Trends in nitrate levels in Iowa's community water systems (2000-2022): Characteristics of systems vulnerable to maximum contaminant level exceedances and future regulatory scenarios

S M Samiul Islam; David M Cwiertny; Ibrahim Demir

doi:10.1002/jeq2.70189

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Trends in nitrate levels in Iowa's community water systems (2000-2022): Characteristics of systems vulnerable to maximum contaminant level exceedances and future regulatory scenarios

Journal article

Open access

Peer reviewed

Trends in nitrate levels in Iowa's community water systems (2000-2022): Characteristics of systems vulnerable to maximum contaminant level exceedances and future regulatory scenarios

S M Samiul Islam, David M Cwiertny and Ibrahim Demir

Journal of environmental quality, Vol.55(3), e70189

05/2026

DOI: 10.1002/jeq2.70189

PMID: 42065233

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Abstract

This study examines trends in nitrate contamination in Iowa's community water systems (CWS) from 2000 to 2022, focusing on the characteristics of CWS that are most vulnerable to elevated nitrate levels and those likely to be impacted by a lower maximum contaminant level (MCL). Using Safe Drinking Water Act (SDWA) compliance data for CWS currently without nitrate removal, we analyzed nitrate levels across CWS types, source water type, well characteristics, and geography. Results show that large CWS serving >100,000 people frequently exceed 5 mg-N/L due to their reliance on surface water that is vulnerable to non-point source pollution. Small systems (<10,000 consumers) often exhibit episodic spikes in nitrate, often during spring and early summer, coinciding with fertilizer use and rainfall-driven leaching. Shallow and pre-1990 wells were disproportionately affected. Geospatial mapping analysis identified nitrate hotspots in agriculturally intensive regions. A future MCL based on an annual average of 5 mg/L-N would only affect ∼25 CWS annually, far fewer than those impacted under a scenario where any instance above 5 mg/L-N would be a violation. These data-driven findings support future policy for nitrate regulation and drinking water protection.

Environmental Monitoring

Drinking Water

Iowa

Nitrates - analysis

Non-Point Source Pollution - legislation & jurisprudence

Non-Point Source Pollution - statistics & numerical data

Water Pollutants, Chemical - analysis

Water Pollution, Chemical - legislation & jurisprudence

Water Pollution, Chemical - statistics & numerical data

Water Supply - statistics & numerical data

UIOWA OA Agreement

Details

Title: Subtitle: Trends in nitrate levels in Iowa's community water systems (2000-2022): Characteristics of systems vulnerable to maximum contaminant level exceedances and future regulatory scenarios
Creators: S M Samiul Islam - University of Iowa
David M Cwiertny - University of Iowa
Ibrahim Demir - Tulane University
Resource Type: Journal article
Publication Details: Journal of environmental quality, Vol.55(3), e70189
DOI: 10.1002/jeq2.70189
PMID: 42065233
ISSN: 1537-2537
eISSN: 1537-2537
Publisher: Wiley
Grant note: 2230710 / National Science Foundation
Language: English
Date published: 05/2026
Academic Unit: Center for Health Effects of Environmental Contamination; Civil and Environmental Engineering; Injury Prevention Research Center; Chemistry; Chemical and Biochemical Engineering
Record Identifier: 9985157522802771

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