Air quality in Tucson

Does Tucson have good air quality?

Tucson is a city located in the state of Arizona, within Pima County, found in the South Central region of the state. It is home to over 520 thousand inhabitants, making it the second largest city in Arizona, as well as the 33^rd largest out of all cities counted within the United States. It has a history of being founded as a military fort city, and has seen continued growth in its population size since its conception in the late 18^th century.

Nowadays it sees much of its economic activity based around higher education and science facilities, tech companies as well as the military having a strong presence, acting as a large employer amongst the population within its various branches. Tourism also accounts for a sizeable portion of the economy, and as such there would be a need to have a large number of hotels and guesthouses throughout the city to host the estimated 3.5 million annual visitors (in the pre-Covid era).

With a considerable population, coupled with the large movement of people in and out of the city, Tucson’s air is subsequently affected by this large scale anthropogenic activity. However, despite this it still manages to maintain very respectable level of air quality, even with such activities going on within the city. In 2020, Tucson came in with a PM2.5 reading of 5.9 μg/m³ as its yearly average, a very good reading that placed it well within the World Health Organizations (WHO's) target goal at 10 μg/m³ or less, for the best quality of air. This very low reading placed it amongst one of the top cities in the world for clean air, coming in at 4373^rd place out of all cities ranked worldwide, as well as 1301^st place out of all cities ranked in America.

What are some causes of polluted air in Tucson?

Even with such a respectable level of air quality present in Tucson, there are inevitably sources of pollution that would drive the PM2.5 count up somewhat, alluding to the fact that the air could be of even better quality. One cause would be regarding the fact that Tucson utilizes a large amount of fossil fuels for its energy supplies.

A majority of this comes from natural gas, which although is a much cleaner alternative to other fossil fuels such as diesel or coal, still carries with it a fair amount of atmosphere polluting capabilities. Of note is that certain factories and power plants will still use coal as a power source which can put out large amounts of chemical pollutants and particulate matter, all of which can raise the PM2.5 count.

The other most prominent cause of pollution would be that of vehicular emissions. With a huge population, coupled with a large amount of tourists moving in and out of the city (as well as the inhabitants commuting on a daily basis), there would subsequently be a large amount of pollution accumulating in certain areas due to the heavy overuse of cars. Vehicles can release the same chemical compounds and hazardous particulate matter as factories can, as well as releasing large amounts of microscopic rubber particles into the air over time due to wear and tear on tire treads. This can have a disastrous effect on the health of humans who respire it, as well as on the environment. These are some of the main causes of air pollution occurring within Tucson, with other ones such as occasional forest fires, construction sites and road repairs all being contributing factors to smoke, haze and fine particulate matter (PM2.5 and PM10).

When is the air at its most polluted in Tucson?

Observing the data gathered over the course of 2020, there emerges a period in which the air pollution levels were distinctly higher than the rest of the year, albeit still coming in within respectable levels due to the exceptionally clean air quality that the city maintains throughout the year. These more polluted months started to occur around the month of August, and running through to the end of the year. For some of the latter months of the year, this can be due to a much higher demand placed on power plants to provide energy for the heating of both homes and businesses, and is a common sight in many cities throughout the world that see a large seasonal drop in temperature. Of note is that hotter months can also see their own spikes in pollution for different reasons

The month of July came in with a very good reading of 34.8 μg/m³, which was then followed by a rise up to 7.5 μg/m³ in August. It was during this month onward whereby the air pollution levels became even higher, with readings of 8.1 μg/m³, 7.4 μg/m³, 7.7 μg/m³ and 8 μg/m³ respectively (from September to December), making them among the highest readings of the year.

One of the colder months of the year in Tucson is December, and this matched accordingly with the pollution reading. December came in with a reading of 8 μg/m³, making it the most polluted month of the year (before it dropped down significantly in the early months of the following year, in accordance with the PM2.5 readings shown in early 2020). This is indicative that August through to December is when the pollution levels would be at their worst in Tucson.

When is the air quality at its best in Tucson?

In opposition to the previous question, after the heightened readings of PM2.5 started to abate early in the year, the air quality entered into a period of time in which the level of air pollution was even lower, making it extremely clean and breathable, free from large amounts of smoke, haze and other air contaminants that many cities throughout the United States are unfortunately subject to.

The months of February through to April showed the cleanest air readings on record, with readings of 3.8 μg/m³, 2.4 μg/m³ and 3.9 μg/m³ all being shown respectively. This made March the cleanest month of the year with its reading of 2.4 μg/m³, an extremely respectable reading. Of note is that the PM2.5 count rose slightly during the summer months, for reasons that will be covered in short.

What are some of the types of pollution found in Tucson?

The main types of pollutants found in the air in Tucson would be ones such as nitrogen dioxide (NO₂) and sulfur dioxide (SO₂), which find a large amount of their release from vehicles, alongside other pollutants such as carbon monoxide (CO), black carbon and volatile organic compounds (VOC's). Another pollutant that is a particular problem in the United States is ozone, which is formed when the various oxides of nitrogen (NOx) and other chemical pollutants or gases are exposed to large amounts of solar radiation, thence converting into ozone (O₃).

This could account for the slight rise in PM2.5 witnessed during the summer months, in which large amounts of ozone can accumulate due to heavy vehicle use coupled with plentiful sunshine coming into contact with the vehicular exhaust fumes. Some examples of the aforementioned VOC's include chemicals such as benzene, toluene, xylene, methylene chloride and formaldehyde.