Qualité de l’air à Alameda County

What is the air quality in Alameda, California?

The city of Alameda is located in Northern California, less than one mile southwest of Oakland in the northeast San Francisco Bay.

Alameda County, which includes the city of Alameda, is considered part of the San Francisco Bay Area, and is the seventh largest county in California by population (20th in the nation). Alameda County includes East Bay cities like Oakland (the county seat), Berkeley, Fremont, Hayward, San Leandro, Livermore, and Alameda (the seventh most populous city in the county).¹

The climate and air quality in Alameda are heavily influenced by the San Francisco Bay to the west of the city and the neighboring city of Oakland to the north and east. The adjacent San Francisco Bay moderates’ temperatures in Alameda and surrounding cities, and winds heading east from the Bay can bring in fresh air that helps clear out airborne pollutants. However, Alameda’s close proximity to Oakland is a detriment to Alameda’s air quality due primarily to industrial pollution and traffic congestion, especially along the busy I-880 freeway and other well-trafficked roadways. Neighboring Oakland International Airport is another negative factor.

The American Lung Association’s State of the Air report for Alameda County gave the county two failing grades for the 2016 to 2018 period, bearing out the negative influence of Oakland and its airport on Alameda’s air pollution levels. The county earned an “F” for both ozone and 24-hour particle pollution. For annual particle pollution, the verdict was slightly more positive, with Alameda County receiving a “Pass” grade, but its rating for PM2.5 was right at the cutoff between pass and fail.² Compared to other U.S. counties, Alameda County ranked 20^th for annual PM2.5 levels, barely passing with 12 micrograms per cubic meter (μg/m³). This measure of PM2.5 concentration is based on the Annual PM2.5 National Ambient Air Quality Standard used by the EPA to determine whether a county’s air quality meets standards.³

Is today a Spare the Air day in Alameda County?

Alameda County Spare the Air alerts are issued by the Bay Area Air Quality Management District (BAAQMD) for the following day no later than 2 p.m. on the day that the alert is made public.⁴

Spare the Air alerts occur when the level of PM2.5 pollution becomes dangerously high. Multiple factors can cause this to happen, such as wildfires in the summer and fall and wood burning in the winter.^5,6

Thermal inversions common in the winter can further cause particle pollution levels to increase by trapping particle pollution near the ground and preventing normal dispersion. Smoke buildup frequently causes air to become unhealthy to breathe triggers both a Spare the Air Alert and Burn Ban.

To reduce this effect, the BAAQMD has taken steps to reduce the frequency of Spare the Air alerts in Alameda County. In 2019, the BAAQMD toughened the Wood Burning Rule in an effort to reduce the amount of wood smoke in the air and help protect people from its harmful effects. This rule made it illegal to burn wood, manufactured fire logs, pellets, or any other solid fuel during a Spare the Air alert. This is especially important during wildfire season to help prevent a rapid spike of harmful PM2.5 pollutants caused by a combination of wildfires and wood burning). To help enforce the amended rule, hefty fines are levied against rule-breakers.

Is air quality in Alameda improving?

The State of the Air report shows that Alameda County experienced some improvements in three key measures of air pollution—annual PM2.5, 24-hour PM2.5, and daily ozone—since the turn of the century, but they have all seen reversals in recent years.

The annual weighted average of high ozone days decreased from a high of 20.2 during the 1996-1998 period to a low of 4.8 during the 2012-2014 period. That number then increased again, reaching 10.8 during 2015-2017. There was some improvement in the next three-year period, with the average going down to 8.8 during 2016-2018. Despite long-term improvement, Alameda County has received a failing grade in every three-year period since 1996-1998 because its annual weighted average of high ozone days has always been above 3.2.

Alameda County’s annual weighted average 24-hour particle pollution (8.2) earned an “F” grade during 2000-2002 (well above 3.2) but improved to a passing average (1) during 2003-2005 –the lowest average recorded for the county. However, the number then fell between 1 and 3.7 for several three-year periods before sharply increasing from 5.5 during 2015-2017 to 11.2 during 2016-2018.

The State of the Air report also reveals that annual particle pollution in Alameda County briefly improved, with annual average PM2.5 concentrations dropping from 12.3 μg/m³ during 2000-2002 to 9 μg/m³ during 2008-2010. However, Alameda County has experienced an upward trend since then. During 2016-2018, the annual PM2.5 concentration average was back up to 12 μg/m³.

This reversal in PM2.5 concentration in Alameda County may result from elevated levels of smoke caused by the increasing number of wildfires in Northern California in recent years.

People who live in or visit Alameda and are members of at-risk groups should actively monitor the air quality in Alameda by regularly checking this page for updated information on the current health status of the city’s air, and Alameda air quality index (AQI) for today and the rest of the week.

