Qualité de l’air à Benicia

What causes bad air quality in Benicia?

Benicia is a small city of 28,306 located in the North Bay region of the San Francisco Bay Area. While Benicia is more sparsely populated than its Bay Area neighbors, such as San Francisco, San Jose, Walnut Creek, and Oakland, its air pollution levels were the highest of these in 2019.

Mobile sources, such as cars and trucks, comprise the largest emission source in US cities. While Benicia air quality also suffers from motor vehicle emissions, this source does not explain Benicia’s high air pollution levels relative to the Bay Area, as there are fewer cars on the road here than in surrounding cities. Rather, elevated air pollution levels in Benicia are more attributable to regional oil refineries and winter wood burning.

Benicia’s Valero oil refinery is one of the largest in the state, and has long been responsible for elevated levels of sulphur dioxide (SO₂), carbon monoxide (CO), and fine particle pollution (PM2.5) across the city.¹

In late March 2019, a malfunction caused huge plumes of toxic smoke to spew from the stacks. Dozens of people called 911 to report difficulty breathing, while the Bay Area Air Quality Management District (BAAQMD) received numerous complaints. The incident led Valero to shut down a large part of its facility, consequently causing oil and gas prices to rise across the state. While the Valero seeks to implement new technologies to reduce the amount of future emissions and incidents like that of March 2019, it remains one of Benicia’s largest emitters of air toxins.

Even on “normal days” at the refinery, Benicia’s air monitors have revealed repeated spikes in particle pollution, often registering far higher than what would be considered safe for daily air quality, raising concerns for the area’s most vulnerable: children, the elderly, and those with lung conditions.

In the winter, wood burning is estimated to account for 40 percent of Benicia’s particle pollution. November and December of 2019 experienced PM2.5 levels more than double those of the summer months, with concentrations of 16.4 μg/m³ and 13.2 μg/m³ respectively. Wood-burning restrictions have been gradually implemented over recent years, promoting gradual air quality improvements. In the last decade, wood-burning regulations have included requiring wood heater manufacturers to comply with EPA standards, mandating that buildings remove non-compliant wood-burning devices, and preventing wood-burning devices from being installed in new buildings.²

There is a recent push to ban all wood burning in the coming years, a measure which would greatly reduce Benicia’s unhealthy pollution levels in the winter. It is yet to be seen if such a drastic step would be accepted by the community and council.

Situated on the North Bay, Benicia’s location near the ocean causes the local climate to be affected by marine inversions. Marine inversions rise measured pollution levels by creating a “trapping” effect. This occurs when surface level air, cooled by the Pacific Ocean, becomes capped under warmer, denser air above. Marine inversions thus cause emissions to accumulate and linger until the weather changes. Surrounding foothills and mountains can exacerbate this effect by further trapping pollution and stagnating air.

Use Benicia’s air pollution map to follow real-time pollution concentrations, wind directions, and better understand the influence of Benicia’s emission sources.

What is the current air quality in Benicia, CA?

Benicia’s air quality levels are generally considered healthy. In 2019, Benicia’s annual air quality average met federal targets, as did all Bay Area cities. Short-term pollution spikes, rather, were the cause for air quality to be described as “unhealthy.”

Benicia’s pollutants of primary concern are PM2.5 and ozone. Every year, Benicia experiences unhealthy levels of each. Generally speaking, PM2.5 is the pollutant of greatest concern in the winter months, while ozone is of greatest concern in the summer months.

According to the American Lung Association’s (ALA) 2019 annual air quality report card, Solano County, of which Benicia is a part, received an “F” for short-term PM2.5 and a “D” for short-term ozone.³

PM2.5 is airborne particulate matter measuring 2.5 micrometers or smaller. Its small size allows particles to penetrate deep into the lungs when inhaled, sometimes entering the circulatory system and causing a wide range of short- and long-term health effects. Exposure to PM2.5 has been definitively linked to health effects such as cardiovascular disease, respiratory illness, cancer, and early death.

Benicia’s failing rating for 24-hour fine particle pollution, or PM2.5, was received for exceeding the federal allowance of unhealthy PM2.5 days set at 3.2. Benicia has an average of 10 unhealthy PM2.5 days a year, as calculated during the 2016 to 2018 monitoring period.

PM2.5 spikes tend to occur in the late summer and early fall as a result of wildfires and during the winter months as a result of domestic wood burning. Benicia’s most polluted months in 2019 were November and December, averaging PM2.5 concentrations of 16.4 μg/m³ and 13.2 μg/m³ respectively.

