Smoking does add a measurable amount of ionizing radiation exposure to a person’s lifetime, expressed in millisieverts (mSv) per year, due to the radioactive substances present in tobacco smoke. Tobacco plants naturally absorb radioactive elements like polonium-210 and lead-210 from the soil and fertilizers, which then become part of the smoke inhaled by smokers. This internal radiation exposure contributes to the overall radiation dose a smoker receives annually.
To understand this better, it helps to know what a millisievert (mSv) is. The sievert is a unit measuring the biological effect of ionizing radiation on the human body, and millisieverts are one-thousandth of a sievert. Average background radiation from natural sources such as cosmic rays, radon gas, and terrestrial sources typically exposes a person to about 2 to 3 mSv per year. This background dose varies by location but is generally consistent worldwide.
When smoking is factored in, the radiation dose increases because of the inhaled radioactive particles. Studies have estimated that a pack-a-day smoker can receive an additional radiation dose ranging roughly from 13 to 20 mSv per year solely from smoking. This is a significant increase compared to natural background radiation and is comparable to or even exceeds some occupational radiation exposures considered safe under regulatory limits.
The radioactive isotopes in tobacco smoke, particularly polonium-210, emit alpha particles. Alpha radiation is highly damaging when it occurs inside the body because it deposits energy over a very short range, causing localized damage to lung tissue and cells. This internal alpha radiation is one of the factors that contributes to the increased risk of lung cancer in smokers, alongside the chemical carcinogens in tobacco.
To put this into perspective, the International Commission on Radiological Protection (ICRP) recommends an occupational exposure limit of 20 mSv per year averaged over five years, with no single year exceeding 50 mSv. A smoker’s additional radiation dose from tobacco alone can approach or surpass these occupational limits, but it is delivered internally and continuously over many years, compounding the risk.
The cumulative effect of this radiation exposure from smoking adds to the overall lifetime risk of cancer. Radiation-induced cancers typically have a latency period of several years to decades, meaning the damage accumulates silently before manifesting as disease. The combined effect of chemical carcinogens and internal radiation makes smoking particularly harmful.
In summary, smoking does contribute a measurable and significant amount of radiation dose annually, expressed in millisieverts, which adds to the lifetime radiation exposure of an individual. This internal radiation dose from radioactive elements in tobacco smoke is an important but often overlooked factor in the health risks associated with smoking.
