Air quality is not often thought about in West Haven, but earlier this month, on Feb. 4, the region experienced an air quality deemed “unhealthy air quality for sensitive groups,” according to the Air Quality Index (AQI).

The AQI was developed by the U.S. Environmental Protection Agency (EPA) as means of providing current and future air quality in various regions throughout the U.S. The range of the index is dependent on the allowable levels of common air pollutants, including ozone and carbon monoxide, according to the Clean Air Act. The index takes numbers from all air pollutants and combines them into one, providing an AQI with a potential range of zero to 500.

“Typically air quality with an AQI below 100 is believed to be neutral towards human health,” said Dr. Chong Qiu, a university professor in the Department of Chemistry and Chemical Engineering. “What we have experienced on Feb 4. when AQI reached 112 was considered harmful to more vulnerable groups, such as children, senior citizens and people with respiratory conditions.”

While 112 is considered above neutral, it is AQI’s above 150 that warrant avoiding outdoor activities. This kind of range is not uncharacteristic of West Haven. Qiu recalls one summer where the AQI “reached 130-150 in the summer last year.”  

According to Qiu, multiple natural and human factors influence “local and regional air quality,” including population density, emissions, air temperature, and season.

“New England region has a higher population density which leads to more ground traffic and higher vehicle exhaust emissions,” said Qiu. “However, this may not be the only reason for a bad AQI.”

Typically, colder air causes increased accumulation of air pollutants. However, when this cold air, bogged down with pollutants, meets warmer temperatures it can cause chemical reactions that lead to even more pollutants. Seasonally, the bottom atmospheric layer is compressed in the winter, which allows for less room for the air pollutants that do exist. Essentially, this condenses all pollutants, leads to higher pollutant concentrations, and keeps it all closer to the ground.

According to Qiu, the colder weather leading up to Feb. 4 and the unseasonably warm weather, created the perfect storm for conditions that cause degraded air quality. Since there are so many factors that can play into air quality, Qiu recommends that everyone check the AQI forecast before planning outdoor activities in the region. This forecast can be found at the Connecticut Department of Energy & Environmental Protection’s website.