Cigarettes contain a small but significant amount of radioactive material, much of which originates from the fertilizers used in growing tobacco plants. The radiation primarily comes from naturally occurring radioactive elements such as uranium, radium, lead-210, and polonium-210, which are present in phosphate fertilizers commonly applied to tobacco crops.
Phosphate fertilizers are derived from phosphate rock, a mineral that naturally contains trace amounts of uranium and its decay products. When these fertilizers are applied to tobacco fields, uranium and its radioactive decay chain—including radium-226, radon-222, lead-210, and polonium-210—can accumulate in the soil and be absorbed by the tobacco plants. Among these, polonium-210 is particularly noteworthy because it emits alpha radiation, which is highly damaging when inhaled or ingested.
The process begins with uranium in the phosphate rock used for fertilizer. Uranium decays into radium-226, which further decays into radon-222 gas. Radon gas can escape into the atmosphere and decay into lead-210, which deposits onto the tobacco leaves. Lead-210 then decays into polonium-210, which remains on the leaf surface and is inhaled by smokers when they consume cigarettes.
The amount of radiation in cigarettes from fertilizer-derived radionuclides is small in absolute terms but significant enough to contribute to the overall health risks of smoking. Polonium-210 in tobacco smoke is one of the factors linked to lung cancer because alpha particles emitted by polonium can damage lung tissue at a cellular level. Studies have shown that tobacco companies were aware of polonium-210 contamination for decades and attempted unsuccessfully to remove it from tobacco leaves.
The radiation dose from polonium-210 and other radionuclides in cigarettes is estimated to be a small fraction of the total radiation exposure a person receives from natural background sources, but it is concentrated in the lungs of smokers, increasing the risk of cancer. The exact proportion of radiation in cigarettes that comes from fertilizers varies depending on the type and amount of phosphate fertilizer used, the soil composition, and tobacco plant uptake, but phosphate fertilizers are the primary source of these radioactive contaminants.
In summary, the radiation in cigarettes largely originates from phosphate fertilizers used in tobacco cultivation, which introduce uranium and its radioactive decay products into the soil. These radionuclides accumulate in tobacco leaves, especially polonium-210, which contributes to the carcinogenicity of cigarette smoke. While the radiation dose is relatively low compared to other sources, its direct delivery to lung tissue through smoking makes it a notable health hazard.
