56 million Americans exposed to second-hand smoke unknowingly, finds study

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New research from the University of Florida reveals a startling lack of awareness regarding secondhand smoke exposure among American adults.

According to the study, 56 million Americans are unknowingly and routinely exposed to toxic secondhand tobacco smoke.

Researchers found traces of nicotine byproducts in the blood of 51% of the more than 13,000 U.S. adults surveyed. However, less than half of these individuals reported being aware of their exposure.

The Risks

“There is no safe level of secondhand smoke exposure,” warns Ruixuan (Roxanne) Wang, the study’s lead author and a doctoral candidate at the University of Florida’s College of Public Health and Health Professions.

Chronic exposure to secondhand smoke is associated with a range of severe health conditions, including coronary heart disease, respiratory diseases, and various forms of cancer.

Demographics and Underreporting

The study found that underreporting was widespread across all demographics but was highest among Black individuals. Wang hopes that these findings will help inform targeted interventions for at-risk groups.

The study analyzed data from the U.S. National Health and Examination Survey, conducted by the Centers for Disease Control and Prevention from 2013 to 2020.

Researchers looked for the presence of cotinine, a byproduct of nicotine, in respondents’ blood, which is the gold standard for detecting exposure to tobacco products.

Why the High Level of Underreporting?

Jennifer LeLaurin, the study’s senior author, pointed out that several factors could contribute to the high level of underreported exposure.

Cotinine measurements can detect even low levels of smoke exposure, which individuals may not notice, especially in public settings. Social stigma associated with secondhand smoke exposure could also play a role in underreporting.


The research, published in the journal Nicotine and Tobacco Research, highlights a significant public health concern: the widespread, often undetected, exposure to harmful secondhand smoke.

It underscores the need for increased public awareness and targeted interventions, particularly for communities at higher risk.

If you care about smoking, please read studies about smoking may increase heart disease risk by 200% and e-cigarette smoke may cause lung cancer and bladder disease.

For more information about brain health, please see recent studies about the cause of weight gain after smoking cessation, and results showing smoking may cause white scars on the brain.

The research findings can be found in Nicotine and Tobacco Research.

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