Indoor Pollution in Your Car

Car Air Pollution

Story at-a-glance -

  • You may be inadvertently exposing yourself to high levels of pollution during your long commute hours to work and school
  • Air pollution in your car may be as much as 15 times higher when you’re sitting at traffic lights or in traffic jams
  • Use recirculated air while in heavy traffic to reduce pollution in your car and remember to draw air from the outside for one to two minutes every 10 to 15 minutes to reduce carbon dioxide levels

By Dr. Mercola

What happens to drivers who spend hours commuting back and forth to work each week? One of the unfortunate risks is the increased number of hours you may spend inactive behind the wheel of your car.

Inactivity may increase your risk of a number of different health conditions including cardiovascular disease, problems with weight management, type 2 diabetes and poor fitness.

However, it isn't only your inactivity in the car that raises your risk of health problems. In a recent study published in Environmental Science Processes and Impacts, researchers reveal how dangerous it is to ride in your car through heavy traffic.1

Air pollution may be significantly greater in your car while you're stuck in traffic than it is walking through streets crowded with cars waiting for traffic lights.

Sitting in Traffic Is Hazardous to Your Health

This study found the air pollution in your car is up to 40 times greater when you're stopped at a red light or caught in a traffic jam than when traffic is moving freely. The aim of the study was to evaluate the ventilation systems of the cars based on measurements of particulate matter in the car during different driving conditions.2

The results of the study became most interesting when it was discovered the levels of air pollution were significantly different for small and large particulate matter.

It appears the ventilation systems of the cars tested more efficiently cleaned the incoming air of coarse or large particulate matter, allowing small particulate matter to slip into the car.3

The study was performed in Guilford, Surrey, described as a typical town in the U.K. with nearly 140,000 inhabitants. Each home owned an average of 1.5 cars, up from the national average of 1.16. The roads experienced congestion in the morning and evening hours and 32 percent of the passenger cars ran on diesel fuel.

The researchers measured the particle size of pollution in the car at each intersection. When the car was stuck in traffic, shutting the windows and turning off the fan and heat improved the air quality by reducing the concentration of the smallest, and most hazardous, particles by 76 percent.4

In comparison, when stopped at traffic lights and the fan was drawing air from the outside, the percentage of large particle pollution fell and small particle pollution rose.

Pollution Levels in Your Car May Be 15 Times Higher Than Outside

Another study published in 2014 evaluated the air pollution in five cars traveling through London. Researchers from King's College London gave five members of parliament (MP) technology to measure air pollution in their car or taxi as they went about their daily business.5

Astonishingly, the researchers found riding in a taxi through the busy streets of London exposed the individual to air pollution up to 15 times higher than walking or cycling through those same streets.6

The intention of this small sampling was part of an investigation to determine why diesel engines were being promoted as environmentally friendly by officials.7  Modern diesel cars can pump out up to four times more pollution than a bus.8

Although effective technology exists to cut nitrogen oxides from diesel engines, car manufacturers are not using it. Greg Archer of Transport & Environment was quoted in The Guardian, saying:9

"Carmakers claims [that] new diesel cars are clean are preposterous. Governments must ignore the bleating of carmakers for lenient limits and fix the problem for good."

Chairwoman of the Environmental Audit Committee (EAC), Joan Walley, and one of the MP participants in the study were quoted in the Daily Mail saying:

"Our monitoring equipment showed that people in vehicles were far more exposed to air pollution than they would be walking. Car makers test exhaust emissions but this raises a question about whether they should also be considering air quality inside vehicles."

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How Much Time Do Americans Spend in the Car?

Another study at the University of Southern California has found similar results, showing air pollution levels are more concentrated inside your car than outside.10

The researchers went so far as to say that an hour long commute per day may double your exposure to air pollution when ventilation settings in your car are not set appropriately.