While the 2019 ALA report gave Solano County a passing grade for ozone pollution, its average of 2.2 unhealthy ozone days is close to the federal allowance of 3.2 unhealthy ozone days. Moreover, ozone pollution has been on the rise since 2015, when Solano County averaged just 1.3 unhealthy ozone days.

Ozone is a highly corrosive gas pollutant. Similar to PM2.5, ozone can cause a wide range short- and long-term health effects, including difficulty breathing, respiratory illness, lung cancer, and early death.

Is Benicia air quality safe?

Benicia air quality is usually safe to breathe. In 2019, Benicia averaged an AQI of 30, passing the US Environmental Protection Agency (EPA) standard requiring an index score of less than 50.

Despite optimistic annual ratings, the Bay Area ranks as one of the most polluted regions in the United States, according to the 2020 ALA State of the Air report. In the most recent monitoring period, the San Jose-San Francisco region (of which Solano County is a part) ranks:

• 8th nationally for high ozone days out of 228 metropolitan areas
• 3rd nationally for high particle pollution (PM2.5) days out of 217 metropolitan areas
• 5th nationally for annual particle pollution (PM2.5) out of 203 metropolitan areas

Follow Benicia’s live air quality index score to understand the level of health risk associated with city-wide pollution measurements. When Benicia’s AQI is under 50, “good,” air quality poses little to no risk to human health. When Benicia’s AQI levels exceed 100, “unhealthy for sensitive groups,” care should be taken to reduce outdoor activity and protect one's health.

Those considered sensitive to air pollution, such as children, the elderly, and those with heart and lung complications, are more likely to experience adverse effects. Solano County has 35,899 residents with asthma, 16,650 with COPD, 24,364 with cardiovascular disease, 98,740 residents under the age of 18, and 70,430 residents over the age of 65, all of whom are more likely to experience adverse effects as a result of Benicia’s unhealthy pollution levels.

Are there any fires near Benicia, CA?

In 2020, California broke records for the most acres burned in a single wildfire season, with 2.2 million acres scotched by early September.⁴ The previous record was set in 2018, with 1.96 million acres burned across the entire year. Long-term data reveals a concerning trend of increasingly frequent and severe wildfires as a result of anthropogenic (human-generated) climate change.

A study published by the Lamont Doherty Earth Observatory at Columbia University found that climate change has doubled the risk of extreme fire conditions in California.⁵ Since 1970, the amount of burned acreage per year has jumped eightfold and continues to climb.

During California’s wildfire season, spanning from July through November, PM2.5 fluctuations across the Bay Area are common. On average, Solano County experiences 10 unhealthy PM2.5 days annually, many of which are attributable to wildfires burning in the Bay Area.

Use IQAir’s air quality map to identify nearby wildfires and resulting air pollution emissions.

Is Benicia affected by fires?

Benicia air quality suffers as a result of wildfires burning near the Bay Area and farther across the state. Smoke can travel hundreds and even thousands of miles due to the extremely lightweight nature of PM2.5 particle pollution. While generally short-lived, burning for just days to weeks at a time, wildfires can dramatically reshape Benicia’s 24-hour and annual air pollution levels.

In late August 2020, Benicia experienced several days averaging “unhealthy” air pollution as a result of a siege of wildfires ignited during a dry lightning storm – namely the “LNU lightning complex” and “SCU Lightning Complex fires”.⁶ Such high pollution levels are generally rare in Benicia.

Use IQAir’s interactive air quality map to locate where fires are burning, see the direction smoke is blowing, and understand how Bay Area air quality is affected in real time. Air quality data is updated hourly, while live fire data is updated every three hours using observations from NASA's Fire Information for Resource Management System (FIRMS) satellites.

+ Article Resources

[1] Goldberg T. (2019, April 10). Valero's March pollution release exposes weaknesses in Benicia's air monitoring system. KQED.
[2] Nguyen A. (2015, October 23). Wood burning regulations in Benicia just got more strict. Bay City News Service.
[3] American Lung Association. (2020). State of the air – 2020.
[4] Stringini M. (2020, September 8). Over 2.2 million acres torched as California experiences record-breaking wildfire season in 2020. Fox 11 Los Angeles.
[5] Ray S, Miller B, and Jones J. (2020, August 25). California’s new normal: How the climate crisis is fueling wildfires and changing life in the Golden State. East Bay Times.
[6] Andrew F, and Knowles H. (2020, August 23). 1.1 million acres burned in nine days in California, as new lightning-ignited blazes forecast into Monday. The Washington Post.