Pollution Exposure Risk in Washington State

Superfund, Brownfield, and Air Facility System sites are sources of pollution that can impact a community’s health, safety, and quality of life. The point sources vary in intensity and geographic impact:

• Superfund sites are designated by the EPA as the worst hazardous sites in the United States. Soil and groundwater contamination are the two greatest risks posed by Superfund sites.
• Brownfields are actually assessed as having “no or limited health risks to communities,” these sites are more numerous and widespread than Superfund sites. They can have secondary impacts of lowering property values, and the site is often used as an unofficial waste dump. 
• Air Facility System locations have a wider impact area, as the pollution travels by air as well as by water, soil, and direct contact with the source. Air pollution is particularly harmful to at risk populations such as young children and elderly adults.

This analysis will assess the combined impact of these pollution point sources in Washington State using data from the EPA's Environmental Dataset Gateway.

Methodology

This analysis begins with a Kernel Density analysis on each pollution point source dataset. All Kernel Density analyses used a cell size of 2000m. However, the search radius varied in conjunction with the estimated reach of each pollutant's impact.

• Search Radii
• Superfund sites: 6,400m 
• Although these sites are areas of more intense toxicity, their impact on the local community would most likely occur through soil or water contamination rather than air.The EPA points out that, “Some pollutants spread quickly, contaminating ground water several miles from the site.” This assessment, therefore, used a search radius of four miles from Superfund sites.
  
• Brownfield sites: 6,400m
• Similar reasoning was used for assessing the potential impact distance for Brownfield sites. These sites will be differentiated from Superfund sites during the weighting process.
• Air Facility sites: 32,000m
•  Air influence is difficult to assess without local conditions and terrain information. This study used only a 20 mile wedge to the North and Southeast because the mountainous terrain inhibits pollution traveling to the east of Tacoma and Seattle, two of the largest air polluters in the state.

The non-zero values of each dataset were classified using a Natural Breaks structure, resulting in 4 classes of 'No Risk,' 'Low Risk,' 'Medium Risk,' and 'High Risk.' Each dataset was then weighted according to the level of estimated impact in the area of influence.

	Risk Level / Actual Value
Risk Factor	0	1	2	3	Weight
Superfund	0	( 0 : 0.01]	( 0.01 : 0.03]	( 0.03 : 0.08 ]	5
Brownfield	0	( 0 : 0.05]	( 0.05 : 0.20 ]	( 0.2 : 0.40 ]	1
Air Facility	0	( 0 : 0.0036]	( 0.0036 : 0.0123 ]	( 0.0123 : 0.274 ]	3

This methodology is limited by the uniformity of the analysis. Local conditions, including terrain, urbanization, and land cover are not taken into consideration in this model. Furthermore, the variation in pollution levels from each site are not considered.

Results

Kernel Density Analysis

Individual Density analysis was conducted on each dataset, producing results such as those displayed above for Superfund Sites, and below for Air Facility Sites.

Reclassification and New Calculations

The density results were then reclassified, assigning values of 0-3 for no, low, medium, and high risk areas. The results of this reclassification were used to calculate a new raster surface in which each pollutant surface was weighted using the following formula:

Total Risk = (5 x Superfund Risk) + (3 x Air Facility Risk) + (Brownfield Risk)

Zonal Statistics for each county calculated the median risk for each county, and the two results were combined to visualize the risk for each county in Washington State.

Exposed Populations

Certain populations, typically young children and elderly adults, are more susceptible to the impacts of pollution. Air pollution in particular is often cited for higher asthma attacks in both populations.

	Total Exposed		Vulnerable Populations
Median  Risk	Exposed      Counties	Population	Children Under 5	Adults Over 65
None	30	1,535,516	101,437	195,168
Low	1	109,006	6,718	15,034
Medium	7	4,300,033	270,615	427,393
High	1	240,745	15,536	24,553

Kitsap County is the only county with combined high exposure risk. The 16.65% of the county's population is vulnerable based solely on age. Conducting further analysis on vulnerable populations with consideration to income or education may reveal further vulnerability that could be addressed through state or county programs to increase awareness in the impacted communities.

Final Thoughts

Combining risk factors that vary in intensity and geographic influence provides a unique perspective on the variety of ways that we distribute pollutants through our soil, water, and air. The results would be greatly improved by adding terrain and land cover data to assess the flow of pollutants through the water and soils, while details on local air flow patterns will improve analysis of Air Facility pollutant impacts. Nonetheless, this analysis can assist state, county, and local communities when contaminants are found, as well as for planning future housing and medical facilities.