Is natural openness or trade policy good for the environment?

In this paper, we estimate the individual effects of natural openness and trade policy on air pollution. Natural openness is the component of the trade share (imports and exports as a percentage of GDP) attributable to population, geography and factor endowment differences. We find that natural openness reduces air pollution, while trade policy has a limited impact. The implication is that 'natural' geographic and endowment differences play a more important role than deliberate trade policy decisions in explaining the trade and environment link.