Wash. state releases Seattle air study

Wash. state releases Seattle air study A major air quality study to be officially released this week will show that South Seattle residents, including the Port of Seattle, may face theoretically higher risks of cancer from air pollution.
   The study was requested by Georgetown and South Park residents in South Seattle and was conducted by the Washington State Department of Health in conjunction with the U.S. Department of Health and Human Services' Agency for Toxic Substances and Disease Registry.
   The WSDOH undertook the study not as a 'final step of the assessment process, but an initial step to identify priorities for future work in the area.'
   Fifty-five percent of pollutants in the south Seattle-area are from motor vehicles, according to the study. Diesel-powered vehicles 'are the leading contributors to theoretical cancer risk near roadways,' the study said.
   Other significant sources of air pollution found by the study include industrial emissions at 13 percent, woodstoves and fireplaces at 9 percent, and outdoor burning at 4 percent. Lawnmowers, boats and other recreational vehicles, aircraft and trains accounted for the remaining 19 percent.
   The study specifically modeled exposure levels for six 'criteria' air pollutants classified by the U.S. EPA: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter and sulfur dioxide (SO2). Criteria pollutants are characterized as being common, originating from many different sources, and with the potential to cause harm to human health, the environment, and property. The study also looked at other toxic compounds that, while not being defined as criteria pollutants, still may find their way into the local environment.
   Four major findings of the study are:
   ' On-road mobile sources contribute to the highest risks near major roadways over a large area of south Seattle.
   ' Risks and hazards are greatest near major highways and drop dramatically about 220 yards from the center of highways.
   ' Point sources, especially those that emit chromium compounds, have the potential to impact residential areas in south Seattle resulting in increased theoretical cancer risk.
   ' Wood stove/fireplace used in the winter season contributes to health risk.
   Despite the determinations, the study's authors acknowledge that much of the findings are based on hypothetical exposure rates and not on real world measurement. Due to a lack of sampling data — only one sampling station in the port area and four others through the entire South Seattle area — study authors were forced to extrapolate much of the air quality concentrations projections through computer modeling. For example, in the Georgetown area, diesel particulate matter was not actually measured during the study and all estimations of this pollutant, often seen as smokestack soot, were entirely modeled by the computer for the area.
   'Exact agreement between the modeled and monitored levels is not expected because of many factors including the accuracy of emissions inventory from all sources, the fact that air models are not expected to be exact, and monitors have analytical limitations,' the study said. 'Although monitoring would be preferred, it is neither practical nor possible to sample continuously for numerous pollutants at an infinite amount of points in an area.'
   In addition, due to the computer modeling method used, the study erred on the side of greater exposure, leading to higher estimations of theoretical cancer risk.
   “Maybe it’s a little worse than what it looks like, based on the model,” Wayne Clifford, director of the state Health Department’s Office of Environmental Health Assessments told the Seattle Press-Intelligencer. “We try not to be alarmist but also to deliver what is the public health message here, based on what this data says: There is an increased cancer risk.”
   However, study authors also warned the study is only a tool and not a predictor of real-world illnesses.
   'Risk estimates generated by a health risk analysis should not be interpreted as the expected rates of disease in the exposed population but rather as estimates of potential risk, based on current knowledge and a number of assumptions,' the study said.
   In addition, the study also made six recommendations for future action:
   ' Refine the point source emissions inventory so priorities can be identified and pollutant control strategies can be developed.
   ' Determine wood stove and fireplace usage in the South Seattle area and the need for a focused wood stove change-out program.
   ' Determine impacts from other mobile sources that were not included in this assessment, including port operations, rail operations and King County Airport.
   ' Clean Air and other regulatory air agencies (and Ecology) should consider cumulative impacts from all emission units at each facility when issuing air permits.
   ' Health agencies should partner with regulatory agencies to increase education about air pollution and steps individuals can take to reduce exposure.
   ' Land use decisions should be made with an attempt to protect sensitive individuals from areas where air pollution is expected.