Its common knowledge that we need fresh air to maintain and live a healthy life, yet it is one of the most often ignored aspect of selection criteria when moving to a new location.
Big cities offer lot more in terms of career, pay, education, lifestyle and entailment but the downside to all this is the possibility of ending up in a polluted city.
More than 5.5 million people die prematurely every year due to air pollution as per Global Burden of Disease project research report.
Now that’s a staggering number for cause of death considering the fact that air pollution is the fourth leading risk factor after high blood pressure, unhealthy diet and smoking.
Outdoor air pollution is a global problem that seems to be affecting some countries more than others. Most affected are countries with economies that are rapidly developing like China and India.
What causes out door air pollution in cities?
The main contributors to air pollution are:
- Fossil fuels burnt in power plants and vehicle engines
- Industrial emissions from certain types of factories
- Burning wood or other materials for cooking and heating
- Forest fires, agricultural burning, erupting volcanoes etc.
Pollutants from these sources can be in the form of aerosols formed by tiny solid or liquid particles dispersed by wind.
Children and elderly population are more at risk by the effects of air pollution. People with certain health conditions like cardiovascular or respiratory diseases are also more likely to feel the negative effects of air pollution.
Types of air pollution
There are mainly 6 common air pollutants also known as criteria pollutants. They are nitrogen oxides, sulfur oxides, photochemical oxidants, carbon monoxide, lead and ground-level ozone.
These pollutions are basically defined by their chemical composition unlike particulate matter pollution which is defined by their size.
There are two types of particulate matter pollution: PM2.5 and PM10. The most dangerous form of these pollutants are very fine particles know as fine particles (PM2.5) or particulate matter of 2.5 μm (micrometers) diameter or smaller.
Particulate matter pollutions can be made up of various components such as organic chemicals, acids, metals, rock dust etc.
Why are fine particles PM2.5 dangerous?
Fine particles (PM2.5) can easily pass though the porous filter membranes inside the lungs and get trapped deep inside the lungs. They also get dissolved into the blood through the lungs and move to others part of the body.
These fine particles can increase the risk of developing heart and lung diseases, cause eye, nose and throat irritation, cause shortness of breath, cough or asthma attacks. It can also cause premature death in people with the above mention conditions.
WHO recommends that PM2.5 should ideally be below 10 µg/m3 (micrograms per cubic meter). Long term exposure to PM2.5 levels above 12 µg/m3 and short terms exposure to levels above 35.5 µg/m3 can be problematic as per guidelines from US Environmental Protection Agency.
Fine particles can also cause smog and reduce visibility, damage public properties, contaminate water, land and agriculture.
It is interesting to note that PM2.5 is smaller than most bacteria and body cells like white and red blood cells.
Air Quality and Pollution Scale for PM2.5
Most countries use color coded scale for air quality indices reporting the current air quality for the given 24-hour period.
List of top 10 most polluted cities by PM2.5
Chinese capital Beijing has made news headlines recently for the alarming rates of air pollution, but when it comes to PM2.5 pollutions, many Indian cities tops the list of most polluted cities.
The main factor contributing to this is heavy dependency of coal powered power plants and increasing use of private vehicles. Lack of strict monitoring and control for automobile emissions also contributes to this growing problem.
This list is compiled based on the average annual PM2.5 readings for major cities around the world.
Lucknow, India: PM2.5 level 96
Lucknow is a north Indian city that is highly industrialized with lots of heavy industries around the city. However, it is believed that major cause of PM2.5 pollutions in Lucknow is due to emissions from vehicles.
Ahmedabad, India: PM2.5 level 100
Ahmedabad is located in the western part of India. It is also a booming economic power house of India, with lots of new factories sprouting up around the city. It also has a booming real-estate market.
Khorramabad, Iran: PM2.5 level 102
Khorramabad is located in the western part of Iran. It is one of the largest cities of Iran and it is suspected that the large number vehicles in the city is the main contributor for the air pollution there.
Rawalpindi, Pakistan: PM2.5 level 107
Rawalpindi is a norther state of Pakistan. This is one of the most rapidly developing regions of Pakistan. It is also home to many large textile industries and other manufacturing which contributes to the city’s air pollution problem.
Peshawar, Pakistan: PM2.5 level 111
Peshawar is also a norther city of Pakistan. Brick manufacturing and the burning of solid waste has contributed to the city’s air pollution problem.
Karachi, Pakistan: PM2.5 level 117
Karachi a southern city of Pakistan and it is also the largest and most populous city in the world. Large number of industries and improper waste disposal has contributed to the air pollution problem in Karachi.
Raipur, India: PM2.5 level 134
Raipur is a city located in central India. It is an important regional industrial and commercial hub of India.
Gwalior, India: PM2.5 level 144
Gwalior is a city located in central India. The usual suspects, power generation and transportation are again to blame for the city’s air pollution problem.
Patna, India: PM2.5 level 149
Patna is the second largest city in eastern part of India. Factors like coal based power generation, industries and rapid construction works contribute to the city air pollution problem.
Delhi, India: PM2.5 level 153
Delhi is the capital of India and as per AQI classification, comes under the “unhealthy” category for PM2.5 level pollution and also tops our list of most polluted cities by PM2.5 levels.
The main reason for this high level of pollution is the large number of factories around the capital city and lack of sufficient regulatory measures to regulate emissions. Another reason is the high number of vehicles in the city.
City officials have been constantly trying to curb emissions from vehicles by introducing laws that prohibit commercial diesel vehicles to ply on city roads if they do not run on CNG (compressing natural gas) fuel.
To reduce the number of vehicles on road a metro rail system has also been functioning for more than a decade, however the city official needs to do a lot more quickly if they need to improve the city’s AQI in near future.
PM2.5 levels in comparison to other major cities around the world
- Beijing, China: 56
- Moscow, Russia: 22
- Washington, DC United States: 20
- Paris, France: 17
- London, UK: 16
- Wellington, New Zealand: 6
So what be done about PM2.5 pollutants?
It is usually the concentration of these fine particles in air that makes the difference between being harmless and hazardous for health.
Unfortunately, using dust masks while outdoor may not offer any benefits other than the false sense of security it can offer it users. PM2.5 can easily pass though these filters because of the microscopic size of these pollutants.
Governments worldwide are starting to take serious measures to combat air pollution, but progress is slow and it may take many decades before air pollution in certain cities around the world comes under control.
The only effective solution would be to select your location wisely taking into considering publically available air quality index (AQI) data.
It is important to note that this list is based on WHO data for PM2.5 levels. If overall pollution or other air pollutants are taken into consideration, then this list may look totally different.
WHO also claims that due to lack of monitoring data from many countries, it is difficult to make a comprehensive list. The same report also claims that other cities might have dangerously high levels of PM2.5 that maybe under reported.