Houston / Galveston Area
The Houston/Galveston/Brazoria area has unique challenges because it is home to the largest petrochemical complex in the world and has a large urban population. Several of the area petrochemical plants emit highly reactive volatile organic compounds (HRVOCs), which under certain circumstances will create ozone faster than anywhere else in the country. Houston, as all large cities, also has a significant level of emissions from motor vehicles which cannot be ignored.
There are challenges to the Houston/Galveston/Brazoria area air quality model. Although the model meets the EPA's quality assurance criteria, 
some research suggests that significant changes must be made to improve the model accuracy and identify the proper control strategies. There are no plans to change the model episode, however new data is continually being incorporated into the model to improve performance.
During TexAQS 2000 aircraft measurements found that almost without exception transient, high level ozone plumes originated from the Houston Ship Channel. Other measurements suggested that VOC emissions from the petrochemical industry were roughly 6 times higher than the number reported. This has raised new concerns about the accuracy of emissions estimating techniques such as AP-42.
Downtown Houston has a high level of NOx due to the high density of motor vehicles. Although NOx is one of the main ingredients that forms ozone, very high levels of NOx actually decrease ozone concentrations. To some extent, as NOx levels are lowered, ozone levels will rise. In order to resolve this issue both NOx and VOCs must be reduced significantly.
Several significant control strategies have been implemented in industry to reduce pollutants over the past few years, including regulations on furnaces and boilers creating a reduction in NOx by 80%. On January 1, 2006 new regulations will apply to flares and cooling water towers to reduce VOCs.
The counties in the HGB area are: Galveston, Harris, Brazoria, Waller, Fort Bend, Liberty, Chambers and Montgomery.
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