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1. Leave the car at home
Many drivers think windows protect them from the pollution they are generating. They are wrong, mostly. A 2012 study of commuters in Barcelona found that car passengers in busy traffic were exposed to 30 per cent more carbon dioxide than cyclists or pedestrians who can move faster along the same route, 25 times more carbon monoxide, and between two and three times more PM2.5 and ultra-fine particles. One reason may be that the air intake on most cars is at the front, right behind the exhaust pipe of the vehicle in front, says Shaddick.
Read more: Cutting through the smog on air pollution
The bad news on bad air seems to get worse by the day, but all is not as it seems over Western cities. We take a look at the numbers
There鈥檚 a catch. Although they were exposed to less pollution, the active commuters inhaled more of it. Overall, bus commuters inhaled the least.
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鈥淐ycle or drive? Cycle, and take the back streets. It鈥檚 win-win: less pollution and more exercise. The same goes for walking.听鈥�
Some studies come to different conclusions. Outcomes vary with traffic speed, vehicle and fuel type, and the weather. 鈥淭here is no one answer,鈥� says Ben Barratt of King鈥檚 College London. 鈥淚n slow-moving congested traffic, you will be more exposed than in free-flowing traffic. But the exercise benefits of walking and cycling generally outweigh any negatives.鈥�
2. Escape to the country, or a side street
Sometimes the simplest solutions are most effective. In this case, that means getting away from the source. Concentrations of NOx and PM2.5 from car engines fall exponentially over the first few metres from the exhaust. 鈥淢oving from a congested road to a quieter street makes a big difference because you are much farther away and there are buildings in between you and the source,鈥� says Barratt.
鈥淚nside or outside of pavements? That鈥檚 a tricky one. Some studies show you get a lot less pollution just by moving a couple metres away from cars, but how the wind interacts with buildings can change everything.鈥�
Levels of NO2, carbon monoxide and particulate matter are higher in towns and cities because of traffic. Country dwellers are less likely to suffer associated health risks, but ozone levels are on average higher in rural settings. Other pollutants can be just as elevated in the countryside as they are in urban environments. But overall, you are better off living in country lanes.
3. Wear a face mask
If you鈥檙e shopping for a face mask, look for one with an N95 rating. It has been certified by the US National Institute for Occupational Safety and Health as filtering out 95 per cent of airborne particles larger than 0.3 碌m. Many dust masks will fit this bill. Lab tests show that cotton handkerchiefs block just 28 per cent of particles from a diesel exhaust engine, and the simple cloth masks that tie behind the head won鈥檛 help much more. Cycling masks vary from 55 to 85 per cent effectiveness. that those with exhalation valves may work better. Surgical masks are surprisingly good: they can filter 80 per cent of particles in the lab. The results might not be replicated on the street though.
Masks won鈥檛 keep out gases like NO2 and SO2 unless they have special components like charcoal filters. Some masks may help keep your blood pressure low. 鈥淚f you have symptoms that worsen in polluted environments, a mask could be a sensible precaution,鈥� says Barratt. The key point in all cases is fit: all bets are off if a mask doesn鈥檛 perfectly follow the contours of your face.
4. Give pushchairs the push
Children are at greater risk from pollution because their lungs and brains are still developing. Most vehicles release their exhaust fumes somewhere between 30 and 60 centimetres from the ground.
鈥淐ar or bus? Bus. Studies suggest you inhale less pollution in a bus than inside a car.鈥�
鈥淏eing at exhaust level is bound to give you a higher exposure,鈥� says atmospheric scientist Rob MacKenzie at the University of Birmingham, UK. One 2009 study found that infants in prams were exposed to twice as much particulate matter from diesel exhaust as the adults accompanying them. Yet research published in February 2017, found no difference between PM2.5 concentrations for babies in buggies and for adults pushing them, but did identify busy intersections and bus stops as pollution hotspots. The lead author of that study, Prashant Kumar of the University of Surrey, UK, suggests parents use pram covers, especially near busy traffic and intersections.
5. Get some fresh air
Air filters in most modern vehicles are designed to block large particles like dust and pollen, but are unlikely to capture all fine soot. Gases such as NOx and ultra-fine particles will get through. Tests have shown that switching to a vehicle鈥檚 recirculation mode can reduce ultra-fine particles by around 90 per cent, but will push up carbon monoxide levels.
Although some of their claims have been questioned, car manufacturers are increasingly including higher performance filters. Tesla says its high efficiency particulate air filter can reduce exposure to PM2.5 from very high to negligible. Air purifiers for buildings are becoming commonplace in China. Such devices can work well on sealed commercial buildings and potentially flats, but are less effective in leaky houses.
This article appeared in print under the headline 鈥淐utting through the smog鈥�
