Although ozone levels have recently declined, Houston still has ample amounts of the ingredients necessary to form ozone in the atmosphere. With the petrochemical industry composing a substantial portion of Houston’s economic base and a population of around 6 million people, the Greater Houston Area produces substantial amounts of NOx and VOCs, both through industrial processes and vehicle miles traveled.
Additionally, these chemicals enter into a climate that is excellent for ozone production with an average high temperature of 79 °F and approximately 2,600 hours of sunlight each year. (source)
Geography also plays a role in Houston’s elevated ozone levels. Because we are located so close to the Gulf of Mexico, we can rely on sea breezes to circulate ozone clouds around the city and its surrounding areas, providing both a medium of transportation for ozone and preventing its dispersion.
Houston Ozone Levels
Although Houston continues to make great strides to improve its air quality and to reduce ambient ozone levels, the city has not met the national ozone attainment standard since it began in 1971. This is due in part to the fact that the national standard changes as new health data becomes available, and it is very difficult to accurately define which sources are contributing to high ozone levels. Without accurate source apportionment models, it is impossible to know which sources to control. Despite these difficulties, Houston has made significant progress. A recent report put out by the City of Houston (source)demonstrates 87.5% of the area’s monitors have a statistically significant improving trend in at least one ozone metric for the five year period from 2004 to 2009.