Secondhand smoke (SHS) contains more than 50 known human carcinogens and has recently been classified as toxic air contaminant [1, 2]. SHS causes premature death and disease in children and adults, and the scientific evidence indicates that there is no risk-free level of exposure to SHS [1–3]. A growing number of local communities and states in the U.S. and in countries throughout the world are therefore adopting stricter policies to curb tobacco use in general and to reduce exposure to SHS exposure in particular [4–6].
The introduction of stricter tobacco control policies is often accompanied by health education campaigns about the harmful effects of tobacco use on smokers and vulnerable groups of nonsmokers [7–10]. The ultimate goals of these efforts are to improve public health through changing personal smoking behavior, community standards, and attitudes toward tobacco use and SHS [2, 8, 11, 12]. According to the 2006 National Health Interview Survey , however, steady declines in smoking rates since the 1960s appear to have stalled, remaining unchanged at 21% since 2004. Thus tobacco control efforts remain a high public health priority, requiring renewed efforts to further reduce tobacco use and SHS exposure.
The present study examined the prevalence of tobacco use and asking prices of used cars in a community that has experienced extensive public health education campaigns since passing comprehensive statewide tobacco control legislation in 1988 . We hypothesized that in such a community, smoke-free cars would be offered at a premium compared to smoker cars, controlling for other factors influencing the value of a car. If this is the case, future research may be warranted to better understand the effects of tobacco use on the value of personal property and how such consumer preferences could help further reduce tobacco use and SHS exposure.
Tobacco Use in Cars
Compared to research on smoking restrictions in the workplace, restaurants, and at home, relatively little is known about smoking restrictions in cars. Existing research suggests that smoking restrictions in cars are less common than those at home. In California, two out of three family cars had a complete smoking ban in 1996 and 1998 [15, 16], compared to almost four out of five homes with complete smoking bans. Among smokers, however, only 29% had a complete car smoking ban, and 43% had a complete home smoking ban. Similar patterns were observed in urban and rural settings of the U.S. outside of California. Halterman et al.  found that among urban households with smokers and children suffering from asthma only 64% had a complete ban on smoking in the home and 49% in the car. Kegler & Halinka Malcoe  examined low-income families of children in rural Oklahoma. They found that 49% of Native American households and 43% of Caucasian households banned smoking in the home, but only 35% and 40%, respectively, banned smoking in the car. A deviation from this pattern was reported by King et al.  among African-Americans who found a higher percentage of nonsmokers had car than home smoking bans (84% vs. 74%). Among smokers, however, only 17% and 21% had similar bans.
Residual SHS Contamination of Used Cars
When tobacco is smoked in the confined environment of a car, tobacco smoke pollutants can reach extremely high levels . Volatile SHS components absorb into surfaces within minutes of emission, contaminating objects with which they come in contact. Subsequently, this residual SHS (also known as aged SHS or third-hand smoke [21, 22]) is re-emitted into the air over days, weeks, and months, accumulates in dust, and deposits on surfaces [23–27], creating a route of exposure for drivers and passengers of smoker cars in the absence of concurrent active smoking.
Unlike mechanical or electronic defects, detecting the signs of previous tobacco use in a car often requires little technical expertise from a potential buyer. Routine tobacco use leaves many telltale signs to prospective buyers. Foremost is a distinct odor caused by the re-emission of SHS contaminants from surfaces and dust that were polluted during active smoking. Matt et al.  have shown that SHS odor and ash marks are significantly associated with the residual contamination of dust, surfaces, and the air in cars. It is this odor and other visible signs that can signal to a potential buyer that a car has been smoked in and that can be difficult and expensive to remove through cleaning or repairs.
Private Party Sales of Used Cars in the U.S
The used car market provides a particularly interesting opportunity to examine the value of a smoke-free personal environment, because a large and diverse cross-section of the general population in the U.S. sells and buys used cars. Moreover, a substantial portion of personal income is spent on the purchase and maintenance of cars. In 2005, 44.1 million used and 16.9 million new cars were sold in the U.S. [29, 30]. These transactions totaled $780 billion, $367 billion of which were accounted for by used car sales. Approximately 30% of used cars were sold by private parties .
Although asking prices for used cars are often informed by published pricing guidelines (e.g., Kelley Blue Book), sellers can advertise their cars for any price, buyers can offer any price, and the eventual sales price is subject to the local market forces of supply and demand. Sellers typically begin gauging an asking price by establishing the standard value of their used car based on its make, model, age, mileage, and condition. In addition, sellers often look up the asking prices of similar cars currently offered for sale by consulting the classified ads of local newspapers and used cars offered by dealers. Sellers then apply additional adjustments for factors believed to affect the value of a car in the community where it is sold that were not – or not sufficiently – included in the standard model. These adjustments may increase (e.g., chrome wheels; smoke-free car) or decrease the value of a used car (e.g., no air conditioning, smoker car). Further price adjustments follow if a car fails to sell and the seller is unable to remediate problems preventing a sale.
The Behavioral Ecological Model (BEM) provides a theoretical framework of the association between the values and norms of communities and the behaviors and preferences of individuals. Briefly put, BEM postulates that culture-wide social contingencies influence health practices at both the individual and the community levels. Changes in norms (e.g., tobacco use in the presence of nonsmokers) can initiate a cascade of social contingencies from the population to the individual levels that affect the strength of a given cultural characteristic (e.g., tobacco tolerance) [31, 32]. Consequently, changes in individual health behavior (e.g., car smoking ban) can be initiated by changing social and economic contingencies at the population (e.g., smoker cars are worth less in the private party market) and individual levels (e.g., family members complain about stale tobacco odor in car). This study offered an opportunity to explore hypotheses about emerging social contingencies with respect to tobacco. We reasoned that cultural changes regarding tobacco use should lead to lower prices for cars offered by smokers than equivalent cars offered by nonsmokers. This would create new social and economic contingencies affecting tobacco use and SHS exposure among seller, buyers, and passengers.