What Is the Air Quality in Middlesex, New Jersey?

Middlesex, New Jersey earns a C — air quality is fair, but not great. With a 5-year median AQI of 43, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.

Middlesex, New Jersey's 5-year median AQI of 43 is right around the national average of 41 across the 1,020 monitored U.S. cities tracked here. Within New Jersey, Middlesex, New Jersey's air quality is roughly typical for the state, where the average city posts a 5-year median AQI of 42.

For context within New Jersey: Hudson, New Jersey currently holds the state's cleanest grade (B, AQI 44), while Essex, New Jersey sits at the bottom (C, AQI 45).

Air quality in Middlesex, New Jersey has been getting worse over the past decade, with median AQI climbing by roughly 0.3 points per year. That bucks the national trend of broad improvement, and most often reflects either growing wildfire smoke exposure (particularly across the West) or rising local emissions from population and freight growth.

In 2014, Middlesex, New Jersey posted a median AQI of 40. By 2023 that figure was 44 — a rise of 4 AQI points dirtier across 10 years of EPA records.

Across the past five years, this area has logged just 22 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 4 days per year, or roughly one every other month. That is a low count by national standards.

Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.