Secondhand smoke (SHS) includes smoke produced by the burning of a cigarette, pipe, cigar, or other smoked tobacco and the smoke exhaled from the lungs of smokers. SHS is involuntarily inhaled by non-smokers, lingers in the air for hours after smoked tobacco has been extinguished, and can cause or contribute to a wide range of negative health effects, including adverse reproductive effects, cancer, cardiovascular disease, respiratory infections, and asthma.^1–5 SHS chemicals include irritants and systemic toxicants, mutagens, and carcinogens, and reproductive and developmental toxicants.¹ More than 60 compounds in tobacco smoke are known carcinogens, and the US Environmental Protection Agency and the International Agency for Research on Cancer have classified SHS as a group A and group 1 carcinogen, respectively, a category indicating the most dangerous cancer-causing compounds.^2,6 SHS exposure causes lung cancer, acute and chronic coronary heart disease (CHD), and eye and nasal irritation in adults.^2,6 Serious effects of SHS on children include asthma exacerbation, bronchitis and pneumonia, chronic middle ear infection, chronic respiratory symptoms, low birth weight, and sudden infant death syndrome.⁷ Studies have concluded that high levels of particulate matter exposure from SHS may account for frequent episodes of short-term respiratory damage in non-smokers⁸ and the risks for CHD from passive smoking are virtually indistinguishable from active smoking.^5,9 Smoke-free policies, as part of a comprehensive tobacco control programme, reduce exposure to SHS and may reduce tobacco users’ daily tobacco consumption and support cessation.¹⁰

The purpose of this paper is to show levels of self-reported exposure to SHS among youth aged 13–15 years using data from the Global Youth Tobacco Survey (GYTS) from 132 World Health Organization (WHO) Member States, territories, or other autonomous regions. For the purposes of this paper, we shall refer to all of these units as “countries” although some samples are drawn from subnational areas, non-Member States, or territories of other countries. Differences in several indicators of SHS exposure among countries in the six WHO Regions are described. The following data are presented: exposure to SHS at home, exposure to SHS in public places, percentage of students who had one or more parents who smoke, percentage of students who had most or all best friends who smoke, and percentage of students who think smoking should be banned in public places.

The Global Youth Tobacco Survey (GYTS)

In 1999, 11 countries (Barbados, China, Fiji, Jordan, Poland, Russian Federation, South Africa, Sri Lanka, Ukraine, Venezuela, and Zimbabwe) pilot-tested the first GYTS. All 11 countries completed successful surveys during 1999. After this initial success, many countries asked WHO and the US Centers for Disease Control and Prevention (CDC) for assistance in participating in GYTS. Data from 132 countries were available for analyses in this report. For countries that have repeated the GYTS, only the most recent data are analysed. The GYTS data in this report include: 37 sites in 25 countries in the African Region; 98 sites in 37 countries in the Region of the Americas; 25 sites in 21 countries in the Eastern Mediterranean Region; 29 sites in 26 countries in the European Region; 11 sites in 7 countries in the South-East Asia Region; and 30 sites in 16 countries in the Western Pacific Region.* Tables 1 and 2 list sites that completed the GYTS by WHO Region and indicate whether the survey was representative of the entire country or subnational areas within the country. The median student response rate was 88.6% (ranging from 55.8–100.0%); only four of the sites reported a school response rate less than 80% and, in total, over two million students in more than 18 000 schools have completed the GYTS.^11,12

The GYTS provides systematic global surveillance of youth tobacco use. Countries can use GYTS data to enhance their capacity to monitor tobacco use among youth; guide development, implementation, and evaluation of their national tobacco prevention and control programmes; and compare tobacco-related data at the national, regional, and global levels.

The GYTS uses a standardised methodology for constructing sampling frames, selecting schools and classes, preparing questionnaires, carrying out field procedures, and processing data. The GYTS includes data on prevalence of cigarette and other tobacco use, perceptions and attitudes about tobacco, access to and availability of tobacco products, exposure to secondhand smoke, school curricula, media and advertising, and smoking cessation.