This study sought to quantify the extent of the exposure to air pollution while people were driving in a variety of conditions. According to the Traffic Score Card using data from the Federal Highway Administration, the average U.S. citizen spends 50 hours in traffic each year.11

However, according to the same data, there are nine cities in which you may spend far more time sitting in traffic, breathing small and large particle air pollution. Those cities include:12

City Number of Hours in the Car

Chicago, IL

Number of Hours in the Car: 60 hours

Boston, MA

Number of Hours in the Car: 64 hours

Seattle, WA

Number of Hours in the Car: 66 hours

New York, NY

Number of Hours in the Car: 73 hours

Houston, TX

Number of Hours in the Car: 74 hours

San Francisco, CA

Number of Hours in the Car: 75 hours

Washington, DC

Number of Hours in the Car: 75 hours

Los Angeles, CA

Number of Hours in the Car: 81 hours

These numbers represent the amount of time spent in the car each year, but not the number of miles traveled. An ongoing study by the AAA Foundation for Traffic Safety is gathering data on both the number of miles traveled and the time in the car.13

Their data indicate that all drivers age 16 and older are spending an average of 48 minutes per day per trip, making an average of two trips per day and driving an average of 29 miles per trip. This is the first year of data gathered on drivers through a telephone survey of over 4,000 households.14

What's in the Air You Breathe?

This short video by the Organization for Economic Cooperation and Development (OECD) explains the high economic and health cost of car emissions and how the lower tax basis for diesel burning vehicles impacts your air quality.

When you're behind the wheel of your car for hours each month, what is in the air you breathe? An update to the World Health Organization (WHO) Global Urban Ambient Air Pollution Database found more than 80 percent of people living in urban areas were exposed to air quality levels exceeding the WHO limits.15

Particle pollutants, also called particulate matter, hydrocarbons, carbon monoxide, sulfur dioxide and nitrogen oxides are the more common pollutants emitted by motor vehicles.16 Motor vehicles are also the largest single source of air pollution in the U.S.

Nitrogen oxide pollution alone may kill up to 23,500 people a year in the U.K.17 People living in larger cities in the U.K. have a lower life expectancy, with London having the worst pollution in the country. In 2010, just over 3,300 people lost their lives as result of air pollution, according to Public Health England.18

Small particulate matter is another concern as it may escape your car's ventilation system and get pumped into the interior of your vehicle. These are the more dangerous particulates as they may be transported into your bloodstream after inhalation and pass through to your heart and brain. Exposure to this pollution may trigger an immediate asthmatic or heart attack, and may be responsible for other long term damage to your health.

Air Pollution Damages More Than Your Lungs

Air pollution is responsible for triggering a variety of health conditions, ranging from asthma and chronic obstructive pulmonary disease (COPD) to heart disease or stroke. The effects of air pollution on your health may be experienced immediately, or even years later. Several factors weigh into the severity of your reaction, including your age and pre-existing medical conditions. People who are most susceptible to the effects of air pollution include those who have or are:19

Coronary artery disease

Congestive heart failure



Chronic Obstructive Pulmonary Disease

Pregnant women

Children younger than 14

Athletes who exercise vigorously

After a single exposure you may experience:20

Worsening asthma

Runny nose or watery eyes



Scratchy throat


These reactions may appear similar to a cold or allergic reaction; however, once you're no longer in the car, your physical symptoms usually subside rather quickly. Long-term health or chronic health conditions do not readily resolve simply by removing yourself from an environment filled with air pollution. These conditions include:21,22

Accelerated aging of your lungs

Loss of lung capacity

Decreased lung function




Lung cancer

Shortened life span

High blood pressure23


Heart attack24


Hospitalization for diabetes

Decreased cognitive function, or ability to make better decisions and be more productive25


Several of the long-term effects of exposure to poor air quality are just being discovered through intensive research delving into the problems associated with exposure to particulate matter. The links to increased hospitalizations, high blood pressure and decrease in cognitive skills are newly discovered challenges facing those who consistently breathe poor air quality.

Roll Up the Windows and Recirculate the Air

The consistent recommendation from each of these studies has been to roll up your windows and use the setting to recirculate the air in your car when you are in heavy traffic or stopping frequently at red lights.26,27 Exposure with the windows open was more than six times greater than for pedestrians at a three or four way intersection.

While shutting the windows and recirculating the air in your car is important to reduce air pollution, in newer and more air tight cars you may experience a build-up of carbon dioxide. The car may begin to feel "stuffy" when two or more people are breathing the same air for an extended period of time.

Too much carbon dioxide in the car may also increase your experience of drowsiness, fatigue, confusion, headache and sleepiness.28 These are dangerous symptoms to experience while driving a car. To prevent this from happening, researchers recommend you pull in outside air for one to two minutes every 10 to 15 minutes to facilitate air exchange, while still minimizing over exposure to air pollution.29

+ Sources and References