Air quality in Contra Costa County, California, United States of America today

Mr. Duck’s Air Quality Score

Moderate air today for Contra Costa County, California, United States of America

⚠️ This website is currently under active development. Some data may be incomplete or temporarily inaccurate. For health-critical decisions, please verify information through official government or environmental sources.

Categories follow US EPA AQI breakpoints for PM (estimate from latest valid measurements; this project does not compute EPA NowCast/24-hour AQI yet).

This friendly indicator summarizes the latest city readings. For health guidance, please see: EPA AirNow or WHO.

Air quality today

The air quality in Contra Costa County, California is currently classified as Moderate. The primary pollutant identified is PM2.5 (fine particles), with a measured concentration of 9.02 µg/m³ based on eleven valid observations reported through OpenAQ.

These measurements reflect the present conditions without implying any trend or cause. This page is informational; for health guidance, use official sources such as EPA AirNow or WHO.

Latest sensor values

PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).

What the data includes

The dataset for Contra Costa County pulls OpenAQ readings from five monitoring sites and a total of twenty‑nine individual sensor records. It covers seven measured pollutants: carbon dioxide (CO₂), particulate matter 1 µm (PM1), PM2.5, PM10, relative humidity, temperature and particle count (UM003). The most recent observations for the majority of these variables were recorded on 2026‑02‑11 at 01:00 UTC, so the freshest data are only a few days old. An exception is CO₂, whose last update time is not reported, and PM10, which comes from an older entry dated 2025‑01‑13 23:00 UTC and is flagged as “old”.

Across the recent measurements, concentrations show a fairly wide spread. For PM2.5 the values range from about 2.5 µg/m³ up to 25.2 µg/m³ with a median of roughly 11.3 µg/m³; PM1 varies between 2.0 and 14.3 µg/m³, centering near 8.4 µg/m³. Relative humidity sits between 50 % and 64.6 %, median 54.5 %; temperature spans 10.8 °C to 22 °C with a typical value of 15.3 °C. Particle counts (UM003) are especially variable, from roughly 417 to 2 518 particles per cm³, median about 679. The single CO₂ reading sits in a narrow band around 411‑426 ppm, but without a timestamp its relevance is uncertain.

Because the data set contains only a handful of stations and several pollutants have limited or outdated entries, conditions can differ noticeably across the county and over time. Users should keep in mind that the freshest snapshot reflects a specific moment at Oakridge for most variables, while other locations such as Diablo contribute older PM10 values, highlighting uneven spatial coverage within the overall picture.

Learn more about sources and filtering: About the data.

Trusted references: WHO (Air pollution) · US EPA AirNow · European Environment Agency (Air)

Latest sensor values (bars)

PM categories follow US EPA AQI breakpoints, shown here as an estimate derived from the latest valid measurements (this project does not compute EPA NowCast/24-hour AQI yet).

Data notes

The data shown reflects 11 valid measurements and is Updated today (last refreshed at 2026‑02‑11T01:00:00+00:00). These values represent a snapshot of air quality across Contra Costa County, California, and may not capture short‑term fluctuations or differences between neighborhoods. Conditions can change rapidly; for the most current information, consult real‑time monitoring stations or local advisories.

OpenAQ station rows