Monona County, IA

ZIP 51040

In ZIP 51040, 5 of the 12 things we check have at least one part graded D or F.

• Drinking water: Onawa Municipal Water Plant meets every EPA legal limit; 9 contaminants are above health goals, led by lead at 50× California’s Public Health Goal.
• Closer to Superfund sites than 0% of U.S. neighborhoods, with no listed site within 10 miles of its center.
• Largest share of modeled toxic air from industry: Cargill Corn Milling North America (87%), mostly acrolein.
• Fine particles (PM2.5) average 6.4 µg/m³; the WHO guideline is 5 and the EPA annual standard is 9.
• About 297,017 kg of agricultural pesticides are applied in the county each year.

Grades for ZIP 51040

• Superfund sites nearbyA
• Factories and industrial sitesA to B
• Oil and gas wellsA
• Parks and nature nearbyD
• Air qualityA
• Drinking water qualityD to F
• Pesticide useF
• Neighborhood health statusD
• Past wildfire impactsA
• Past flood impactsC
• Noise levelsA to C
• Radiation signalsD to F

Based on 4 census tracts · compiled September 10, 2026 · how each grade works and its sources

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