Many people know that cigarette smoking is harmful. Smoking is linked to cancer, heart disease, lung disease, and many other health problems.
However, even people who do not smoke may still be exposed to harmful substances if they regularly breathe in cigarette smoke from other people.
New research suggests that one hidden danger of secondhand smoke is exposure to cadmium, a toxic metal that can stay in the body for decades. The study found that adults who are regularly exposed to secondhand smoke have about 1.5 times more cadmium in their blood than people who live in smoke-free environments.
The study was conducted by researchers at Texas A&M University’s School of Public Health and was published in the journal Biological Trace Element Research.
Cadmium is a naturally occurring metal found in the environment, but it becomes dangerous when it accumulates in the body. Scientists have linked long-term cadmium exposure to several serious health conditions.
High levels of cadmium can damage the kidneys, weaken bones, and increase the risk of several cancers, including kidney, lung, and prostate cancer. The metal has also been associated with chronic breathing problems such as asthma and bronchitis.
One of the most worrying features of cadmium is that the body has great difficulty getting rid of it. Small amounts can build up slowly over many years. In fact, cadmium can remain in the kidneys for up to 30 years.
The researchers wanted to understand whether secondhand smoke contributes to cadmium exposure in the same way that active smoking does. While scientists already knew that smokers absorb cadmium from cigarettes, much less was known about the effects of simply breathing other people’s smoke.
For the study, the researchers analyzed national health data collected between 2015 and 2020. They examined information from 3,686 adults and 1,380 children and teenagers.
The team measured levels of cadmium and cotinine in blood and urine samples. Cotinine is a substance produced when the body processes nicotine. Because cotinine remains in the body for a short period, it provides a useful way to determine recent exposure to tobacco smoke.
The researchers divided participants into several groups based on their exposure levels, including no exposure, light exposure, heavy exposure, and active smoking.
The findings showed a clear pattern among adults. The more tobacco smoke adults were exposed to, the higher their cadmium levels became.
Active smokers had more than three times as much cadmium in their blood as nonsmokers. Adults with heavy secondhand smoke exposure had about one and a half times more cadmium than people living in smoke-free environments.
Interestingly, the same pattern was not seen in children and teenagers. Their cadmium levels did not change significantly according to smoke exposure. The researchers believe this may be because cadmium accumulates gradually throughout life. Adults have had more years for the metal to build up inside their bodies, and older kidneys become less efficient at removing it.
The study also uncovered differences between men and women. Women consistently had higher cadmium levels than men across all age groups. Researchers believe biology plays a role.
The female digestive system naturally absorbs cadmium more efficiently than the male digestive system. Hormonal changes during menstruation, pregnancy, and menopause may further increase this absorption.
Social and economic factors also appeared to influence cadmium exposure. People from racial minority groups and those with lower incomes or less education tended to have higher levels of exposure. The researchers believe these differences cannot be explained by smoking habits alone.
For some people, exposure may occur because they live in crowded apartment buildings where cigarette smoke travels through shared ventilation systems.
Other sources of cadmium exposure include contaminated food, polluted soil, and traffic-related air pollution. In addition, people with fewer educational opportunities may have less access to information about smoking risks and smoking cessation programs.
The study has several strengths. It included a large number of participants and used objective laboratory measurements rather than relying entirely on questionnaires. The researchers also considered many demographic factors that could affect the results.
However, the study has limitations. Cotinine remains in the body for only about 15 to 20 hours. Because of this short time frame, a single test cannot always distinguish between someone who briefly entered a smoky room and someone who smokes occasionally. The study also could not measure dietary exposure to cadmium over many years.
Importantly, this research cannot prove that secondhand smoke directly causes higher cadmium levels, but it does show a strong association. Future studies that follow people over longer periods may provide a clearer understanding of cause and effect.
Overall, the findings provide another reason to avoid exposure to tobacco smoke. Secondhand smoke may not only irritate the lungs but may also quietly increase exposure to a toxic metal that remains in the body for decades and contributes to serious chronic diseases.
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Source: Texas A&M University.
