Environmental tobacco smoke an avoidable environmental pollutant

October 2003

Among children, the most common outcomes studied include asthma, exacerbation of asthma, acute otitis media (AOM), chronic middle ear effusions and lower respiratory tract infections to include respiratory syncytial virus (RSV). Both the Surgeon General’s Office (U.S. DHS, 1986) and the Environmental Protection Agency (U.S. EPA, 1992) summarized scientific observations on the effect of ETS, or second-hand smoke, on these endpoints (NCI. Health Effects of Exposure to Environmental Tobacco Smoke: The Report of the California Environmental Protection Agency. Smoking and Tobacco Control Monograph no. 10 Bethesda, MD. HHS, NIH, NCI, NIH Pub. No. 99-4645, 1999).

The relationship between second-hand smoke exposure and childhood upper respiratory tract infections, including acute and chronic otitis media, has been demonstrated in multiple studies. In five case-control, four prospective and three retrospective investigations, all but three of these 12 studies showed a statistically significant relationship between second-hand smoke and outcomes for middle ear disease. Two of these 12 studies used objective measures of secondary smoke exposure (salivary and serum cotinine levels) and found a statistically significant relationship between quantitative exposure and outcomes. Additional studies have used prospective screening for middle ear disease, thus eliminating differential utilization of medical services by parents as a possible confounder. Again, both of these studies found statistically significant associations between second-hand smoke exposure and middle ear disease.

Overall, studies have never shown a protective effect, such as would be expected in at least some studies if all findings were a product of random variation.

This association of second-hand smoke exposure and upper respiratory tract disease, to include AOM, passes the test of biological plausibility from animal experiments on eustachian tube dysfunction. There are at least three mechanisms whereby second-hand smoke might produce eustachian tube dysfunction: decreased mucociliary clearance, decreased eustachian tube patency and decreased patency and impaired mucociliary clearance secondary to increased frequency of viral respiratory tract infections. Estimates from California suggested in 1992 that approximately 135,000 (78,615-188,767) office visits per year among California children under the age of 3 were for AOM episodes attributed to passive smoke inhalation.

Risks identified

Studies evaluating the association between second-hand smoke and invasive bacterial disease in children and adults have relied primarily upon epidemiological evidence. Although the overall data are inconclusive primarily due to design issues, suggestive epidemiology-based studies have identified risks. Studies have suggested an association between high levels of passive exposure to tobacco smoke and bacterial meningitis, invasive meningococcal disease, clusters of meningococcal meningitis and carriage of Neisseria meningitidis. Animal experiments and human investigations have shown enhanced bacterial binding to epithelial cells of smokers and to individuals with passive exposure to second-hand smoke. In an article published in 2000 (N Engl J Med 2000; 342: 681-9), Pekka and colleagues identified cigarette smoking as the strongest independent risk factor for invasive pneumococcal disease among immunocompetent adults. Public health officials have concluded that because of the high prevalence of smoking (and passive smoke) and the large attributable risk based on populations, programs to reduce both smoking and exposure to passive smoke have the potential to reduce the incidence of pneumococcal disease.

There is now sufficient evidence to conclude that passive smoke inhalation is associated causally with additional episodes and increased severity of asthma in children. The relationship of parental smoking to the risk of respiratory tract infection has been extensively investigated. Nearly two dozen reports reviewed by the Department of Health and Human Services and the EPA have established that second-hand smoke exposure increases the risk of acute lower respiratory tract disease in young children by 1.5 to 2-fold. Outcome trials in the United States, Canada, United Kingdom, Denmark and Japan all identified crowding and exposure to tobacco smoke as significant and independent risk factors for disease severity of RSV.

