Ecotoxicity of pesticides

The DEMETRA project [20, 26] represents the first important case of a European project to develop QSAR models for regulatory purposes. DEMETRA developed five free models to determine the ecotoxicity of pesticides using endpoints that include trout, daphnia, bees, and quails (oral and dietary exposure). Since the target was to develop models for the user, these five endpoints were decided by them, not by the developers. 

In this chapter, we use data on the ecotoxicity of pesticides and their associated transformation products to illustrate the relationships between parent and transformation product toxicity we describe the possible reasons why a transformation product may be more ecotoxic than its parent compound and explore the use of predictive models for estimating the ecotoxicity of transformation products in the absence of data. Finally we discuss the concept of parent compound and metabolite interactions and discuss how the risks of these mixture, which will occur in the natural environment, can be assessed. 

As discussed earlier extensive data are available on the ecotoxicological effects of pesticide transformation products whilst only limited ecotoxicological data are available on the ecotoxicity of transformation products of other classes of compound such as human and veterinary pharmaceuticals, industrial chemicals and biocides. Generally transformation products are considered to be less toxic to non-target organisms, however some exhibit an equivalent or increased potency when compared to the parent compound. Therefore, in the following sections we take data on the aquatic (daphnid) and terrestrial (earthworm) ecotoxicity of pesticide transformation products and compare this to data on the ecotoxicity of the associated parent pesticide in order to explore the relationships between parent and transformation product ecotoxicity in aquatic and terrestrial systems. 

Sinclair CJ, Boxall ABA (2003) Assessing the ecotoxicity of pesticide transformation products. Environ Sci Technol 37 4617-4625... 

Oxime carbamates are generally applied either directly to the tilled soil or sprayed on crops. One of the advantages of oxime carbamates is their short persistence on plants. They are readily degraded into their metabolites shortly after application. However, some of these metabolites have insecticidal properties even more potent than those of the parent compound. For example, the oxidative product of aldicarb is aldicarb sulfoxide, which is observed to be 10-20 times more active as a cholinesterase inhibitor than aldicarb. Other oxime carbamates (e.g., methomyl) have degradates which show no insecticidal activity, have low to negligible ecotoxicity and mammalian toxicity relative to the parent, and are normally nondetectable in crops. Therefore, the residue definition may include the parent oxime carbamate (e.g., methomyl) or parent and metabolites (e.g., aldicarb and its sulfoxide and sulfone metabolites). The tolerance or maximum residue limit (MRL) of pesticides on any food commodity is based on the highest residue concentration detected on mature crops at harvest or the LOQ of the method submitted for enforcement purposes if no detectable residues are found. For example, the tolerances of methomyl in US food commodities range from 0.1 to 6 mg kg for food items and up to 40 mg kg for feed items. ... 

Kenaga, E. E. (1980) Predicted bioconcentration factors and soil sorption coefficients of pesticides and other chemicals. Ecotox. Environ. Saf. 4, 26-38. 

In response to the concern expressed by the shellfish farmers operating in the Ebro River delta about the potential positive role of pesticides on the oyster and mussel mortalities observed in the area, our group, commissioned by and with the collaboration of the Catalan Water Agency (ACA), carried out a comprehensive study in which chemical and toxicity data were combined to assess potential toxic presures present in the delta. To this end, a combined approach scheme integrating the measurement of various general physicochemical parameters in water, quantitative chemical analysis of pesticides in water and biota, and ecotoxicity assays in water was applied to a series of samples collected at springtime (between mid-April and mid-June 2008) from six selected sites of the delta the two (northern and southern)... 

Acheta domestlcus. toxicity of aminocarb, 218-20 Additives for spray dispersion performance, 100-15 ecotoxicity, 351-61 Adsorption of pesticides in aquatic sediment, 267 in soil, 195-96 Aerial applicators, exposure monitoring, 323-29... 

US Environmental Protection Agency [USEPA], Office of Pesticide Programs, Environmental Fate and Effects Division. 2001. Environmental effects database (EEDB). ECO-TOX Database System, http //www.epa.gov/ecotox/ (accessed July 23, 2005). 

Very recently the EC funded project DEMETRA (http //www.demetra-tox. net) developed a series of QSAR models for the prediction of toxicity of pesticides toward five endpoints trout, daphnia, quail (oral and dietary exposure), and bee [80]. This project introduced a number of innovative issues, compared to previous QSAR models. The target of the project was to develop models for pesticides to be used for regulatory purposes in accord with European legislation. A questionnaire was distributed to a great many end-user to identify their needs. The endpoints to be modeled were chosen from among those defined in writing by the end-user, and not by the modeler, in order to make the models as useful as possible. This attention to the needs of the end-users is unique in the use of QSAR for ecotoxicity prediction. Other novel... 

The results gained with the ecotoxicity tests are presented in Table 5.2.4. With its standard application times, Microtox test showed positive results (inhibition 9.8%) only for PAHs, (RM14) after 15 min, which means that this tests is not sensitive to the presence of pesticides at the tests concentration ranges. The Daphnia test detected the presence of both target compound groups, however, only with 48 h of tests time. It proved more sensitive to present concentration of pesticides than PAHs. The Tham-nocephalus test was the most sensitive out of the applied ones for pesticides, but did not react at all to the PAH concentration of RM14. 

