Disclaimer

Last updated: April 2026

Informational use only

AirHistory publishes data, scores, rankings, and analysis about U.S. air quality and pollution monitoring. Everything on airhistory.org is provided for general informational and educational purposes only. It is not professional advice and should not be relied on as the sole basis for any consequential decision.

Nothing on airhistory.org constitutes financial, legal, medical, tax, investment, real-estate, insurance, or engineering advice. Always consult a qualified, licensed professional for decisions that affect your money, health, safety, legal status, or property.

Data source and accuracy

The underlying data displayed on airhistory.org is derived from the EPA Air Quality System (AQS). We do our best to process that data faithfully, but we make no representations or warranties — express or implied — about the completeness, accuracy, reliability, suitability, or availability of any information, analysis, or related graphics.

Source records may contain errors, be incomplete, be reported late, or be restated by the issuing agency after publication. Where the source corrects a record, AirHistory will follow on the next refresh — but there may be a lag. Always verify any figure against the original source before acting on it.

How we process this data: We aggregate EPA AQS monitor-by-monitor readings into annual averages for ozone, PM2.5, PM10, NO2, SO2, CO, and lead, then compute county- and state-level trends over the full reporting history. Pages surface both the raw EPA AQI and plain-English day counts in each AQI bucket so readers can skip the jargon.

Refresh cadence: Refreshed from the EPA AQS API roughly every four months, tracking the cadence at which EPA closes out each reporting quarter.

Known limitations of this source: AQS data lags real-world readings by several months because states run quality checks before submitting monitor data to EPA, and not every county has a monitor — rural counties are often represented by the closest upwind monitor rather than a local one.

No warranties

airhistory.org is provided on an "as is" and "as available" basis, without warranty of any kind, either express or implied, including but not limited to warranties of merchantability, fitness for a particular purpose, non-infringement, or course of performance.

No professional relationship

Reading, using, linking to, or sharing airhistory.org does not create any advisor-client, attorney-client, doctor-patient, or fiduciary relationship between you and AirHistory or its operators.

Third-party links and advertising

airhistory.org contains links to third-party websites and displays advertisements served by third parties (including Google AdSense). We do not endorse, control, or assume responsibility for the content, products, services, or practices of any third party. Following a link or clicking an ad is at your own risk.

Rankings and scores

Any rankings, grades, or composite scores published on airhistory.org are editorial opinions derived from public data using documented methodologies. They are not professional certifications, accreditations, or endorsements, and they are not a substitute for independent due diligence.

Limitation of liability

In no event will AirHistory, its operators, contributors, or data providers be liable for any loss or damage — including, without limitation, indirect, incidental, consequential, or punitive damages, or any loss of profits, data, or goodwill — arising out of or in connection with the use of airhistory.org or reliance on any information it contains.

External sites

When airhistory.org links out to government agencies, research organizations, or news publications, those external sites are governed by their own terms and privacy policies. AirHistory is not responsible for their content or practices.

Changes to this disclaimer

We may update this disclaimer at any time. Continued use of airhistory.org after changes are posted constitutes acceptance of the updated disclaimer. The "Last updated" date above reflects the most recent revision.

Contact

Questions about this disclaimer or a specific page? [email protected].