In a study by Carbonell-Etrany, X. (Pediatr Infect Dis J 2001, 20: 874), significant independent prognostic variables for high risk of RSV hospitalization included: chronologic age <3 months at the onset of RSV season, living with school-age siblings and exposure to tobacco smoke. Barton and colleagues argued in another publication (Pediatric Pulmonology 2001, 32: 20), that education emphasizing frequent hand-washing, avoidance of passive tobacco smoke, and lessening the exposure to sick children remains the least expensive prevention tool for high-risk infants during RSV season.

The economic impact of environmental and parental smoking is an important preventable cause of morbidity and mortality among American children; second-hand smoke results in an estimated annual direct medical expenditure of as much as $4.6 billion and loss of life costs of $8.2 billion (Aligne, CA: Archives Pediat & Adoles Med 1997, 151: 648).

Environmental pollutant

This discussion brings us to this RSV season and an important consideration. Is tobacco smoke an environmental pollutant? Only the most ardent proponent of smokers’ rights or shareholders of tobacco company stock would even consider arguing this point. But is this an avoidable environmental pollutant? I would argue that it is when the issues of education, avoidance of second-hand smoke, hand-washing, avoidance of child day care (where feasible) and sick contacts are compared with the new recommendations for the use and cost of preventive therapy of high-risk infants against RSV.

The 2003 Red Book provides a clear set of recommendations for the use of palivizumab (Synagis, MedImmune) in high-risk infants with chronic lung disease, congenital heart disease and premature infants in the first year of life. Of the “risk factors” to be considered is the identification of “environmental pollutant exposure.” The Committee on Infectious Diseases recommends: “Although palivizumab and RSV-IGIV have been shown to decrease the likelihood of hospitalization in infants born between 32 and 35 weeks of gestation (ie, between 32 weeks, 1 day and 35 weeks, 0 days), the cost of administering prophylaxis to this large group of infants must be considered carefully. Therefore, most experts recommend that prophylaxis should be reserved for infants in this group who are at greatest risk of severe infection and who are younger than 6 months of age at the start of the RSV season. Epidemiological data suggest that RSV infection is more likely to lead to hospitalization for these infants when the following risk factors are present: child care attendance, school-age siblings, exposure to environmental air pollutants, congenital abnormalities of the airways, or severe neuromuscular disease. However, no single risk factor causes a very large increase in the rate of hospitalization, and the risk is additive as the number of risk factors for an individual infant increases. Therefore, prophylaxis should be considered for infants between 32 and 35 weeks of gestation only if two or more of these risk factors are present. Exposure to tobacco smoke is a risk factor that can be controlled by the family of an infant at increased risk of RSV disease, and preventive measures will be far less costly than palivizumab prophylaxis” (2003 Red Book, 26th edition, pages 525-526).

“High-risk infants never should be exposed to tobacco smoke” (2003 Report of the Committee on Infectious Diseases). I would agree. Individual assessment of the patient, the home environment and education of parents on issues of crowding, child day care, sick contacts, home isolation procedures, good hand-washing practices, and the avoidance of second-hand smoke needs to be explored and enhanced. Palivizumab does not prevent all infections due to RSV. It reduces severe disease and the associated complications and morbidity in high-risk infants identified in extensive clinical trials. These common sense educational and environmental “policies” can prevent RSV (at least significantly reduce it). Why not ask parents for a verbal (or even written) contract that they really will “smoke outside!” We obviously have not translated the tobacco literature into an effective plan to prevent tobacco use or to help our parents stop smoking. In a recent special article (N Engl J Med 2003; 349: 868-74), Dr. Claude Lenfant mourned this loss of translation between clinical research and clinical practice. When analyzing the differences between life expectancy in the United States and that in other economically developed countries, the issue of societal differences was called into question. However, Lenfant believes that the answer lies in the fact that health providers and the public are not applying what we know. We know that avoidance of second-hand smoke, limitation of contact of high-risk infants to crowding and sick contacts, good hand-washing techniques and home infection control measures will prevent or reduce RSV infections in these high-risk infants. When will we learn that more “cents” does not equal “common sense”?