The answer to this question is yes For example, EMs are useful for extrapolating recovery processes and identifying the ecological relevance of effects observed in standard lab tests, in particular for birds and mammals. However, care must be taken not to model only species that are used in generation of standard ecotox endpoints because these are often chosen for their ease of culture rather than for the representativeness of their life histories. It is important to include vulnerable species in order to get a representative picture of the effects of pesticides on nontarget organisms (Chapter 4). 

Abstract While a large hody of information is available on the environmental effects of parent chemicals, we know much less about the effects of transformation products. However, transformation products may be more toxic, more persistent and more mobile than their parent compound. An understanding of the ecotoxicity of transformation products is therefore essential if we are to accmately assess the environmental risks of synthetic chemicals. This chapter therefore uses data on pesticides and their transformation products to explore the relationships between parent and transformation product ecotoxicity to aquatic and terrestrial organisms and describes the potential reasons why a transformation product may be more toxic than its parent compound. As it is not feasible to experimentally assess the ecotoxicity of each and every transformation product, this chapter also describes and evaluates the use of expert systems, read-across methods and quantitative structme activity relationships for estimating transformation product ecotoxicity based on chemical structme. Finally, experimental and predicted ecotoxicity data are used alongside monitoring data for parent pesticides and their transformation products to illustrate how the risks of parent and transformation product mixtiu es can be assessed. 

In order to explore the relationships between parent and transformation product ecotoxicity to invertebrates, data relating to the acute aquatic ecotoxicity of transformation products and their respective pesticides to the water flea Daphnia sp. were collated. The majority of data points were for the species Daphnia magna whilst some data were for either Daphnia pulex or undefined daphnid species, all these data were treated as comparable. Data collection focused on the end-point stipulated in the OECD guidehne, 48 h ECso (immobilisation) [16]. Data collection principally focused on pesticides evaluation documents and were supplemented with data collated for the EU SEEM project [17]. Where multiple values were identified for a pesticide or transformation product a geometric mean value was used. Where transformation product ecotoxicity data were identified in the evaluation documents with no respective pesticide data, alternative data sources were used to provide a comparison [18,19]. Initially 255 pesticide/transformation product data comparisons were identified which comprised 120 pesticides and 245... 

To undertake an assessment of the different approaches an experimental ecotoxicity data set was generated by randomly selecting fifty transformation products from the daphnid data set described previously. An assessment of the predictive performance of five techniques was undertaken by comparing predictions from each approach to the experimentally determined data. The data set included transformation product ecotoxicity data from a range of pesticide classes, i.e. insecticides, herbicides and fungicides and chemical classes, e.g. organophosphorus insecticides, sulfonylureas and azoles. 

Most work on transformation product ecotoxicity has been done on transformation products of pesticides. While some data are available for other transformation products (e.g. veterinary medicines, industrial chemicals and pharmaceuticals), these data are quite limited. We should begin to assess the effects of transformation products from these other groups and establish whether the relationships described in this chapter for pesticides hold true for the wider chemical universe. 

Most ecotoxicity is linked to the use of pesticides. The use of formalin in disinfection plays a smaller role, although as discussed above exposure in enclosed environments is not modelled. In industries dominated by smallholders with low capital, it is crucial to train farmers to use these effectively and safely, as incorrect practices can incur serious health risks. For a more complete assessment of occupational health risks in sericulture and reeling, USEtox should be used in conjunction with models to assess indoor exposure (see, e.g. Rosenbaum, 2014). 

Dutta K, Bhattacharyay D, Mukherjee A, Setford SJ, Tumta- APF, Sarkar P (2008) Detectirai of pesticide by polymeric enzyme electrodes. Ecotox Envirrai Safe 69(3) 556-561. doi 10. 1016/j. ecoenv.2007.01.004... 

Are there also negative impacts for the technology Most likely, although these are not quantified in the analysis. If one increases the growth of soybeans for the production of the resin, then one may need to convert forested land into farmland, resulting in a loss of biodiversity. In addition, increased use of fertilizers and pesticides leads to increased eutrophication of lakes and streams. One should also evaluate the ecotoxicity of the pesticides and their impact on wildhfe. While a full environmental assessment is needed to properly evaluate this new process, even a preliminary analysis suggests the value of this particular innovation. 

With improvements in scientific knowledge and related technology, there is an expectation that more environmentally friendly pesticides will continue to be introduced, and that ecotoxicity testing procedures will become more sophisticated. There is much interest in the introduction of better testing procedures that work to more ecologically relevant end points than the lethal toxicity tests that are still widely used. Such a development should be consistent with the aims of organizations such as FRAME and ECVAM, which seek to reduce toxicity testing with animals. Mechanistic biomarker assays have the potential to be an important part of... 

Walker, C.H. (2006). Ecotoxicity testing of chemicals with particular reference to pesticides. Pest Management Science 62, 571-583. 

Sabaliunas, D. and Sodergren, A. 1996, Uptake of organochlorine pesticides by solvent-filled cellulose and polyethylene membranes. Ecotox. Environ. Safe. 35 150-155. 

The PAN Pesticide Database brings together a diverse array of information on pesticides from many different sources, providing human toxicity (chronic and acute), ecotoxicity and regulatory information for about 5400 pesticide active ingredients and their transformation products, as well as adjuvants and solvents used in pesticide products. ... 

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