EnviroNearby

Somerset County, New Jersey air quality history

Daily Air Quality Index summaries from EPA monitors in Somerset, New Jersey, 1980–1983.

78%
Good days in 1983
35
Median daily AQI, 1983
0
Days above 100 in 1983
185
Days with an AQI in 1983 (of 365)

In 1983, EPA reported a daily Air Quality Index (AQI) for Somerset, New Jersey on 185 days. 144 of those days (78%) were in the Good range, and the median daily AQI was 35. That median is lower than the typical monitored county in New Jersey (median 48.5 across 16 counties), and lower than the typical monitored U.S. county (40). The main pollutant was carbon monoxide (CO) on 185 days.

EPA did not report an AQI for every day of 1983 here (185 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

The most recent year with data for this county is 1983; EPA's files for 1984–2025 contain no row for it, which usually means its monitors stopped reporting.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1980: Good 239 of 355 days1980: Moderate 92 of 355 days1980: Unhealthy for Sensitive Groups 16 of 355 days1980: Unhealthy 6 of 355 days1980: Very Unhealthy 2 of 355 days19801981: Good 260 of 346 days1981: Moderate 71 of 346 days1981: Unhealthy for Sensitive Groups 13 of 346 days1981: Very Unhealthy 2 of 346 days19811982: Good 264 of 359 days1982: Moderate 84 of 359 days1982: Unhealthy for Sensitive Groups 8 of 359 days1982: Unhealthy 2 of 359 days1982: Very Unhealthy 1 of 359 days19821983: Good 144 of 185 days1983: Moderate 41 of 185 days1983
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001980: 90th percentile AQI 791981: 90th percentile AQI 681982: 90th percentile AQI 711983: 90th percentile AQI 611980: Median AQI 431981: Median AQI 361982: Median AQI 381983: Median AQI 351980198119821983
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 1983

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Carbon monoxide (CO)185100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
1983185144410000356178CO
19823592648482103871207CO
198134626071130203668219CO
198035523992166204379209CO

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

All monitored counties in New Jersey

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–1983 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem