We all know the dangers of leading a sedentary lifestyle, smoking tobacco and sunbathing without sunscreen.

But many of us may not realise that one of the biggest health threats comes from an invisible killer – the polluted air that we breathe.

A damning report released last week by the Royal College of Physicians estimates that air pollution will contribute to 30,000 premature deaths this year in the UK. It warns that air pollution affects almost every organ in the human body and has a significant health impact, even at low concentrations.

‘We breathe in 11,000 litres of air every day and you only need a tiny amount of pollution in each breath for a lot to enter your body,’ says Professor Frank Kelly, director of the Environmental Research Group at Imperial College London.

‘Heart disease, stroke, respiratory conditions, cancer and even neurodegenerative diseases such as dementia are all linked to the quality of air we breathe.’

And this onslaught from polluted air begins at a young age, he adds. ‘We know the lungs of children living in urban areas exposed to too much pollution don’t develop to a full size.’

Children with under-developed lungs are more likely to face respiratory problems later in life.

Meanwhile, pregnant women can pass on harmful inhaled pollutants in their blood to their unborn child, potentially damaging the way their organs develop, and air pollution is known to heighten the risks of heart attacks, strokes and asthma attacks in general.

A 2019 study by King’s College London found days with above-average pollution levels led to an extra 124 out-of-hospital cardiac arrests a year, as well as 231 additional strokes and 193 hospital admissions for asthma.

The main pollutants we face are gases such as nitrogen dioxide (from the combustion of fossil fuels, gas cookers and diesel engines), ozone (from a chemical reaction between other pollutants) and sulphur dioxide (also from burning fossil fuels).

Then there is particulate matter (PM) – specifically, PM2.5 which are tiny particles of carbon and metals with a diameter smaller than 2.5 micrometres (30 times smaller than the diameter of a strand of hair). PM2.5 can enter the lungs and bloodstream, affecting all major organs. Yet it’s not only the pollutants themselves that do the damage – it’s also the body’s response to them.

The immune system detects their presence and tries to destroy them, as it would bacteria or viruses, triggering an inflammatory cascade that wreaks havoc in our organs and tissues. But what many people might not realise is that indoor pollution can be just as bad as outdoor air pollution.

The Royal College of Physicians report says poor ventilation, damp and mould, and emissions from domestic heating, gas cooking, wood burners and household cleaning products all contribute significantly to poor health.

Professor Kelly adds: ‘If you use a gas hob, for example, rather than an electric one, you’ll be exposed to more particles of nitrogen dioxide.

‘Meanwhile, spray deodorants, candles and cleaning chemicals all release volatile organic compounds (VOCs) – gases that you can usually smell – that are pollutants and can be dangerous to our health if we’re exposed to them over months and years.’ But how much of these pollutants are we all breathing in? In a unique experiment, we teamed up with the University of Birmingham to analyse air pollution – indoor and outdoor – five people were exposed to while going about their daily lives.

They were given pollution monitors – devices that measure PM2.5 exposure – to wear for at least 24 hours during the same two days.

The World Health Organisation (WHO) suggests that annual average exposure of PM2.5 should not exceed 5 mcg per cubic metre, while 24-hour average exposures to PM2.5 should not be higher than 15 mcg/m3.

Here, we examine the levels and – at times unexpected – sources of air pollution our volunteers encountered, while experts advise how you can reduce the impact on your health.

EXPOSURE PEAKED WATCHING TV IN BED

Marianne Horton, 38, a health coach, lives in Solihull, West Midlands, with her husband Ben, 32, a technical director, and their daughters, aged seven and 16 months.

Highest reading: 74 mcg/m3 (while in bed)

Lowest reading: 0.1 mcg/m3 (while driving)

MARIANNE SAYS: I am currently on maternity leave and spend my days doing the school run for my eldest daughter, going to baby classes and visiting local shops and parks.

I’ve always had concerns about outdoor air pollution because we live close to Birmingham Airport, and when planes fly over our house they get so close I can name the airline.

Additionally, my eldest daughter suffers from seasonal allergies and had to have her tonsils and adenoids (glands in the upper airway) removed two years ago because they were chronically inflamed.

I worry about air quality affecting her health and I don’t let her play outside for too long on days when air quality is particularly bad (I use apps such as Ventusky to monitor local pollution levels). But my highest air pollution reading was actually when I was watching TV in bed at 9.50pm. I didn’t expect to be exposed to the most air pollution in my bedroom – but it seems the particulate matter was high there, because of the dust.

