Qualité de l’air à Pittsburgh

Is Pittsburgh a city with polluted air?

Pittsburgh is a city located in the American state of Pennsylvania, being the administrative center of Allegheny County. It is known by other names such as the city of steel, as well as the city of bridges, both of which allude to its large amount of steel-related production facilities and businesses as well as its many bridges throughout the city. Both of these are features that can lead to higher amounts of pollution, as with a well-developed road-based infrastructure often comes a larger amount of traffic. Furthermore, the many steel plants (amongst others) in operation would also release their own pollutants from the production process, along with requiring more freight vehicles to transport these materials.

In late June of 2021, Pittsburgh was seen on record with a US AQI reading of 53, placing it into the 'moderate' rating bracket of air pollution. US AQI refers to the United States air quality index and is used prevalently throughout the world due to the more stringent rating systems that it has in place. This reading of 53 indicated that on the day and time the air quality reading was taken, people with a sensitive disposition towards chemical pollutants or fine particles may start to experience mild irritation or aggravation of pre-existing respiratory conditions.

The PM2.5 concentration was also found to be slightly more than the World Health Organization's (WHO's) exposure recommendation, indicating that whilst the level of air quality was not overtly dangerous, there may still be chances of adverse health issues occurring, particularly amongst more vulnerable groups of the population. Forecasts for early July indicated that large elevations may sweep across the city, although weather forecasts can be subject to change due to a multitude of different factors (with ones such as meteorological conditions having a large role in this, with strong prevailing winds or higher rainfall helping to remove said pollutants from the immediate atmosphere of a city).

PM2.5 refers to particles that are 2.5 micrometers or less in diameter, going down to sizes many microns smaller. They are considered as one of the most dangerous forms of air pollution present in Pittsburgh, as well as worldwide, due largely to their minute size. As well as this, they are formed from several different materials, with a majority of them being highly hazardous to human health, as well as the environment and ecosystems. Some of these materials include ones such as metals, sulfates, soot, water vapor, and finely ground materials such as silica dust or gravel.

Due to its inherently dangerous property, PM2.5 is used as a prominent measure of air pollution, with yearly averages being taken in PM2.5 units. US AQI readings are a number aggregated from the volume of several main pollutants found in the air, both in the state of Pennsylvania and worldwide (due to many polluting sources being reoccurring themes throughout the world, with slight variations being present depending on local laws, traditional practices, and other such differences).

The chemical pollutants that go into making up the US AQI index and its related figure are ones such as sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), carbon monoxide (CO), and the two forms of fine particles, which are PM2.5 and PM10, with the first of the two being the most dangerous, due to the properties that were mentioned above.

Other readings of US AQI taken in Pittsburgh throughout June were readings such as 21 and 27, both of which fell into the 'good' rating bracket. Based on the air quality data, it can be seen that there was a mix of days that were rated across the two air quality brackets. A 'good' reading is the most optimal and is color-coded as green for ease of use and reference when looking at the various air quality maps, graphs and forecasts present on this page as well as throughout the IQAir website. The 'moderate' reading of air quality is color-coded as yellow and had further readings in June that came in at 69, 76, and 86.

This high of 86, taken in early June would indicate that the air in Pittsburgh would have significantly more smoke, haze, and other contaminating elements in it when compared to the days where the US AQI reading was closer to 0. A 'moderate' reading of US AQI requires a figure of anywhere between 51 to 100, and as mentioned, when the number rises towards the upper ceiling of this rating bracket, the likelihood of adverse effects appearing amongst vulnerable individuals goes up with it accordingly.

People that fall into this vulnerable grouping within Pittsburgh would be individuals such as the elderly, young children, and babies, along with pregnant women. Expecting mothers are particularly at risk due to the highly detrimental effect that high levels of air pollution can have on the health of an unborn child. Problems include babies being born prematurely, with low birth weight, along with a significantly heightened risk of a miscarriage occurring, thus raising the infant mortality rate.

Young children are also highly susceptible due to them going through their vital formative years, and as such, any damage incurred to the tissue of the lungs or skin can have lifelong effects, with conditions like asthma arising and potentially persisting through to their adult life. Furthermore, hypersensitivity towards chemical pollutants and fine particles can also develop, leading to rashes and other skin conditions, as well as inflammation of the respiratory tract and many other problems.

Other vulnerable groups in Pittsburgh that should take extra care during spells of high pollution would be those with pre-existing health issues, compromised immune systems, along with an overall poor level of health accompanied by other bad habits such as a sedentary lifestyle or smoking. On days where the pollution levels rise significantly (with the days following the above-mentioned US AQI reading predicted to go up into the 'unhealthy' rating bracket, color-coded as red), preventative measures should be taken.

These include avoiding outdoor activity, particularly if it is strenuous or involves any form of exercise. The wearing of particle filtering masks can also be of great aid, along with sealing off windows and doors and running indoor air purifiers, if possible, to keep the indoor air pollution level at a minimum and thus reducing the adverse health effects.

