Adults exposed to secondhand cigarette smoke may be carrying significantly higher levels of the toxic metal cadmium in their bodies, according to new research.
The study found that adults with heavy exposure to secondhand smoke had about 1.5 times more cadmium in their blood than people living in smoke-free environments. Active smokers had more than three times the amount.
Researchers say the findings are significant because cadmium, a toxic metal found in tobacco smoke, can accumulate in the body for decades and has been linked to kidney, lung and prostate cancers, as well as kidney disease, bone damage and chronic respiratory problems.
Nandita Sarker, a doctoral student at Texas A&M University’s School of Public Health and the study’s lead author. said: ‘We knew that cigarette smoke exposes people to cadmium, but until now, we didn’t know about the association with secondhand smoke.’
The researchers analysed national health data collected between 2015 and 2020 from more than 5,000 participants, including 1,380 children and teenagers and 3,686 adults. They measured cadmium levels in blood and urine samples and compared them with nicotine exposure, which was assessed through cotinine, a chemical produced when the body processes nicotine.
Blood samples were used to measure recent cadmium exposure, while urine samples helped researchers assess long-term accumulation because cadmium can remain stored in the kidneys for up to 30 years.
While the association between smoke exposure and cadmium levels was clear among adults, researchers found no significant increase among children and teenagers. The difference may be due to cadmium accumulating gradually with age, making long-term exposure easier to detect in adults.
Sarker said: ‘In short, breathing in cigarette smoke – either from active smoking or secondhand exposure – significantly raises toxic cadmium levels in adults.’
The study also identified disparities across demographic groups. Women consistently had higher cadmium levels than men, which researchers attributed to biological differences that allow women to absorb the metal more efficiently. Higher exposure was also observed among racial minority groups and people with lower incomes or less education.
Sarker said: ‘This disparity cannot be explained by smoking habits alone, but likely is the result of broader social, environmental and financial inequalities.’
Study supervisor Taehyun Roh said: ‘Our findings suggest that secondhand smoke may contribute to the long-term accumulation of cadmium, a toxic metal associated with cancer and other chronic diseases.
‘These results highlight the importance of protecting people from tobacco smoke exposure not only for respiratory health, but also for reducing exposure to harmful environmental contaminants that can accumulate in the body over time.
The researchers noted that the study cannot prove cause and effect and called for longer-term studies to better understand how secondhand smoke contributes to cadmium buildup over time.
The full research can be accessed here.
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