This paper investigates how openness to international goods markets affects
pollution concentrations. We develop a theoretical model to divide trade's
impact on pollution into scale, technique, and composition effects and the
n examine this theory using data on sulfur dioxide concentrations. We find
international trade creates relatively small changes in pollution concentra
tions when it alters the composition of national output. Estimates of the t
rade-induced technique and scale effects imply a net reduction in pollution
from these sources. Combining our estimates of all three effects yields a
somewhat surprising conclusion: freer trade appears to be good for the .