中文摘要
关于转基因（GM）作物的公共争论集中于环境和健康风险，但证据仍然有限，且主要集中于耐除草剂品种或局部暴露，使抗虫作物的广泛后果尚不明确。抗虫作物可减少农药使用，并产生超越直接暴露农户的健康效应。然而其净效应并不明确，因为任何环境收益都可能被作物替代、害虫抗性、工业扩张和土地利用变化所抵消。我们利用 Bt 棉花在中国各地的分批批准，并结合将棉花种植区与下游居民联系起来的河网。Bt 棉花的批准使下游五岁以下儿童死亡率显著下降4.2%，其驱动因素是农药使用减少和水质改善。总体而言，Bt 棉花的批准使全国农药使用量减少3.2%。研究结果表明，抗虫转基因作物的社会价值可能被显著低估，因为它们通过环境溢出产生了正向健康外部性。
Abstract
Public debates on genetically modified (GM) crops center on environmental and health risks, yet evidence remains limited and focuses largely on herbicide-tolerant varieties or on local exposure, leaving the broad consequences of insect-resistant crops unclear. Insect-resistant crops can reduce pesticide use and generate health effects beyond directly exposed farmers. Yet their net effects are ambiguous, as any environmental gains may be offset by crop substitution, pest resistance, industrial expansion, and land-use change. We exploit the staggered approval of Bt cotton across China, combined with river networks that link cotton-growing areas to downstream residents. Bt cotton approval leads to significant downstream reductions in under-five mortality by 4.2%, driven by reduced pesticide use and improved water quality. In aggregate, Bt cotton approval reduces national pesticide use by 3.2%. The findings show that the social value of insect-resistant GM crops can be significantly underestimated, as they generate positive health externalities through environmental spillovers.