This paper extends the argument in H.L.A. Hart's 'Are there any natural rights?' to argue that there is an environmental moral right against pollution. This right is composed of a right against negligent, reckless or intentional risk imposition, together with the liberty to act in a way that does not negligently, recklessly or intentionally impose risks on others. This right is understood as overrideable or prima facie, and this paper does not claim that this right is the only basis of (...) moral judgment in the cases it considers. The hypothesis that there is a right against pollution does, however, explain some moral reasoning about pollution that otherwise is difficult to explain. (shrink)