Humans first start pumping pollutants into the atmosphere back when they were still living in caves, with smoke from cooking fires unable to escape due to a lack of ventilation. However, fast forward a few thousand years and the issue becomes of much greater concern, with far deadlier chemicals in the air and which are causing a huge range of health issues and on a significantly larger scale.
The Industrial era is when most people probably think air pollution really started, as technological advances brought vast numbers of factories to the big cites of England, as well as accompanying smog which brought with it death in great numbers¹. Although a number of Parliamentary Acts were introduced to minimize the negative impacts of factory emissions, the use of nicknames such as the ‘Big Smoke’ for London and ‘Auld Reekie’ for Edinburgh suggest that they weren’t entirely successful. One London smog in 1873 killed more than 700 people but 75 years later, around 4000 people died during the Great London Smog of 1952². It was this last event which caused the introduction of the Clean Air Act of 1956 and which moved factories out of the cities and into rural areas. Reductions in the use of domestic and industrial coal burning and the increasing use of smokeless coal helped reduce emissions of sulphur dioxide, one of the key contributors to acid rain.
However, although further legislation followed around the world, thanks to increasing awareness of the chemicals used in industrial processes, the problem is one which remains today. Carbon dioxide is perhaps the biggest contributor to atmospheric pollution, which formed 82% of all US greenhouse gas emissions in 2013.
Although naturally present in the atmosphere, human activities which alter the carbon cycle, such as the burning of fossil fuels and mass deforestation, are what are causing concern³. The main effects of increasing carbon dioxide levels are a rise in global temperatures, causing innumerable impacts for species and humans, and increased ocean acidification, which detrimentally affects marine species. For example, pteropods are tiny creatures fed on by whales but when exposed to water with higher levels of pH and carbonate, their shells dissolve, while acidification also negatively affects the ability of coral reefs to produce their skeletons, with fertilization, larval settlement and survivorship also at risk⁴.
Power plants, factories and industrial plants are also major contributors to air pollution, spitting out everything from sulphur dioxide, mercury, acid gases, nitrogen oxides, to particulates and which can have numerous dramatic effects on human health. Mercury for example, is known to cause neurological damage, such as reduced IQ, in unborn babies and young children who are exposed to emissions⁵. Metals like arsenic, nickel and chromium can cause cancer, while acid gases cause lung damage and contribute to asthma, bronchitis and other respiratory diseases, and with particulates causing premature death and a range of lung and heart diseases⁶.
Volatile Organic Compounds (VOCs) are gases which are emitted from a variety of indoor sources, with concentrations typically higher indoors that outside. One of the most common VOCs is formaldehyde, which is found in building materials such as plywood, while it is also emitted from the burning of gas, wood and kerosene as well as a variety of other sources. A colourless gas with a strong smell, formaldehyde is known to cause nausea and skin problems in low amounts, but with higher concentrations damaging lungs, kidneys, liver and the central nervous system and potentially even cancer⁷. Studies in China for example, have highlighted VOC emissions as a key area of concern, thanks mainly to a lack of control over their use⁸.
Mexico City is one of the largest cities in the world and unsurprisingly, it is also famously polluted. Its label as the most dangerous city in the world for children comes not only due to the sheer number of inhabitants and associated sources of emissions, but also from its geography⁹. The city is located in the crater of an extinct volcano around 2000 meters above sea level, with the reduced oxygen levels at that altitude leading to incomplete fuel combustion in engines and to higher emissions of a number of pollutants. The intense sun then turns these potent gases into a suffocating blanket of smog which perpetually hangs over the city, impacting negatively on its millions of inhabitants, in terms of both health and social effects, such as decreased productivity and increased burdens on the health system¹⁰.
It’s a nightmare image but one which is unfortunately repeated the world over, in cities as diverse as Ahwaz in Iran, Ulaanbaatar in Mongolia and Ludhiana in India¹¹. Although steps are being taken to improve matters in many countries, with the introduction of alternate energy sources, the problem remains unsolved in developing countries which lack the technology and finances to implement such changes. For these unfortunate citizens, air pollution casts a pall over their entire lives which they are unlikely to ever escape.