We argue that misallocation across firms amplifies industrial water pollution by distorting the firm size distribution in China. Firm-level data indicate that larger firms are more likely to use clean technology but face higher distortions. In a heterogeneous firms model with an endogenous choice of pollution treatment technologies, we show that distortions that increase with firm-level TFP lower the adoption of clean technology, amplify aggregate pollution intensity, and lower aggregate output. Quantitatively, eliminating these correlated distortions would increase output by 30 percent and decrease pollution by 20 percent. Meanwhile, environmental regulations have sizable impact on pollution but limited effects on aggregate output. (JEL O13, O14, P28, P31, Q52, Q53, Q58)
