Clean air is not a luxury

Dhaka recorded an Air Quality Index, or AQI, reading of 167 on Sunday. The index classifies that level as unhealthy. AQI turns measurements of air pollutants into a number that communicates how clean or polluted the air is and what risks may follow.

A reading of 167 is not merely a warning of mild pollution. It places Dhaka in a category where pollution can affect everyone, while people with health conditions may face greater risks. The article gives no pollutant-by-pollutant breakdown, but the overall index clearly indicates poor air.

The timing is important. Winter is fast approaching, and the article warns of an imminent threat from air that is not fit to breathe. Dhaka has long ranked among the world's most polluted cities, yet little is being done to address the problem. The Sunday reading shows that the crisis remains immediate.

The Air Quality Index, or AQI, is a public information scale. It summarizes pollution levels and links them to possible health effects. Rather than requiring people to interpret several pollutant measurements, it offers one number and a category, such as good, moderate, or unhealthy.

On the commonly used AQI scale, 0 to 50 is considered good, while 151 to 200 is unhealthy. Therefore, Dhaka's reading of 167 sits inside the unhealthy band. It means the air contains enough pollution to pose a health concern for the general population, with greater concern for sensitive groups.

The article does not identify which pollutant drove the reading. It does establish the key message: Dhaka's air was unhealthy on Sunday. That warning matters because the city already has a long record of severe pollution, and winter may bring conditions that make the problem worse.

For the commonly used AQI scale, readings from 0 to 50 are considered good for human health. Higher readings indicate increasing pollution and increasing health concern. The article reports Dhaka at 167, placing the city in the 151-to-200 unhealthy category.

Numerically, 167 is 117 points above the top of the good range and about 3.3 times higher than 50. That comparison shows the gap between Dhaka's Sunday air and levels generally considered clean. AQI categories are more useful than simple multiplication, however, because health risk does not rise in a perfectly linear way.

The article gives no separate safe-limit measurement for Dhaka or for individual pollutants. Its clear comparison is categorical: the city's air was unhealthy. Because Dhaka is already among the world's most polluted cities, the reading adds urgency as winter approaches and breathing conditions may deteriorate.

Air classified as unhealthy contains enough pollution to affect health across the population. Short-term exposure can irritate the eyes, nose, throat, and airways. It can also cause coughing, wheezing, chest discomfort, headaches, and shortness of breath. Children, older adults, pregnant people, and those with asthma or heart disease may be more vulnerable.

Fine particles are especially concerning because they can travel deep into the lungs. Some can pass into the bloodstream, contributing to inflammation and stress on the heart and blood vessels. Exposure may trigger asthma attacks and worsen chronic lung or heart conditions. Repeated exposure is linked with greater long-term risks, including reduced lung function and cardiovascular disease.

The article does not list specific illnesses. It does establish that Dhaka's air was unhealthy at 167. That classification makes the reading a public-health warning, especially with winter approaching and the city continuing to face persistent pollution.

The provided article does not identify particular pollution sources in Dhaka. That limitation matters because an AQI reading describes the overall condition of the air, not automatically the activities responsible for it. Identifying sources requires pollutant measurements, emissions data, and local monitoring.

In Dhaka and other large cities, established sources commonly include vehicle exhaust, industrial emissions, construction dust, road dust, brick kilns, and burning waste or other materials. These sources release gases and particles that can accumulate in the atmosphere. Their relative importance can change by location, weather, and season.

Those examples provide useful context, but they should not be presented as findings from this short article. The source confirms only that Dhaka is persistently among the world's most polluted cities and recorded an unhealthy AQI of 167 on Sunday. Effective action would require identifying major contributors and reducing their emissions before winter worsens conditions.

Winter pollution often intensifies when weather prevents pollutants from dispersing. Dry conditions provide less rain to wash particles from the air. Calm winds also reduce the movement of polluted air. In some situations, a temperature inversion traps cooler, polluted air beneath warmer air, keeping emissions close to where people breathe.

The mechanism is simple: pollution continues to enter the atmosphere, but removal slows. Traffic, industry, dust, and burning can then accumulate near the ground. Shorter or weaker atmospheric mixing can make the same emissions produce higher measured concentrations than they would during wetter, windier periods.

The article does not detail Dhaka's winter weather or name specific sources. It does warn that winter is fast approaching and that air may become unfit to breathe. Since Dhaka has long been among the world's most polluted cities, seasonal buildup could make an existing problem more dangerous.

PM2.5 means particulate matter measuring 2.5 micrometres or less in diameter. These particles are far smaller than visible dust. Their size makes them important for health because the body's upper airways cannot reliably stop them. They can remain suspended in air and be inhaled during ordinary breathing.

After entering through the nose or mouth, PM2.5 can pass down the airways into the deepest parts of the lungs, including the air sacs where oxygen moves into the blood. Some particles or their chemical effects can then cross into the bloodstream. This may trigger inflammation and stress in the lungs, heart, and blood vessels.

The article does not mention PM2.5 specifically. It reports an unhealthy AQI of 167, which may reflect one or more pollutants. PM2.5 is a key example of why polluted air can harm health even when particles are too small to see.