PM2.5 refers to all fine particles. PM10 refers to all particles less than 10 m m in size. PM2.5 levels now being measured, but trends are not yet known. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. Around midday during summer months 13.
Air quality is considered satisfactory and air pollution poses little or no risk.
Unusually sensitive people should consider limiting prolonged outdoor exertion. Unhealthy for sensitive groups. Active children and adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion. Everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.