Dhaka Gripped by Severe Air Pollution, Ranks Second Globally
Dhaka, the sprawling and densely populated capital of Bangladesh, found itself once again at the grim forefront of global air quality concerns. On Tuesday morning, the city registered a concerning Air Quality Index (AQI) of 265 at 9:17 am, placing it second among the world’s most polluted urban centers. This alarming reading categorised Dhaka’s air as ‘very unhealthy’, signaling a significant and immediate threat to public health.
The AQI report highlighted a critical situation, with other major cities also facing severe air quality issues. Dakar, Senegal, topped the list with an AQI of 466, indicating hazardous conditions. Following Dhaka, Lahore in Pakistan and Kolkata in India occupied the third and fourth positions, respectively, with AQI scores of 223 and 222, both falling into the ‘very unhealthy’ category.
Understanding the AQI scale is crucial for comprehending the risks associated with these readings:
- 0-50: Good – Air quality is considered satisfactory, and air pollution poses little or no risk.
- 51-100: Moderate – Air quality is generally acceptable. However, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
- 101-150: Unhealthy for Sensitive Groups – Members of sensitive groups may experience health effects. The general public is less likely to be affected.
- 151-200: Unhealthy – Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
- 201-300: Very Unhealthy – Health alert: everyone may experience more serious health effects.
- 301+: Hazardous – Health warnings of emergency conditions. The entire population is more likely to be affected.
The AQI serves as a vital daily report, offering residents a clear picture of the air they are breathing and its potential impact on their well-being. In Bangladesh, the calculation of this index is meticulously based on the concentration of five key atmospheric pollutants:
- Particulate Matter (PM10 and PM2.5): These microscopic particles, especially PM2.5, can penetrate deep into the lungs and bloodstream, causing significant health problems.
- Nitrogen Dioxide (NO2): Primarily emitted from vehicle exhaust and industrial processes, NO2 can irritate the respiratory system.
- Carbon Monoxide (CO): A colourless, odourless gas produced by incomplete combustion, CO can reduce the oxygen-carrying capacity of the blood.
- Sulfur Dioxide (SO2): Largely from burning fossil fuels, SO2 can exacerbate respiratory conditions like asthma.
- Ozone (O3): Ground-level ozone, a major component of smog, is formed when pollutants react in sunlight and can damage lung tissue.
Dhaka’s struggle with persistent air pollution is a well-documented and ongoing challenge. Historically, the city experiences a marked deterioration in air quality during the winter months, a period characterized by lower temperatures, reduced wind speed, and increased emissions from various sources. Conversely, the air quality tends to improve with the onset of the monsoon season, which helps to disperse pollutants.
The global health implications of air pollution are stark and far-reaching. The World Health Organization (WHO) estimates that air pollution is responsible for approximately seven million premature deaths worldwide each year. These fatalities are primarily attributed to a range of serious health conditions, including stroke, heart disease, chronic obstructive pulmonary disease (COPD), lung cancer, and acute respiratory infections. The consistent high AQI readings in Dhaka underscore the urgent need for comprehensive and effective strategies to mitigate air pollution and protect the health of its millions of residents.
