Air pollution is one of the most significant environmental and public health issues facing the world today. Over the past 30 years, researchers have unearthed a wide array of health effects which are believed to be associated with air pollution exposure. Among them are respiratory diseases, cardiovascular diseases, and even death. Those most susceptible to severe health problems from air pollution are people with lung diseases such as asthma, emphysema or chronic obstructive pulmonary disease (COPD). People with cardiovascular disease are also very susceptible to air pollution.
Even healthy people can experience health impacts from air pollution including respiratory irritation or breathing difficulties during exercise or outdoor activities. Outdoor air pollution otherwise known as ambient air pollution, is a major environmental health problem affecting everyone in developed and developing countries alike. In both cities and rural areas, it was estimated to cause 3 million premature deaths worldwide in 2012. Some 88% of those premature deaths occurred in low- and middle-income countries, and the greatest number in the Western Pacific and South-East Asia regions. This mortality is due to exposure to small particulate matter of 10 microns or less in diameter (PM10), which cause cardiovascular and respiratory disease, and cancers.
The "WHO Air Quality Guidelines" provide an assessment of health effects of air pollution and thresholds for health-harmful pollution levels. In 2014, 92% of the world population was living in places where the WHO air quality guidelines levels were not met. WHO estimates that in 2012, some 72% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and strokes, while 14% of deaths were due to chronic obstructive pulmonary disease or acute lower respiratory infections, and 14% of deaths were due to lung cancer.
A 2013 assessment by WHO’s International Agency for Research on Cancer (IARC) concluded that outdoor air pollution is carcinogenic to humans, with the particulate matter component of air pollution most closely associated with increased cancer incidence, especially cancer of the lung. According to the Agency for Toxic Substances & Disease Registry, an arm of the Centers for Disease Control and Prevention (CDC), increases in air pollution have been linked to decreases in lung function and increases in heart attacks. This is a worrying state of affairs because in many parts of the world, air pollution has reached dangerous levels.
Types of Pollution
Particulate Matter - This come in various shapes and sizes and can be either solid particles or in liquid droplets. The smaller particles are called PM2.5 because they are less than 2.5 micrometers. That is 100 times thinner than a human hair. So there are particles floating around out there that are basically invisible to the human eye.
PM10 means particles of less than 10 microns (10 millionths of a meter or 10µm in diameter). In cities, most particulates come from traffic fumes.These particles are made up of toxic organic compounds and heavy metals from cars, smelting, processing metals, burning plants, forest fires etc. These toxins can travel deep into the lungs and cause health issues such as aggravating asthma, respiratory difficulty, decreased lung function and premature death as reported in various studies.
Sulphur dioxide - Coal, petroleum, and other fuels are often impure and contain sulfur as well as organic (carbon-based) compounds. When sulphur burns with oxygen from the air, sulfur dioxide (SO2) is produced. Coal-fired power plants are the world's biggest source of sulfur-dioxide air pollution, which contributes to smog, acid rain, and health problems that include lung disease.
Carbon monoxide - This highly dangerous gas forms when fuels have too little oxygen to burn completely. It can build up to dangerous levels inside the home as a result of poorly maintained gas boilers, stoves, gas fires or other fuel burning appliances. If you are burning fuel indoors, then it is wise to install a carbon monoxide detector.
Nitrogen oxides - Nitrogen dioxide (NO2) and nitrogen oxide (NO) are pollutants produced as an indirect result of combustion, when nitrogen and oxygen from the air react together. Nitrogen oxide pollution comes from vehicle engines and power plants, and plays an important role in the formation of acid rain, ozone and smog. Nitrogen oxides are also "indirect greenhouse gases" (they contribute to global warming by producing ozone, which is a greenhouse gas).
Volatile organic compounds (VOCs) - These carbon-based (organic) chemicals evaporate easily at ordinary temperatures and pressures, so they readily become gases. That's precisely why they're used as solvents in many different household chemicals such as paints, waxes, and varnishes. Unfortunately, they're also a form of air pollution: they're believed to have long-term (chronic) effects on people's health and they also play a role in the formation of ozone and smog.
Ozone: Also called trioxygen, this is a type of oxygen gas whose molecules are made from three oxygen atoms joined together (so it has the chemical formula O3), instead of just the two atoms in conventional oxygen (O2). In the stratosphere (upper atmosphere), a band of ozone ("the ozone layer") protects us by screening out harmful ultraviolet radiation (high-energy blue light) beaming down from the Sun. At ground level, it's a toxic pollutant that can damage health. It forms when sunlight strikes a cocktail of other pollution and is a key ingredient of smog (see box below).
Chlorofluorocarbons (CFCs) - Once thought to be harmless, these gases were widely used in refrigerators and aerosol cans until it was discovered that they damaged Earth's ozone layer. We discuss this in more detail down below.
Unburned hydrocarbons: - Petroleum and other fuels are made of organic compounds based on chains of carbon and hydrogen atoms. When they burn properly, they're completely converted into harmless carbon dioxide and water; when they burn incompletely, they can release carbon monoxide or float into the air in their unburned form, contributing to smog.
