Texas A&M associate professor of atmospheric sciences at Texas A&M University found that air pollution in Houston is 67 percent to 150 percent above the government's National Ambient Air Quality Standard (NAAQS) and could cause serious health problems for the millions of people who live in Houston and the surrounding areas.
In his study funded by the Texas Air Research Center and NASA, Renyi Zhang used a chemical transport model to examine Houston's air quality. The chemical transport model evaluated emissions from different sources and examined how the air chemistry and meteorological transport in Houston affects the air quality, Zhang said.
Large amounts of volatile organic compounds and nitrogen oxides are emitted into the air every day from cars and petrochemical plants and refineries in the Houston area. The air quality is the worst during the day because the sun causes these volatile organic compounds to react with the nitrogen oxides to produce high levels of ozone in the air, Zhang said.
John Nielsen-Gammon, A&M professor of atmospheric sciences, said the pattern of air currents in Houston adds to the problem of concentrated ozone in the area.
"Houston is subject to frequent brief periods of air stagnation and recirculation due to the effect of the sea breeze cycle," Nielsen-Gammon said. "These periods allow emitted pollution to build up in a single, concentrated location in the atmosphere."
During the day, the ozone level in Houston soars above the NAAQS and poses a serious threat to the health of people who live there. The government standard for ozone concentration in an area is 120 pats per billion (PPB) air, and on hot summer afternoons, the ozone concentration in Houston can escalate to 200 PPB or 300 PPB, Zhang said. Ozone is a poisonous gas, and is dangerous for humans and animals to breathe.
"There are around five million people in the greater Houston area," Zhang said. "And many of these people could (develop) health problems associated with breathing bad air, such as emphysema and asthma."
At night, the ozone level falls drastically, almost to zero. This occurs because the industrial plants continuously emit nitric oxide throughout the night, which removes the ozone in the air and results in a "hole" of surface ozone over Houston, Zhang said.
Zhang said these results suggest that a decrease in emissions that lead to the formation of ozone is necessary to control the dangerous ozone levels in Houston.
"Houston has some of the worst ozone levels in the country, due to its large population and surrounding industries," Zhang said. "(Houston contains) nearly 50 percent of the nation's petroleum refining capability."
Zhang said regular control of the emissions from these refineries and plants would help the ozone levels stay lower and would improve the quality of the air in Houston.
"Reduction needs to be made for emissions from industry, such as power plants, refineries, and petrochemical plants," Zhang said.
"Alternative energy sources and a more efficient means of transportation are also needed."
Nielsen-Gammon agrees that the high ozone levels in Houston are a substantial concern and that there needs to be more control of emissions that lead to the formation of ozone to make the air safer for people to breathe.
"The problem is so severe that reductions in pollution will have to come from all segments of society," Nielsen-Gammon said. "For example, speed limits are already low in the Houston area (and) industry will be responsible for cutting a larger fraction of their emissions than will most other pollution sources."
Nick Shaver, a sophomore aerospace engineering major, lives in downtown Houston and is concerned about the high ozone levels in the area.
"I think the government has a responsibility to try to control the harmful emissions in order to make a safer environment," Shaver said. "As I see it, the problem can only get worse, and I don't want future generations to have health problems because power plants would rather be cost efficient than environmentally safe."
