Why pollution increases in winter

The lower level of precipitation means there just isn’t enough rain to wash away the pollutants.

As winter approaches, a sinister grey cover blankets the city of Lahore, Pakistan. On 17th Nov 2021, Lahore was declared the most polluted city on the planet. The air quality index (AQI) value reached 348, more than the mentioned hazardous level of 300 by the World Health Organisation (WHO). A similar situation was observed in the city of Delhi, India, where the hospitals suddenly reported an increased number of patients with respiratory problems. Other symptoms include irritation in the nose as well as itchy eyes. The authorities have shut down schools and colleges due to the worst air quality. About 50% of the private sector staff were told to work from home amid the smog. 

This air quality index value of 348 was unprecedented. Those wondering what these numbers mean can refer to the table below:

Daily AQI colourLevels of ConcernIndex valueDescription
GreenGood0-50Satisfactory. No risk or threat
YellowModerate51-100Acceptable. But it may affect people who are sensitive to air quality
OrangeUnhealthy for sensitive groups101-150Sensitive groups may experience health effects. The general public is less likely to be affected
RedUnhealthy151-200The general public may experience health effects. Sensitive groups may experience more serious health effects
PurpleVery unhealthy201-300Health alert: the risk of health effects increased for everyone
MaroonHazardous301+Health warning or emergency: everyone is more likely to be affected
(Source: https://www.airnow.gov/aqi/aqi-basics/)

Something’s in the air

So the question here is, why does air quality decline in winter? 

To understand this, we have to take a look at what smog is! Smog is a combination of two words – smoke and fog. The main constituents of smog are generally hydrocarbons, vehicular emissions, industrial smoke and agriculture waste burning, and dust. One must consider weather and climate to understand how and why the concentration intensifies, especially in winter.

We all have learned in school that warm air rises and cool air sinks. This is because the colder air is denser than, the warmer air. Being denser means the gas molecules have less space between each other than in warm air. We also know that because particles in smog are suspended in the air, the particles do not have much free space to move or escape in the colder air. Also, cold air does not move as quickly as warm air and does not allow the pollutants to disperse. Hence why, air pollution in winter remains for much longer. This increases people’s exposure to polluted air for extended periods, causing respiratory problems.

 Rain acts as a natural cleanser of contaminants in the atmosphere. Additionally, cold air is dryer and generally cannot sustain moisture. This leads to lower levels of precipitation in winter. The lower level of precipitation means there just isn’t enough rain to wash away the pollutants.

‘Tis the season

During winter, energy demand substantially increases to keep up with the weather. More and more electricity and gas are consumed to keep our homes warm. We often leave our cars idle to defrost or to wait till a point where the heater starts to warm up the car. These activities contribute to increased air pollution. People in rural areas burn wood and coal to keep themselves warm.

Considering Lahore, one of the reasons for hazardous air quality is the burning of stubble and other agricultural waste in the surrounding region, which significantly increases pollutants in the atmosphere. Other sources include using low-grade fuels for farming purposes, emissions from brick kilns, industries including steel mills and vehicles, etc., and construction sites. Incomplete data makes it difficult to point out the exact sources and their contribution in this regard.

In contrast to the areas of the world that have moist winters, the seasonal experience can differ. Moist air brings high precipitation, cleansing the pollution from the air by natural means.

Why it matters

Air pollution has been a major cause of respiratory diseases as well as heart and kidney problems. An estimated seven million people die due to diseases related to air pollution every year in the world. A recent estimate by WHO (March 2019) shows the mortality rate has increased to 8.8 million people annually. That’s roughly 75% more than the deaths caused by COVID-19 until Dec 31, 2020. China and India are the worst-affected regions, where air pollution accounted for 9.85% and 8% of total deaths in 2017, respectively.

Steps to reduce air pollution

We have seen that most of the air pollution is caused by vehicular, industrial, and agricultural emissions. In order to prevent air pollution, every one of us has to play our part in it. The reason is that we and only us are responsible for this. We can start by taking little steps towards a better society.

  • Drive less and take public transport. According to the US Environmental Protection Agency (EPA), vehicles cause 75% of the total carbon monoxide emissions. Less number of cars on the road will definitely help in reducing air pollution. Using cars that follow the standards of cleaner emission standards. The use of greener and cleaner fuels can help lessen vehicular emissions. Furthermore, people often walk or ride bicycles to work. This is not just a healthy activity but better for the environment. The government can help by funding research towards greener and cleaner technologies.
  • Conserve energy. Turning off extra lights and using less power-consuming appliances and energy-efficient devices at home can help conserve energy. Insulating your homes properly helps reduce energy consumption and bills. By doing this, you will also reduce energy production, which is a major cause of air pollution
  • Shift to renewable energy sources. Solar energy is an efficient way to reduce your carbon footprint and help minimize your electricity bills. However, the installation cost can be high, but it will be worth it in the longer run.
  • Plant trees and stop deforestation. Trees absorb carbon dioxide gas from the atmosphere and provide us with oxygen, consequently reducing the greenhouse effect. Trees planted in urban areas can also reduce the warming effect caused by the concrete, providing a natural cooling system.

Final words! If every one of us, as an individual, cared about our environment rather than pointing fingers at each other, our world would be a better place for us and others. Secondly, we should start promoting green technologies and ventures. The government should promote and fund projects that do not cause pollution in the first place. Investing in cleaning technologies does help, but promoting intrinsically green technologies helps a lot more. In short, just do your part well!






Also, read: Air Pollution: The Invisible Murderer