San Francisco's Pollution: A Growing Concern?

San Francisco is known for its good air quality, which can be attributed to its coastal location, natural topography, and sparse level of factories and industrial production plants. However, in recent years, the city has experienced periods of high pollution, particularly in certain neighbourhoods. The primary sources of air pollution in San Francisco are transportation emissions from vehicles, planes, and ships, as well as wildfires in the Bay Area, which have increased in frequency due to climate change. While the city has taken steps to improve air quality and protect public health, it continues to face challenges in reducing pollution and improving the health and welfare of its citizens.

San Francisco's air quality is generally good, but some areas have higher pollution levels

San Francisco generally enjoys good air quality for most of the year. Its coastal location, natural topography, and sparse level of factories and industrial production plants all contribute to its good air quality rating. However, not all parts of the city experience the same air quality.

The Outer Sunset neighbourhood, near Ocean Beach and the Upper Great Highway, has consistently been found to have high levels of particulate matter (PM 2.5) – tiny inhalable particles that can cause serious health issues. This is surprising because the area does not have obvious sources of pollution, such as oil refineries, and traffic does not seem to be a significant factor either. Some scientists suggest that the sensors could be detecting pollution related to nearby wastewater facilities or sea spray aerosols.

While many areas of San Francisco have good air quality, areas close to freeways, ports, or industrial activities generally have higher levels of pollution. The majority of air pollutants in the Bay Area are generated from vehicle emissions, with cars, trucks, and other automobiles being the primary source. Wildfires in the Bay Area, which are becoming more common, also contribute to drastic spikes in air pollution, usually during the summer and fall.

To address these issues, the City and County of San Francisco have implemented various measures to improve air quality and protect public health. For example, new residential construction projects in areas with higher levels of air pollution are required to install enhanced ventilation systems and use the cleanest available construction equipment. The city has also adopted an all-electric new construction ordinance to reduce air pollution emissions.

The Outer Sunset neighbourhood has high levels of particulate matter, PM 2.5

San Francisco is known for its good air quality, which can be attributed to its coastal location, natural topography, and sparse level of factories and other industrial production plants. However, in April 2022, sensors detected high levels of particulate matter PM 2.5 in the Outer Sunset neighbourhood, near Ocean Beach and the Upper Great Highway. This area is known for attracting people seeking fresh air, and the high levels of pollution are puzzling to air quality and policy experts.

The Outer Sunset neighbourhood's high levels of PM 2.5 are particularly concerning because these are tiny inhalable particles that can cause serious health problems. The area does not have obvious pollution sources, such as oil refineries, and traffic does not seem to be a significant factor either. Michael Flagg, an air quality scientist and surfer who lives in the Outer Sunset, first noticed the high readings on PurpleAir monitors during periods of high surf and calm wind conditions.

Flagg's theory is that a phenomenon called sea spray aerosol could be contributing to the high PM 2.5 levels. Sea spray aerosol consists of tiny particles ejected from the ocean when waves crash into the shore, and it tends to occur under specific meteorological conditions, such as high surf and light winds. While sea spray aerosol is a likely contributor, scientists are still working to understand the full range of factors influencing the high PM 2.5 levels in the Outer Sunset neighbourhood.

It is important to note that the PurpleAir sensors used to detect the high PM 2.5 levels in the Outer Sunset are low-cost and may not be present in many of San Francisco's low-income and disadvantaged communities, which often have poorer air quality. As a result, the PurpleAir sensors may not provide a comprehensive picture of air quality across the city, and further investigation is needed to determine if the Outer Sunset truly has the worst air quality in San Francisco.

Wildfires in the Bay Area negatively impact air quality

San Francisco is known for its good air quality, which can be attributed to its coastal location, natural topography, and sparse level of factories and industrial production plants. However, wildfires in the Bay Area negatively impact the air quality in the region.

Wildfires in the Bay Area have been growing in size and frequency over the last two decades, coinciding with rising temperatures and changing weather patterns due to anthropogenic climate change. Environmental scientists expect the number of acres burned per year to continue rising, presenting a growing challenge for maintaining healthy air quality in the Bay Area.

