I’m feeling under the weather in my home city right now. And, boy oh boy, that pun is intended. I’m suffering from an excess of fine particulate matters – known in the trade as PM 2.5 and PM 10. Never heard of them? But you’ll face them daily if you live in a polluted city. And so will everyone else walking around. You see, the PMs harm us equally, rich or poor, gay or straight, black or white. I’ll say this for them – they don’t discriminate.

The sky outside is a strange mixture of grey and yellow as I write this. The usually sharp contours of the mountains are blurred, and a trip outdoors triggers a coughing fit and an overwhelming need to spit. And small wonder. Concentrations of air pollutants, specifically PM 2.5 and PM 10, are cited in micrograms per cubic meter (µg/m3). And the latest figures show that my part of the city has been registering near to, or above, the safety ceiling of 50 µg/m3.[1]

Even the poor visibility stems solely from air pollution – PM 2.5 and PM 10 – which endangers our health. I have long since given up smoking heavily but I bet if you looked at my lungs right now you’d think I was a pack-a-day smoker!

PM 2.5 and PM 10 are invisible but lethal

Epidemiologists divide particulate matter into two main categories: PM 2.5 and PM 10. PM literally means particulate matter. Now, if you’re in the countryside away from heavy industry or coal burning, you need not worry. But chances are that you still have a relative in a big city who will be affected.

You can’t see PM 2.5 and PM 10, of course.  Just like you can’t see bacteria or viruses. But that doesn’t mean they aren’t there. These minute particles can pass from our lungs into our blood supply and be carried throughout our bodies. They may be invisible to the human eye but in sufficient quantities, they raise air pollution to intolerable levels. The result is that you not only end up spluttering through the day, but you get headachy, listless and rheumy-eyed. So what are PM 2.5 and PM 10 composed of? Let’s take them one at a time.

Little particles – so what’s the difference and where do they come from?

PM 2.5 are 2.5 micrometres in diameter or smaller, which is around 3 percent of the diameter of a human hair. They are only detectable under a microscope. PM 2.5 are produced from all types of combustion, including motor vehicles, power plants, residential wood burning, forest fires, agricultural burning, and some industrial processes.  Sadly, it is precisely because PM 2.5 are so small that they penetrate deep into the respiratory tract, bypassing your system’s defences, reaching the lungs. Your body simply isn’t designed to block PM 2.5. They are lighter and go deeper into our body than PM 10, causing greater damage to our health; they also stay in the air longer and travel farther.

PM 2.5 and PM 10 size. How big are fine particles?

How do they affect our health?

Before serious illnesses become evident – and of course this results from cumulative exposure without wearing some form of protection – there are other short-term effects: nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath. People with lung and heart problems, children and the elderly are thought to be particularly sensitive to PM 2.5.[2]

Fact is, people who live in cities with high concentrations of PM 2.5 and PM 10 have more heart attacks, reduced lung function, worse asthma, and die younger overall than those lucky people who can breathe clean air.

Indices that measure urban air pollution typically focus more on PM 2.5 than PM 10 levels. What is certain is that levels of both are worse during winter, hence your writer is suffering unduly at present.

Read: Why Is Air Pollution Worse During Winter?

PM 10 are considered less harmful

Coarse dust particulate matter (PM 10), on the other hand, are less than 10 micrometres in diameter. Sources include crushing or grinding operations and dust stirred up by vehicles on roads. These small particles, 30 times smaller than the width of a hair on your head, are small enough to get caught up in our defensive nose hairs and into the upper airways of our lungs.

PM 10 irritates human airways, especially among asthmatics and the elderly. They make your eyes burn and throat dry. Public health experts, however, are less concerned about these larger forms of particulate matter because your body’s defences are reasonably effective against them. Tiny hairs along the respiratory tract block a portion of PM 10. Fortunately, you can also cough and sneeze some of it out. And your throat’s mucus elevator ejects some of it back out of your mouth or harmlessly into your digestive tract.

In addition, PM 10 particles can stay in the air for minutes, perhaps up to a couple of hours, while PM 2.5 particles can linger for days or (weather permiting) up to weeks. As a result, even though levels of both PM 2.5 and PM 10 are under constant surveillance, experts believe that PM 2.5 is the more harmful of the two.

Both PM 2.5 and PM 10 are health hazards, according to experts

There is a growing awareness of the danger posed both by PM 2.5 and PM 10. The World Health Organisation (WHO) believes they affect more people worldwide than any other pollutant. In their 2005 report, the organisation concluded that ‘all the population is affected, but susceptibility to the pollution may vary with health and age. The risk for various outcomes has been shown to increase with exposure and there is little evidence to suggest a threshold below which no adverse health effects would be anticipated’. [3] In other words, even short-term exposure carries the risk of health consequences.

Fortunately, city authorities are also gradually becoming more aware of the importance of clean air and monitoring levels of PM 2.5 and PM 10. But only as a result of constant protests from city dwellers and environmental groups. Let’s keep the pressure constantly high otherwise, we will all be spluttering our way to hospitals and emergency care facilities. And I will have to get out of my home city every winter.

How can I reduce my exposure to fine particles?

Finally, you are facing one of those dreadful days where you find yourself struggling to breathe outside. The air quality map confirms your fears. It shows orange, veering towards crimson. Those dreaded PM 2.5 fill the atmosphere. Retreating indoors will probably reduce the risk to your health, although some outdoor particles will inevitably follow you. If levels of PM 2.5 are really stratospheric, however, then air quality inside homes and offices may not be that much better.

Fortunately, there are ways to reduce your exposure to PM 2.5. Try to cut down on activities that exacerbate the problem – such as burning fires outside and lighting candles indoors. Avoid any stressful physical activity in those areas where fine particle levels are high. You could, for example, plan your journey to work along more sheltered ‘cleaner’ routes. And try to use some kind of protective equipment, gadget or method both indoors and outdoors.

[1] https://maps.luftdaten.info/

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4740125/

[3] http://apps.who.int/iris/bitstream/10665/69477/1/WHO_SDE_PHE_OEH_06.02_eng.pdf