Answer
Jun 14, 2025 - 01:20 PM
PM 2.5 refers to fine particulate matter with a diameter of 2.5 micrometers or smaller, which can pose health risks when inhaled. According to the U.S. Environmental Protection Agency (EPA), a PM 2.5 level above 35.4 micrograms per cubic meter (µg/m³) over a 24-hour period is considered unhealthy for sensitive groups, while levels above 55.4 µg/m³ are unhealthy for the general population. Prolonged exposure to high levels of PM 2.5 can lead to respiratory and cardiovascular issues.
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