PM1

PM1 refers to airborne particulate matter with an aerodynamic diameter of 1 micrometer or less. It is a subset of fine particles that can penetrate deeply into the respiratory tract and reach the gas-exchange region of the lungs. Compared with PM2.5, PM1 particles are smaller on average and may have different chemical compositions and atmospheric lifetimes.

Sources of PM1 include combustion processes such as vehicle exhaust, residential heating, industrial activities, and wildfires. Secondary formation from atmospheric reactions of sulfur dioxide, nitrogen oxides, ammonia, and volatile organic compounds also contributes to PM1 mass, often after aging in the atmosphere.

Health effects associated with PM1 exposure include adverse cardiovascular and respiratory outcomes, inflammation, reduced lung function, and increased risk of heart disease and stroke. Because of their small size, PM1 particles can cross the alveolar barrier and enter the bloodstream, posing higher risks for children, the elderly, and individuals with preexisting conditions.

Measurement and monitoring of PM1 are conducted at air quality stations using specialized samplers and analyzers. Techniques include gravimetric analysis, TEOM, and optical particle counters designed to size-select to 1 μm. Concentrations are reported in micrograms per cubic meter (μg/m³) and are often expressed as a fraction of PM2.5.

Regulatory and research context varies by jurisdiction. PM2.5 and PM10 standards are common, while PM1 is not universally regulated but is increasingly used in scientific studies to assess finer particle risks and exposure. Monitoring networks may report PM1 separately or as part of PM2.5 data.

Environment and climate considerations include PM1’s impact on visibility and climate forcing through light scattering and absorption. Their small size allows longer suspension times and potential involvement as cloud condensation nuclei, influencing precipitation patterns in some regions.

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