Air Quality Index - AQI
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The weather forecast is a very useful tool because it helps us, for example, to know what we should wear during the day or whether we should take an umbrella with us. But there is another kind of forecast that we should check every day and that, like the weather, changes all the time; it is called the “Air Quality Index – AQI” and it provides information on the quality of the air we breathe and that can greatly affect our health and the way we live. The AQI not only tells us how clean or unhealthy the air we breathe is but also, and more importantly, what the potential effects associated with our health may be.
The higher the AQI value, the greater the level of air pollution and, consequently, the greater the concern for our health. The AQI is divided into six levels:
- Good: air quality is satisfactory, associated to GREEN colour.
- Moderate: air quality is acceptable, associated to YELLOW colour.
- Unhealthy for Sensitive Groups: some people may experience some health effects, associated to ORANGE colour.
- Unhealthy: all people may begin to experience some health effects and members of Sensitive Groups may experience more severe effects, associated to RED colour.
- Very Unhealthy: all people may experience more serious health effects, associated to PURPLE colour.
- Dangerous: the entire population is even more likely to experience severe health effects, associated to BROWN colour.
Among the various air pollutants identified in the Kyoto Protocol (a famous international environmental treaty published in December 1997 at the COP3 where 180 countries participated and signed it), there are at least four most significant pollutants that are measured by the AQI, namely: Particulate Pollution (PM); Ozone (O3); Carbon Monoxide (CO) and Sulphur Dioxide (SO2). In order to facilitate the measurement and interpretation of their values, some colours have conventionally been adopted. Each colour not only describes a precise value of the pollutant (value within a range), but also indicates (or rather, suggests) the preventive actions to be taken to reduce the symptoms or negative effects that the pollutant itself can cause to each individual (categories of people identified not only by age group, but also identified by previous pathologies that each of them has suffered for some time). Let us discover them together, bearing in mind that the higher the AQI rating, the greater the health impact.
Particle pollution (also known as “particulate matter”) is a mixture of liquid droplets and solids of different materials with a very small sizes. In some cases the particles are emitted directly into the atmosphere (volcanic eruptions) while in others they are formed when pollutants emitted from various sources react in the atmosphere (forest fires and vehicle exhaust gases ). Very unhealthy and dangerous, particles smaller than 10 micrometres in diameter (smaller than the width of a single human hair) can very easily enter the lungs, aggravating disease and causing early death.
Subjects most at risk:
- young people, adults and the elderly alike, even healthy people if exposed for a long time
- people with previous heart or lung disease
Health effects:
- dust poisoning with subsequent emergence of respiratory infections such as coughing and asthma
- worsening of respiratory infections such as chronic bronchitis
- shortness of breath and increased fatigue, increased chest pains and palpitations
- in the worst cases, an increase in the frequency of heart attacks and arrhythmias leading to death
Prevention actions:
AQI Value Index
Actions to protect your health from Particle Pollution (PM)
WHO Target
(0 or 0 – 10 µg/m³)
None – Desiderable Air Quality level
Good
(0 – 50 or 10 – 12 µg/m³)
None
Moderate
(51 – 100 or 12.1 – 35.4 µg/m³)
Unusually sensitive people should consider reducing prolonged or heavy exertion
Unhealthy for Sensitive Groups
(101 – 150 or 35.5 – 55.4 µg/m³)
The following groups should reduce prolonged or heavy exertion:
• People with heart or lung disease
• Children and older adults
Unhealthy
(151 – 200 or 55.5 – 150.4 µg/m³)
The following groups should avoid prolonged or heavy exertion:
• People with heart or lung disease
• Children and older adults
Everyone else should reduce prolonged or heavy exertion
Very Unhealthy
(201 – 300 or 150.5 – 250.4 µg/m³)
The following groups should avoid all physical activity outdoors:
• People with heart or lung disease
• Children and older adults
Everyone else should avoid prolonged or heavy exertion
Hazzardous
(301 and higher or > 250.4 µg/m³)
Health warning of emergency condition: everyone is more likely to be affected
Ozone is a gas found in the air we breathe and, depending on where it is found, it can be good or bad. Good ozone, found in the Earth’s upper atmosphere (6 to 30 miles above the Earth’s surface), protects us from the sun’s harmful ultraviolet rays. Bad ozone, on the other hand, forms near the ground when pollutants (emitted by sources such as industrial boilers, power stations, chemical plants, refineries and cars) react chemically with sunlight. Generally, it is in the warmer months that ozone pollution forms.