What causes air pollution in Alameda?

Interstate 880 is one of the Bay Area’s busiest freeways, a major vehicle artery that serves Alameda (just east of the city) as well as Oakland, the Port of Oakland, Oakland International Airport, and other areas along the East Bay. This freeway also handles the most truck traffic in the Bay Area.⁷ High volumes of traffic emissions along the I-880 corridor can drastically elevate the amount of air pollution in Alameda as well as in Oakland and other Bay Area cities.

Air pollution in Oakland also exerts a major influence on Alameda’s air quality since the two cities are less than a mile apart, separated only by a thin estuary. In particular, data from East Oakland between 2015 and 2016 indicated higher amounts of airborne pollutants in that section of the city due in part to its high-traffic roads, industrial activity, and freight corridor. As a result, poor air quality in Oakland may also be a source of poor air quality in Alameda.

Another influence on Alameda’s air pollution levels is Oakland International Airport. Located directly south of Alameda, plane traffic to and from one of the Bay Area’s major airports has a negative impact on Alameda’s air quality, especially in the southern sections of the city like Bay Farm Island on the border of the airport.

Wildfires near Alameda can also greatly increase the amount of unhealthy fine particle pollution in Alameda. These spikes in PM2.5 are particularly harmful to the lungs. Furthermore, increased temperatures in or near burn areas can cause increased ozone formation. The combination of fire smoke and elevated ground-level ozone can result in extremely unhealthy air. Unfortunately, wildfire events are becoming more common as summers have trended hotter in recent years, and wildfires rank among the biggest sources of high air pollution levels in Alameda as well as in Alameda County.

Smoke from woodburning also contributes to air pollution in Alameda. Many homes tend to burn wood for heat during the colder months of winter and early spring, leading to greater amounts of smoke from residential chimneys. According to the BAAQMD, there are 1.4 million fireplaces and wood stoves in the greater Bay Area region (spanning Alameda County plus eight other counties), which together constitute the greatest source of unhealthy particulate pollution during winter months.

What is Alameda doing to reduce air pollution?

Officials in Alameda have taken steps to reduce traffic congestion in the area with the goal of reducing pollution and thereby improving air quality in Alameda. In 2017, the Alameda City Council adopted the Transportation Choices Plan in order to focus on ways to shift people away from single occupancy cars and toward public transportation, carpooling, biking, and walking.⁸

This plan aims to increase morning non-drive-alone trips across the Oakland Estuary from 27 percent to 39 percent. This which would result in about 2,500 more person-trips at estuary crossings involving walking, bicycling, carpooling, or public transportation during the morning peak-hour. The plan also aims to increase the daily share of walking, bicycling, public transport, and carpooling trips in Alameda by upping the number of non-drive-alone trips from 37 percent to 42 percent. This would mean an increase of roughly 3,300 walking, bicycling, public transport, and carpool person-trips throughout the day.

Alameda has made some progress towards these goals. In 2015, commutes to work consisted of:

• 60 percent drive-alone trips
• 17 percent public transportation
• 5 percent biking and walking.

A year later, commutes to work consisted of:

• 59 percent drive-alone trips
• 18 percent public transportation increased
• 7 percent walking and biking

To help promote non-driving transportation options, the city has also been pursuing strategies like bike-share and car-share programs.

Alameda air quality may also benefit from a coalition called the Community Action for a Sustainable Alameda (CASA). CASA’s mission is to raise awareness, mobilize action, and advocate for programs to achieve the main goal of cutting the city’s carbon emissions to 25 percent below 2005 levels by the year 2020.⁹ The results of this goal have yet to be determined as data following the year 2020 is collected and analyzed.

+ Article Resources

[1] U.S. Department of Commerce. (2010). 2010 Decennial Census.
[2] American Lung Association. (2020). State of the Air report.
[3] American Lung Association. (2020). State of the Air 2020 report.
[4] Bay Area Air Quality Management District. (2020). An overview of the Wood Burning Rule in the Bay Area.
[5] Thadani T. (2020, September 29). Bay Area choked by wildfire smoke: Spare the Air runs through Friday. San Francisco Chronicle.
[6] Echeverria D. (2020, September 2). Smoke could linger over Bay Area for months, even after fires are contained. San Francisco Chronicle.
[7] Environmental Defense Fund. (2020). Air pollution and health in East Oakland.
[8] Van Lieshout M. (2017, October 6). Reducing traffic congestion and improving air quality in Alameda. Community Action for a Sustainable Alameda.
[9] CASA. (2020). About. Community Action for a Sustainable Alameda.