| The fundamental concern about agricultural chemicals is their environmental fate and toxicologic risk to humans and other non-targeted animals. The application of pesticides to soil is typically direct or through post-emergence methods. Degradation of pesticides is typically considered to be a detoxification process and, therefore, a positive thing; but, evidence is insufficient to conclude that degradation always yields detoxification. While clay minerals are often regarded as catalysts for enhancing or decreasing the availability of pesticides to microorganismal degradation, recent studies have found that the iron (Fe) oxidation state in smectites directly affects the degradation of pesticides without microbial intervention. Yet, what does degradation mean when attempting to assess toxicologic risk? The objective of this study was to measure the influence of Fe oxidation state on the toxicity of pesticides to mammalian cells. Alachlor, oxamyl, dicamba, and 2,4-D were reacted with both oxidized and reduced ferruginous smectite (SWa-1). The supernatant from each pesticide/clay mixture was separated by centrifugation, filter sterilized, and used in multiple toxicity assays including those for cytotoxicity and genotoxicity. Results revealed that treatment with reduced smectite produced mixed effects on mammalian cell health, depending on the pesticide. Oxamyl and alachlor reacted with reduced SWa-1 showed a decrease in their overall cytotoxic potential. In addition, oxamyl showed a decrease in its overall genotoxic potential. Dicamba reacted with the reduced-clay treatment was more cytotoxic and genotoxic then the other treatments. Finally, no differences were observed between redox treatments for 2,4-D. The significance of these results is that oxidized smectites have virtually no influence on the toxicity of pesticides; whereas, reduced-Fe smectite plays a definite role in altering the cytotoxic and genotoxic potential of some agricultural pesticides. These results suggests Fe oxidation state of clay minerals should be taken into account in pesticide management programs. |
