Sensitive Groups

Detailed Explanation

The EPA defines several population groups as particularly sensitive to the health effects of air pollution. Children are vulnerable because their lungs are still developing, they breathe more air relative to their body weight, and they tend to spend more time outdoors. Older adults are at increased risk because of the higher prevalence of heart and lung disease and the natural decline in respiratory and immune function with age. People with asthma, chronic obstructive pulmonary disease (COPD), and cardiovascular disease face elevated risk because air pollution can trigger attacks and worsen existing conditions. Pregnant women are considered sensitive because air pollution exposure during pregnancy has been linked to preterm birth, low birth weight, and developmental effects. Active adults — joggers, construction workers, and others who exercise or work outdoors — are also at heightened risk because increased breathing rates draw more pollutants into the lungs. The "Unhealthy for Sensitive Groups" AQI category (101-150) is specifically calibrated to these populations. AirHistory's tracking of unhealthy air days is particularly relevant for sensitive groups, as even a few days of elevated pollution can trigger acute health events. Cities with low unhealthy day counts are generally safer for sensitive populations.