Data Visualization in Environmental Public Health: From Data to Insight
Figure 5 Choropleth Map Example: Inspection Violation Rates by ZIP Code
Choropleth Maps Choropleth maps use shading or color to represent values within geographic areas such as census tracts, ZIP Codes, cities, or service districts. The color variations make it easy to identify geographic patterns and compare locations at a glance. Examples include: • Childhood lead exposure rates
• Foodborne illness rates • Inspection activity rates • Environmental justice indicators
Choropleth maps work best for displaying rates, percentages, or other normalized values. Mapping raw counts can be misleading because larger geographic areas or more populous communities naturally tend to have higher totals. For example, a map showing the number of complaints could primarily reflect where more people live. In contrast, a map showing complaint rates could provide a more meaningful comparison of conditions across communities.
Map image is the intellectual property of Esri and is used herein under license. Copyright © 2026 Esri and its licensors. All rights reserved. Data: King County Food Establishment Inspections, 2022–2025 Sources: Esri, TomTom, Garmin, FAO, NOAA, USGS, © OpenStreetMap
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