I’ve had a bit of concern today from vapers and a libertarian about the evidence on secondhand smoke exposure and lung cancer. They plied my with a small range of documents eagerly anticipating…um..not sure what..to change my mind perhaps. However I’m touched by their interest in my knowledge and point of view. Anyone getting enthusiastic about science is a good thing.
I’ve read some of the material. Thought well perhaps this is a good time for another one of my mini-reviews on the subject of secondhand smoke exposure and disease.
There’s a list of 5 the articles referred to in the tweets at the end of this blog.
One of the papers is a genetic study and whilst it finds some genetic differences between lung cancers in smokers and some lung cancers in non-smokers it is not evidence that second-hand smoke does not cause lung cancer in non-smokers.
One study is unpublished, not peer reviewed and is funded by the tobacco industry. This study does not outline any methodology and the written interpretation of the data is different to my conclusions from the same data. Their reasons for not interpreting the data as it should be are attributed to a vague discussion of possible bias. Nor are the relative merits of each study included discussed or summarized. This is important – if you lump loads of crap studies with good ones the results tend to get clouded. Bigger is not necessarily better either. A poorly designed study with a big sample size just gives you a bigger pile of bullshit.
The Boffetta et al study is a case-control study conducted in 1998. They found no association between childhood exposure to secondhand smoke and lung cancer. They found weak evidence of a dose-reponse relationship between exposure to smoke and lung cancer. However their study was conducted across many different sites, had varying site methodologies and there is large variation in study outcomes per site.
The Enstrom et al study is a reasonably good one. Thanks for this reference. However as stated by the author it suffers greatly from mis-classification of exposure and focuses only on exposure to smoke via spouse when there would have been considerable exposure to environmental tobacco smoke for people with non-smoking spouses via work and recreation.
Then beyond this selection there are some more recent reviews. One very comprehensive one is the US Department of Health and Human Services published in 2006. This report finds:
Major Conclusions This report returns to involuntary smoking, the topic of the 1986 Surgeon General’s report. Since then, there have been many advances in the research on secondhand smoke, and substantial evidence has been reported over the ensuing 20 years. This report uses the revised language for causal conclusions that was implemented in the 2004 Surgeon General’s report (USDHHS 2004). Each chapter provides a comprehensive review of the evidence, a quantitative synthesis of the evidence if appropriate, and a rigorous assessment of sources of bias that may affect interpretations of the findings. The reviews in this report reaffirm and strengthen the findings of the 1986 report. With regard to the involuntary exposure of nonsmokers to tobacco smoke, the scientific evidence now supports the following major conclusions:
1. Secondhand smoke causes premature death and disease in children and in adults who do not smoke.
2. Children exposed to secondhand smoke are at an increased risk for sudden infant death syndrome (SIDS), acute respiratory infections, ear problems, and more severe asthma. Smoking by parents causes respiratory symptoms and slows lung growth in their children.
3. Exposure of adults to secondhand smoke has immediate adverse effects on the cardiovascular system and causes coronary heart disease and lung cancer.
4. The scientific evidence indicates that there is no risk-free level of exposure to secondhand smoke.
5. Many millions of Americans, both children and adults, are still exposed to secondhand smoke in their homes and workplaces despite substantial progress in tobacco control.
6. Eliminating smoking in indoor spaces fully protects nonsmokers from exposure to secondhand smoke. Separating smokers from nonsmokers, cleaning the air, and ventilating buildings cannot eliminate exposures of nonsmokers to secondhand smoke.
There is also this very recent meta-analysis with a detailed and transparent methodology and an analysis of bias from Japan. A very thorough study. This study finds that
Secondhand smoke exposure in the home during adulthood results in a statistically significant increase in the risk of lung cancer.
In addition to those studies there are numerous studies which show significant reductions in a range of serious illness and deaths following laws which prevent people from smoking inside public spaces. For example, this study on hospitalisation for acute coronary syndromes (bad things happening to hearts) in Scotland which found a 67% decrease. There are other studies like this with consistent results.
Basically taking the cigarette smoke outside has resulted in a much more pleasant, safer environment indoors for both smokers and non-smokers. I’m not about to worry that there is a lack of good evidence for laws requiring people to take the smoke outside. My conclusions remain unchanged despite the smoking guns aka damp squibs offered. There is sufficient evidence of second-hand smoke causing a range of horrible diseases including lung cancer.
These are the research studies and information from various tweets.
1. Hainaut P, Pfeifer GP Patterns of p53 G–>T transversions in lung cancers
reflect the primary mutagenic signature of DNA-damage by tobacco smoke. Funding from National Cancer Institute and European Community
2. Enstrom James E, Kabat Geoffrey C, Smith Davey. Environmental tobacco smoke and tobacco related mortality in a prospective study of Californians. Funding from the American Cancer Society however one of the authors has competing interest and received support from tobacco companies
3. Boffetta et al Multicenter case-control study of exposure to environmental tobacco smoke and lung cancer in Europe. Funding from European Commission DG-XII (contract No. EV5V-CT94-0555) for the coordination; in France, Association pour la Recherche sur le Cancer, European Commission (90CVV01018), and Caisse Nationale d’Assurance Maladie des Travailleurs Sociaux; in Germany 1, the Federal Ministry for Education, Science, Research and Technology (grant No. 01 HK 546) and the Federal Ministry of Work and Social Affairs (grant No. IIIb 7-27/13); in Germany 2, the Federal Office of Radiation Protection, Salzgitter (grant No. St Sch 1066, 4047, 4074/1); in Germany 3, the Federal Office of Radiation Protection, Salzgitter (grant No. St Sch 4006, 4112); in Italy 1, MURST, the Italian Association for Cancer Research (AIRC), and the Regione Piemonte-Ricerca Finalizzata; in Italy 2, the National Research Council (contract No. 91.00327.CT04) and the Italian Association for Cancer Research; in Portugal 1, Junta Nacional de Investigao Cientifica e Tecnolo’gica (JNICT, contract No. PMCT/C/SAU/815.90); in Portugal 2, Comissa ~p de Fomento de Investigao em Cuidados de Salde; in Spain, the Spanish Ministry of Health (Ref. 89002300); in Sweden, the Swedish Match (8913/9004/ 9109/9217) and the Swedish Environmental Protection Agency (5330071-1); and in the U.K., the Imperial Cancer Research Fund, the Department of Health, the Department of the Environment, and the European Commission.
4. Peter Lee, Barbara Forey, Jan Hamling and Alison Thornton Epidemiological evidence on environmental tobacco smoke and lung cancer. Funded by Tobacco Company
5. A blog by Frank Davis. 110 Passive Smoking Studies. Source of table of studies doesn’t have a reference – Frank links back to another blogger and there’s no clear indication of the source of the table in his blog either.