Minnesota air quality index trends:

Transcription

1 Minnesota air quality index trends: The Air Quality Index (AQI) was developed by the U.S. Environmental Protection Agency (EPA) to provide a simple, uniform way to report daily air quality conditions to the public. The Minnesota Pollution Control Agency (MPCA) collects hourly air pollution measurements at about 30 locations across the state and posts hourly AQI results on the MPCA website, In addition to reporting current air quality conditions, each day the MPCA issues a 5-day air quality forecast for the Twin Cities and Rochester areas. The MPCA utilizes air quality forecasts and real-time monitoring results when issuing an air pollution health alert. How it works Measurements of five pollutants including fine particles, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide are collected hourly from monitoring sites across Minnesota. Hourly pollution concentration results are converted to an AQI value based on health benchmarks established by the EPA. Overtime, these health benchmarks can change to better reflect new science on the health effects of air pollution. For example, the AQI for fine particles was recently updated during revisions to the annual fine particle standard. The AQI is calculated separately for each pollutant measured. If an area has multiple pollutants or sites, the pollutant or site with the highest AQI value is used to describe overall air quality in that area. AQI values are ranked as good, moderate, unhealthy for sensitive groups, unhealthy for all, or very unhealthy. The MPCA issues an air pollution health alert if an air quality forecast or measured pollution readings indicate that air quality is ranked as unhealthy for sensitive groups or higher. AQI categories and index values Air Quality Alert Levels Good Moderate Unhealthy for Sensitive Groups Unhealthy Very Unhealthy Factors leading to poor air quality On most days air quality across Minnesota is healthy to breathe, but on several days each year pollutants such as ozone and fine particles can reach unhealthy levels. The amount of pollution in the air varies by how much pollution is emitted within an area, how much pollution is blown in from other areas, and the weather. In Minnesota, poor air quality days are most often the result of weather conditions interacting with local and transported pollution emissions. Ozone pollution, which is formed in the air through the reaction of nitrogen oxides and volatile organic compounds, can reach unhealthy levels on days that are very hot, sunny, and stagnant. Fine particle pollution, which is emitted directly and formed from other pollutants reacting in the air, can reach unhealthy levels at any time of year. Factors which most commonly result in elevated fine particle levels include prolonged periods of high pressure, high humidity, low wind speeds, and temperature inversions. Poor air quality can also be caused by a specific pollution emission event, such as wildfire smoke or fireworks. Minnesota Pollution Control Agency TTY or Available in alternative formats

2 Trends in AQI days The AQI is a valuable tool in communicating real-time air quality conditions to the public so that they can make informed decisions to protect against potential health effects associated with short-term exposures to air pollution. The AQI can also be used to evaluate general trends in air quality. For example, an increasing trend in the number of good air quality days suggests that overall air quality has improved over time. However, the AQI also has some limitations when describing trends. For reporting purposes, the daily AQI is based on the highest pollutant measured across all monitoring sites each day. This reporting method, while easier to understand, may obscure local or pollutant specific improvements. Additionally, because the AQI is based on daily measurements, it is more susceptible to year to year differences in meteorology than a trends analysis based on an annual average. Statewide AQI trends The MPCA measures hourly pollution levels at nearly 30 locations across Minnesota. About half of these monitors are located in the Twin Cities metropolitan area while the remaining monitors are located in communities across greater Minnesota including: Brainerd, Detroit Lakes, Duluth, Ely, Grand Portage, Marshall, Rochester, and St. Cloud. To calculate statewide AQI trends, the highest AQI value measured across all monitoring sites each day is used to represent the statewide AQI for that day. The statewide AQI trend shows significant improvements in air quality over time. Since 2003, the number of days with good air quality has nearly doubled. In 2003, air quality was considered good in all areas of the state on less than 25% of all days that year. In 2013, air quality was good in all areas of the state on more than half of all days. Trend in statewide AQI days Recent changes to the AQI Page 2 of 7 During the 2012 revision of the federal fine particle standard the EPA revised the AQI for fine particle pollution. As a result, fine particle concentrations greater than 12 µg/m 3 are now considered moderate, versus the previous threshold of 15.4 µg/m 3. This change is reflected in all data included in this report.

3 Regional AQI trends In addition to the statewide AQI trend, regional AQI trends have been calculated for the Twin Cities, Brainerd, Detroit Lakes, Duluth, Ely, Grand Portage, Marshall, Rochester, and St. Cloud. Regional AQI trends provide more accurate information on local changes in air quality over time. In the sections below two charts are shown for each AQI region. The first chart, on the left, describes the AQI trend for the reporting region. The second chart, on the right, describes the number of air quality alert days issued for that region and identifies whether the alert was due to ozone or fine particle pollution. AQI and air quality alert days in the Twin Cities AQI and air quality alert days in Brainerd Page 3 of 7

4 AQI and air quality alert days in Detroit Lakes AQI and air quality alert days in Duluth Page 4 of 7

5 AQI and air quality alert days in Ely AQI and air quality alert days in Grand Portage* *Ozone is not monitored in Grand Portage Page 5 of 7

6 AQI and air quality alert days in Marshall AQI and air quality alert days in Rochester Page 6 of 7

7 AQI and air quality alert days in St. Cloud Where to find current AQI results On the web: Current air quality conditions, historical results, and daily air quality forecasts, Mobile: Current air quality conditions and daily air quality forecasts via the Minnesota Air app available for ios, Android, and Windows mobile devices, or text: Daily air quality forecasts and air quality alert notifications are available via or text message through EnviroFlash, For more information For more information on the AQI, please call the MPCA at or and ask for air quality index staff. Page 7 of 7