In my first-ever wet lab, my tutor handed me a flaccid, disembodied lung and asked if I could identify the oblique fissure.

I couldn’t. I was two weeks into medical school straight out of an Arts degree, and had absolutely no idea what was going on in any of my classes. So, I tried to wriggle my way out of answering the question by asking the tutor what horrible disease had turned the patient’s lungs all black and spotty.

“That? That’s not a disease, that’s just someone who lived in a city!” the tutor scoffed. “It’s carbon from air pollution. That’s probably what your lungs will look like by the time you die, too.” He reclaimed the lung and handed it to the person next to me. (She successfully identified the fissure.)

That afternoon, I went home to my house — on a busy street, right in the middle of Sydney — and wondered what the traffic rumbling past my window was doing to my lungs. I pictured my young, healthy respiratory system slowly being poisoned and tarred by invisible particulate matter streaming out of nearby exhaust pipes. A few days later, I went out and bought a fiddle leaf fig tree to put in a pot next to my bed, in the vague hope that it might somehow clean the air in my room enough to save my lungs from a supposedly inexorable decline into carbon-black spottiness.

Notwithstanding the current trend for keeping indoor plants in our bedrooms, urban air pollution is a significant and growing health issue in Australia. The World Health Organisation (WHO) has found that a number of Australian cities, including Melbourne, Hobart and Canberra, have air pollution levels well above what they deem to be safe for human health. This puts residents in these cities at an increased risk of all sorts of health problems; not just the lung cancer, COPD and asthma issues that immediately spring to mind when we think of air pollution, but also stroke and ischaemic heart disease. Across Australia, cars, factories and power stations all seep tiny, invisible particles of pollution into the air – which build up in our bodies, turn our lungs black, and often make us sick.

Worldwide, the statistics are genuinely startling. The WHO has estimated that no less than 90% of the world’s population is currently breathing unsafe air, and that air pollutants are responsible for about a third of deaths from stroke, chronic respiratory disease and lung cancer, as well as a quarter of heart attack deaths. And, of course, air pollution also exacerbates climate change, which has been described by the Lancet as “the greatest global health challenge of the 21st century.”