The Greater Houston Region is growing by leaps and bounds—in 2011, our region’s population topped six million people! More people mean more cars, more miles traveled by those cars, more construction and lawn equipment, and more demand for electric power. All of those sources of emissions, combined with emissions from Houston’s businesses and industries, have the potential to create a lot more ozone pollution. But the opposite happened – ozone levels in Houston were 18% lower in the year 2012 than in 2000.

How did this happen? Ozone is formed when two types of chemicals—volatile organic compounds (VOC) and nitrogen oxides (NOx) combine on hot, sunny days with little or no wind. Some years the weather is more favorable for making ozone and some years the weather is less favorable, so we often see small year-to-year changes in ozone levels. But the real story is the reductions that have been made in the chemicals that form ozone.

There are dozens of regulations that have been adopted by the Texas Commission on EnvironmentalQuality (or TCEQ), the U.S. EPA, and local government agencies as well as voluntary actions that have been taken by business and industry. In addition, many citizens have made lifestyle changes that have reduced pollution.


These bar charts show emissions from all of the different types of sources of VOC and NOx—industry, small business and consumers, off-road equipment, and cars and trucks. Between 2002 and 2011 (the last year for which we have data), total emissions of NOx decreased by 44%, and VOC emissions decreased by 28%.

Source: (pages 2-15)