Industries Tally Air Pollution Poorly
Raloff, Janet, Science News
Companies in the United States that annually spew 100 tons or more of smog-forming volatile organic chemicals (VOCs) must provide the federal government with a quantitative breakdown of those emissions. These inventories--best estimates of releases from various processes, operations, and plumbing--often fall somewhere between fantasy and fraud, a new study reports.
Most policy makers "assume these numbers are gospel" and use them to fine-tune smog-control strategies, observes Ronald C. Henry of the University of Southern California in Los Angeles, who led the study. The faulty inventories can hurt public and polluter alike, he argues, if they lead to costly process- or pollution-control changes that provide little smog relief.
The state of Texas employed Henry to help home in on the sources and conditions most responsible for Houston's continuing smog-ozone problem--the nation's second worst. He applied a sophisticated mathematical formula to the data collected over 6 months by an automated air-sampling monitor. This device provides hourly parts-per-billion readings of more than 50 different industrial smog-fostering VOCs in Houston air.
By correlating the hourly VOC readings with wind direction and speed in this leading petrochemical hub, Henry could project not only where many VOCs originated but also "how many [different industrial] sources there must have been and what the composition of their emissions was." This approach works, he explains, because each source tends to emit its own signature mix of VOCs over time, though quantities may vary. In a test in Atlanta, the technique successfully apportioned VOCs to their largely vehicular sources.
By comparing the chemical signatures detected and the reports from each Texas firm upstream of the monitor, Henry's team found that, with a few notable exceptions, industrial inventories appear very "inaccurate" in terms of location, composition, and emission rates. The researchers describe their findings in the June 24 Proceedings of the National Academy of Sciences. …