National Contaminant Occurrence Database (NCOD)

Drinking water contaminant occurrence data maintained by the U.S. Environmental Protection Agency (EPA). The data includes measurements of chemical, microbial, and radiological contaminants collected from 1988 to the present. This information supports EPA regulatory decision-making, research, and public transparency under the Safe Drinking Water Act.

Use Cases

• Analyzing trends in regulated contaminant levels based on the Six-Year Review datasets mentioned in the description
• Identifying potential emerging risks from unregulated contaminants based on the Unregulated Contaminant Monitoring Rule data
• Supporting regulatory impact assessments using the chemical, microbial, and radiological measurement data
• Conducting longitudinal studies on drinking water quality using data collected since 1988

Strengths

• Data collection spans from 1988 to the present, providing a long-term temporal scope
• Includes measurements for chemical, microbial, and radiological contaminant types as stated
• Sourced from authoritative EPA regulatory reviews and monitoring rules

Limitations

• Column-level documentation is absent; field semantics must be inferred after download
• Row count is unknown, which may limit suitability assessment
• Description metadata is limited; actual data quality requires manual inspection after download

Provenance

Source

U.S. Environmental Protection Agency (EPA)

Collection Method

Collected from EPA's Six-Year Reviews of national drinking water regulations and Unregulated Contaminant Monitoring Rule datasets

Time Range

1988 to present

Freshness

Last updated 2026-05-04 15:58:28; freshness should be verified

Geography

United States (implied by EPA jurisdiction and Safe Drinking Water Act)