Do livestock environmental regulations reduce water pollution in China?

China has implemented the world's most robust regime of livestock environmental regulations (LERs) to control water pollution caused by livestock production. However, little is known about the effectiveness of LERs on water pollution and its cost-benefit. This article delves into the treatment effects of LERs on water pollution in China by using a difference-in-differences (DID) estimator based on manually collected LERs data from 101 counties in China during 2006-2017. The results show that LERs reduce chemical oxygen demand (COD) by an average of 17.82%, but have no continuous dynamic effect on COD reduction. Several robustness checks justify this finding. The heterogeneity analysis finds that the effect of LERs on water pollution is greater for counties in upstream and developed areas, and with high initial pollution levels. A back-of-the-envelope calculation indicates that the total health benefit from reduced mortality and morbidity as a result of LERs amounts to $73.27 billion-$219.53 billion, which is 2.99-8.96 times of the cost of LERs from decreased farmers' income.