I typically vacuum my bedroom about once a fortnight and our woollen carpets trap a lot of dirt and dust. But knowing the results, I can see cleaning – or lack of it – has more of an impact on air pollution than I’d thought, and I’ll try to vacuum more often. I’d rather suck up these particles in a machine than have them in my lungs.

EXPERT COMMENT: Dust is a major source of indoor air pollution, as it gets redistributed when we, for example, move bedding around, says Francis Pope, a professor of atmospheric science at the University of Birmingham.

‘The particles all fall down slowly and then they stick to the carpet. When we then walk over the carpet, we re-suspend them into the air again.’

Marianne’s highest reading lasted around 15 minutes – after getting into bed and watching TV before going to sleep. Dr Dimitrios Bousiotis, a researcher in atmospheric processes and air pollution at the University of Birmingham, says PM2.5 ‘spikes’ like this don’t tend to have a significant impact on the 24-hour average (which in Marianne’s case was 4.8).

However, any high exposure of this level can be dangerous for those with lung conditions such as asthma and chronic obstructive pulmonary disease (COPD), explains Dr Pujan Patel, a consultant respiratory clinician at Royal Brompton Hospital in London.

‘Exposure even for up to an hour can affect lung function – and even more so in people with underlying lung disease,’ he says.

‘High levels of PM2.5 exposure repeatedly over time leads to a reduction in forced expiratory volume [a measure of lung function which shows how much air someone can exhale in one second].

‘In a healthy person, this is something that changes gradually, so it might take 20 years before they develop symptoms caused by pollution – whereas someone with asthma or COPD would experience greater and faster declines in their lung function.’

And what of Marianne’s concerns about airport pollution? Professor Kelly says: ‘Aircraft produce pollution during take-off and landing but that’s generally well away from where anybody lives and, once above 600 ft, any pollution is diluted so much in the air that it’s not an issue for local neighbourhoods.’ 

RISK OF OPEN WINDOW FOR ME AND MY DOG SID 

Noel O’Connor, 58, owns a building company and lives in Selly Park, Birmingham.

Highest reading: 140.7 (drinking coffee near a major road)

Lowest reading: 1.7 (while sleeping)

NOEL SAYS: My readings showed I was exposed to high levels of pollution while drinking a coffee mid-afternoon outside a cafe close to a dual carriageway, even though I was a good 20 metres away. I’d think again about doing that.

The second highest readings occurred while driving my diesel truck around central Birmingham in the morning, reaching 19.5 (my average reading for the day was 4.3). I always have the passenger window open because I have a dog, Sid, who likes sticking his head out.

I also drove through tunnels underneath the city centre. Now I’m aware how much pollution this exposes me to, I’ll avoid opening my windows when driving through heavy traffic and through busy tunnels. The various building sites I visited had low levels of PM2.5 exposure because we work in the residential market and I insist the properties are left clean and tidy.

My lowest readings came while I was at home, which was a relief. I try to keep my home as clean and dust-free as possible and it mainly has tiled or wood floors, which probably helps.

EXPERT COMMENT: ‘Traffic is associated with greater emissions of PM2.5, especially in urban environments,’ says Dr Bousiotis.

‘They come from the exhaust – these are smaller particles – or larger ones from other sources such as tyre or brake wear. The closer to the source, the more you’ll inhale.

‘The worst thing you can do is drive with open windows, especially in traffic.’

And as for Sid, animals are affected by air pollution as well as humans, adds Professor Pope.

In slow-moving or stationary traffic, particles from other vehicles get in through an open window and find their way into your lungs. In a moving vehicle, it’s less of an issue, as they get dispersed into the environment.

While the building sites Noel visited didn’t cause spikes in air pollution readings, they weren’t large, dusty sites.

‘Construction sites typically produce larger particles called PM10, rather than PM2.5,’ adds Dr Bousiotis. While PM10 can enter the lungs, they don’t enter the bloodstream.

SPRY-ON DEODORANT GAVE HIGHEST READING

Lavania Oluban, 37, a food tech teacher, lives in Northfield, Birmingham, with her seven-year-old son.

Highest reading: 1,921.3 (spraying deodorant)

Lowest reading: 0.2 (while driving)

LAVANIA SAYS: I expected my highest readings to come from cooking pizzas in my classroom, which contains seven gas ovens.

But I was, in fact, exposed to significantly more air pollution – a whopping 1,921.3mcg/m3 – after spraying deodorant at the gym.

I was early for my class, so I went into a cubicle, got changed, sprayed my deodorant and sat there for five minutes of peace after a busy day.

