Does secondhand smoke cause lung cancer in adults who do not smoke?

01

The causal conclusion concerns involuntary exposure

CDC, NCI and the Surgeon General conclude that secondhand smoke causes lung cancer among adults who do not smoke.

Involuntary exposure is not active smoking, thirdhand surface residue or a single odour observation, and those evidence categories cannot be merged.

[1][2]

02

Settings and numbers need their own definitions

Home, work and shared-setting studies define duration and intensity differently; a setting label does not reconstruct inhaled dose.

Relative risk, absolute risk, attributable deaths and personal probability answer different questions, and US burden figures are not global estimates.

[1]

03

Why a cancer in a nonsmoker does not name its cause

A person who has never smoked can develop lung cancer through several pathways. A study may report the proportion of lung cancers found in never-smokers, the risk comparing exposed and unexposed never-smokers, or deaths attributed to exposure in a country. Those have different denominators. “Some lung cancers occur in never-smokers” does not refute the causal smoke conclusion, and it does not show that every such cancer was caused by secondhand smoke.

Other factors include radon, air pollution, asbestos and inherited changes. A tobacco explanation should not erase those separately documented factors.

[1][2][3]

04

Use the conclusion for source control

A home and car without smoking removes new smoke sources in those spaces. Personal symptoms, imaging and screening questions belong with qualified care; the population conclusion does not select a test. NCI’s US resource links do not define another country’s services.

[2]