Subjects most at risk:
- children, adults and the elderly
- people with lung diseases, such as asthma, chronic bronchitis and emphysema
- active people (of all ages who exercise or work outdoors)
- healthy people who are more sensitive to ozone (for genetic reasons)
Health effects:
- irritation of the respiratory system
- reduced lung function
- inflammation and damage to cells lining the lungs
- lungs more susceptible to infection and risk of permanent damage
- aggravation of asthma
- aggravation of other chronic lung diseases such as emphysema and bronchitis.
Prevention actions:
AQI Value Index
Actions to protect your health from Ozone (O3)
WHO Target
(0 or 0 – 10 µg/m³)
None – Desiderable Air Quality level
Good
(0 – 50 or 10 – 12 µg/m³)
None
Moderate
(51 – 100 or 12.1 – 35.4 µg/m³)
Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion
Unhealthy for Sensitive Groups
(101 – 150 or 35.5 – 55.4 µg/m³)
The following groups should reduce prolonged or heavy outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
• People who are active outdoors
Unhealthy
(151 – 200 or 55.5 – 150.4 µg/m³)
The following groups should avoid prolonged or heavy outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
• People who are active outdoors
Everyone else should limit prolonged outdoor exertion
Very Unhealthy
(201 – 300 or 150.5 – 250.4 µg/m³)
The following groups should avoid all outdoor exertion:
• People with lung disease, such as asthma
• Children and older adults
• People who are active outdoors
Everyone else should limit outdoor exertion
Hazzardous
(301 and higher or > 250.4 µg/m³)
Health warning of emergency condition: everyone is more likely to be affected
Odourless and colourless, carbon monoxide is a gas that arises when the carbon in fuels does not burn completely. Exhaust fumes from vehicles in densely populated cities contribute about 95 per cent of all carbon monoxide emissions. Natural sources such as fires or fuel combustion in industrial processes are other important sources of carbon monoxide production. During the cold season, carbon monoxide levels are generally higher because low temperatures make combustion not only less complete but also trap pollutants close to the ground.
Subjects most at risk:
- foetuses and young people without particular diseases
- healthy people if exposed for a long time
- people with general cardiovascular diseases (individuals with even partially occluded coronary arteries)
- people with a compromised cardiovascular and respiratory system (people with anaemia, chronic obstructive pulmonary disease, congestive heart failure or cerebrovascular disease)
Health effects:
carbon monoxide manages to enter our bloodstream through the lungs by binding to haemoglobin (a substance in the blood that carries oxygen to cells). This gas is capable of reducing, even drastically, the amount of oxygen reaching the body’s organs and tissues.
- Decreased mental and visual alertness
- chest pain and other cardiovascular symptoms (if exposed for too long and, in particular, during exercise)
Prevention actions:
AQI Value Index
Actions to protect your health from Carbon Monoxide (CO)
WHO Target
(0 or 0 – 10 µg/m³)
None – Desiderable Air Quality level
Good
(0 – 50 or 10 – 12 µg/m³)
None
Moderate
(51 – 100 or 12.1 – 35.4 µg/m³)
None
Unhealthy for Sensitive Groups
(101 – 150 or 35.5 – 55.4 µg/m³)
People with heart disease, such as angina, should reduce heavy exertion and avoid sources of carbon monoxide, such as heavy traffic
Unhealthy
(151 – 200 or 55.5 – 150.4 µg/m³)
People with heart disease, such as angina, should reduce moderate exertion and avoid sources of carbon monoxide, such as heavy traffic
Very Unhealthy
(201 – 300 or 150.5 – 250.4 µg/m³)
People with heart disease, such as angina, should avoid exertion and sources of carbon monoxide, such as heavy traffic
Hazzardous
(301 and higher or > 250.4 µg/m³)
Health warning of emergency condition: everyone is more likely to be affected
Colourless, sulphur dioxide is a gas produced when fuels containing sulphur (such as oil or coal) are burned. As you would expect, the highest levels of sulphur dioxide are concentrated in large industrial complexes and the main sources are refineries, power plants and industrial boilers.
