This paper reports a test of the endowment effect in an economic analysis of localized air pollution. Regression techniques are used to test the significance of perceived property rights on household WTP for improved air quality versus WTA compensation to forgo an improvement in air quality. Our experiment contributes to the research into the WTP/WTA divergence by providing a new basis for supporting the existence of an endowment effect. Our results are in contrast to recent work by Shogren et al. which supports the substitution proposition of Hanemann while rejecting the endowment effect.