POLLUTANTS IN THE AIR
The Air Quality Index (AQI) is a numerical scale used to communicate the quality of air in a specific location and its potential impact on health. It provides a way to convey complex air quality information to the public in a simple and easily understandable format. The AQI is calculated based on the concentrations of various air pollutants, including particulate matter (PM10 and PM2.5), ground-level ozone, sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO).
The AQI typically ranges from 0 to 500, with higher values indicating poorer air quality and a greater potential for adverse health effects. The scale is divided into different color-coded categories, each corresponding to a different level of health concern:
- 0-50: Good (Green) - Air quality is considered satisfactory, and air pollution poses little or no risk.
- 51-100: Moderate (Yellow) - Air quality is acceptable; however, some pollutants may be a concern for a small number of people who are unusually sensitive to air pollution.
- 101-150: Unhealthy for Sensitive Groups (Orange) - Members of sensitive groups (e.g., individuals with respiratory or heart conditions, children, and older adults) may experience health effects, but the general public is less likely to be affected.
- 151-200: Unhealthy (Red) - Everyone may begin to experience adverse health effects, and members of sensitive groups may experience more serious effects.
- 201-300: Very Unhealthy (Purple) - Health alert; everyone may experience more serious health effects.
- 301-500: Hazardous (Maroon) - Health warnings of emergency conditions; the entire population is more likely to be affected.
- These particles are classified as extremely fine particulate matter (PM), and the accompanying numbers denote their diameter.
- For instance, PM 10 and PM 2.5 have diameters smaller than 10 and 2.5 microns, respectively.
- To provide a sense of scale, one micron is about a thousandth of a millimeter. The minute size of these particles plays a crucial role in their impact on human health, as finer particles pose greater challenges for self-protection.
- Due to their diminutive size, PM 2.5 particles can easily bypass the nose and throat, gaining entry into the circulatory system.
- These particles have the potential to contribute to chronic diseases such as asthma, heart attacks, bronchitis, and other respiratory issues.
- Originating from emissions produced by factories, vehicular pollution, construction activities, and road dust, these particles do not disperse easily and remain suspended in the air we breathe
Ozone is a gas that is present in the upper layers of the atmosphere, protecting human health from the impact of the Sun’s UV rays.
However, surface-level ozone is among the most significant air pollutants. It is formed by the reaction of atmospheric pollutants in the presence of sunlight.
According to a 2017 study published in the International Journal of Medical Public Health, “With increase in surface ozone levels, there is likelihood of an increase in risk of hospital admissions for Chronic Obstructive Pulmonary Diseases (COPD) and the number of cardiovascular and respiratory deaths.”
Sulphur dioxide (SO2)
According to the US government’s Environment Protection Agency, the largest source of SO2 in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities. Additional sources are industrial processes and natural sources such as volcanoes.
As with other gases, SO2 exposure is harmful to the cardiovascular system and can lead to the development of respiratory illnesses. SO2 can also react with other compounds to form particulate matter. “At high concentrations, gaseous SOx can harm trees and plants by damaging foliage and decreasing growth,”
Ammonia (NH3)
A 2017 NASA-funded study said that in India, “A broad increase in fertilizer use coupled with large contributions from livestock waste have resulted in the world’s highest concentrations of atmospheric ammonia.”
In the troposphere – the lowest, most dense part of the atmosphere where all weather takes place and where people live – ammonia gas reacts with nitric and sulfuric acids to form nitrate-containing particles. Those particles contribute to aerosol pollution that is damaging to human health. Ammonia gas can also fall back to Earth and enter lakes, streams and oceans, where it contributes to harmful algal blooms and “dead zones” with dangerously low oxygen levels
Lead (Pb)
Lead is a naturally occurring toxic metal found in the Earth’s crust. But in increased quantities, exposure to it becomes extremely dangerous to health. Important sources of environmental contamination come from mining, smelting, manufacturing and even recycling activities, according to the WHO
Carbon Monoxide (CO)
A toxic, colourless and odourless gas, it is given off when fuel containing carbon, such as wood, coal and petrol, is burned. If CO levels are high enough, a person may become unconscious and die. Long-term exposure has been linked with an increased risk of heart disease
5. Way forward
Government agencies and environmental monitoring stations use the AQI to provide real-time or forecasted information about air quality, helping individuals make informed decisions to protect their health, such as limiting outdoor activities during times of poor air quality.
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Previous Year Questions 1.In the context of WHO Air Quality Guidelines, consider the following statements : (UPSC CSE 2022) 1. The 24-hour mean of PM2.5 should not exceed 15 μg/m³ and annual mean of PM2.5 should not exceed 5 μg/m³. 2. In a year, the highest levels of ozone pollution occur during the periods of inclement weather. 3. PM10 can penetrate the lung barrier and enter the bloodstream. 4. Excessive ozone in the air can trigger asthma. Which of the statements given above are correct? A.1, 3 and 4 B.1 and 4 only C. 2, 3 and 4 D.1 and 2 only Answer (B) |
Source: Indianexpress