How Air Pollution Affects Your Lungs and Health
Generally if you are young and in a good state of health, moderate air pollution levels are unlikely to have any serious short term effects. However, elevated levels and/or long term exposure to air pollution can lead to more serious symptoms and conditions affecting human health. This mainly affects the respiratory and inflammatory systems, but can also lead to more serious conditions such as heart disease and cancer. People with lung or heart conditions may be more susceptible to the effects of air pollution.Long-term exposure to polluted air can have permanent health effects such as: Accelerated aging of the lungs. Loss of lung capacity and decreased lung function. Development of diseases such as asthma, bronchitis, emphysema, and possibly cancer.
High air pollution levels can cause immediate health problems including:
Long-term exposure to polluted air can have permanent health effects such as:
Pollutant Health Effects at High Levels
Nitrogen Dioxide - This gas inflames the lining of the lungs, increasing the symptoms of those suffering from lung diseases. It can also reduce immunity to lung infections. which can cause problems such as wheezing, coughing, colds, flu and bronchitis.
Sulphur Dioxide - This gas irritates the nose, throat, and airways which causes coughing, wheezing, shortness of breath, or a tight feeling around the chest. The effects of sulfur dioxide are felt very quickly and most people would feel the worst symptoms in 10 or 15 minutes after breathing it in. Studies indicate that a proportion of people with asthma experience respiratory symptoms and changes in pulmonary function when exposed to Sulphur Dioxide for as little 10 minutes.
Particulate Matter (PM) - Fine particles can be carried deep into the lungs where they can cause inflammation and a worsening of heart and lung diseases. PM causes changes in blood chemistry that can result in clots that may lead to heart attacks. It can also increase susceptibility to viral and bacterial pathogens leading to pneumonia in vulnerable people who are unable to clear these infections.
Carbon Monoxide - This gas prevents the uptake of oxygen by the blood. This can lead to a significant reduction in the supply of oxygen to the heart, particularly in people suffering from heart disease
Ozone - This gas can cause coughing, shortness of breath and, throat irritation and chest pain. It may also worsen chronic respiratory diseases such as asthma as well as compromise the ability of the body to fight respiratory infections.
Dealing with High Levels of Pollution
On days when high pollution levels are expected, take these extra steps to reduce pollution:
Research published in 2014 showed that consuming broccoli sprouts enhances the detoxication of some airborne pollutants and may provide a frugal means to attenuate the associated long-term health risks of air pollution. Broccoli sprouts are a convenient and rich source of the glucosinolate, glucoraphanin, which can generate the chemo-preventive agent, sulforaphane.
Research shows that sulforaphane is an effective anti-carcinogen, and acts in part, through inducing detoxication enzymes. This placebo-controlled, randomized intervention trial was conducted with two hundred and ninety-one study participants who were recruited from Qidong, in the Yangtze River delta region of China. This area is characterised by exposures to substantial levels of airborne pollutants. This trial used a beverage with a blended, well-defined content of sulforapane and it’s precursor glucoraphanin every day for 12 weeks. Excretion of the metabolites of the pollutants, benzene, acrolein, and crotonaldehyde, were measured before and during the intervention. The key finding from this clinical trial was the observed rapid and highly durable elevation of the detoxication of benzene, a known human carcinogen, and acrolein metabolites in the participants.
This is a powerful piece of research that we can take action on. It certainly justifies the old saying of ‘eat your greens’. The health benefits of broccoli and indeed all cruciferous vegetables are undisputed; however, obtaining an optimal amount of the nutrients contained in these vegetables, such as sulforaphane, may be a challenge. Are you going to eat broccoli every day? It is certainly possible if you absolutely love your greens, but may be a challenge if your taste buds disagree. There are broccoli extracts, however, such as sulforaphane supplements, that can be used to augment our diets.
Air pollution is a major environmental risk to health. By reducing air pollution levels, countries can reduce the burden of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma. The lower the levels of air pollution, the better the cardiovascular and respiratory health of the population will be, both long- and short-term.
It is important for us to consider the quality of the air we are breathing on a daily basis. But how can we do this if we live in towns and cities where pollution is high? Unfortunately, in the short term, there are few options in these environments other than to move to a less polluted areas. However, that is easier said than done and may not even be an option with work and life commitments. In this case, getting away to the coast or to a forest every so often is a good way to relax and get some quality air into our body. We can also take some of the steps mentioned above to avoid pollution on days when it is particularly high as well as consider dietary intervention to help our bodies detoxify airborne pollutants. In the longer term, there are many groups lobbying for cleaner air in our towns and cities and this is starting to have an impact. However, this may take time. What we need is a Clean Air Act that is fit for the 21st Century that tackles the sources of air pollution we've discussed in this article. We need improved legislation that ensures the our air quality gets better, not worse.
Rapid and Sustainable Detoxication of Airborne Pollutants by Broccoli Sprout Beverage: Results of a Randomized Clinical Trial in China. DOI: 10.1158/1940-6207.CAPR-14-0103 Published June 2014
International Agency for Research on Cancer. Press Release N° 221, 17 October 2013
IARC: Outdoor air pollution a leading environmental cause of cancer deaths.
World Health Organization. Ambient (outdoor) air quality and health. Fact Sheet Updated September 2016.
Sports & fitness nutritionist, researcher and author on a mission to improve the human condition. Focusing on evidence-based and outcome-based nutrition, training, mindset & environment