A Survey of Recreational Activity To Determine Site-specific Exposure Frequencies for Use in Human Health Risk Assessment. H. Bruckert, M. H. Henning, N. D. Wilson, and T. R. Barber, ARCADIS, N.D. Wilson & Associates, LLC
When defining exposure parameter values for use in human health risk assessment, exposure frequencies are typically based on default values or professional judgment. However, in the case of recreational scenarios, default values are not available and actual exposure frequencies are likely to be highly site-specific and variable. In the summer of 2001, a human use survey was designed and conducted to determine exposure frequencies for child and adult recreators using a small creek system in southwestern Ohio. This twelve-week non-interrupt survey documented the variety, locations and frequency of human use activities in the creek. The stratified random sampling design ensured that data collected covered the range of possible observation times and locations and that the surveyors’ behaviors were not predictable (and therefore avoidable) by people who use the creek. The survey design was stratified by day type (i.e., weekday vs. weekend/holiday), time of day, starting reach and whether the survey moved progressively upstream or downstream. A survey form was developed in a software package for use on a personal digital assistant (PDA). The creek was divided into seven reaches that were each visited for 30 minutes per observation day. During each visit, the survey team recorded the location, time of day, cloud cover, temperature, precipitation and wind conditions at the site. If recreators were observed, a record was made of their activities, gender, approximate age, identifying features and if the person had been observed before. By using descriptive statistics to calculate extrapolation factors from the percentage of yearly recreational opportunities that were observed, site-specific population sizes and exposure frequencies for each activity and age group were determined. The maximum number of angler-days per year was determined to be 13. This observation provided strong evidence that the stream is not utilized for subsistence angling.
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