Qualité de l’air à Minnesota

Does Minnesota have polluted air?

Minnesota is an American state located in the Upper Midwestern region of the country, also being known by the name ‘Land of 10,000 lakes’, pertaining to the many different bodies of water found throughout the state. It is counted as the 22^nd most populous state throughout the whole of the U.S.A, being home to over 5.63 million inhabitants, a sizeable number of people that can be a determining factor in the level of air quality, as with more anthropogenic or human based activity, there are typically higher levels of air pollution occurring as a result.

Minnesota has seen a large amount of its economy in years past centered around industries such as agriculture, railways and timber, although in recent times it has made more of a shift towards modernized industries such as finance or services. These are also factors that can play a part in the air quality levels, as with all industries there is inevitably a larger amount of pollutive fallout as a result of their increased presence, as well as the larger amount of people from out of state that they can potentially draw in.

In 2020, it can be seen that every city registered in Minnesota came in with a PM2.5 reading that fell within the World Health Organizations (WHO's) target goal at 10 μg/m³ or less, for the best quality of air. Whilst this is a good achievement that indicates that much of the year presents its citizens with a great quality of air to breathe, when observing the numbers, it can be seen that there are also many months where the PM2.5 count jumps significantly higher, indicating some pollutive issues occurring within the state. To cite some examples, the city of Minnetrista came in with a yearly PM2.5 average of 9.5 μg/m³, placing it just within the WHO's target goal.

This placed the city in 1^st place out of all 22 cities ranked in Minnesota, as well as 2830^th place out of all cities ranked worldwide. As mentioned, there were several months across both Minnetrista and other cities in the state that had months with particularly worse air quality readings, with the reasons as to why being discussed in short. Overall, it can be said that Minnesota maintains a respectable level of air quality throughout its various cities, albeit with occasional spikes in PM2.5 that can cause the air to become more dangerous to breathe at certain times of the year.

What causes polluted air in Minnesota?

Minnesota has a number of main air pollution causes that assist in elevating the PM2.5 count throughout the year. PM2.5 refers to fine particulate matter that is 2.5 micrometers or less in diameter, having the ability to go down to sizes of 0.001 microns across, and beyond, which presents major health risks when respired. This is partially due to its extremely small size, as well as the large range of materials that PM2.5 (and PM10) can consist of. Due to this and the danger that it presents, it is used as one of the major components in the calculation of the overall AQI, or air quality index of any given area, along with several other pollutants.

To look at some sources that cause the numbers of these pollutants to rise, they would typically be ones that have combustion sources occurring within them, such as vehicular engines, as well as boilers in both factories and power plants. Other sources of pollution include ones such as agriculture and livestock keeping, which can all be major sources of air contaminants in today’s world, with little regulations on certain chemicals such as ammonia, which is released from the waste of animals as well as fertilizers used on crops.

Forest fires and even the burning of firewood or charcoal in certain homes can have an impact on the pollution levels, with these burning practices typically carried out during certain months of the year when the temperature sees a significant drop, with the state of Minnesota being somewhat renowned for its extremes of temperatures between the different seasons. Forest fires can cause smoke clouds to drift many miles from their original source, depending on wind direction and strength, and as such, fires occurring large distances away can end up causing massive spikes in PM2.5 in cities or states a sizeable distance away from the source.

Referring back to vehicles, with its large population Minnesota would have hundreds of thousands of cars and other personal vehicles on the road at any given time, all of which would give out large amounts of exhaust fumes, which contain numerous chemical compounds and hazardous particulate matter. Furthermore, tires can also be a significant source of both air, ground and water pollution, putting out tons of microscopic rubber particles as a result of excessive wear and tear that comes inevitably with the use of vehicles.

When is the air quality at its most polluted in Minnesota?

Observing the levels of pollution recorded over the course of 2020, it can be seen that there is a distinct pattern amongst the various cities in Minnesota where the PM2.5 count rises significantly. To use some cities once again as examples, the top five most polluted cities in the state all saw their highest PM2.5 counts come in at both the very end of the year as well as the very beginning. This correlates directly with the coldest winter months, and is indicative that the demand for energy from power plants for the heating of both homes and businesses, as well as even the burning of firewood and other similar materials would be on the rise, in order to provide warmth during these periods of colder weather.

The city of Minnetrista came in with a respectable reading of PM2.5 in the month of October at 7.5 μg/m³, still well within the WHO's target bracket. This rose significantly in the following two months, with readings of 10.6 μg/m³ and 13.1 μg/m³ being taken in November and December.

These elevations in pollution were also shown in the first few months of the year, with readings of 14.6 μg/m³, 10.5 μg/m³ and 10.9 μg/m³ being taken respectively from January through to March. After March, the pollution levels abated somewhat down to more respectable levels within the WHO's target goal, but it is still indicative for Minnetrista that the months of November and December, as well as January through to March, were the most polluted of the year. January was the most polluted, with its reading of 14.6 μg/m³, putting it in the ‘moderate’ ratings pollution bracket, which requires a PM2.5 reading of anywhere between 12.1 to 35.4 μg/m³ to be classified as such.

Other cities that also followed this exact trend were Saint Paul, with its highest readings taken in December and January at 12.3 μg/m³ and 12.5 μg/m³ respectively (both within the moderate ratings bracket once again). Stillwater also had its highest readings through the months of November, December and January, with readings of 12.4 μg/m³, 14.5 μg/m³ and 12.1 μg/m³ present.

The most polluted month on record in Minnesota over the course of 2020 was taken in December in the city of Rochester, with a PM2.5 reading of 14.9 μg/m³. In closing, the winter months had the highest levels of pollution in the state, with both December and January taking the top spots through many of the cities.

What are the main types of pollution found in Minnesota?

With much of its pollution stemming from combustion sources, as well as other ones that release high volumes of fine particulate matter into the air, Minnesota has a large number of main pollutants found in its air. These would include ones such as black carbon (the main component of soot) and volatile organic compounds (VOC's), both of which can be released from the incomplete combustion of both fossil fuels and organic material.

This demonstrates that they can be released from vehicle engines, factories, as well as the burning of wood or other organic matter. Black carbon is a potent carcinogen when inhaled, and can cause a number of other harmful effects on the human body due to its potential to go down to immensely small sizes. It can often be found coated on roadside areas that see a high volume of traffic.

Some other pollutants would be ones such as carbon monoxide (CO), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and other fine particulate matter such as finely ground gravel or silica dust, with the latter one also having known carcinogenic properties, as well as being able to cause irritation and damage to the lung tissue when inhaled.

When is the air quality at its cleanest and least polluted in Minnesota?

Once again referring to the data collected over 2020, it can be seen that whilst the earliest and latest months of the year had the highest levels of pollution, there were also periods in which the PM2.5 count was considerably lower. Between the months of April through to October were when many cities in Minnesota had the best quality of air, with particular emphasis on the months of June and October.

Some of the cleanest readings taken over the course of 2020 were ones such as 6.5 μg/m³ in June, recorded in Minnetrista, 4.8 μg/m³ taken in September in Rochester, and looking at the absolute best readings, 2.5 μg/m³, 2.3 μg/m³ and 2.4 μg/m³ recorded in the months of April, August and October in the city of Grand Portage. Although the summer months can sometimes have issues with ozone accumulations due to excesses of solar radiation from the sunlight, it seems that Minnesota sees its best readings taken in this time period.