The GYTS questionnaire is self-administered in classrooms, and school, class, and student anonymity is maintained throughout the GYTS process. Country-specific questionnaires consist of a core set of questions† that all countries ask and unique country-specific questions. The final country questionnaires are translated in-country into local languages and back-translated to check for accuracy. GYTS country research coordinators conduct focus groups of students aged 13–15 to further test the accuracy of the translation and student understanding of the questions.

Estimates presented in this study include exposure to smoke at home (defined as the percentage of students who answered “1 or more days” to the question, “During the past 7 days, on how many days have people smoked in your home, in your presence?”), exposure to smoke in public places (defined as the percentage of students who answered “1 or more days” to the question, “During the past 7 days, on how many days have people smoked in your presence, in places other than in your home?”), parental smoking (defined as the percentage of students who answered “both”, “mother only”, or “father only” to the question “Do your parents smoke?”), best friends who smoke (defined as the percentage of students who answered “most of them” or “all of them” to the question “Do any of your closest friends smoke cigarettes?”), and support for bans on smoking in public places (defined as the percentage of students who answered “yes” to the question “Are you in favour of banning smoking in public places (such as in restaurants, in buses, streetcars, and trains, in schools, on playgrounds, in gyms and sports arenas, in discos)?”).

METHODS

The GYTS is a school-based survey of defined geographic sites that can be countries, provinces, cities, or any other sampling frame including subnational areas, non-Member States, or territories. The GYTS uses a two-stage cluster sample design that produces representative samples of students in grades associated with ages 13–15. The sampling frame includes all schools containing any of the identified grades. At the first stage, the probability of schools being selected is proportional to the number of students enrolled in the specified grades. At the second sampling stage, classes within the selected schools are randomly selected. All students in selected classes attending school the day the survey is administered are eligible to participate. Student participation is voluntary and anonymous using self-administered data-collection procedures. The GYTS sample design produces representative, independent, cross-sectional estimates for each site. Respondents younger than 13 or older than 15 were excluded from these analyses because the objective of this paper is comparisons of same aged children 13–15 years old.

A weighting factor is applied to each student record to adjust for non-response (by school, class, and student) and variation in the probability of selection at the school, class, and student levels. A final adjustment sums the weights by grade and sex to the population of school children in the selected grades in each sample site. We used SUDAAN, a software package for statistical analysis of correlated data, to compute standard errors of the estimates and produced 95% confidence intervals by multiplying the standard errors by 1.96.¹³

RESULTS

Exposed to smoke at home

Overall, more than four in 10 students (43.9%) were exposed to smoke at home (table 1). Among the six Regions, exposure to SHS at home was highest in the European Region (mean 78.0%) and lowest in the African Region (mean 30.4%). In the other four Regions, exposure at home ranged from 50.5% (Western Pacific Region) to 37.0% (South-East Asia Region).

More than half the students were exposed to SHS at home in one of 37 sites in the African Region, 12 of 97 sites in the Region of the Americas, seven of 25 sites in the Eastern Mediterranean Region, 26 of 29 sites in the European Region, six of 11 sites in the South-East Asia Region, and 15 of 30 sites in the Western Pacific Region.

Exposed to smoke in public places

More than half (55.8%) of all students were exposed to SHS in public places (table 1). Exposure to SHS in public places was highest in the European Region (mean 84.8%). For the other five Regions, exposure to SHS in public places ranged from 63.0% (Region of the Americas) to 46.3% (African Region and Eastern Mediterranean Region).

Across Regions, more than 50% of students were exposed to SHS in public places in 18 of 37 sites in the African Region, 65 of 96 sites in the Region of the Americas, eight of 25 sites in the Eastern Mediterranean Region, all sites in the European Region, eight of 11 sites in the South-East Asia Region, and 10 of 18 sites in the Western Pacific Region.

