| Genetically-modified crops expressing insecticidal crystalline proteins derived from a soil bacterium, Bacillus thuringiensis (Bt), were commercialized almost two decades ago as a means to combat agricultural pests. The Bt proteins are highly specific and only lethal upon ingestion, limiting the scope of toxicity to target insects. However, evidence for risk to non-target organisms and negative public perceptions on the use of Bt crops has caused controversy surrounding their use. The objective of this research was to monitor the fate and transport of a Bt protein, Cry1Ab, in a large-scale agricultural field and in aquatic microcosms. Quantitative methods were validated using enzyme-linked immunosorbent assay (ELISA) and then used to evaluate field and laboratory samples. The highest environmental concentrations of the Cry1Ab protein were found in runoff water and sediment, up to 130 ng/L and 143 ng/g dry weight, respectively, with the Cry1Ab protein detected in both Bt and non-Bt fields. As surface runoff and residual crop debris can transport Bt proteins to waterways adjacent to agricultural fields, a series of laboratory experiments were conducted to determine the potential risk to non-target aquatic organisms. The results showed that sediment type and temperature can influence the degradation of the Cry1Ab protein in an aquatic system and that the Cry1Ab protein can persist for two months. While Cry1Ab protein concentrations measured in the field soil indicate little risk to terrestrial organisms, the consistent input of Bt-contaminated runoff and crop debris into agricultural waterways impart chronic risk to non-target aquatic species. |
