Pesticides transformation products

L. Somasundaram and. R. Coats, eds.. Pesticide Transformation Products Fate and Significance in the Environment, ACS Symposium Series No. 459, American Chemical Society, Washington, D.C., 1991, 308 pp. 

Camper, N.D. Effects of pesticide degradation products on soil microflora, in Pesticide Transformation Products. Fate and Significance in the Environment, ACS Symposium Series 429, Somasundaram, L. and Coats, J.R., Eds. (New York American Chemical Society, 1991), pp. 205-216. 

Miles, C.J. Degradation products of sulfur-containing pesticides in soil and water in Pesticide Transformation Products. Fate... 

Another import field of development is the investigation of pesticides transformation products in food. Some examples are the investigation of the acaricide amitraz and its transformation products, 2,4-dimethylaniline (DMA), 2,4-dimethylformamidine (DMF), and N-2,4-dimethylphenyl-N-methylformamidine (DMPF) in pears [220] Antioxidant pesticides as well as their metabolites used in postharvest treatment have been investigated in pears and apples with concentrations in the ranges 0.002-0.672 ng/g (ethoxyquin), 0.94-11.86 ng/g (imazalil), 0.024-0.902 ng/g (diphenylamine), 0.012-2.59 ng/g (thiabendazole). 

TABLE 16.16 Some Pesticides and Pesticide Transformation Products Listed as Hazardous Air Pollutants0... 

Pesticide Transformation Products Fate and Significance in the Environment... 

Numerous studies worldwide have documented the presence of pesticide transformation products in the environment [27-32]. The below investigations are provided as examples documenting the importance of including transformation products for pesticide studies of both streams and ground-water. 

Fig. 2 Seasonal variability of pesticides and pesticide transformation products near the headwaters and the mouth of the Iowa River, 1996-98 [41]. Total parent compoimd concentration was the sum of detected concentrations for 21 agricultimal herbicides, three nonagricultiu al herbicides, and nine insecticides. Total transformation product concentration was the smn of detected concentrations for seven chloroacetanilide transformation products and four triazine transformation products...

The availabiUty of partition coefficients between and/or solubilities for water, organic matter and air, i.e., Kh and Koc, Sw (water solubiUty), V p (vapor pressure), and Kow, is usually fairly good for most industrial compoimds. However, partitioning data are scarce for transformation products. Whereas we were still able to find experimental Koc values for 18 of the 53 pesticide transformation products introduced in Sect. 3.4, no such information is usually available for transformation products of other compound classes. 

Except for pesticides, some high-production-volume chemicals and, more recently, some pharmaceuticals and biocides, measured half-hves are usually scarce. Experimental half-hves for transformation products, except for soil half-hves of some well-known pesticide transformation products, are usually not available. Therefore most of the degradation information entered into multispedes multimedia models is estimated. 

Fig. 8 Comparison of BIOWIN PSM output with experimental soil half-lives for 38 pesticides and pesticide transformation products. In addition, three possible methods for translating BIOWIN PSM output into actual half-lives are also indicated EPISuite translation rules with modifications for PSM scores <2.25 as suggested in [60] (indicated as EPISuite Soil ), the Arnot et al. [61] regression and our own regression based on the pesticide data. The finely dashed lines indicate uncertainty intervals of a factor of ten around the EPISuite translation rules. Reprinted with permission from [62], p 688. (2006) Swiss Chemical Society...

For reasons discussed in preceding chapters, there is a concern, as well as an uncertainty, regarding the identity and concentrations of the wide array of transformation products that are entering the environment (including drinking water supplies) from wastewater treatment plants and other sources. There are even more uncertainties with respect to which transformation products are commonly formed within water treatment plants, as well as their fate after formation. Detailed study of the formation, identity, and fate of pesticide transformation products in drinking water treatment is of considerable interest and is the subject of ongoing research (e.g., Adams et al. 2007). 

The environmental risk and human-health risk of these transformation products are related, in both cases, to a combination of exposure and toxicity. Each synthetic organic chemical entering a treatment plant could form many different transformation products via oxidation, hydrolysis, reduction, and/or biodegradations. Thus, thousands of transformation products are possible, many of which are difficult or impossible to analyze, and most of which have not yet been identified analytically. Sinclair et al. (2006) addressed this issue for pesticides used in the United Kingdom (UK) and the United States (US) by prioritizing the risk associated with pesticide transformation products. The pesticide degradates that have been identified with the highest risk are tabulated in Tables 1 and 2 for the UK and US, respectively. 

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. 

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... 

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

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