Chernobyl
| Population (years exposed) | Number | Average total in 20yrs (mSv) |
| Liquidators (1986-1987) (high exposed) | 240 000 | 100+ |
| Evacuees (1986) | 116 000 | 33+ |
| Residents SCZs (555+ kBq/m2)(1986-2205) | 270 000 | 50+ |
| Residents low contam. (37 kBq/m2)(1986-2005) | 5 000 000 | 10 - 20 |
| Natural Background | 48 |
While the effective doses of most of the residents of the contaminated areas are low, for many people, doses to the thyroid gland were large from ingestion of milk contaminated with radioactive iodine. Individual thyroid doses ranged from a few tens of mGy to several tens of Gy.
A large increase in the incidence of thyroid cancer has occurred among people who were young children and adolescents at the time of the accident and lived in the most contaminated areas of Belarus, the Russian Federation and Ukraine. This was due to the high levels of radioactive iodine released from the Chernobyl reactor in the early days after the accident. Radioactive iodine was deposited in pastures eaten by cows who then concentrated it in their milk which was subsequently drunk by children. This was further exacerbated by a general iodine deficiency in the local diet causing more of the radioactive iodine to be accumulated in the thyroid. Since radioactive iodine is short lived, if people had stopped giving locally supplied contaminated milk to children for a few months following the accident, it is likely that most of the increase in radiation-induced thyroid cancer would not have resulted.
The Expert Group concluded that there may be up to 4 000 additional cancer deaths among the three highest exposed groups over their lifetime (240 000 liquidators; 116 000 evacuees and the 270 000 residents of the SCZs). Since more than 120 000 people in these three groups may eventually die of cancer, the additional cancer deaths from radiation exposure correspond to 3-4% above the normal incidence of cancers from all causes.