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City of Pleasanton—Hidden Canyon Residences and Preserve Draft EIR Air Quality FirstCarbon Solutions 3.2-7 https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480016/EIR/3 - Draft EIR/21480016 Sec03-02 Air Quality.docx Particulate Matter Airborne particulate matter (PM) refers to a wide range of solid or liquid particles in the atmosphere, including solids and aerosols made up of tiny liquid droplets, dry solid fragments, and solid cores with liquid coatings. Respirable particulate matter with an aerodynamic diameter of 10 micrometers or less is referred to as PM10 while PM2.5 includes a subgroup of finer particles that have an aerodynamic diameter of 2.5 micrometers or less. Some PM, such as pollen, is naturally occurring. PMs can either be directly emitted from sources (primary particles) or formed in the atmosphere through chemical reactions of gases (secondary particles) such as sulfur dioxide (SO2), nitrogen oxides (NOX), and certain organic compounds. These organic compounds can originate from natural sources, such as trees and vegetation, as well as human-made (anthropogenic) sources, including industrial activities and vehicle exhaust. 2 Nitrogen Dioxide NO2 is a reddish-brown gas that is a by-product of combustion processes. Although automobiles and industrial operations are the main sources of NO2, much of it in the ambient air is produced through atmospheric reactions between nitric oxide (NO) and other pollutants which require sunlight (photochemical reactions). Nitrogen dioxide contributes to the formation of several other pollutants, including ozone (O3), nitric acid (HNO3), and nitrate (NO3-) particles, which also form through photochemical reactions. The levels of NO2 in the air fluctuate based on direct emissions and changing atmospheric conditions, especially the amount of sunlight. 3 Carbon Monoxide CO is an odorless, colorless gas. It is formed by the incomplete combustion of carbon-containing fuels, such as natural gas, gasoline, and wood from stationary and mobile sources. CO can also be formed through photochemical reactions in the atmosphere involving methane, non-methane hydrocarbons, other volatile organic compounds (VOCs), and organic molecules found in surface waters and soils. 4 Sulfur Dioxide SO2 is a colorless acid gas with a pungent, irritating odor prevalent in ambient temperatures. It is formed the combustion of sulfur-containing fuel, such as from motor vehicles, locomotives, ships, and off-road diesel equipment. Additionally, SO2 is emitted from some industrial processes such as natural gas and petroleum extraction, oil refining, and metal processing as well as during volcanic activity and geothermal fields. 5 Lead Lead is a relatively soft and chemically resistant metal present in many soils (especially urban soils) and which can get resuspended into the air. As a result of the phase-out of leaded gasoline, metal 2 California Air Resources Board (ARB). 2023. Inhalable Particulate Matter & Health (PM2.5 and PM10). Website: https://ww2.arb.ca.gov/resources/inhalable-particulate-matter-and-health. Accessed October 10, 2024. 3 California Air Resources Board (ARB). 2023. Nitrogen Dioxide & Health. Website: https://ww2.arb.ca.gov/resources/nitrogen- dioxide-and-health. Accessed October 10, 2024. 4 California Air Resources Board (ARB). 2023. Carbon Monoxide & Health. Website: https://ww2.arb.ca.gov/resources/carbon- monoxide-and-health. Accessed October 10, 2024. 5 California Air Resources Board (ARB). 2023. Sulfur Dioxide & Health. Website: https://ww2.arb.ca.gov/resources/sulfur-dioxide-and- health. Accessed October 10, 2024.