively small likelihood of underestimating effects due to interactions.
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            Occurrence of fipronil and its biologically active derivatives in urban residential runoff.

             Wan Gan,  S Bondarenko,  L Oki (2012)
            Insecticides are commonly used around homes for controlling insects such as ants, termites, and spiders. Such uses have been linked to pesticide contamination and toxicity in urban aquatic ecosystems. Fipronil is a relatively new and popular urban-use insecticide that has acute toxicity to arthropods at low-ppb levels. In this study, we collected runoff water from 6 large communities, each consisting of 152 to 460 single-family homes, in Sacramento County and Orange County, California, and evaluated the occurrence of fipronil and its biologically active derivatives over 26 months under dry weather conditions. Statistical modeling showed that the levels of fipronil and derivatives in the runoff water were both spatially and temporally correlated. More than 10-fold differences were observed between the Sacramento and Orange County sites, with the much higher levels for Orange County (southern California) coinciding with heavier use. The median concentrations of combined fipronil and derivatives for the Orange County sites were 204-440 ng L(-1), with the 90th percentile levels ranging from 340 to 1170 ng L(-1). These levels frequently exceeded the LC50 values for arthropods such as mysid shrimp and grass shrimp. The highest levels occurred from April to October, while decreases were seen from October to December and from January to March, likely reflecting seasonal use patterns and the effect of rain-induced washoff. Fipronil and fipronil sulfone (oxidation derivative) each accounted for about 35% of the total concentrations, with desulfinyl fipronil (a photolytic product) contributing about 25%. Results of this study clearly established residential drainage as a direct source for pesticide contamination in urban waterways, and for the first time, identified fipronil as a new and widespread contaminant with potential ecotoxicological significance.
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              Pyrethroid insecticides and sediment toxicity in urban creeks from California and Tennessee.

              Pyrethroid pesticides have replaced organophosphates for many urban applications, including structural pest control, landscape maintenance, and residential home and garden use. This study was intended to determine if pyrethroids are detectable and widespread in diverse urban systems and if concentrations are high enough to cause associated aquatic toxicity. Urban creeks in California and Tennessee were tested on up to four occasions for pesticide residues in sediments, and aquatic toxicity was determined by acute toxicity tests using the amphipod, Hyalella azteca. In California, 12 of the 15 creeks tested were toxic on at least one sampling occasion, and sediment pyrethroid concentrations were sufficient to explain the observed toxicity in most cases. The pyrethroid bifenthrin, due to its high concentrations and relative toxicity as compared to other pyrethroids, was likely responsible for the majority of the toxicity at most sites. Cypermethrin, cyfluthrin, deltamethrin, and lambda-cyhalothrin also contributed to toxicity at some locations. The source of cypermethrin and deltamethrin was probably almost entirely structural pest control by professional applicators. Bifenthrin, cyfluthrin, and lambda-cyhalothrin may have originated either from professional structural pest control or from lawn and garden care by homeowners. None of the sediments collected from the 12 Tennessee creeks were toxic, and pyrethroids were rarely detectable. Regional differences between Tennessee and California are possibly attributable to climate, differences in types of residential development, and pesticide use practices.
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                Author and article information

                Journal
                Environmental Toxicology and Chemistry
                Environ. Toxicol. Chem.
                Wiley-Blackwell
                07307268
                May 2013
                May 29 2013
                : 32
                : 5
                : 1040-1047
                Article
                10.1002/etc.2147
                © 2013

                http://doi.wiley.com/10.1002/tdm_license_1.1

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                Self URI (article page): http://doi.wiley.com/10.1002/etc.2147

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