Scientists have known for some time that increasing amounts of air pollution come from outside the U.S. Pollutants from Asia, such as ozone and particulate matter, are carried across the oceans at high altitudes and deposited across western states. Houston is often impacted by pollutants coming from Mexico and even as far away as Africa (read more about this at https://houstonairquality.com/texas-is-in-central-american-smoke-season-will-it-impact-houston/). With the growth of the global economy, overseas pollutants will have an increasing impact on air quality in Houston and across the U.S. This contribution may limit Houston’s ability to meet national air quality standards through regional programs alone.
For a map illustrating the impact of these foreign sources, go to https://www.uschamber.com/above-the-fold/map-shows-why-epa-s-new-ozone-standard-makes-no-sense. The Environmental Protection Agency is aware of these concerns through their work to address transboundary air pollution. Read more at https://www.epa.gov/international-cooperation/transboundary-air-pollution.