Area-Based Geocoding: An Approach to Exposure Assessment Incorporating Positional Uncertainty.

Area of Science:

• Environmental epidemiology
• Geographic Information Systems (GIS) in public health
• Exposure science

Background:

• Accurate spatial resolution of exposure surfaces is crucial for health risk assessment.
• Limitations in precisely locating individuals in space hinder accurate exposure assessment.
• Geocoding uncertainty can significantly affect environmental exposure estimations.

Purpose of the Study:

• To evaluate the impact of geocoding uncertainty on ambient pesticide exposure and breast cancer risk estimation.
• To compare traditional point-based geocoding with a novel area-based geocoding method.
• To assess how different geocoding approaches influence odds ratio estimates in a case-control study.

Main Methods:

• A case-control study was conducted in California's Central Valley.
• Residential and occupational histories were collected and geocoded using both point-based and area-based methods.
• Ambient pesticide exposure and breast cancer risk were estimated using both geocoding approaches.

Main Results:

• Area-based geocoding, retaining the complete address match area, provided different exposure classifications and odds ratio estimates compared to point-based geocoding.
• Odds ratio estimates varied by at least 6% and up to 35% depending on the pesticide.
• The direction and magnitude of differences in odds ratios were pesticide-specific.

Conclusions:

• Geocoding methodology is critical for accurate exposure estimation in epidemiological studies.
• Area-based geocoding offers a more nuanced approach by accounting for geocode quality and potential exposure areas.
• Future exposure assessments should prioritize considering geocode certainty and quality beyond simple exclusion of low-quality points.