Estimating terrestrial amphibian pesticide body burden through dermal exposure

Hepatic effects of the clomazone herbicide in both its free form and associated with chitosan-alginate nanoparticles in bullfrog tadpoles

The use of agrochemicals in agriculture is intense and most of them could be carried out to aquatic environment. Nevertheless, there are only few studies that assess the effects of these xenobiotics on amphibians. Clomazone is an herbicide widely used in rice fields, where amphibian species live. Thus, those species may be threatened by non-target exposure. However, nanoparticles are being developed to be used as a carrier system for the agrochemicals. Such nanoparticles release the herbicide in a modified way, and are considered to be more efficient and less harmful to the environment. The aim of this study was to comparatively evaluate the effect of clomazone in its free form and associated with nanoparticles, in the liver of bullfrog tadpoles (Lithobates catesbeianus) when submitted to acute exposure for 96 h. According to semi-quantitative analysis, there was an increase in the frequency of melanomacrophage centres, in the accumulation of eosinophils and in lipidosis in the liver of experimental groups exposed to clomazone - in its free form and associated with nanoparticles - in comparison with the control group, and the nanotoxicity of chitosan-alginate nanoparticles. The increase of melanomacrophage centres in all exposed groups was significant (P < 0.0001) in comparison to control group. Therefore, the results of this research have shown that exposure to sublethal doses of the herbicide and nanoparticles triggered hepatic responses. Moreover, these results provided important data about the effect of the clomazone herbicide and organic nanoparticles, which act as carriers of agrochemicals, on the bullfrog tadpole liver.

Pesticide Uptake Across the Amphibian Dermis Through Soil and Overspray Exposures

For terrestrial amphibians, accumulation of pesticides through dermal contact is a primary route of exposure in agricultural landscapes and may be contributing to widespread amphibian declines. To show pesticide transfer across the amphibian dermis at permitted label application rates, our study was designed to measure pesticide body burdens after two simulated exposure scenarios. We compared direct exposures, where amphibians were present when spraying occurred, to indirect exposures, where amphibians were exposed to soils after pesticide application. During summer 2012, we reared barking (Hyla gratiosa) and green treefrogs (H. cinerea) through 60-90 days post-metamorphosis at a United States Environmental Protection Agency research laboratory. We tested exposure for 8 h to five pesticide active ingredients (imidacloprid, atrazine, triadimefon, fipronil, or pendimethalin) in glass aquaria lined with soil in the laboratory. We quantified total pesticide body burden and soil concentrations using liquid chromatography-mass spectrometry. All individuals in both treatments had measurable body burdens at the end of the study. A randomized block design analysis of variance (n = 18) showed that body burdens (p = 0.03) and bioconcentration factors (BCFs) (p = 0.01) were significantly greater in the direct overspray treatment relative to the indirect soil spray treatment for both species and tested pesticides. BCFs ranged from 0.1 to 1.16 and from 0.013 to 0.78 in the direct and indirect treatments, respectively. Our study shows dermal uptake for multiple pesticides from both direct spray and indirect soil exposures and provides empirical support for the degree to which terrestrial phase amphibians have higher body burdens after overspray pesticide exposure.