Secondhand smoke (SHS) exposure has been causally linked to adverse health outcomes, including heart disease and lung cancer in adults, and increased risk of acute respiratory infections, ear problems, and sudden infant death syndrome in children.^1–4 The U.S. Surgeon General has concluded that there is no risk-free level of SHS exposure.¹ Nonetheless, during 2011–2012, approximately 58 million U.S. nonsmokers (25.3%), including 15 million children aged 3–11 years, were exposed to SHS.⁵

Over the past several decades, there have been substantial achievements in tobacco control.¹ However, though cigarette smoking has decreased, the use of other tobacco products, including combustible (e.g., cigars, cigarillos, and little cigars), noncombustible (e.g., chewing tobacco and snus), and emerging products (e.g., electronic nicotine delivery systems [ENDS], including electronic cigarettes [e-cigarettes]) has remained unchanged or increased.^3,6 This diversification of the tobacco product landscape presents new challenges to public health and makes it increasingly important to shape tobacco prevention and control efforts in the context of all forms of tobacco use.³ For example, the aerosol from some ENDS products has been shown to contain nicotine and other harmful and potentially harmful substances.^7–9 Therefore, exposure to ENDS aerosol has the potential to involuntarily expose bystanders to aerosolized nicotine and other harmful substances.

Exposure to SHS has been successfully reduced in public settings through comprehensive smoke-free laws prohibiting smoking in all indoor areas of worksites and public places, including restaurants and bars.^10–12 However, these laws do not include private settings such as the home, which is a primary source of SHS exposure for children.¹ Smoke-free home rules can help reduce SHS exposure among nonsmokers, prevent smoking initiation among youth and adults, support tobacco cessation among current smokers, and reduce the social acceptability of smoking.^1,13–15 From 1992–1993 to 2010–2011, smoke-free home rule prevalence in U.S. households increased from 43.0% to 83.0%.¹⁶ However, many U.S. households still lack smoke-free home rules, including 53.9% of households with at least one adult smoker.¹⁶

Residents of multiunit housing (MUH), as well as employees and visitors, are particularly susceptible to involuntary exposure to SHS in this environment, which can enter living units from nearby units and shared areas where smoking occurs.^17–20 SHS can transfer throughout MUH via walls, ductwork, windows, and ventilation systems, among other routes.^17,18,20 More than one quarter of the U.S. population, or 80 million individuals, reside in MUH, and a nationally representative survey found that among MUH residents with smoke-free home rules, an estimated 44% had experienced SHS incursions in their unit within the past year that originated from outside their unit.²¹ This is compounded by the fact that certain types of MUH, including government-subsidized housing, are occupied by large proportions of vulnerable population groups that are already at higher risk for chronic disease and poor health outcomes, including those with low income, racial/ethnic minorities, children, the elderly, and the disabled.^20,22

Previous research has assessed the extent of cigarette smoking, smoke-free home rules, and SHS exposure among U.S. MUH residents.^17–21 However, no study has assessed the extent of non-cigarette (tobacco use other than cigarette smoking) use among MUH residents. The assessment of non-cigarette tobacco products, particularly other combustible products and ENDS products, is becoming increasingly important, given the diversification of the tobacco product landscape in recent years.³ To address these gaps, this study assessed the reported prevalence and sociodemographic correlates of tobacco use, smoke-free home rules, and SHS incursions among U.S. MUH residents; to assess reported variations by housing type, these estimates were compared with adults in single family homes.

The percentage of adults who used tobacco products was higher in MUH than in single-family housing for any tobacco product use (24.7% vs 18.9%) and combustible-only product use (19.8% vs 13.6%, p<0.05; Table 1). However, non-combustible only use (1.9% vs 0.9%) and no tobacco use (81.1% vs 75.3%) were higher in single-family housing than MUH, respectively (p<0.05). Any tobacco use was higher among MUH residents than those in single-family housing for each sociodemographic characteristic (p<0.05; Table 1).

Within single-family housing, any tobacco use and combustible-only use were significantly associated with each of the assessed sociodemographic factors (sex, age, race/ethnicity, education, income, marital status, sexual orientation, and region; p<0.05). Specifically, the use of any tobacco products in single-family housing was highest among men; adults aged 18–24 years; non-Hispanic blacks; those with less than a high school education or income <$20,000; unmarried adults; lesbian, gay, or bisexual adults; and those living in the South (p<0.05).

