• Posted September 21, 2023

Millions Are Exposed to Secondhand Smoke and Don't Know It

A lot of people who think they don't have secondhand smoke exposure actually do, according to a new study that compared survey answers with blood tests.

According to the results of sensitive blood tests, more than half of American adults in the study had recently been exposed to secondhand tobacco smoke. Most were not aware of it.

"There is no safe level of secondhand smoke exposure, and long-term exposure can increase the risk of many chronic conditions, such as coronary heart disease, respiratory disease and cancers,"said lead author Ruixuan (Roxanne) Wang, a doctoral candidate in the College of Public Health and Health Professions at the University of Florida.

"We want people to be aware of their exposure so they can take protective actions,"she said in a university news release.

Researchers analyzed data from 13,000 participants in the National Health and Examination Survey between 2013 and 2020.

They looked for the presence of cotinine in respondents' blood. This indicates exposure to nicotine in the last few days and is the gold standard for determining tobacco exposure.

The study detected this nicotine byproduct in the blood of 51% of people. But less than half of participants reported being exposed to smoke.

People of all demographics significantly underreported their exposure, but Black respondents had the highest rates of exposure and underreporting.

"We think this report will inform targeted interventions for at-risk groups,"Wang said.

It's not clear why people were unaware of this exposure, but cotinine can detect low levels.

"It could be the case that for low-level exposure, maybe you don't notice it. You're in a public setting, and maybe you're not even aware someone is using tobacco around you. Maybe it's so minor you forgot,"said senior author Jennifer LeLaurin, a professor of health outcomes and biomedical informatics at the University of Florida.

"There's also the possibility that some of the respondents were aware of some secondhand smoke exposure but chose not to report it due to the stigma," LeLaurin said in the release.

Applied nationally, this may mean that 56 million Americans are unknowingly and routinely exposed to toxic secondhand smoke.

Study findings were published recently in Nicotine & Tobacco Research.

More information

The American Cancer Society has more on the risks of secondhand smoke.

SOURCE: University of Florida, news release, Sept. 18, 2023