Air quality in Santa Cruz County

What is the air quality in Santa Cruz right now?

Santa Cruz is a coastal city located on the northern edge of Monterey Bay. Air quality here is generally considered healthy, owing to the city’s moderate climate, ocean-side location, relatively small population of roughly 70,000, and sparse industrial activity. While daily emissions and resulting air quality measurements in Santa Cruz are relatively low, periods of short-term PM2.5 and ozone pollution can contribute to unhealthy air.

Fine particulate matter, or PM2.5, describes airborne particles with a wide variety of chemical makeups and sources that measure 2.5 micrometers in diameter or smaller. Due to the microscopic size of these particles, they are able to penetrate deep into the lungs and become absorbed into the body’s circulatory system, causing widespread damage.

PM2.5 sources include fossil fuel combustion (such as in motor vehicles and industry), wood burning, wildfires, and windblown dust from agricultural or construction sites, among numerous others. Santa Cruz averages healthy PM2.5 concentrations overall. In 2017, 2018, and 2019, annual PM2.5 concentrations were 7.5 μg/m³, 8.5 μg/m³, and 6.5 μg/m³, respectively, thus meeting the US standard of 12 μg/m³ as well as the more stringent World Health Organization (WHO) standard of 10 μg/m³.

Santa Cruz did not, however, meet federal requirements for short-term or 24-hour PM2.5. In recent years, wildfires have created strings of unhealthy PM2.5 air pollution that last days and even weeks. From 2016 to 2018, there was an average of 5.2 days deemed unhealthy for PM2.5 pollution in Santa Cruz, exceeding the federal allowance of 3.2 days.¹

Ozone is another pollutant of concern for the city, though levels have been within federal attainment since monitoring began in 1996. While Santa Cruz frequently experiences ozone highs of “moderate,” it only experiences an average of 0.3 days a year that dip into “unhealthy for sensitive groups” levels or worse.

Breathing polluted air can cause long-term consequences, including heart and lung disease, cancer, and early death. Checking Santa Cruz live air quality data is paramount to making informed decisions to reduce pollution exposure. While the WHO warns that no level of air pollution has been shown to be free of health effects, most can remain healthy by taking action when Santa Cruz’s AQI exceeds 101. After this threshold, air quality is deemed “unhealthy for sensitive groups” and more acutely impacts adults over 65, children under 18, and those with pre-existing heart and lung conditions.

Santa Cruz County, which stands at roughly 4 times the population of Santa Cruz itself, has 22,188 residents with asthma, 25,924 with heart and lung disease, 52,852 children under the age of 18, and 45,127 over the age of 65 who are considered at-risk for “orange” air pollution days.

Are the wildfires affecting Santa Cruz air quality?

Santa Cruz’s most polluted days are often attributable to wildfires. During the 2016 to 2018 monitoring period, the only air quality parameter Santa Cruz failed to meet was the federal allowance for short-term PM2.5 pollution. Santa Cruz County experiences an average of 5.2 unhealthy PM2.5 days a year, while the US EPA targets no more than 3.2.

In 2019, November was Santa Cruz’s most polluted month, averaging a PM2.5 concentration of 12.9 μg/m³ – more than 2 times the average of all other months (5.7 μg/m³). This dramatic gain in ambient PM2.5 coincides with the Kincade Fire, the largest fire of the year, which burned 77,758 acres in Sonoma County by November 6.² By all accounts, however, 2019 was a mild year for wildfires. Years 2017, 2018, and 2020 all had more severe wildfire seasons and higher PM2.5 averages as a result.

In 2020, California hit a grim milestone, surpassing 3 million burned acres for the year – an area larger than the state of Connecticut.³ Several wildfires made the ranking for worst in state history. Taking the top spot, California’s largest wildfire is the August Complex Fire that blazed through the Mendocino National Forest, burning 846,812 acres by late September. The SCU Lightning Complex and LNU Lightning Complex fires, both ignited by a “lightning siege” dry lightning storm, became the 3rd and 4th largest-ever California wildfires, respectively.

During this period in September 2020, while each of these wildfires raged, Santa Cruz experienced 5 consecutive days of “unhealthy” air quality (September 10 to 14), and two weeks of air quality failing to meet the US EPA “good” standard (September 2 to 15).

Use the IQAir Santa Cruz air quality map to discover whether city-wide air quality is currently being affected by wildfires. Fires are pinned on the map based on satellite observations provided by NASA's Fire Information for Resource Management System (FIRMS). When wind and heat-mapped air pollution correspond and appear to be blowing toward Santa Cruz from active wildfires, it is possible to say that air is being affected by the pollution events.

Is there smoke in Santa Cruz?