Any tobacco use among MUH residents was significantly associated with each sociodemographic factor. Any tobacco product use and combustible-only use in MUH was highest among men; adults aged 45–64 years; non-Hispanic blacks; those with only a high school education or income <$20,000; unmarried adults; lesbian, gay, or bisexual adults; and those living in the Midwest (p<0.05).

The prevalence of smoke-free home rules was lower in MUH than single-family housing overall (80.9% vs 86.7%), and among users of any tobacco product (53.7% vs 62.5%) and combustible-only products (49.7% vs 58.0%), respectively (p<0.05; Table 2). Among any tobacco users, smoke-free home rule prevalence was higher in single-family housing than in MUH across selected subpopulations (i.e., men and women, adults aged ≥25 years, non-Hispanic whites, adults with at least a high school degree or income ≥$50,000, adults of all marital statuses, heterosexuals, and adults living in all regions except the West; p<0.05).

Within single-family housing, smoke-free home rule prevalence was highest among women; adults aged 25–44 years; Hispanics; those with a college degree or income ≥$100,000; married or cohabitating adults; those who are heterosexual, straight, or have unspecified sexual orientation; and those living in the West (p<0.05). Among any tobacco users, smoke-free home rule prevalence was highest among men, adults aged 25–44 years, Hispanics, those with a college degree or income ≥$100,000, married or cohabitating adults, those who are heterosexual/straight or have unspecified sexual orientation, and those living in the West (p<0.05).

Smoke-free home rules prevalence in MUH was highest among women, adults aged ≥65 years, Hispanics, those with a college degree or income ≥$100,000, married or cohabitating adults, those who have not specified their sexual orientation, and those living in the West (p<0.05). Among any tobacco users, smoke-free home rule prevalence was highest for the same sociodemographic characteristics, with the exception of sex and age (p<0.05).

Among MUH residents with smoke-free home rules, 34.4% reported experiencing SHS incursions (Table 3; 7.8% reported exposure every day, 9.0% reported exposure a few times a week, 6.9% reported exposure a few times a month, and 10.8% reported exposure once a month or less [data not shown]). The prevalence of experiencing an SHS incursion was highest among women (36.0%, p<0.05); adults aged 25–44 years (38.1%, p<0.05); Hispanics (41.8%, p<0.05); adults with no high school degree (38.6%, p<0.05); those with annual household income <$20,000 (38.9%, p<0.05); lesbian, gay, or bisexual adults (37.2%, p<0.05); and those living in the West (39.6%, p<0.05).

Following adjustment, the odds of an SHS incursion among MUH residents with smoke-free home rules was higher among women (OR=1.2, 95% CI=1.06, 1.36) versus men, and non-Hispanic blacks (OR=1.37, 95% CI=1.16, 1.62) and Hispanics (OR=1.32, 95% CI=1.10, 1.60) versus non-Hispanic whites (p<0.05). By contrast, the odds of experiencing SHS incursions was lower among adults aged ≥65 years (OR=0.49, 95% CI=0.40, 0.60) versus adults aged 18–24 years, those with annual household income ≥$100,000 (OR=0.70, 95% CI=0.55, 0.91) or unspecified income (OR=0.76, 95% CI=0.60, 0.95) versus those with annual household income <$20,000, and those living in the Midwest (OR=0.79, 95% CI=0.67, 0.96) or South (OR=0.73, 95% CI=0.62, 0.86) versus those in the Northeast (p<0.05).

This study reveals that U.S. MUH residents have a greater prevalence of tobacco use, particularly combustible tobacco use, and lower prevalence of smoke-free home rules than single-family home residents, especially among combustible tobacco users. Additionally, about one third of MUH residents who have adopted smoke-free home rules have recently experienced SHS incursions in their home that originated from nearby living units or shared areas, with variations apparent across population groups. This finding is consistent with studies from the general population of adults, which indicate that SHS exposure remains prevalent in the U.S. and that disparities in exposure persist.⁵ Taken together, these findings underscore the importance of efforts to promote tobacco cessation and the adoption of smoke-free building policies in all MUH to protect the public from the harmful effects of tobacco use and exposure to SHS and secondhand e-cigarette aerosol. Given the evolving tobacco product landscape, it is important for such strategies to consider the diversity of tobacco products being used by MUH residents, including combustible, noncombustible, and electronic products.

