This study investigates a new problem in the area of environmental valuation: how much is a public environmental asset worth to a private company? We ask this question in the context of dust abatement, where the asset is air quality. A company wants to know what level of dust abatement is optimal, given the engineering costs of abating and the social costs of not abating. We show that the optimal point for the company lies in between the textbook cases of so-called private optimum and social optimum, which constitute, respectively, a lower and an upper bound for dust abatement. We calculate the upper bound and provide elements for the calculation of the lower bound.