Introduction to air quality
Anthropogenic activities are a major cause of air pollution. Whilst historically it was the actions of the industrial sector which led to major air pollution events (such as the famous Great Smog of London in 1952) in the Western world, today the transport sector plays an increasingly devastating role in making our air unsafe for breathing (Kampa & Castanas, 2008). The burning of fossil fuels through the use of motor vehicles releases nitrous oxides (NOx), particulate matter and carbon monoxide into the atmosphere, which can cause significant negative health impacts to people (Frank & Engelke, 2005). This essay will look at the different types of air pollutants we are exposed to every day, particularly those which derive from the transport sector. The effects of these pollutants on the body will be discussed, as well as the measures undertaken to combat air pollution.
What are air pollutants?
Kampa & Castanas (2008) define four main categories of air pollutants: gaseous pollutants (sulphur dioxide, nitrous oxides and carbon monoxide), persistent organic pollutants, heavy metals (such as lead and mercury) and particulate matter. The latter is especially important with reference to health effects on humans, because particles of dust, dirt, diesel soot and metals can cause havoc on the body, and especially its respiratory system; fine and ultra-fine particulate matter (smaller than one nanometre, or a 10-millionth of a centimetre) damage the alveoli in the lungs, often causing irritation and difficulty breathing (Kampa & Castanas, 2008; Frank & Engelke, 2005).
“Particulate matter is the generic term used for a type of air pollutants, consisting of complex and varying mixtures of particles suspended in breathing air… produced by a wide variety of natural and anthropogenic activities” – Kampa & Castanas (2008)
Persistent organic pollutants (POPs) are those which remain in the environment for long periods of time (Kampa & Castanas, 2008). Pesticides are examples of POPs, which nicely illustrate the second important characteristic of POPs, which is that they become more deadly as they move up the food chain. For example, if a rabbit consumes pesticides, it will have these pesticides in its body. When a fox comes along to eat the rabbit, it consumes the rabbit and the pesticides within it, and probably several other rabbits in the same situation – meaning the fox will have a much larger concentration of pesticides in its body. This process of increasing the concentrations of a substance through the food chain is called biomagnification. Note: This relates less to air pollution, but is nonetheless important to remember when thinking about what you are eating and what it has been exposed to.
“Human health effects [of air pollution] can range from nausea to difficulty in breathing to skin irritation to cancer. They also include birth defects, serious developmental delays in children and reduced activity of the immune system” – (Kampa & Castanas, 2008)
Gaseous pollutants are another form of pollutant which a person might be exposed to: these include carbon monoxide and nitrous oxides, the two big ones which come directly from the burning of fuel in cars. A number of studies have attempted to measure exposure to gaseous pollutants by using sensors – Hu (2014) is an example of a study where participants wore sensors to measure the air pollution around them whilst jogging, driving or cycling. Their findings show that a person is typically more exposed to carbon monoxide whilst driving, than compared to cycling or jogging, due to proximity to a road. However, when considering the increased heart and breathing rates of joggers compared to drivers, total intake of air pollutants is actually higher (Hu, 2014).
Another interesting paper by Frank & Engelke (2005) looked at the relationship between city design (and therefore transport links and routes) and air pollution levels in urban areas, as a proxy for human health. They found that through recent history, public health problems such as poor sanitation and overcrowding have been high on the city-planner’s agenda – this led to the development of suburbs, in an effort to reduce populations in city centres (Frank & Engelke, 2005). This priority has been somewhat forgotten in recent years, with many cities consistently surpassing legal limits on air pollutant concentrations (see if you can spot your nearest city’s pollution levels here https://www.theguardian.com/cities/datablog/2017/feb/13/most-polluted-cities-world-listed-region). The study goes on to suggest that investing in greener transport, and discouraging the use of motor vehicles in cities through policy changes, might be a more effective way of combating air pollutants than redesigning cities and suburbs.
Should I be worried?
A study by Rojas-Rueda et al. (2011) looked at the health effects of cycling instead of taking a car whilst commuting. It studied the effectiveness of a bicycle-sharing scheme in Barcelona, Spain, and found that when considering intake of particulate matter of less than 2.5 micron size, the health benefits of physical activity and the risk of traffic accidents, the overall benefits of cycling outside in the city outweigh the risks. This was primarily as a result of the high physical benefits of cycling instead of driving compared to the lower risk presented by air pollution in the city (Rojas-Rueda et al., 2011). This might suggest then that it is better to exercise outdoors in spite of air pollution, in some cities.
However, another study set in Malaysia looked at the contribution of air pollution levels to mortality (Mahiyuddin et al., 2013). They found that there was a significant association with some pollutants, such as PM10 and ozone (lower in the atmosphere than the famous ‘ozone layer’) and mortality – in particular, where the levels of PM10 were 3x the Malaysian air quality guidelines limits, there was a highly significant association with mortality.
These studies demonstrate not only how air pollution problems differ between countries, but of course also how risk changes between countries. The easiest way to determine what you are being exposed to, as well as the legal limits for each pollution, is to look it up online – local councils and national governmental departments should publish air quality records, and compare them to the World Health Organisation limits.
Kampa, M. & Castanas, E. (2008) Human health effects of air pollution. Environmental pollution, 151(2), pp.362-367
Frank, L.D. & Engelke, P. (2005) Multiple impacts of the built environment on public health: Walkable places and the exposure to air pollution. International Regional Science Review 28, 193–216
Hu, K. (2014) Personalising pollution exposure estimates using wearable activity sensors, in: IEEE ISSNIP 2014 – 2014 IEEE 9th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, Conference Proceedings. IEEE Computer Society.
Rojas-Rueda, D., de Nazelle, A., Tainio, M. & Nieuwenhuijsen, M.J. (2011) The health risks and benefits of cycling in urban environments compared with car use: health impact assessment study. Bmj, 343, p.d4521
Mahiyuddin, W.R.W., Sahani, M., Aripin, R., Latif, M.T., Thach, T.Q. & Wong, C.M. (2013) Short-term effects of daily air pollution on mortality. Atmospheric environment, 65, pp.69-79