Fact check: Second-hand smoke is dangerous

An online post claimed it is a “lie that passive smoking (is) dangerous to non-smokers”.

Evaluation

The NHS, Cancer Research UK and the US Centers for Disease Control and Prevention (CDC) all say that passive smoking is bad for people.

The poster cites a study which was funded by a body set up by the tobacco industry and has been “roundly criticised in the scientific community”, according to a US judge.

The facts

According to the NHS, “second-hand smoke is dangerous, especially for children”.

It adds: “People who breathe in secondhand smoke regularly are more likely to get the same diseases as smokers, including lung cancer and heart disease.”

Cancer Research UK says: “All passive smoking is unsafe, and it is particularly dangerous for children.”

The CDC says: “There is no safe level of exposure to second-hand smoke (SHS); even brief exposure can cause immediate harm.”

The study

The poster linked to a 2003 study called “Environmental tobacco smoke and tobacco related mortality in a prospective study of Californians, 1960-98”. It looked at health outcomes for people who did not smoke, but who were married to smokers.

That study found that “the association between exposure to environmental tobacco smoke and coronary heart disease and lung cancer may be considerably weaker than generally believed”.

This study has proven controversial since its publication in the British Medical Journal.

The study was funded by the Center for Indoor Air Research, a group founded by tobacco companies Philip Morris, Reynolds, and Lorillard.

Following its publication, the International Agency for Research on Cancer said the study’s “conclusions are not supported by the weak evidence they offer, and, although the accompanying editorial alluded to ‘debate’ and ‘controversy,’ we judge the issue to be resolved scientifically, even though the ‘debate’ is cynically continued by the tobacco industry”.

According to the judge’s final opinion in a 2006 lawsuit, the American Cancer Society – whose data the study’s authors had used – “repeatedly warned” one of the co-authors that utilising its data “in the manner he was using it would lead to unreliable results”.

The study “used only a small subset of the overall data, and, more importantly, the data corresponded to participants who enrolled in 1959, a time when exposure to tobacco smoke was common”.

The judge’s final opinion in that same lawsuit said the study had been “roundly criticised in the scientific community”.