Smoke typically exists in high concentrations as a result of biomass burning from wood stoves, wildfires and other activity. When biomass, such as trees and forest underbrush, burns, a range of air toxins is released, including particulate matter (PM2.5 and PM10), carbon monoxide, and nitrogen dioxide. Of these, fine particulate matter, or PM2.5, exists at the highest individual AQI levels and is thus the best indicator for smoke in Santa Cruz.

Air pollution from smoke is not always seen. Sometimes smoke can travel hundreds and even thousands of miles from the source, increasing air pollution levels in distant locations. Follow Santa Cruz live air quality advisories for pertinent health information.

The US EPA’s Air Quality Index (AQI) summarizes overall air quality conditions by translating concentration levels of six major air pollutants to a single value. When the color-coded scale reaches “orange,” or AQI in excess of 101, air is considered unhealthy for at-risk groups, including individuals with heart and lung disease, children, and the elderly. Air pollution rated above an AQI of 151 is considered unhealthy for all populations.

How is Santa Cruz for ozone pollution?

Ozone, commonly referred to as “smog,” is a highly corrosive gas pollutant that frequently exists at harmful levels across US cities. It is considered a relatively difficult pollutant to manage because it is not emitted directly, but rather is formed in the air from ambient precursor pollutants reacting in sunlight.

The components are required for ozone formation are:

• Nitrogen dioxide (NO₂): primarily released from vehicle exhaust and the combustion of fossil fuels as well as industrial activity, commercial manufacturing, and food manufacturing.
• Volatile organic compounds (VOCs): fuel combustion from vehicles, industrial processes, and naturally occurring sources like cattle farms, plants, and biomass burning.
• Sunlight and heat: UV radiation and temperatures over 84 degrees.

High temperatures in Santa Cruz typically occur during the fall, not the summer, an occurrence referred to as an Indian summer. As a result, Santa Cruz peak ozone season spans from August to October, when the city experiences its warmest temperatures. Throughout the year, there are an average of roughly 39 days that have conditions ideal for ozone formation.⁴

Since wildfires are a source of both NO₂ and VOCs, and wildfire season coincides with Santa Cruz’s Indian summer, these unpredictable events can contribute to ozone spikes in addition to unhealthy PM2.5 (which tends to be of primary concern).

Climate change is expected to increase the frequency and severity of wildfires and additionally increase ozone levels as a result of increased temperatures by prolonging the ozone season and accelerating ozone formation.⁵

Despite this, ozone levels in Santa Cruz are typically not a significant problem. In the 2016 to 2018 monitoring period, Santa Cruz County averaged just 0.3 days per year of unhealthy ozone, meeting the federal allowance of 3.2 days. The 2020 “State of the Air” report graded Santa Cruz county a “B” for ozone, highlighting further room for improvement, despite a passing grade.

In order to improve Santa Cruz ozone levels against a backdrop of worsening climate change, additional action is necessary. Reducing the prevalence of precursor pollutants by transitioning to cleaner vehicles (such as electric or hybrid vehicles), cleaner energy, and mitigating the threat of wildfires through activities like prescribed fires all offer significant opportunity for further reducing Santa Cruz air pollution levels.

Why is it polluted in Santa Cruz?

Located just 30 miles south of San Jose and 75 miles south of San Francisco, transboundary air pollution from neighbors with larger economies and denser populations is a concern in the city. Santa Cruz air quality is cleaner on average than San Francisco air quality, Oakland air quality, and Fremont air quality, though in line with San Jose air quality.

According to the American Lung Association’s 2020 “State of the Air” report, the greater San Jose-San Francisco-Oakland area, of which Santa Cruz is a part, ranked as one of the most polluted regions in the United States for both PM2.5 and ozone pollution. In the 2016 to 2018 monitoring period, the region ranked:

• #8 for high ozone days, out of 228 included metropolitan regions
• #3 for 24-hour particle pollution out of 217 metropolitan regions
• #5 for annual particle pollution out of 203 metropolitan regions

Emission sources in the Bay Area include vehicular traffic, port activity, industrial processes, agriculture, wood burning, and wildfires.

Use the Santa Cruz air quality map to discover the origin of emissions by following air quality to the densest pollution levels.

+ Article Resources

[1] American Lung Association. (2020). State of the air – 2020.
[2] Cal-Fire. (2020). - Kincade Fire.
[3] CBS San Francisco Bay Area. (2020, September 14). California wildfires: 2020 blazes burn area larger than Connecticut, Cal Fire says.
[4] Current Results. (2020). Santa Cruz temperatures: averages by month.
[5] Hill A. (2020, September 16). Why U.S. wildfires will only get worse. Council on Foreign Relations.