Walk along a busy road, and you are likely to get a lungful of exhaust. However, you are probably breathing cleaner air than people in the cars passing by you. For decades, research has focused on the air quality outside of vehicles. Researchers are now realizing the air inside our cars can be far worse – as much as fifteen times worse than the air just a few meters away.
The air inside cars can be 15x worse than just a few meters away.
The worst exposure is when we’re in our cars waiting for others to move along. That’s bad news, because traffic on roads has significantly increased in the U.S. and elsewhere over the past twenty years. Although we spend only about 6% of our day driving, we get up to half of our exposures to vehicle-related pollutants during that time.1
Why is the air inside a car worse than outside?
Pollutant levels are often higher inside because cars take in emissions from surrounding vehicles and recirculate them. Studies have found that as much as half of the pollutants inside cars come from the vehicles immediately ahead, especially if those vehicles are heavy polluters, such as diesel trucks. Pollutants enter the car cabin through air vents and other openings, because vehicles are not built to be air tight.
Pollutant levels are often higher inside because cars take in emissions from surrounding vehicles and recirculate them.
Roadway concentrations of vehicle-related pollutants are typically several times higher than ambient (outdoor) concentrations. Levels of some pollutants and toxic compounds can be as much as ten times higher inside vehicles than alongside the road, and overall air quality can be fifteen times worse.
Furthermore, concentrations at the centerline of the road are highest and can be several times higher again than concentrations on the side of the road. It is these centerline concentrations that reflect the air getting into your vehicle.2
What’s in vehicle exhaust?
Vehicle exhaust is a cocktail of dangerous pollutants, including:
- Nitrogen dioxide (NO2) – Harsh-smelling gas that can cause breathing problems, lung irritation, and lowers resistance to respiratory infections.
- Ozone (O3) – Naturally occurring compound that helps block harmful UV light from the sun. However, at ground level, it is toxic. When vehicles emit nitrogen oxides (NO), sunlight acts on them to create ground-level ozone. Ozone is the primary component of smog and is a major lung irritant. Long-term exposure may cause asthma and can result in serious and permanent structural damage to the lungs.
- Carbon monoxide (CO) – Colorless, odorless, poisonous gas that causes short-term effects similar to oxygen deprivation, such as dizziness, fatigue, and confusion.
- Sulphur dioxide (SO2) – When this gas is inhaled, it can cause shortness of breath and chest pain. In the long term, it can cause acute respiratory illness and permanent changes to the lungs.
- Fine particles (PM2.5) – Particles ranging in diameter between 0.1 and 2.5 microns. For comparison, the diameter of a single human hair ranges from 17 to 181 microns. When inhaled, these particles can lodge in lung tissue, triggering respiratory illnesses such as asthma, bronchitis, and emphysema. PM2.5 exposure has been linked to increasing the potential for cardiovascular problems, such as arrhythmic heartbeats and heart attacks. PM2.5 represent about 9% of all airborne particles.
- Ultrafine particles (UFPs) – Particles smaller than 0.1 microns in diameter. About 90% of all airborne particles are this size. Not only are UFPs the most numerous of airborne particles, but they are also the most dangerous to your health. The tiny size of ultrafine particles enables them to be easily inhaled, deposited into the lungs and absorbed directly into the bloodstream. From there, they travel with your bloodstream to all vital organs, including your brain. It’s estimated that the 6% of our days we spend in our cars can result in more than half of our UFP exposure.
Intersections, red lights, and stop signs
Research published in the journal Atmospheric Environment measured air pollutants inside and outside vehicles at traffic intersections in urban and suburban areas. Their findings include:
- Stopping at red lights greatly increases exposure to air pollution
- Intersections with traffic signals have up to 29 times higher concentrations of particulate matter than open roads
- Drivers spent 2 percent of their time passing through intersections, which accounted for 25 percent of their pollution exposure
Air pollution levels are high at intersections with traffic lights because drivers decelerate, idle, and accelerate there. The same result will occur anywhere cars idle, such as drive-through windows at restaurants.3
Heavy traffic = heavy pollution
Pollution inside cars stuck in heavy traffic is as much as 40 percent higher than when traffic is moving. A study published in the journal Environmental Science: Processes & Impacts found the level of pollution was seven times higher inside cars that were stuck in traffic if the windows were open, compared to the exposure of pedestrians standing at major intersections.
Pollution inside cars stuck in heavy traffic can be 40% higher than when it's moving.
Keeping the windows closed with the fan on (which brings in outside air) also significantly increased in-car pollutants.
How you can reduce in-car air pollution
- Use a high-powered in-car air purifier. The Atem Car combines IQAir’s patented HyperHEPA particle filtration technology (only HyperHEPA filters are proven to filter ultrafines) with the industry’s best gas-phase media for complete in-car air protection. The Atem Car is easily portable and highly versatile. Use it as your personal air purifier at home, at work, and when traveling – it’s small enough to easily fit in your carry-on bag!
- Keep a safe distance from vehicles ahead of you, especially diesel trucks.
- When you’re in traffic or at a stop sign or light, close your windows, keep some distance from the vehicle in front of you, and put your air on recirculate
- Try to use less congested roads with fewer traffic lights, even if they take a little longer. Try to avoid rush hour.
- Don’t rely on traditional in-car air filtration systems. They are not effective at removing ultrafine particulates, volatile organic compounds, carbon monoxide, or other pollutants. Also, they don’t filter air entering your car cabin through windows and door cracks.
- Avoid car air fresheners or deodorizers; they are full of harmful VOCs and make your air quality worse – not better.
- Keep your car interior clean. Pollutants in cars can combine with dust particles and be inhaled. However, avoid chemical cleaners. Use a microfiber rag instead.
Our reliance on cars is likely to continue, but there is something that we can do to minimize our exposure to traffic pollutants. Following these easy steps can help you minimize your exposure in the car and thus, minimizing about 50% of your exposure to these dangerous airborne pollutants. Just turn on your Atem Car and breathe easily.
 Schrank D & Lomax T. (2007).
 Kumar P. & Goel A. (2016). Concentration dynamics of coarse and fine particulate matter at and around signalised traffic intersections. DOI: 10.1039/C6EM00215C
 Goel A. & Kumar P. (2015). Characterisation of nanoparticle emissions and exposure at traffic intersections through fast-response mobile and sequential measurements. DOI: 10.1016/j.atmosenv.2015.02.002