You are here:
GIS ANALYSIS FOR EPIDEMIOLOGIC RECREATIONAL WATER SUTDIES
Citation:
Sams, E A., R L. Calderon, T. J. Wade, M. Beach, K P. Brenner, A. H. Williams, AND A P. Dufour. GIS ANALYSIS FOR EPIDEMIOLOGIC RECREATIONAL WATER SUTDIES. Presented at International Society for Environmental Epidemiologists, New York, New York, August 1-4, 2004.
Description:
Introduction: The Beaches Act of 2000 requires that the Agency develop new rapid method water quality indicators (2 hours or less) that predict whether or not coastal water is safe for swimming. This new set of water quality indicators must be validated through the epidemiologic studies (NEEAR Water Study).
Geographic information tools, such as GIS, can be a valuable addition to the new epidemiologic assessments of recreational water exposure. Past epidemiologic research that formed the basis for the current water quality standards did not incorporate GIS, although positional location was noted. For example, a recent epidemiologic study conducted in Santa Monica, CA, noted a relationship between the proximity of self-reported swimming and a point source of potential fecal contamination. Thus, the 1986 Ambient Water Criteria were only based on general beach locations to identify participant location. Accordingly, it is difficult to make spatial comparisons between the participant exposure in relation to their environment. Integration of GIS technology in future epidemiologic water studies will enable scientists to refine data collection and analysis.
The objective of utilizing GIS in the NEEAR Water Study study is to assess the relationships between environmental exposure and the demographic variables and spatial distribution of beach-goers.
Methods: Depending on the beach length and target population density, an approximate center point was chosen to include all beachgoers. The beach area chosen for water quality sampling was divided into 20 meter increments beginning at the approximate center and extended outward on either side. Within this target area, all beachgoers were approached and asked to participate in the study. Geographic Positioning System (GPS) coordinates were collected for each beach-goer prior to participant enrollment, and at each transect prior to water sample collection. Environmental measurements, including air and water temperatures, rainfall, wind speed and direction and cloud cover also were collected when water samples were taken each day.
Results: GIS analyses of environmental exposure and beach-goer location will be presented. Results for these basic study questions will include:
1. Can spatial correlation between the beach-goer location and subsequent illness and point source of fecal contamination be established?
2. Are the data collected a spatially representative sample of the beach-goer population?
3. Does the spatial distribution of beachgoers differ by age, race, gender and other demographic variables?
4. Are there systematic differences between the distribution of swimming and non-swimming beach-goers?
5. Do the health effects of beach-goers differ, according to their location?
6. Do weather conditions and other environmental factors affect the spatial distribution of beach-goers and their subsequent health?
Discussion: GIS is a tool that can characterize spatial relationships between study participants, geographical characteristics, and other study interests. This spatial information, in combination with known health effects of each of the participants, is expected to be valuable in describing the beach-going population ( hypothesis-generation and the identification of confounding factors).