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China is among the greatest emitters of air pollution in the world and one concern is the effects of intercontinental air pollution traveling across the Pacific Ocean from China to the U.S. We exploit a natural experiment by observing the effects of changes in intercontinental air pollution associated with Chinese New Year, a 7-day national holiday, and sandstorms from China on air quality and morbidity in California. The timing of these events are unlikely correlated to other factors affecting air quality and health in California. Chinese New Year follows the Lunar New Year which varies each traditional calendar year while sandstorms are a naturally occurring phenomenon. We examine effects on morbidity using restricted emergency department and inpatient hospitalization data for the universe of patients with respiratory and heart disease between 2005 and 2012 in California. This is the first study to use patient-level data to examine the effects of trans-Pacific air pollution from China on morbidity in the U.S. We show that heavy sandstorms are associated with a modest increase in acute respiratory disease per capita, representing 0.5–4.6% of average weekly hospitalizations. However, we find no significant effect on morbidity in California from Chinese New Year. Results suggest that policymakers could prepare for changes in air quality following major sandstorms in China.Heavy sandstorms are a major pollution source in China.Trans-Pacific air pollution from sandstorms in China affect health in California.Policymakers could plan for worsened air quality in California following sandstorms.