We all know that our homes can reveal a lot about the people who live in them and their unique lifestyles — from the photos on the walls to the food in the fridge, down to the toiletries in our bathrooms, a quick snoop around tells you a great deal about the inhabitants of a house.
But what we might not know is that the air around us can also tell its own tales about our lives. The bacteria that you bring in from the street on your shoes, the tiny fibres from your furniture, the volatile gases given off by your deodorant — particles many times smaller than the size of a human hair can create a detailed picture of an environment, and it’s the job of an elite team of “air pollution detectives” to piece that story together and better understand how pollution can spread around a home.
Gem McLuckie, an advanced research scientist at Dyson’s lab in Malmesbury, UK, is one of those detectives. Along with a small team, she and her counterparts at Dyson’s facility in South Korea, spend their days analysing the pollutants that have collected on their air purifiers’ filters.
“Some of the filters come from employees’ homes,” she explains. “And sometimes, if we’re interested in studying a certain area, we will contact customers in that area and ask if they’d be willing to swap their old filters for new ones and let us analyse them.”
1. RUBBER — Rubber can come from different sources — you might
get rubber from car tyres in the filter, but the presence of rubber doesn’t automatically mean the air purifier was in the city, it’s just as possible that the owner was a keen runner, as trainers can also produce rubber particles like this.2. COOKING OILS — The presence of oil particles shows that the filter probably comes from a device that was located in a kitchen. The concentrations of oil can indicate whether the user was a fan of a regular fry-up, or only cooked with oil occasionally, while further analysis could probably tell you whether they favoured olive oil or sunflower oil.
3. TAR DEPOSITS — If a house were surrounded by dirt tracks, you’d be less likely to find tar deposits on a filter so this generally indicates an urban environment. Hotter climates can mean more tar is likely to be picked up from the roads outside so you might expect to find a higher concentration of tar on the filter.
This isn’t just professional nosiness. “If we can get a better idea of the sort of pollutants that our customers are exposed to, and can understand the different problems in different environments, we can ensure we’re creating products that best serve the needs of the people using them,” says Gem whose work focuses on the small particles — everything from plastic to pollen — found in HEPA filters.
Before you can begin to identify a particle, you have to be able to see it, and to do that these detectives use Scanning Electron Microscopy (SEM), an imaging technology many times more powerful than your average magnifying glass.
“We fire electrons at the surface of something and when they bounce off it, we pick up the pattern that the scattered electrons make to create a 3D image of the particle that we’re looking at,” explains Gem.
To analyse an entire filter in this way would take weeks. Instead, the scientists take representative samples from different areas of the filter. Even then the process can still take several days. “I recently spent three days having ‘a quick look’ at a filter,” laughs Gem.
Sometimes it’s apparent just from looking at the particle exactly what it is — a grain of pollen, for example, has a very characteristic shape. But at other times, chemical analysis is needed.
“At first glance, an organic particle and a rubber particle can look similar,” says Gem.
And while some particles might be easier to identify than others, to date, they’ve not stumbled across anything that’s been a total mystery.
“You might need to do more tests, or look into more literature, but you normally figure it out eventually.”
1. INORGANIC MATERIAL — It’s hard to say for sure what this particular organic particle is, but it is most likely a tiny piece of bark. Even in cities we live in the presence of a lot of organic matter which is small enough for us to breathe in, including: bark, plants, leaves. Their presence may also suggest that the filter has come from a more rural environment.
2. POLLEN — Dyson’s “pollution detectives” can actually tell what season it is from the pollen present — tree pollen is around from March to May, while weed pollen occurs between June and September. If there’s more pollen it also generally means a more rural area, while high concentrations of a certain pollen can tell you what plants can be found in the garden.
3. SILICON BALL — The presence of a lot of silicon balls in a filter shows that it has probably come from a home where a lot of synthetic products are used — these types of particles are carrier molecules and so are often found in scented products like household cleaners, make-up and other toiletries, such as deodorant and hairspray.
Each particle helps to build a picture of the environment where the filter was used. And while sometimes the pollution detectives will be aware of the provenance of the filter, at other times they may have no information whatsoever, gradually pulling together an idea of where the filter has come from, like a combination of Jilly Goolden doing a blind wine tasting and Keith Lemon peering Through The Keyhole.
“You can quickly work out whether it’s from an urban environment or a rural one,” says Gem. “Filters from towns and cities have a lot of particles from cars — particles from tyres and brakes — and industrial activity. While in the countryside you’ll find more organic and plant matter.”
Once they’ve established a rough location, it’s not hard to identify a room.
“Those in the kitchen tend to have a lot of natural and vegetative fibres from chopping food and you’ll also see particles from cooking oils. In the bedroom, you see a lot of skin cells from when people change the bedding, and we also find dead dust mites, excretions from dust mites, and lots of silica balls which tend to come from spraying hairspray, perfume, or deodorant. Then filters from the living room tend to have more plants and pollen in there, as well as residue from burning candles and fibres from the furnishings. We’ll know if you have a red sofa or a red cushion on your sofa, and whether it’s made from natural or synthetic material.”
And it doesn’t stop there.
1. BACTERIA — All filters will contain bacteria — from humans (we’re covered in the stuff), pets, the soil nearby — and a separate analysis can identify precisely which bacteria are present. The exact strains can give information on where the filter comes from as the bacteria found in a hospital environment, for example, would be different to those found in a home.
2. MOULD — The presence of a lot of mould in the filter indicates that it has come from a damp environment — the more moisture in the air, the more mould you’re likely to find. Further analysis can tell you more about the environment as certain moulds are common to damp dark areas, while others are wood or brick-based.
“We can tell if you have a pet, whether there’s damp in your home which is causing mould, whether you spend a lot of time outside and bring in a lot of mud, whether you buy cheap silicone-soled trainers, what type of flowers you like…” the list goes on.
After two years in the job, I wonder if anything she’s discovered has shocked or surprised Gem.
“I’ve started spraying deodorant in the bathroom with the window open to try to improve the air quality in the house,” she admits. “But most of all I’m shocked at how much of the urban world can get into our houses when we think it’s behind our front door. And that’s not something we as individuals can do much about. It would be lovely if some of the data we’ve found could influence emissions targets at a higher level.”
Words: Claire Coleman, freelance journalist
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