Had one or more parents who smoke

Nearly half of all students (46.5%) said one or more of their parents smoke (table 2). Students in the Western Pacific Region (mean 59.7%) and the European Region (mean 59.6%) were most likely to have one or more parents who smoke. Students in the African Region were least likely to have one or more parents who smoke (mean 22.7%). For the other Regions, the prevalence of parents who smoke ranged from 43.5% (South-East Asia Region) to 35.6% (Eastern Mediterranean Region).

More than half of students had at least one parent who smoked in none of 37 sites in the African Region, 12 of 95 sites in Region of the Americas, five of 24 sites in the Eastern Mediterranean Region, 25 of 29 sites in the European Region, five of 10 sites in the South-East Asia Region, and 17 of 23 sites in the Western Pacific Region.

Had most or all best friends who smoke

Nearly one in five of all students (17.9%) reported that most or all of their best friends smoke (table 2). Students in the Region of the Americas were most likely to report that most or all of their best friends smoke (mean 39.3%). About one in seven students in the European Region (17.5%) reported that most or all of their best friends smoke. Less than one in 10 students reported most or all best friends who smoke in the other four Regions (means of 7.2%, 6.9%, 7.0%, and 5.1% in the African Region, Eastern Mediterranean Region, South-East Asia Region, and Western Pacific Region, respectively).

More than 50% of students reported most or all best of their friends smoke in 17 of 95 sites in the Region of the Americas and 3 of 27 sites in the Western Pacific Region. The other four Regions did not have any sites in which more than 50% of students reported most or all their best friends smoke.

Thought smoking should be banned in public places

More than three quarters (76.1%) of all students in all Regions thought smoking should be banned in public places (table 2). However, there were differences among Regions. Only six in 10 students (mean 60.2%) in the African Region thought smoking should be banned in public places, compared with slightly over seven in 10 students in the South-East Asia (75.3%) and Western Pacific (72.9%) Regions and more than eight in 10 students in the other three Regions (means of 80.4%, 82.8%, and 82.1%, in the Region of the Americas, the Eastern Mediterranean Region, and the European Region, respectively).

More than 80% of students support smoke-free environments in eight of 37 sites in the African Region, 68 of 96 sites in the Region of the Americas, 13 of 25 sites in the Eastern Mediterranean Region, 15 of 29 sites in the European Region, seven of 11 sites in the South-East Asia Region, and eight of 23 sites in the Western Pacific Region.

DISCUSSION

Exposure to SHS is a significant health risk for non-smokers and smokers^1–9; thus, reduction of SHS exposure should be a primary component of national comprehensive tobacco control programmes. This report shows that more than half of all students surveyed were exposed to smoke in public places. Also, nearly half of all students were exposed to smoke at home and had one or more parents who smoke. One fifth of all students said most or all of their best friends smoke. Changing these patterns to reduce the chronic disease burden associated with long-term tobacco smoke exposure is a significant challenge to the tobacco control community. Fortunately, the majority of students surveyed by the GYTS between 1999 and 2005 support implementation of measures to reduce SHS exposure, including banning smoking in public areas.

Initiatives are under way in all six WHO Regions to reduce exposure to SHS. Many countries are making important policy and legislative advances to ban smoking in public places, especially hospitals, restaurants, and public transportation, and some have passed workplace smoking bans. Comprehensive bans on smoking in the workplace, including restaurants and bars, exist for the entire countries of Bermuda, Bhutan, Ireland, Italy, Malta, Norway, Sweden, Spain, New Zealand, and Uganda. In addition, 10 of 50 US states and 11 of 13 provinces and territories in Canada have enacted smoke-free workplace legislation. See table 3 for examples of secondhand smoke policies and laws by Region and country.

