Data collected by the Texas Commission on Environmental Quality and analyzed by the city show that 13 monitors that track benzene saw increases in the amount of time that benzene concentrations exceeded healthy levels.
"It's not looking good," Elena Marks, the mayor's health policy director, said in Sunday editions of the Houston Chronicle.
It appears the chemical industry and the city are headed for a showdown. Industry officials dispute claims that benzene levels are rising. They rely on different data that includes measurements from 2004 to 2006.
Russ Roberts, a spokesman for the East Harris County Manufacturer's Association, said data just released by the federal Environmental Protection Agency showed a 12 percent decline in Harris County benzene emissions from 2004 to 2006.
"The mayor has promised to applaud industry for benzene reductions," Roberts said. "If those aren't numbers that can be applauded, then I'm not sure what we can do for the city of Houston."
The EPA report relies on self-reported data from the companies.
"These are industry-reported estimates of emissions," said Matthew Tejada, executive director of the Galveston-Houston Alliance for Smog Protection. "If the numbers do not line up with monitor results, then something is wrong."
Marks said the mayor will put more emphasis on the air-quality monitors.
"What we care about are the ambient air levels, because that's what people are breathing," she said.
In November, a report from the Houston Regional Air Quality Task Force recommended 18 steps for reducing toxic chemicals in the city's air such as benzene and chlorine.
The measures include petrochemical plants installing infrared cameras to identify emissions from roof storage tanks and other equipment. The task force also called for new programs to reduce car and truck emissions.
The plan sought to stem an effort by the mayor to regulate local polluters and avoid a standoff between the city and its powerful chemical industry.
"If we have eight meetings about this, but the level of benzene goes up, the community has been defrauded," White said then.