The Connecticut Environmental Health Association

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Air Quality Index

The Air Quality Index reports and forecasts air pollution levels based on the measurement of three pollutants: Ozone, sulfur oxides, particulates. Air pollution levels are monitored and forecast by the Connecticut Department of Environmental Protection (DEP), and the DEP is responsible for implementing and enforcing regulations to meet Federal health standards. Readings are taken from various locations, and the Air Quality Index is released to the media every weekday afternoon. Forecasts are given for the following day and weekends.

The Index is based on a numerical rating, in which 100 equals the Federal health standard. Health-based labels correspond to the numerical ratings. The pollutant with the highest measured reading is reported.

Index labels can be interpreted as:

GOOD - (0-50) No significant effects of pollution.

MODERATE (50-100)    Some damage to materials & vegetation, but human health not affected unless levels continue for many days.

UNHEALTHFUL (100-200)    High-risk individuals experience mild aggravation. Those with lung or heart disease should reduce activity. Healthy individuals experience eye/throat irritations.

VERY UNHEALTHFUL (200-300) People with heart/lung disease experience significant aggravation, and should stay indoors. Widespread irritation among healthy population.

HAZARDOUS (300-400)    High-risk individuals should stay indoors. Significant aggravation of symptoms and decreased exercise tolerance in healthy population. Premature onset of certain diseases. General population should avoid outdoor activity.

(401-500) Premature death of some members in high-risk group. Healthy population will experience symptoms that affect routine activity. All people should remain indoors with windows and doors shut, avoid vehicular activity.