Humans: Polluting the air that gives us life

Welcome back fellow readers! Having gained an overview of air pollution previously, aren’t you curious about how air pollution occurs? Well, there is little surprise here but we naughty humans are at the forefront of poisoning the very air we breathe. From simple, everyday activities to processes imperative for economies to function, much of what we do is leaving irreversible harm on the air around us. In this entry, let us explore some anthropogenic (human-induced) sources of air pollution.

The world is driven by energy – but where is this energy derived from? This interactive chart (hover your mouse around the different years!) shows us that global fossil fuel consumption has multiplied twenty-fold since the industrialization era of the mid-20th century. Today, humans rely heavily on fossil fuels for a wide range of purposes like electricity generation, transportation, and industrial operations. Perera (2017) reports that fossil fuel combustion is responsible for emitting 85% of particulate matter and almost all of the sulphur dioxide as well as nitrogen oxide in the air. What I found really disturbing was that just by extracting or producing fossil fuels produces huge amounts of methane, a greenhouse gas highly efficient at trapping heat (Perera, 2017). Despite the proliferation of endeavours on developing clean and renewable energy sources, approximately 84% of global energy demand continues to be supplied by fossil fuels, which are readily available and difficult to substitute (Rapier, 2020)

If only mankind’s wrongdoings were limited to burning fossil fuels… Unfortunately, the reality is a far cry away. Soaring global demand for food has necessitated large-scale land use changes involving the clearing of large tracts of forests for conversion into agricultural use. A study by Nowak et al. (2014) found that trees remove up to 23.2 million tonnes of air pollution per year through intercepting particulate matter and absorbing gaseous pollutants. Given that agricultural land use has increased to nearly 50% of habitable land today (Ritchie and Roser, 2019), that’s a lot of pollutants remaining in the air because of the trees we remove!

The rapidly evolving tastes and preferences of affluent global consumers have also stimulated greater livestock production. “Surely there can’t be anything wrong with growing those innocent little cows!” – or so I thought, until Rivera and Chará’s (2021) reminder that livestock digestion and waste account for 37% of methane and 65% of nitrous oxide emissions respectively. The next time you chomp down on a cheeseburger at McDonald’s, or tuck into a steak at your favourite restaurant, ponder over your pollutive footprint as some *extra* food for thought!

Figure 1. Process of methane emission from livestock and amount of methane emission by type of livestock (Gustin, 2020)

Finally, let us shift our attention away from where fossil fuels are burnt or where agricultural production is, towards the cosy confines of our homes. For decades prior to 1987, the unregulated use of refrigerators was responsible for emitting ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) that eventually culminated in the stratospheric ozone hole. While CFCs and HCFCs were gradually phased out years after the 1987 Montreal Protocol,  the replacement “ozone-friendly” hydrofluorocarbons (HFCs) have a greenhouse effect believed to be 4000 times more potent than carbon dioxide (ScienceDaily, 2012). Moreover, the residence time of CFCs, HCFCs, and HFCs are in the magnitude of decades, indicating that their pollutive impacts can neither be stopped nor controlled so long as we continue to use refrigerators. What goes into the air stays in the air – remember?

Figure 2. Differences between HCFC and HFC (Madhu, 2021)

The list of anthropogenic causes of air pollution goes on and on, but I have summarised a few of what I thought were the most worrying and/or relatable in this entry. Indeed, it does appear that the onset and sustenance of human civilization has brought forth unprecedented destruction to the air, which has and will continue to already returned to haunt us. But what if humans did not exist? Would air pollution still occur, and to what extent? Tune in to my next entry to find out.

Until then, breathe safe and be safe!

 

References

Gustin, G. (2020). As beef comes under fire for climate impacts, the industry fights back. Inside Climate News. Retrieved January 23, 2023, from https://insideclimatenews.org/news/21102019/climate-change-meat-beef-dairy-methane-emissions-california/