Subjects most at risk:
- children, adults and the elderly without distinction, even healthy people
- people with asthma
- people with chronic lung diseases or cardiovascular diseases
Health effects:
very irritating to nasal passages. It is when we have heavy breathing (so-called breathlessness) during or after exercise that sulphur dioxide starts to cause its undesirable and harmful effects on our bodies.
- Even with very brief exposures of only a few minutes, narrowing of the airways can occur, resulting in bronchial-constriction characterised by wheezing, shortness of breath and chest tightness. As sulphur dioxide levels increase through increased breathing frequency, negative symptoms increase. After exposure to the gas, lung function returns to normal after about sixty minutes
- high levels of gas exposure mean that wheezing, shortness of breath and chest tightness can occur even in healthy individuals
- long-term exposure to gas causes all symptoms of respiratory diseases (cough and asthma in particular) to develop or worsen
Prevention actions:
AQI Value Index
Actions to protect your health from Sulphur Dioxide (SO2)
WHO Target
(0 or 0 – 10 µg/m³)
None – Desiderable Air Quality level
Good
(0 – 50 or 10 – 12 µg/m³)
None
Moderate
(51 – 100 or 12.1 – 35.4 µg/m³)
None
Unhealthy for Sensitive Groups
(101 – 150 or 35.5 – 55.4 µg/m³)
People with asthma should consider reducing exertion outdoors
Unhealthy
(151 – 200 or 55.5 – 150.4 µg/m³)
Children, asthmatics, and people with heart or lung disease should reduce exertion outdoors
Very Unhealthy
(201 – 300 or 150.5 – 250.4 µg/m³)
Children, asthmatics, and people with heart or lung disease should avoid outdoor exertion Everyone else should reduce exertion outdoors
Hazzardous
(301 and higher or > 250.4 µg/m³)
Health warning of emergency condition: everyone is more likely to be affected
Visible CO2
It is now possible to observe man-made CO2 emissions with the naked eye thanks to animations created by NASA. The data used to create these images are based on emissions recorded in 2021.
Carbon dioxide emissions envelop and overheat our Planet and today, thanks to a study realised by Nasa‘s Scientific Visualization Studio, it is possible to observe them. The following three videos highlight the dynamics of CO2 in different continents (Europe, Africa and the Middle East – the Americas – Asia and Australia) and show very clearly the origin and movements of atmospheric CO2 in each of these territories.
In the videos, each colour gives a precise indication: orange makes it easy to visualise and identify emissions from fossil fuels; red refers to emissions from biomass combustion; blue dots show the areas where most carbon uptake by ocean waters occurs; and green dots indicate areas of reabsorption by terrestrial ecosystems.
VIDEO 1 shows a significant amount of pollutants overshadowing Beijing (China). It appears, however, from the same images in this video, that emissions from fossil fuels in Australia are almost completely absent due to the low population density.
VIDEO 2, focusing on the Americas, highlights an emissions hotspot in the north-eastern part of the United States; in green, the carbon reabsorption by the Amazon rainforest is highlighted, particularly during daylight hours.
Finally, VIDEO 3 shows large concentrations of fossil fuel emissions from Saudi Arabia and European countries. There is also a much less visible red spot over Central Africa in the video that shows the presence of emissions from burning agricultural residues.
Video 1
Video 2
Video 3