Auvergne Rhone Alpes is a state located in the southeastern region of France, with much of its territory extending into the central areas as well. Its creation was the result of the 2014 reformation of French territories, the result of the merging together of Auvergne and Rhone Alpes. There are some 7.9 million inhabitants statewide, and its total area sum is close to 69,711km2, making it the third largest region in France.
Looking at the numbers when it comes to Auvergne Rhone Alpes air pollution levels, there were a wide range of different PM2.5 readings across the state, with some considerable difference between the most and least polluted. Overall, it can be considered a clean state, with a year round good quality of air, free from large volumes of pollution, although some cities do have year round ambient readings that may be detrimental to certain demographics of the population, with months that go fairly high in terms of their PM2.5 readings, causing issues for sensitive groups such as the young, the elderly, the sick and immunocompromised as well as those with preexisting illnesses and pregnant mothers.
PM2.5 refers to particulate matter that is 2.5 micrometers or less in diameter, making it approximately 3% the size of a human hair, and with the potential to go down to much smaller sizes, as low as 0.001 or less. Thus, due to this incredibly small size it poses significant risks to human health, and although there are other pollutants that are used in calculating the overall air quality, such as nitrogen or sulfur oxides and ozone (O3), PM2.5 will be the main pollutant used to gauge the air quality levels in Auvergne Rhone Alpes.
To look at some tangible numbers, the most polluted city in the state over 2019 was La Mulatiere, coming in with a yearly average of 12.8 μg/m³, a reading that placed it into the ‘moderate’ pollution bracket, which requires a PM2.5 reading of anywhere between 12.1 to 35.4 μg/m³ to be classified as such. For many of the cities statewide, there were certain months of the year that came in with readings far in excess of this average, which will be discussed in short.
So as an overview, in 2019 one city came in with a moderate pollution rating, four cities with a ‘good’ rating of air quality as their yearly average (10 to 12 μg/m³ required), with the other 22 cities coming in within the World Health Organizations (WHO's) target goal of 0 to 10 μg/m³, for the best quality of air. This shows that whilst there are many cities and months in the state that have a very good quality of clean breathable air, there are still pollutive issues afflicting the region.
There are many different causes of pollution in Auvergne Rhone Alpes, that along with compounding each other, can also be made worsened via accumulating, often due to meteorological factors coupled in some cases with geographical ones. As an example, a landlocked city surrounded by hills or mountains, or even high humidity levels is far more likely to have greater accumulations of pollution than a coastal or high altitude town that is subject to heavy winds.
Pollution can be created and then retained, unable to disperse under certain circumstances, with even the temperature playing a role, with the colder months seeing worse readings for several reasons.
One of the main causes of pollution in Auvergne Rhone Alpes would be that of vehicular fumes and emissions, with its millions of inhabitants travelling back and forth for work, or to other cities, pushing up the ambient year round pollution levels through massive vehicular use.
Personal vehicles such as cars and motorbikes can populate the road, some of which will still run on diesel fuels and thus release more potent types of pollution and in higher quantities. There are also the heavy duty vehicles to consider, those above a certain weight class such as trucks, lorries and buses. These too may also run on diesel fuel and give off far more black soot and dangerous forms of carbon due to the combustion of fossil fuels.
Besides pollution caused by vehicles (which is even more prominent in areas near main roads or motorways, as one would imagine), there would also be factory based emissions, with factories and industrial areas often relying on coal to power their processes, as well as giving off whatever chemical effluence that is a result of the product or items they are manufacturing (for example any factory that recycles or creates plastic based products will inevitably give off some variety of plastic fumes).
Other sources of pollution would be the burning of organic material such as wood or other dried plant matters, for heating stoves in traditional homes, mainly for providing heat in the winter. The collective burning of this material would lead to a much larger reading of PM2.5 in the air due to all the various forms of carbon and other pollutants released.
Looking at the data taken over 2019, there start to be some patterns emerging that show when the most polluted times are, across all the different months and cities. The months that show up the most prominently and consistently with higher levels of pollution are the winter months, with air quality starting to show a decline in October, and then November and December have significantly higher readings, which carries on into the next year, with January and February also showing higher readings.
March and April are also somewhat elevated in their readings, but not as prominently as the last 4 months mentioned. During the winter months, far more indoor fires are burnt for the purpose of heating in stoves, very popular in low income districts as well as more provincial areas outside of the big cities. Besides the burning of these materials, people also resort to turning up their heating which in turn leads to higher amounts of energy being consumed, and factories working harder to produce this energy.
Over 60 percent of all cities in Auvergne Rhone Alpes followed this trend of higher pollution levels, and to use the city of Lyon as an example (being the second most polluted city in the state), in October its PM2.5 reading was 8.4 μg/m³. This was followed by 12 μg/m³ in November, and then a further 18.7 μg/m³ in December. January also came in at 14,2 μg/m³, before reaching a high at 25.4 μg/m³ in February, making it the most polluted month of the entire year for Lyon, with many other cities seeing the same pattern. Thus, the first two and last two months of the year are when Auvergne Rhone Alpes pollution levels are at their worst.
Contrasting to the previous question, after the highly polluted winter months are over, there is a universal improvement in air quality levels through the middle months of the year, with the occasional abnormality in the most polluted city of La Mulatiere, which had slightly raised readings in June and July, albeit considerably lower than its winter month readings, with numbers that came in within the ‘good’ rankings category of 10 to 12 μg/m³, and all the other months surrounding them such as May, August and September coming in within the WHO's target goal, with readings of 8.2 μg/m³, 8.5 μg/m³ and 7.1 μg/m³ respectively.
This continues extensively for all cities in the state, with March through to October having large amounts of WHO target readings, meaning that Auvergne Rhone Alpes air would be at its cleanest and most free from smoke, haze and smog during the summer months of the year, more prominently so in cities near to larger areas of greenery and vegetation such as Aurillac, further away from the larger and busier cities like Lyon.
With much of its pollution stemming from the use of cars, factory emissions and the burning of organic materials in homes and on people’s land or properties, the subsequent pollution would all be related to the combustion of these various materials.
Some of the main ones released from vehicles would be nitrogen dioxide (NO2) and sulfur dioxide (SO2), with nitrogen dioxide being the most prominent pollutant when it comes to vehicular fumes, often being found in high quantities over areas that see larger volumes of traffic, so much so to the point that levels of nitrogen dioxide in the atmosphere can be used to accurately determine how much pollution is coming from vehicles alone.
Other pollutants would include ozone, formed from the combination of various other compounds when subject to sunlight, and as such would be more prominent in the summer months. Black carbon and volatile organic compounds (VOC's) would all be present, some of which would include dangerous chemicals like benzene, toluene, xylene, methylene chloride and formaldehyde. All of these are extremely dangerous to breath, and can come from factory emissions, as well as the burning of biomass and organic matter. Their volatile nature also makes them easier to respire, due to them being gases at a lower temperature, increasing the hazards associated with having such contaminants in the air.