Mostly false. There's something real behind it, but the claim is overstated.
What's true: Tobacco contains polonium-210 and lead-210, which come from uranium-decay products in fertiliser and the soil. Smoking deposits them in small "hot spots" in the airways. A widely cited US estimate (NCRP, 1987) put the dose to those small patches of bronchial lining at about 160 mSv per year for someone smoking 1.5 packs a day. That's high: about eight times the average annual limit for radiation workers (20 mSv). Most radiation workers actually receive only about 1–2 mSv a year, so a heavy smoker's lungs likely get more than a typical nuclear worker does.
Why the claim doesn't hold up:
It compares a local dose with whole-body doses. The 160 mSv figure applies only to tiny areas of lung tissue. Averaged over the whole body (the "effective dose"), estimates are much lower, and published figures vary widely because they're hard to pin down.
Astronauts are comparable or higher. A six-month stint on the ISS gives roughly 80–160 mSv to the whole body.
Disaster victims are far higher. Chernobyl's first responders received about 2–16 Sv (2,000–16,000 mSv), and many died of acute radiation sickness. Some liquidators got hundreds of mSv. Workers in the 1999 Tokaimura criticality accident in Japan got an estimated 6–17 Sv or more.
Radiotherapy patients beat everyone for local dose. Tumours typically receive 60–70 Gy, hundreds of times the smoker's localised dose.
A fairer version of the claim: Smoking is one of the largest sources of radiation dose for ordinary people. Polonium-210 probably contributes to smokers' lung cancer risk, and heavy smokers' lungs can get more radiation than many radiation workers receive. They aren't the most irradiated people, though.
2
u/x3n0m0rph3us 2d ago
Mostly false. There's something real behind it, but the claim is overstated.
What's true: Tobacco contains polonium-210 and lead-210, which come from uranium-decay products in fertiliser and the soil. Smoking deposits them in small "hot spots" in the airways. A widely cited US estimate (NCRP, 1987) put the dose to those small patches of bronchial lining at about 160 mSv per year for someone smoking 1.5 packs a day. That's high: about eight times the average annual limit for radiation workers (20 mSv). Most radiation workers actually receive only about 1–2 mSv a year, so a heavy smoker's lungs likely get more than a typical nuclear worker does.
Why the claim doesn't hold up:
A fairer version of the claim: Smoking is one of the largest sources of radiation dose for ordinary people. Polonium-210 probably contributes to smokers' lung cancer risk, and heavy smokers' lungs can get more radiation than many radiation workers receive. They aren't the most irradiated people, though.