Abstract
BackgroundLocation is often an important component of exposure assessment, and positional errors in geocoding may result in exposure misclassification. In rural areas, successful geocoding to a street address is limited by rural route boxes. Communities have assigned physical street addresses to rural route boxes as part of E911 readdressing projects for improved emergency response. Our study compared automated and E911 methods for recovering and geocoding valid street addresses and assessed the impact of positional errors on exposure classification.MethodsThe current study is a secondary analysis of existing data that included 135 addresses self-reported by participants of a rural community study who were exposed via public drinking water to perfluorooctanoate (PFOA) released from a DuPont facility in Parkersburg, West Virginia. We converted pre-E911 to post-E911 addresses using two methods: automated ZP4 address-correction software with the U.S. Postal Service LACS database and E911 data provided by Wood County, West Virginia. Addresses were geocoded using TeleAtlas, an online commercial service, and ArcView with StreetMap Premium North America NAVTEQ 2008 enhanced street dataset. We calculated positional errors using GPS measurements collected at each address and assessed exposure based on geocoded location in relation to public water pipes.ResultsThe county E911 data converted 89% of the eligible addresses compared to 35% by ZP4 LACS. ArcView/NAVTEQ geocoded more addresses (n = 130) and with smaller median distance between geocodes and GPS coordinates (39 meters) than TeleAtlas (n = 85, 188 meters). Without E911 address conversion, 25% of the geocodes would have been more than 1000 meters from the true location. Positional errors in TeleAtlas geocoding resulted in exposure misclassification of seven addresses whereas ArcView/NAVTEQ methods did not misclassify any addresses.ConclusionsAlthough the study was limited by small numbers, our results suggest that the use of county E911 data in rural areas increases the rate of successful geocoding. Furthermore, positional accuracy of rural addresses in the study area appears to vary by geocoding method. In a large epidemiological study investigating the health effects of PFOA-contaminated public drinking water, this could potentially result in exposure misclassification if addresses are incorrectly geocoded to a street segment not serviced by public water.
Highlights
Location is often an important component of exposure assessment, and positional errors in geocoding may result in exposure misclassification
Participants were all residents of three towns in Wood County, West Virginia located near the Ohio River who were exposed to PFOA via public drinking water serviced by the local water district
Bearing in mind the small numbers, our analysis showed that the county Enhanced 911 (E911) data table appears to perform better than the Locatable Address Conversion System (LACS) database in ZP4, substantially converting more self-reported addresses
Summary
Location is often an important component of exposure assessment, and positional errors in geocoding may result in exposure misclassification. Successful geocoding to a street address is limited by rural route boxes. Communities have assigned physical street addresses to rural route boxes as part of E911 readdressing projects for improved emergency response. Our study compared automated and E911 methods for recovering and geocoding valid street addresses and assessed the impact of positional errors on exposure classification. An additional concern for rural areas is that successful geocoding of these newly converted addresses is limited by the accuracy of street map files and their ability to keep pace with E911 readdressing projects. As part of the exposure assessment for community health studies investigating the potential health effects of perfluorooctanoate (PFOA, C8), addresses of residents living in the mid-Ohio River Valley will be geocoded http://www.c8sciencepanel.org/index.html. The settlement established a Science Panel of public health scientists to assess whether or not there is a probable link between PFOA exposure and disease in the community
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