My second highest reading (152) was around 7am the next morning, when I again used body spray – this time in the car. Seeing these results, I’ll replace the spray in my bag with a roll-on deodorant. It’s worrying that the level of PM2.5 was so high and I was breathing it in within a confined space.

EXPERT COMMENT: It’s not a good idea to sit in a confined area and breathe in particles of sprays such as deodorants, which contain lots of VOCs, says Professor Pope, as they ‘can be harmful to health in high concentrations’.

In fact, aerosols emit more VOCs than all the vehicles in the UK combined, according to a 2021 study by the University of York and the National Centre for Atmospheric Science.

While Lavania’s daily average of 6.4 was below the daily limit of 15, it was above the WHO’s annual average limit.

‘This suggests Lavania should try to minimise her exposure to PM2.5 as, if this is typical of what she is exposed to every day, then it would exceed the annual limit and could have health implications,’ says Professor Pope.

WORST OUTSIDE HOME DUE TO TRAFFIC RAT RUN 

Simon Brown, 45, a managing director, lives in Solihull, West Midlands, with his wife Victoria, 44, a business coach, and their children, aged six and eight.

Highest reading: 10.7 (standing on a busy road)

Lowest reading: 0.1 (while driving)

SIMON SAYS: Usually, I commute from Solihull to Exeter, London or Reading by car or train at least once a week. On the day of the experiment, I drove to Exeter and back, a two-and-a-half hour journey each way, mainly on the M5.

You worry about all the exhaust fumes outside, so I keep my windows closed and air conditioning on. It was reassuring to know that this helped keep my air pollution readings low, despite driving on a busy motorway for so long.

My highest reading came loading up my car before heading to Exeter shortly before 6am. At this time of the morning, we have a lot of traffic passing through our road as it’s a cut-through for a local car factory.

I was pleased that my average reading was low, at just 2.6 – although I still wonder if I’m exposed to higher levels of PM2.5 when I’m making long journeys by train.

EXPERT COMMENT: ‘We can see Simon managed to make his car journeys healthier through the use of air conditioning, which filters the air and removes air pollution – limiting exposure,’ says Professor Pope.

Dr Bousiotis notes that it’s essential that vehicle air filters are changed once a year (for example, during an MoT) to ensure they are working at an optimal level.

POLLUTANTS SPIKED WHEN WE USED THE AIR FRYER 

Jenni Fryer, 51, chief executive of a community garden charity, lives in Sutton Coldfield with her two teenagers.

Highest reading: 155.8 mcg/m3 (getting ready for work)

Lowest reading: 0.6 (while driving)

JENNI SAYS: My highest readings occurred while I was getting ready in my bedroom at around 8am – when I sprayed deodorant and perfume, and shook out my feather duvet.

My two dogs, Peggy and Dali, regularly come up into my bedroom, so it could be cleaner. I don’t vacuum every day.

I usually keep my smaller bedroom windows slightly open but they have blinds over them, which limits the air flow.

Now I know how much indoor air pollution I’m exposed to, I’ll definitely consider using roll-on instead and avoid spraying my perfume unless the windows are open. 

In the evening, my children cooked chicken strips in the air fryer, producing a spike of 48.3 in air pollutants. I don’t tend to open the kitchen windows, as they’re difficult to reach, and I rarely use my extractor fan because it’s noisy – but now I know it could reduce pollution levels, I’ll definitely use it more.

EXPERT COMMENT: Air pollution can rise when we get ready in the mornings because dust particles that may have settled, for example on clothes, are moved back into the air, explains Dr Dimitrios Bousiotis, a researcher in atmospheric processes and air pollution at the University of Birmingham. ‘Particles from products such as aerosols and perfumes can settle in carpets and soft furnishing and also re-enter the air with people’s movements.’

Francis Pope, a professor of atmospheric science at the University of Birmingham, recommends reducing spray use, frequent vacuuming and ventilation through air conditioning or opening windows. ‘This removes particles trapped in the room.’ And ‘pets can be a source of air pollution by creating extra dust’.

Professor Frank Kelly, director of the Environmental Research Group at Imperial College London, adds: ‘Even an air fryer can be harmful in terms of pollution levels.

‘But the main three factors to consider are the method of cooking [steaming is least polluting], the type of food [vegetables are better than meat because they contain less fat], and the type of stove [gas is worst and induction hobs are best].’ Use extractor fans or open windows, to get clean air in when cooking, says Professor Pope.

Jenni’s average reading was 6.4 so she should take steps to reduce her exposure.