The term “air pollution” conjures up a broad array of images – from hazy smog to acid rain and buildings stained from exhaust fumes. Equally broad are its causes and negative effects on human and environmental health. In fact, the vast majority the world’s population is adversely affected by air pollution, perhaps without even realizing it. The good news is, since most air pollution is caused by human activity, it's a problem that all of us can do something about.
According to the World Health Organization (WHO), 90 per cent of people around the world are breathing polluted air, and an estimated seven million people lose their lives annually because of exposure to the combined effects of ambient (outdoor) or household (indoor) air pollution. Air pollution refers to harmful chemicals and particles released into the air by various natural and human activities. These include but are not limited to: particulate matter such as dust, smoke and soot; ozone (O3); nitrogen dioxide (NO2) and sulphur dioxide (SO2).
Generally, air pollution is referred to as being either ambient (outdoor) or household (indoor). These terms primarily refer to the sources of pollutants. For instance, motor vehicles are a source of ambient air pollution, and solid-fuel-burning cooking stoves are an indoor source.
The WHO puts forth standard guidelines for air quality based on the average concentration of fine particulate matter in the air. PM10 refers to particulate matter between 2.5 and 10 micrometres in size. PM2.5 is 2.5 micrometres or smaller and includes pollutants harmful to human health such as sulfate, nitrates and black carbon. The WHO recommends countries reduce their air pollution to annual mean values of 20 μg/m3 for PM10 and 10 μg/m3 for PM2.5. However, some major cities still exceed those numbers by as many as five times over.
Urban areas typically pose a greater risk. According to available WHO data, more than 80 per cent of people living in urban areas where air pollution levels are tracked are exposed to air that exceeds recommended levels. Low- and middle-income countries experience the greatest exposure.
The Roots of the Problem: How Did This Happen?
The air pollution question is a tricky one, and there is no single cause for it. Some sources are natural – e.g. forest fires and dust storms – but the vast majority are caused by human activity. These include: coal and oil power plant emissions, industrial facilities such as factories and mines, agricultural waste burning, motor vehicles and solid fuel burning in households.
Economic development has exacerbated the effects in some areas. India, for example, has experienced rapid economic growth in recent years, meaning India's demand for energy has also increased. To satisfy that demand, India turned to their most abundant resource available, coal. Despite the decreasing cost of renewable energy, coal still provided 80 per cent of India’s total power in 2016-17.
The problem with coal is particulate matter. In fact, fine particle air pollution is the No. 1 environmental risk factor worldwide, responsible for more deaths than alcohol consumption, high-sodium intake and sedentary lifestyles.
Vehicle emissions are another major contributor to ambient air pollution. In 1992, the UN named Mexico City the world’s most polluted city. The number of cars in Mexico City increased from 3.5 million in 2005 to 6.8 million in 2013, and worsening traffic congestion has led the city to implement driving restrictions to reduce the number of private vehicles on the roads.
Diesel-fueled vehicles are particularly problematic. Churning out nitrogen dioxide (NO2), sulfur dioxide (SO2) – both of which can react with sunlight to create ground level ozone (O3) which is extremely harmful – and particulate matter, vehicles running on diesel fuel have contributed massively to air pollution in many parts of the world. While diesel cars produce similar emissions to cars running on petrol, they emit significantly more amounts of particulate matter.
Fortunately, there has been a recent surge in enthusiasm for banning vehicles that run on fossil fuel. In 2016, Mexico City was one of four major cities to commit to banning all diesel vehicles by 2025. Others have followed suit, with entire countries such as Germany, China, India and Norway vowing to eliminate diesel and petrol vehicles and/or setting targets for electric vehicle sales.
Another major source of outdoor and indoor air pollution is the use of traditional cooking stoves, particularly prevalent in low- and middle-income countries in Asia and Africa. In 2016, 2.45 billion people were exposed air pollution at home, according to the State of Global Air. The main cause of household air pollution is the use of solid fuels – e.g. coal, charcoal, wood, dung – for heating and cooking. Burning these solid fuels creates an indoor cloud of carbon monoxide and nitrogen oxide. Both can cause health problems like anemia, nutritional deficiency and stunted growth in children; in adults, strokes and heart attacks are common. The WHO estimated that in 2016, 3.8 million deaths were caused by household air pollution from cooking with polluting fuels and technologies.
The causes of poor air quality vary widely - other contributors include sand and desert dust and deforestation. Yet, the consequences are the same. Resulting airborne particles and chemicals have combined to create dangerous levels of air pollution in places all over the world.
The Health and Environmental Consequences
High levels of pollutants in the air can profoundly affect a population spread over a large area and cause significant health problems. Check out the video below for a comprehensive overview.
The production of ozone (O3) - the principle component of smog - is also a significant contributor. Ozone is created when emissions from cars and factories react to sunlight, and inhaling it can cause a number of respiratory ailments. In fact, long-term exposure is thought to be connected to one million premature deaths per year due to respiratory diseases, according to researchers from the University of York’s Stockholm Environment Institute (SEI).
Children can be particularly vulnerable. In 2017, the WHO reported more than one in four children under the age of five die because of unhealthy environments. Indoor and outdoor air pollution are risk factors, along with second-hand smoke, unsafe water, lack of sanitation, and inadequate hygiene. The rise in cases of children suffering from asthma has also been blamed on the increase in air pollution. A study published in The Lancet Respiratory Medicine found children exposed to air pollution at an early age might be more likely to develop asthma throughout childhood and adolescence.
Beyond the health risks, air pollution can affect general safety as well. For instance, smog created through air pollution forms a dense haze which blocks out landmarks and streets. It produces hazardous road conditions for motorists and has forced busy international airports to cancel or redirect flights.
The issue of air pollution was sidelined for many years, while focus was instead placed on supporting growing economies in countries like China and India. However, many are now waking up to the environmental repercussions of leaving the issue unaddressed.
The use of renewable energy sources - ones which aren't as polluting as burning fossil fuels - such as solar energy, wind power and hydropower are on the rise. According to the International Renewable Energy Agency, the global capacity for renewable generation has been steadily increasing. Solar photovoltaics (PV) experienced 32 per cent growth in 2017, and wind followed with 10 per cent. India has committed to source 40 percent of its power from renewables by 2030.
When it comes to vehicle emissions, cities and countries can take measures to reduce the number of vehicles on the roads, cut emissions and encourage people to use alternative forms of transport. For example, Norway plans to eliminate all petrol-fueled cars by 2025. And London’s congestion charge – which requires a fee for driving within a designated zone during working hours – reduced traffic levels by 10.2 percent in its first 10 years.
The issue of indoor pollution also urgently needs to be addressed. People in low and middle-income countries that still rely on polluting, solid-fuel burning stoves for cooking and heating, and kerosene lamps for light, need access to innovative solutions – cheaper, cleaner alternatives that won't pollute the air around them. Some examples that are already in use around the globe include: the Recycoal project which is transforming raw waste into a cleaner-burning coal in Rwanda; peer-to-peer solar energy sharing in Bangladesh; and an electricity- and battery-free light powered solely by gravity in Kenya.
The benefits of fighting air pollution almost go without saying. It reduces the threat to human health posed by particulate matter and other toxic chemicals, assists the fight against global warming by reducing greenhouse gasses, can contribute to a more sustainable economy, improves the health and quality of life of citizens and removes the smog and other unpleasant physical effects which can make many cities dark and gloomy places to live. The multifaceted underlying causes make the issue a difficult but not impossible one to solve - with the right initiatives and investment, air pollution can be managed and its negative side effects kept in check.