What does this measure?
The percentage of days for which air quality was monitored and found to be good, indicating healthy air both for sensitive groups, such as people with asthma, and for the population as a whole. The Air Quality Index (AQI) summarizes levels of ground-level ozone, particulate matter (soot and other particles), carbon monoxide, sulfur dioxide, and nitrogen dioxide into one measure.
Why is this important?
Exposure to these pollutants can cause short-term health effects such as irritation to the eyes, nose and throat, coughing, sneezing, runny nose, and shortness of breath. Continued exposure can also worsen medical conditions such as asthma and heart disease.
How is Norfolk County doing?
In 2021, 88% of days were good air days, down from the rate in 2020, but 17 points higher than 2000.
Norfolk had the lowest percentage of good air days in 2021, just behind Essex County at 89%. Middlesex County, MA had the highest at 93%. All counties have had an increase in the number of good air days since 2000.
Notes about the data
Comparable national and state data is not available due to the quantity and location of EPA monitoring stations. Data for this indicator are expected to be released annually in July.
| 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Norfolk County | 71% | 63% | 55% | 74% | 76% | 74% | 77% | 74% | 74% | 84% | 82% | 83% | 81% | 88% | 88% | 87% | 90% | 93% | 95% | 97% | 96% | 88% |
| Essex County | 68% | 74% | 73% | 80% | 75% | 65% | 70% | 63% | 67% | 76% | 72% | 68% | 74% | 76% | 83% | 82% | 88% | 88% | 86% | 90% | 90% | 89% |
| Middlesex County | 75% | 76% | 80% | 93% | 92% | 86% | 83% | 83% | 88% | 90% | 87% | 92% | 90% | 94% | 95% | 95% | 94% | 96% | 91% | 93% | 93% | 93% |
Notes: The availability of data depends on the location of air monitoring stations.
| 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Norfolk County | 45 | 30 | 132 | 145 | 212 | 234 | 268 | 246 | 270 | 305 | 300 | 297 | 294 | 322 | 323 | 319 | 330 | 337 | 337 | 352 | 352 | 320 |
| Essex County | 250 | 270 | 265 | 293 | 274 | 239 | 254 | 229 | 247 | 276 | 262 | 248 | 270 | 276 | 304 | 299 | 321 | 321 | 314 | 329 | 330 | 324 |
| Middlesex County | 275 | 278 | 292 | 338 | 337 | 313 | 304 | 302 | 321 | 330 | 318 | 334 | 328 | 335 | 338 | 345 | 341 | 341 | 333 | 337 | 340 | 338 |
Notes: The availability of data depends on the location of air monitoring stations.
| INDICATORS | TREND |
|---|