Such air quality forecasts can be followed either on this page, as well as via the AirVisual app. In closing, whilst Pittsburgh is not overtly terrible in its levels of pollution, it could do much to improve its standing, with its global ranking, coming in way behind other cities throughout the US.

Why does Pittsburgh have such polluted air?

As mentioned, the ranking of Pittsburgh could stand to see significant improvements. In 2020, the yearly average of Pittsburgh taken in PM2.5 was 10.1 μg/m³. This placed the city into the 'good' air quality rating bracket, which when taken by PM2.5 standards, is recorded in micrograms per cubic meter (as opposed to the different measurement process that goes into the US AQI reading).

This also placed Pittsburgh in 2509^th place out of all cities ranked worldwide, as of 2020, as well as in 12^th place out of all cities ranked in the state of Pennsylvania for the same year, coming in just behind Chester and Clairton. Whilst the average air quality reading still came in on the lower end of 'good', there were many months of the year in which the PM2.5 reading went up even further, moving into the 'moderate' pollution bracket. This indicates that several prominent pollution-causing factors are occurring both within the city and statewide.

One of these would be that of vehicular fumes or emissions, with numerous cars on the road at any given time churning out large amounts of chemical compounds as a result of the combustion process taking place within the engines, as well as fine particle pollution also being released. For industrial needs, as was mentioned at the start, with Pittsburgh having a prominent metal industry presence along with a well-connected series of bridges in and out of the city, the amount of heavier freight vehicles on the road would be significant.

These can often utilize fossil fuels such as diesel, giving out far more pollution per vehicle than a cleaner or more sustainable fuel source would. Furthermore, the gradual wear and tear of tires on all vehicles can lead to many tons of microscopic rubber particles entering into the atmosphere, causing widespread health issues to those that are exposed to it and thus breathe it into their lungs, as well as being highly detrimental to the environment, able to enter into large bodies of water or topsoil and find its way into the food chain due to being consumed by various animals.

Other sources of pollution include emissions from factories and power plants, all of which would utilize some form of fossil fuels in their combustion units and boilers. Material such as oils, coal, natural gas, and diesel for heavy machinery would all churn out large amounts of pollution, which when combined with the ambient pollution levels released from vehicles, can add up to higher amounts of pollution being present in the air. Lastly, pollution can also be released from construction sites, road repairs, demolition sites, as well as any activity that sees large-scale disturbance of earth or dust.

Construction sites alone can release large amounts of fine particles along with heavy metals, with even the heavy machinery used on such sites generating their pollutants. The formation of secondary pollutants such as ozone are also ones that are of continuing concern, monitored closely by many organizations such as the American Lung Association.

Primary pollutants are released directly from a singular source, such as a fire or the motor of an engine, whilst secondary ones such as ozone are formed afterwards in the atmosphere, hence their name as a secondary pollutant. This occurs when the numerous oxides of nitrogen (NOx) are exposed to solar radiation, forcing a reaction that results in the formation of ground-level ozone.

What are the main types of pollution found in the air in Pittsburgh?

Other pollutants that would be found in the air across varying parts of the city would be the ones used in the calculation of the US AQI, along with many others, depending on the activities going on in the surrounding area, particularly when industrial works are taken into consideration.

Some of these pollutants would be ones such as black carbon, along with volatile organic compounds (VOCs), both of which find their release from the incomplete combustion of fossil fuels, as well as organic material. As such, they can be formed from any combustion source (with cars, factories, and power plants all falling into this, along with natural disasters such as forest fires), and amongst the VOC collective are chemicals such as benzene, xylene, methylene chloride, and formaldehyde.

When does Pittsburgh have the worst air pollution levels?

Observing the air quality data taken throughout 2020, it can be seen that the months that had the highest levels of pollution were July, November, and December, all of which came in with PM2.5 readings of 13.6 μg/m³, 12.6 μg/m³ and 12.7 μg/m³.

Whilst these may appear somewhat random, it appears that Pittsburgh has a seasonal pattern to its pollution levels, with slight elevations in pollution also being present at the start of the year. This could indicate that at year's end, the PM2.5 starts to elevate, following on into the early months of the next year before receding to more optimal levels.

When does Pittsburgh see air quality improvements?

Over the last four years, Pittsburgh has remained largely the same with its air quality, fluctuating between different rating systems but not showing any significant improvements or worsening of its air quality, save for 2019 when the PM2.5 yearly average was much higher than normal.

The PM2.5 readings from 2017 to 2020 were 10 μg/m³, 10.1 μg/m³, 12.2 μg/m³ and 10.1 μg/m³ respectively, showing that 2017 was cleaner by a small margin, despite the imposed lockdowns of 2020 due to the covid-19 crisis. Out of all of the months on record in 2020, April and May were the cleanest, with readings of 7.6 μg/m³ and 6.7 μg/m³, indicating the cleanest level of air throughout the year.