Spatial Risk Issues

SADA will convert any geospatial estimation map into a geospatial risk map. This conversion is performed by using each modeled block concentration value as the exposure concentration in the risk models.

From a risk standpoint, individual block risk may not provide useful information, especially for small block sizes. The scenario parameters often assume the receptor will be exposed to the contaminant over a number of years. This translates into an assumption that the individual will be exposed to a single block for a number of years and/or a large portion of the day. For small block sizes (e.g., 1ft x 1ft), this is not reasonable. However, for block sizes that are equivalent to the exposure area, block sizes can give an accurate perspective on the potential areas of concern at the site.

The spatial risk map does, however, provide useful information from a decision standpoint. With the risk map visible, areas of concern are more easily identified. These areas can then be captured within a reasonable exposure unit size by polygons. By pressing the Statistics button on the main toolbar, the average risk over these blocks in the polygon can be calculated by selecting "Mean". Note: this corresponds to averaging the block concentration values for the polygonal area and applying the result to the risk models.

Spatial risk maps play important roles in other decision frameworks, as well. See area of concern maps, probability maps, area of concern boundary sample design, and minimizing/maximizing area of concern sample design.

SADA provides three spatial risk maps for human health: data screen map, point risk map, and contoured risk map.