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Smoker in a Car We have published a new article on secondhand smoke levels occurring in automobiles for a variety of speeds and ventilation conditions.

Please see the Stanford News Article and visit the Download Page.

How severe are the pollutant levels in a car with a smoker?

A nonsmoker can expect to be exposed to some tobacco smoke in many types of outdoor pubs, cafes, and restaurants, even if only a single cigarette is active. In some cases, appreciable exposure can still occur out to 10+ feet, and when there are more smokers present, being up to 50 feet or more from tables of smokers would be required to avoid exposure.

The presence of multiple smokers in outdoor settings is likely to increase exposure substantially from the single-smoker case. Our data can be used to estimate exposures for situations with multiple smokers. Since it is reasonable to assume that average smoke levels increase in proportion to the number of outdoor smokers, we can then roughly estimate levels of particle exposure for different distances from groups of smokers.

While we found that exposure can occur in most outdoor venues with smoking, as part of the study we also performed careful experiments of pollution level as a function of distance, so that the results of our study could be used to quantify exposures that would likely occur when nonsmokers are positioned at a variety of distances from the smoker(s).

Our results show that a nonsmoker, who is near a smoker at an outdoor pub, cafe, or restaurant, can potentially inhale toxic smoke produced from a cigar or cigarette at very high levels. Our research proves that drifting secondhand smoke can indeed pose a significant nuisance or health risk for nonsmokers sitting or standing near smokers on outdoor patios.

Some representatives of so-called "smokers' rights" organizations have been mischaracterizing the findings of our recently published study of outdoor tobacco smoke performed at Stanford University. Therefore, I have written this memorandum to clarify the findings of our research with respect to exposures occurring on outdoor dining patios.

--Neil Klepeis

Yes. Concentrated streams of outdoor tobacco smoke can, at the very least, act as a respiratory or eye irritant. But outdoor tobacco smoke may also pose a serious health hazard for severe asthmatics even if the exposure is transient, since tobacco smoke may act as a trigger. Those with compromised cardiovascular systems may be at risk from even brief exposures. People spending time near outdoor smokers over multiple hours, such as waiters or dinner guests, can receive exposure that exceeds the current USEPA limit on fine particulate matter pollution.

Some critics try to diminish the impact of outdoor air pollution from smoking by saying that air pollution from other combustion sources (for example, cars, trucks, and power plants) is much worse. This argument is flawed.

In fact, when no smokers were present, we consistently measured background air pollution levels that were practically zero. We found the air in typical urban locations in California, even near roadways, to be generally quite clean compared to air in the vicinity of smokers.

Some have argued that exposure to toxic chemicals can result from being near campfires or barbeques (outdoor grilling) -- in addition to from cigarettes -- but that no one is talking about banning these sources. This argument is a red herring and irrelevant to the consideration of smoking bans. Other sources should be considered independently from tobacco. In fact, we are unaware of the ability of people to indiscriminately burn campfires or have BBQs at cafes and on city sidewalks.

We used five different types of real-time airborne particle monitors in our outdoor study of tobacco smoke. With these instruments, we were able to measure air pollution every few seconds or minutes, and, therefore, to pinpoint the high peak levels of air pollution that could occur. Another benefit of these instruments was the ability to correlate pollution levels directly with the presence of active cigarettes. An important feature of most of the instruments was their small size and portability. They are kind of like having a "laboratory in a lunch box".

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Dr. Wayne R. Ott - pioneer in the field of human exposure

Dr. Neil E. Klepeis - long-time secondhand smoke research scientist

James L. Repace - international secondhand smoke expert

Dr. Lance A. Wallace - pioneer in the field of human exposure


U.S. Surgeon General - Report on health consequences of exposure to secondhand smoke

ETS Exposure and Outdoor ETS - California Air Resources Board info pages

ETS Documents and Notices - OEHAA California government site

Smoke Free Homes - USEPA federal government site

SimSmoke.Org - simulate exposure to tobacco smoke

ExposureScience.Org - research articles, reports, and software

ExposureAnalysis.Org - resources for students