By Y.M. Lowy

For the second day in a row, an air quality alert is in effect for parts of New York, as officials warn that pollution levels are expected to rise above an Air Quality Index (AQI) of 100.

When the AQI reaches between 101 and 150, it falls into the category labeled “Unhealthy for Sensitive Groups.” That doesn’t mean everyone will feel it, but certain people could notice symptoms, especially if they’re spending a lot of time outdoors.

So what’s causing it? The issue is something called PM2.5 — extremely small airborne particles that are about 30 times thinner than a human hair. Because they’re so tiny, they can travel deep into the lungs when breathed in. During periods of higher concentrations, these particles can irritate the respiratory system and make existing conditions worse.

Children, older adults, and people with heart or lung conditions are considered more sensitive. Outdoor workers are also at higher risk simply because they’re exposed for longer periods.

Those in sensitive groups could experience coughing, shortness of breath, or chest discomfort.

Air quality levels can change throughout the day depending on weather patterns and wind conditions, so residents are encouraged to stay updated while the alert remains in effect.