Why and how do societies transform the environmental rules of economic development, or fail to do so? This article compares the experiences of Chile and Peru in the regulation of smelting activities between 1990 and 2010. Air pollution from smelters in Chuquicamata and La Oroya, each emblematic of the two countries' mining industries, did not give rise to nationally destabilising protest. Nevertheless, despite the absence of pressing discontent with pollution, the environmental rules for mining could still be improved as a result of policy network activism and through highly idiosyncratic institutional channels. The analysis shows that policy entrepreneurship for Chuquicamata was enhanced by a national institutional environment that favoured bureaucratic autonomy, while parallel action for La Oroya was constrained by a political economy of state weakness and elite disregard. © 2014 Cambridge University Press.