How much pollution do we actually breathe in every day? Are masks or air purifiers more benefiting to our health? Do we really need both? The answer to this comes down to how and where we are spending most of our time every day.
There are two possible theories: masks might seem more effective since when you’re outside, where PM2.5 levels are generally higher than indoors (almost double in the places we tested). On the other hand, we spend most of our time indoors, so maybe an air purifier is more important?
To find the answer to this, I looked into how much dirty air we’re breathing every day.
Where Do We Hang Out?
According to the US Bureau of Labor Statistics, here’s how an average working person aged between 25-45 split their day between the 4 most-visited places:
(“Out and about” means places like restaurants, cinema, and gyms) Find out more here.
Now that looks a lot like my day. I spend most of my time in the office or at home sleeping (don’t call me lazy!)
Most of us can’t control the air we breathe when we’re out in restaurants, bars or the gym, but we have more control over the air we breathe in our home, outside, and hopefully in our office (that is, if you’re lucky enough to have an office like Smart Air!).
In total, we spend 80% of our time in these 3 places which means we can control 80% of the air we breathe, that’s not bad.
Counting the Particles
The next question is: if we didn’t have masks or purifiers, how much pollution would we be breathing in these four places?
First, we need an average value for the PM2.5 concentration where we are. Choosing Beijing, in 2016, the average PM2.5 was 72 micrograms per cubic meter. When we’re outside we get the full whack of this pollution, but when we’re inside we only get about half the dose.
Armed with this, and knowing that we breathe between 4.5-42.5L of air per minute (depending on the activity we’re doing) we can work out how many PM2.5 particles we breathe in one day…
The Total: 220,000,000 Particles!
Wow, we’re breathing around 220 million tiny PM2.5 particles every day, or just over 2,500 per second. Looking at their weight, in one day we’re breathing 622 micrograms of PM2.5!
Now, micrograms are tiny. So that’s about the equivalent of 1/20th of a grain of rice. Or in other words: we’re breathing a grain of rice’s worth of PM2.5 pollution every three weeks.
It might not sound like much, but since these particles are 20 times smaller than the width of a human hair, that’s still a lot! And these particles include toxic junk like coal and arsenic.
Where Are We Breathing These Particles?
We can split this number up into the four different places where we spend most of our day to see where we’re breathing the most pollution.
Here are the factors we take into consideration when calculating this:
· Length of time we spend in each place
· Amount of air we breathe per minute in each place
· PM2.5 concentration in each place
From that pie chart, there are some obvious things to point out.
Crazy Fact #1
Even though we spend most of our time at home, it’s not when we breathe in the most PM2.5. Research has found we breathe almost six times more air when we’re walking than when we’re sleeping. So that means when we’re at home and sleeping, we’re breathing in less pollution as well!
Crazy Fact #2
Crazy fact #1 being said, it means that even though we’re only outside for short periods of time, we’re actually breathing more! Coupled with the fact that there is more pollution outside, we’re breathing almost a third of our daily pollution outside (31% from the pie chart).
So back to the question: what helps the most – masks or air purifiers? Well, since we spend most of our time inside (over 90% of our day in our home and office, according to research), we’d be reducing our daily intake of PM2.5 by 60% by installing purifiers in these two places (assuming the purifiers are working well!).
For outdoors, by simply buying a 4RMB mask, we’re able to lower our daily intake of PM2.5 by almost a third. That’s less than US$1 for drastically cleaner air, pretty good deal?
Put simply, for the places where we’re breathing harder (outside) or the places we’re breathing for longer periods of time (the office and at home) we need to make sure we protect ourselves (turns out that’s everywhere).
If you’re someone who thinks masks aren’t useful or are too uncomfortable – they’re definitely needed! And if you’re someone who already wears a mask but thinks you’re safe from PM2.5 inside your home – you’re not!
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Choon Khin is a Smart Air engineer from Singapore, studying chemical engineering at the National University of Singapore