The smoke and fumes released by these wildfires can dramatically increase air pollution levels in the region, even if the overall yearly average air quality remains relatively low. For example, in 2018, the Camp Fire burned 153,336 acres of land, causing San Francisco's Air Quality Index (AQI) to reach 137, which is considered "unhealthy for sensitive groups." Other fires in 2018, such as the Kincade, Carr, and Mendocino Complex Fires, further elevated San Francisco's air pollution levels.

Wildfires significantly increase direct PM2.5 emissions and emissions of PM2.5 and ozone precursors. PM2.5 refers to tiny inhalable particles that can cause serious health problems. The impact of wildfires on PM2.5 levels is particularly notable in the San Francisco Bay Area, as seen in the case of the 2020 wildfires that ravaged Northern California. These fires surrounded the Bay Area, covering the skies with smoke and raising air pollutant concentrations to hazardous levels.

The Bay Area Air Quality Management District (BAAQMD) has issued air quality advisories due to wildfire smoke from fires in Canada and California. During these periods, residents are advised to stay alert to news coverage and health warnings related to smoke and take steps to protect their health. While the Bay Area typically enjoys good air quality, the impact of wildfires can temporarily degrade air quality to unhealthy levels, particularly for sensitive groups such as young children, the elderly, and those with respiratory issues.

Transportation emissions are a major source of air pollution

San Francisco is known for having good air quality for most of the year. Its coastal location, natural topography, and sparse level of factories and industrial production plants all contribute to its clean air. However, transportation emissions are a major source of air pollution in the city, with vehicles such as cars, motorbikes, trucks, planes, and ships contributing to ambient levels of air pollution.

The Bay Area Air Quality Management District (BAAQMD) recognizes that San Francisco's population density and transportation system contribute to air quality problems in the Bay Area air basin. Emission from automobile tailpipes is the major source of air pollution in the region, and the high number of visitors and commuters who drive to the city exacerbates this issue. Diesel fuel in older motor vehicles, in particular, creates a significant amount of air pollution, including fine particulate matter (PMT10).

While traffic is a significant source of pollution, it is not the only factor. Wildfires in the Bay Area have also impacted air quality, with five of the most destructive California wildfires in recent years occurring relatively close to San Francisco. These fires have released noxious fumes and particulate pollution into the air, causing drastic spikes in pollution levels. Additionally, the winter months tend to be more polluted than summer due to increased heating and wood burning.

To improve air quality, San Francisco has implemented policies to reduce emissions from mobile sources, such as replacing diesel buses with electric buses or other low-emission alternatives. The city has also committed to net-zero emissions by 2050, demonstrating its dedication to long-term air quality improvement. Overall, while transportation emissions are a significant contributor to air pollution in San Francisco, the city is taking steps to mitigate this issue and improve the air quality for its residents and visitors.

The Bay Area Air Quality Management District works to improve air quality

San Francisco typically enjoys good air quality for most of the year, thanks to its coastal location, natural topography, and sparse level of factories and industrial production plants. However, the city is not immune to air pollution, which primarily comes from transportation emissions and, increasingly, wildfires in the Bay Area.

The Bay Area Air Quality Management District (BAAQMD) is a public agency that works to improve and regulate air quality in the nine counties of California's San Francisco Bay Area: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, southwestern Solano, and southern Sonoma. The district has been in operation since 1955, when it was known as the Bay Area Air Pollution Control District, and has since undergone several name changes.

The BAAQMD's board of directors is made up of 24 locally appointed representatives from the nine Bay Area counties. The board has the authority to adopt and enforce air pollution regulations, declare Spare the Air alerts, and allocate funding for initiatives that improve air quality in the region. For example, in June 2022, the board approved $4 million in Community Air Protection Incentives funding to support home and school air filtration programs in Bay Area communities. Of this, $1.3 million was allocated for upgrades to public schools in Richmond, North Richmond, San Pablo, and Tara Hills, and $1 million was designated for the Air District's Home Air Filtration program.

The BAAQMD also works to keep residents informed about air quality conditions and potential health risks. For instance, in June 2022, the district issued an air quality advisory due to smoke from Canadian wildfires, which was expected to impact the entire Bay Area. The advisory urged residents to stay alert to news coverage and health warnings, and to take steps to protect their health from smoke exposure.

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