Exposure assessment is an essential part of epidemiological studies evaluating the health effects of atmospheric environments. Asian dust exposure has been assessed by using 1) particulate matter concentration, 2) visibility, and 3) extinction coefficients for non-spherical particles measured by light detection and ranging (LIDAR). We evaluated the association between Asian dust exposure and emergency ambulance dispatches using a LIDAR-derived extinction coefficient for nonspherical particles in Nagasaki. In this study, we examined how the altitude and the cut-off values of extinction coefficient to determine that the Asian dust exposure influenced the magnitude of health effects estimated to result from Asian dust exposure. We found an increasing risk of emergency ambulance dispatches for Asian dust exposure at and above the cut-off level of 0.07/km dust extinction coefficient.The effect estimates were greater when dust extinction coefficients at a lower altitude were used.