Air pollute stats for Middlesex Co in 2007
| County | Middlesex Co |
| State | Massachusetts |
| Data from year | 2007 |
| Total number of days monitored | 181 |
| Good air | 170 (93.92%) |
| Moderate air | 9 (4.97%) |
| Unhealthy for sensitive groups | 2 (1.10%) |
| Unhealthy for all | 0 (0.00%) |
|
| Worst pollutants |
|
| Carbon monoxide | 2 (1.10%) |
| Nitrogen dioxide | 0 (0.00%) |
| Ozone | 0 (0.00%) |