Explainer: What is AQI, and Why Should We Be Concerned When It is High

The Air Quality Index (AQI) is a numerical scale used to measure and communicate air quality, indicating how clean or polluted the air is based on harmful pollutants. These include particulate matter (PM2.5 and PM10), ground-level ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2). The AQI helps individuals understand the potential health risks associated with exposure to these pollutants and is divided into categories from “good” to “hazardous,” aiding in decision-making about outdoor activities and health precautions.

In Mumbai, the air quality is deteriorating as PM2.5 and PM10 levels increase. PM2.5 refers to very fine particles smaller than 2.5 microns, which can penetrate deep into the lungs, causing respiratory issues, heart disease, and lung cancer. PM10 particles, though slightly larger, are still harmful and can contribute to similar health problems. These pollutants are released by sources such as vehicle emissions, industrial activities, wildfires, and construction. They can travel long distances, affecting both urban and rural areas. The global consistency in measuring these pollutants enables health organizations to track air quality and take necessary actions.

In December, Mumbai experienced an alarming rise in air pollution levels, with the Air Quality Index (AQI) soaring to approximately 400, indicating a hazardous situation for public health. The severe deterioration in air quality, particularly due to elevated concentrations of particulate matter (PM2.5 and PM10), led to stringent measures being implemented across the city. Construction activities and other work operations were suspended in areas such as Borivali and Byculla, where pollution levels were especially critical. This crisis underscored the pressing need for effective measures to combat air pollution and protect the well-being of residents.

Another factor exacerbating Mumbai’s air quality is temperature inversions. Inversions occur when a layer of warm air traps cooler air near the surface, preventing it from mixing with the atmosphere. This traps pollutants close to the ground, worsening air quality. In colder months, increased use of fireplaces releases additional PM2.5 into the air. If an inversion occurs during this time, PM2.5 particles remain trapped near the ground, affecting vulnerable groups like children, the elderly, and those with respiratory conditions.

The AQI is categorized into different levels: 0-50 is “good,” with little or no health risk; 51-100 is “moderate,” where pollutants may affect sensitive individuals; 101-150 is “unhealthy for sensitive groups,” with risks for people with respiratory or heart conditions; 151-200 is “unhealthy,” where everyone may experience health effects; 201-300 is “very unhealthy,” prompting health warnings; and 301 or higher is “hazardous,” with serious health risks for the entire population.

Exposure to high AQI levels can lead to various health issues, including respiratory problems like shortness of breath, coughing, and wheezing, as well as aggravated asthma and chronic bronchitis. Cardiovascular problems such as heart attacks and strokes are also more common, particularly in those with existing heart conditions. Long-term exposure can cause reduced lung function and increase the risk of lung cancer. Vulnerable groups, such as children, the elderly, and people with pre-existing conditions, are at greater risk. Additionally, poor air quality can reduce outdoor physical activity due to health concerns.

To protect health during high AQI times, it’s important to stay indoors, limit outdoor activities, and use air purifiers. Wearing masks that filter particulate matter when going outside and avoiding pollution sources like burning fuels or unnecessary driving can help reduce exposure. Staying updated on local air quality reports and taking actions to reduce pollution individually and collectively is essential to improve air quality and safeguard public health.

Shruthi Singh

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