Do Public Smoking Bans Really Clear the Air for Nonsmokers?

Key Point

Legislation banning smoking in public areas appears to have the intended result—namely, to significantly reduce nonsmokers’ exposure to environmental tobacco smoke.

In recent years, smoking bans in public areas and the workplace have been implemented in the United States and countries around the world. Some have questioned whether these bans are actually reducing nonsmokers’ exposure to secondhand smoke or, as smokers are restricted to mostly smoking at home, if nonsmokers are exposed to higher levels of environmental tobacco smoke than ever before.

However, data from several recent studies published in the September 15 BMJ demonstrate that since smoke-free legislation was instituted in Scotland in March 2006, there have been dramatic decreases in nonsmokers’ exposure to tobacco smoke and its carcinogenic byproducts.

COTININE LEVELS FALL IN NONSMOKERS

Sally J. Haw and Laurence Gruer of the National Health Service Scotland conducted a study in adults as part of a health education population survey. A repeat cross-sectional design was used, with data collected both before and after the ban. The intention of the study was to determine if changes in exposure to secondhand smoke could be quantified and, in particular, if there was any evidence of increased exposure to secondhand smoke among nonsmokers living with smokers as a result of displacement of smoking into the home.

Interviews were conducted about participants’ experiences of smoking restriction in public areas and private locations (home and car) and exposure to secondhand smoke in those places. All participants were asked to provide saliva samples to test for cotinine. A total of 1,170 nonsmokers participated in the prelegislation survey, and 1,190 participated in the postlegislation survey. Cotinine measurements were available for 627 nonsmokers before legislation and 592 after legislation.

Before the legislation was enacted, the median cotinine concentration was 0.4 ng/mL, with concentrations below the level of detection (0.1 ng/mL) in 11.3% of samples. By contrast, the median cotinine value fell to 0.2 ng/mL in the postlegislation period, with concentrations below the level of detection in 27.6% of samples.

Geometric mean cotinine levels for nonsmokers fell by 39% following the smoking ban. Among nonsmokers living in nonsmoking households, the reduction in geometric mean cotinine level was 49%; however, in the subgroup of nonsmokers living in smoking households, the reduction did not reach significance (from 0.92 to 0.81 ng/mL before and after legislation, respectively).

There was no evidence of a displacement of smoking from bars and other public areas to homes after the ban, the researchers noted. “The now large differential in exposure to secondhand smoke between nonsmokers who live in smoking and nonsmoking households underlines the importance of developing interventions designed to reduce smoking in the home and in cars,” they concluded.

TOBACCO EXPOSURE IN CHILDREN

A second study used a similar methodology to quantify environmental tobacco smoke exposure in children, according to Patricia C. Akhtar of the Child and Adolescent Health Research Unit, University of Edinburgh, and colleagues. About 2,400 children from 116 primary schools were surveyed in January 2006 about their smoking status and that of their friends and parents, as well as their exposure to tobacco smoke in public and private locations. An equal number of children were surveyed in January 2007. In either group, saliva samples were collected at both interviews.

Median cotinine concentrations in these children fell from 0.3 ng/mL at baseline to 0.2 ng/mL after the smoking bans. The percentage of children with cotinine levels below the limit of detection increased from 20% before the bans to 34% after. As was true in the adult study, the mean cotinine concentrations fell by 39%—from 0.36 to 0.22 ng/mL.

Although exposure to tobacco smoke was higher in private than in public locations both before and after legislation, the percentages did not change significantly—with 27.8% and 6.7% of children reporting exposure in the home and in a car, respectively, prior to the ban, and 27.4% and 6.5% after. In contrast, there was a slight decrease in children’s exposure to environmental tobacco smoke in other people’s homes following the legislation (11.6% in 2006 vs 9.5% in 2007). “This finding suggests some modification of smoking behaviour in front of non-family members after the legislation,” the investigators observed.

Children with the lowest levels of exposure to environmental tobacco smoke experienced the greatest proportional reductions in exposure, the investigators found. Specifically, among pupils of nonsmoking parents, the geometric mean cotinine concentration fell 51%, and among those with a smoking father, the concentration fell 44%. But among those with a smoking mother or with two smoking parents, it fell only 11%. As with the first study, these results in children confirm that there is no evidence of a displacement of smoking from public places to the home.

An important observation is that this 39% fall in mean cotinine concentration in one year compares favorably with a 52% fall in mean cotinine concentration levels noted in studies on smoking restrictions conducted between 1988 and 2003 in En-gland among children ages 11 to 15, noted the researchers. The annual change is an order of magnitude higher in the Scottish study than seen in the studies conducted in England, they added.

EFFECT OF SMOKING BANS IN NONPUBLIC PLACES

In the third study, Richard Phillips, from the Division of Community Health Sciences at the University of Edinburgh, and colleagues conducted qualitative semi-structured interviews with 50 smokers and nonsmokers who lived with smokers about the impact of the legislation in Scotland. Participants were asked about the times and places they smoked or were exposed to environmental tobacco smoke, and about their views and experiences.

A total of 36 participants believed that secondhand smoke carried some form of health risk; five smokers and one nonsmoker believed that secondhand smoke was not a health hazard at all. Most respondents reported imposing total or partial restrictions on smoking in the car, especially in the presence of children and nonsmokers.

As was true of the other studies, the nonsmokers in this study did not report increased exposure to secondhand smoke as a result of the smoking bans. In addition, the researchers found that the attitudes about restrictions on smoking within the home are shaped by sociocultural forces, including perceptions of the acceptability or unacceptability of smoking, particularly in front of children, and concerns about being seen as a morally and socially responsible person.

—Laurel McKee Ranger

Suggested Reading
Akhtar PC, Currie DB, Currie CE, Haw SJ. Changes in child exposure to environmental tobacco smoke (CHETS) study after implementation of smoke-free legislation in Scotland: national cross sectional survey. BMJ. 2007;335(7619):545-549.

Chapman S. The future of smoke-free legislation: will cars and homes follow bans on smoking in public spaces? BMJ. 2007;335(7619):521-522.

Department of Health. Health survey for England. www.dh.gov.uk/en/Publicationsandstatistics
PublishedSurvey/HealthSurveyForEngland/index.htm. Accessed June 22, 2007.

Haw SJ, Gruer L. Changes in exposure of adult non-smokers to secondhand smoke after implementation of smoke-free legislation in Scotland: national cross sectional survey. BMJ. 2007;335(7619):549-552.

Jarvis MJ, Goddard E, Higgins V, et al. Children’s exposure to passive smoking in England since the 1980s: cotinine evidence from population surveys. BMJ. 2000;321(7257):343-345.

Phillips R, Amos A, Ritchie D, et al. Smoking in the home after the smoke-free legislation in Scotland: qualitative study. BMJ. 2007;335(7619):553-557.

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