| Summary: | The potential risk of Bt (Bacillus thuringiensis) crops on non-target organisms (NTOs) has drawn a lot of public concerns. Despite a series of risk assessments of Bt crops on NTOs has been conducted, a quantitative approach which could support a precise judgment of their safety is required. In the present work, hazard quotient (HQ) was applied in the safety evaluation of three Bt rice events (Cry1Ab, Cry1C and Cry2Aa rice) on NTOs. Eight NTOs in different functional guilds associated with Bt rice were selected to conduct the tests. The results showed that the HQs of three Bt rice events for eight NTOs were all below the trigger value 1, while the HQ of Cry1Ab rice for one target pest Chilo suppressalis was three times higher than 1. Our results assured the reliability of the HQ and indicated that the three Bt rice events would pose no risks to the eight NTOs. Further testing of three Bt proteins on biological parameters of one NTO Nasonia virtipennis under no observed adverse effect concentration (NOAEC) confirmed the robustness of HQ assessment. We recommend that the HQ could be applied in tier-1 risk assessments of Bt crops on NTOs as a reference data standard, which would provide more clear and credible safety information of transgenic crops for the public and policy makers.
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