You do not have to smoke cigarettes to be exposed to dangerous chemicals from tobacco.
A new study has found that simply breathing in secondhand smoke can significantly increase levels of cadmium, a toxic metal linked to cancer and other serious health problems.
Researchers at Texas A&M University discovered that adults exposed to secondhand cigarette smoke had about 1.5 times more cadmium in their blood than adults who lived in smoke-free environments.
Active smokers had even higher levels, with more than three times the amount of cadmium in their blood compared with nonsmokers.
Cadmium is a naturally occurring metal, but it becomes harmful when it builds up in the body. It is known to increase the risk of kidney, lung, and prostate cancers.
High levels of cadmium have also been linked to kidney failure, painful and brittle bones, and long-term breathing problems such as bronchitis and asthma.
Although smoking rates have declined in many countries, tobacco smoke remains a major public health concern.
The new findings suggest that even people who do not smoke may still be exposed to harmful amounts of cadmium if they regularly breathe in secondhand smoke.
For the study, researchers analyzed national health data collected between 2015 and 2020. They examined blood and urine samples from more than 5,000 people, including 1,380 children and teenagers and 3,686 adults.
The researchers also measured cotinine, a substance produced when the body breaks down nicotine. Cotinine is widely used to determine recent exposure to tobacco smoke. Participants were classified into different groups, ranging from no exposure to active smoking.
Both blood and urine samples were important because they provide different information. Blood tests reveal recent exposure to cadmium, while urine tests can show long-term accumulation. This is especially important because cadmium can remain in the kidneys for up to 30 years.
Interestingly, the study found that smoke exposure did not significantly affect cadmium levels in children and teenagers. The researchers believe this may be because cadmium gradually accumulates throughout life, and younger people simply have had less time to build up the metal in their bodies.
The study also revealed that women consistently had higher cadmium levels than men. Researchers say this difference is partly due to biology. The female digestive system naturally absorbs cadmium more efficiently, especially during hormonal changes such as menstruation, pregnancy, and menopause.
Social factors also played a role. People with lower incomes, less education, or who belonged to racial minority groups tended to have higher levels of cadmium exposure.
Researchers suggest that these differences may result from broader social and environmental inequalities. For example, people living in crowded apartment buildings may be more likely to inhale secondhand smoke that travels through shared ventilation systems. Exposure may also come from polluted soil, traffic exhaust, and certain foods.
The researchers note that their study cannot prove cause and effect because it measured exposure at only one point in time. They say longer-term studies are needed.
Still, the findings send a clear message: avoiding tobacco smoke is important not only for protecting your lungs but also for reducing exposure to toxic substances that can silently accumulate in the body for decades.