Although previous research has reported higher cigarette smoking among MUH residents compared to single-family home residents,²¹ this is the first national study to document higher prevalence of any tobacco use and combustible tobacco use among MUH residents. This study is also the first to document that smoke-free home rule adoption is lower among MUH residents than single-family home residents. However, consistent with the literature, disparities in smoke-free home rules were observed by tobacco use, race/ethnicity, education, and income.^26–28 The higher prevalence of combustible tobacco use, coupled with lower prevalence of smoke-free home rules among smokers who live in MUH, likely contributed to the finding that one third of MUH residents experience SHS incursions. These findings highlight the importance of implementing 100% smoke-free building policies in MUH to protect all occupants, employees, and visitors from the adverse effects of SHS exposure, including those residents who have implemented voluntary smoke-free home rules, but are still exposed to SHS from their neighbors who have not implemented such policies. Furthermore, to address the high burden of all forms of tobacco use observed among MUH residents, it is critical that such policies be implemented in coordination with efforts to promote tobacco cessation and encourage tobacco-free norms, including the provision of evidence-based tobacco-cessation services through healthcare providers and other population-based resources, such as quitlines.³

Studies have found that smoke-free building policies are favored by most MUH residents^21,27,28; could result in significant cost savings for MUH owners and managers²⁹; and are legally permissible in subsidized, public, and market-rate housing. Additionally, the U.S. Department of Housing and Urban Development has encouraged public housing authorities, and owners and managers of multifamily housing rental assistance programs, such as Section 8, to implement smoke-free policies in their properties.³⁰ Moreover, on November 12, 2015, the U.S. Department of Housing and Urban Development proposed a policy for U.S. public housing, that if implemented as proposed, would prohibit “lit” tobacco products (cigarettes, cigars, or pipes) in all living units, indoor common areas, administrative offices, and all outdoor areas within 25 feet of housing and administrative office buildings.³¹ As of October 2015, several hundred public housing authorities across the U.S. had instituted such policies, including all 20 in Maine.³² Additionally, at least 12 communities in California have enacted laws that prohibit smoking in all private units in market-rate MUH and do not permit “grandfather” clauses that allow current residents to continue smoking in the prohibited areas.³² A growing number of owners and managers of MUH have also voluntarily implemented such policies on their properties.^32,33

However, despite existing evidence of the legal permissibility of smoke-free MUH buildings policies, strong support among residents, considerable cost savings, and strong momentum to implement such policies in both government subsidized and private market rate housing, prevalence of such policies remains low.^21,28,29 This may be due to misperceptions about barriers to implementing such policies, including concerns about increased vacancy, turnover, and enforcement problems among MUH owners and managers.^34,35 Concerns have also been raised that smoke-free MUH building policies could amplify sociodemographic disparities by adversely affecting low-income people and other vulnerable populations, which often have the highest prevalence of tobacco use, by displacing residents who do not comply.³⁶ However, these policies have strong potential to considerably reduce health disparities and the associated costs of SHS exposure.^29,37,38 Prohibiting smoking in public housing would yield an annual cost savings of $153 million, including $94 million in SHS-related health care, $43 million in renovation of smoking-permitted units, and $16 million in smoking-related fire losses.²⁹ This knowledge gap underscores the importance of educating MUH owners and managers about the health and economic benefits of prohibiting smoking on their properties, including disseminating information on the experiences of their peers who have already implemented such policies.^29,37,38

Completely eliminating smoking in indoor spaces is the only way to fully protect nonsmokers from SHS; separating smokers from nonsmokers, cleaning the air, and ventilating buildings do not completely eliminate SHS exposure.¹ Accordingly, interventions are warranted to promote tobacco use cessation and smoke-free building policies in MUH to reduce tobacco use and protect all residents, employees, and visitors from SHS exposure. Continued efforts to implement smoke-free building policies in all MUH, along with comprehensive smoke-free laws to eliminate SHS exposure in indoor public areas and workplaces, are critical to protect against this known and preventable health hazard.