ADDITIONAL INFORMATION ON DIFFERENT DRIVING TIMES TO SHARPS AND PHARMACEUTICAL WASTE COLLECTION SITES
As discussed in the Audit Results, we defined reasonable access to sharps and pharmaceutical waste collection sites as a 20‑minute driving distance. We based this distance on market analyses for trading and economic areas and studies that discuss access to health care, which provide examples of a 10-minute to 30-minute drive time used as a measure of accessibility or trade areas. An example of such a study is Northern Illinois University’s Measures of Spatial Accessibility to Health Care in a GIS Environment: Synthesis and a Case Study in the Chicago Region, which used a driving time of 30 minutes as a service area threshold. We recognize that individuals use means of transportation other than driving their own vehicles, but we believe our approach provides a reasonable basis for estimating the percentage of Californians who have reasonable access to collection sites. However, our sources, and therefore our analysis, did not differentiate consistently between those pharmaceutical waste collection sites that do and do not accept controlled substances.
Table A provides our estimates for the total population that has access to sharps and pharmaceutical waste collection sites within a driving time of between 10 minutes and 30 minutes. We based our analysis on census block groups—statistical divisions of census tracts that the U.S. Census Bureau generally defined to contain between 600 and 3,000 people. To ensure that we did not overestimate these populations, we counted the population of a census block group only when it was wholly within the service area radius covered by the driving time. Thus, we did not count the entire population of a census block group if any part of it was outside of the driving‑time radius. This method of analysis is less appropriate when judging access to collection sites within very short drive times. For example, when we limit the driving time to five minutes, the service areas are disconnected and small, with the driving‑time radius cutting through many urban census block groups and not fully covering larger suburban and rural blocks. As the service area increases to 10 minutes, the driving‑time radius becomes larger and it is increasingly integrated because the service areas from individual collection sites merge into unified service areas. As a result, using a driving time of 10 minutes or greater reduces the margin of error for our estimates.
|Service Area Radius (in Minutes of Drive Time)||Population in Service Area||Percentage||Population in Service Area||Percentage|