All six WHO Regions are using GYTS data to develop Regional Tobacco Action Plans to address the challenges of tobacco control and identify specific regional needs. These plans focus on implementing the most cost-effective tobacco control measures, as called for in WHO’s Framework Convention on Tobacco Control (WHO-FCTC), including price and tax measures; comprehensive bans on advertising, promotion, and sponsorship by tobacco companies; smoke-free environments in public places and workplaces; and graphic health warnings on tobacco packaging.¹⁴ With regard to SHS exposure, Regional plans provide examples of how WHO Member States in these regions can address related issues such as promoting awareness of SHS dangers, introducing and strengthening existing legislation to make public places smoke-free, banning indoor and outdoor smoking on the premises of all educational institutions, and banning smoking on the premises of all health institutions and government facilities. The South-East Asia Region developed a specific objective “to promote awareness on the dangers of exposure to secondhand smoke and to protect the youth from exposure to secondhand smoke by taking measures to ban smoking within educational facilities, in public places, and in public transport” after reviewing data gathered under the GYTS.¹⁵ The Western Pacific Region referred to the value of GYTS data in the most recent five-year Regional Action Plan whose goal is to improve the comprehensiveness of tobacco control efforts.¹⁶ In the Region of the Americas, the PAHO Smoke Free Americas Initiative used GYTS data showing widespread exposure to secondhand smoke in students’ homes to identify the need “to raise awareness about the harmful effect of exposure to secondhand tobacco and to support efforts to implement 100% smoke-free environments in all public places and workplaces.”¹⁷

More than 30 countries have conducted a second GYTS, and public health officials are using these data to monitor and evaluate tobacco control efforts such as laws and policies that reduce exposure to SHS. For example, the Philippines introduced several high-profile tobacco control and smoke-free initiatives between 1999 and 2003. GYTS data showed that, over the same period, prevalence of current cigarette smoking declined significantly, exposure to smoke in public places declined significantly, and support for bans on smoking in public areas rose from 39.2% of students in 2000 to 88.7% in 2003.¹⁸

The WHO-FCTC, signed by 168 countries and ratified by 116 as of January 2006, is the world’s first public health treaty.¹⁴ Although the focus of the Convention is on a comprehensive approach to reducing tobacco use, Article 8 identifies tobacco smoke as harmful to public health and calls for parties to protect their populations from exposure:

Parties recognize that scientific evidence has unequivocally established that exposure to tobacco smoke causes death, disease, and disability. Each Party shall adopt and implement in the areas of existing national jurisdiction as determined by national law and actively promote at other jurisdictional levels the adoption and implementation of effective legislative, executive, and administrative and/or other measures, providing for protection from exposure to tobacco smoke in indoor workplaces, public transport, and, as appropriate, other public places.¹⁴

Full implementation of the principles and obligations contained in the WHO-FCTC will likely limit tobacco use, initiation of smoking, and exposure to secondhand smoke, and will promote cessation.

The findings in this report are subject to at least three limitations. First, these data apply only to youth aged 13–15 years who attended school and therefore are not representative of all persons in this age group. However, in most countries, the majority of young people aged 13–15 attended regular, private, or technical schools.¹⁹ Second, these data apply only to youth who were in school the day the survey was administered and who participated in the survey. School response rates have been high throughout GYTS, and only 21 of 395 survey sites have recorded student response rates less than 80%. Third, findings are based on self-reports from students who may under- or over-report their behaviour and the behaviour of others. Though the extent of potential reporting bias cannot be determined in all countries that participate in GYTS, responses to questions about cigarette smoking and other tobacco use have shown good test-retest reliability in a study of American students.²⁰

Conclusion

Tobacco use and SHS exposure are major contributors to global chronic disease mortality. Findings from the GYTS suggest that projections that tobacco-associated deaths will double over the next decade may be conservative if tobacco use prevalence and widespread SHS exposure among youth remain at current rates.²¹ In addition to preventing youth from starting to smoke and helping current smokers to quit, this report shows that the global tobacco control community must improve efforts to reduce SHS exposure. Creating smoke-free areas and educating the public about the dangers of SHS will have complementary effects on tobacco control efforts by reducing the social acceptance of tobacco use around non-smokers.²² Ongoing surveillance is necessary to measure progress toward eliminating SHS exposure, track implementation of laws and policies to reduce exposure and enforcement of these measures, and gauge public support for a smoke-free society. GYTS data have shown widespread and strong support among students for bans on smoking in public areas all over the world. Countries should engage this positive public health attitude among youth to promote and enforce smoke-free public places and workplaces.