The form of radiation that causes the most cancers, year after year, remains sunlight.
That's a good point
In the aftermath of the accident, 237 people suffered from acute radiation sickness (ARS), of whom 31 died within the first three months (...) over 6000 cases of thyroid cancer have been reported
So, 6000 cases of cancer over 30 years, which is around 200 per year. Are you saying that there are less then 200 cases of skin cancer per year worldwide? Even if all of those 6000 cases where in the same year, the number of skin cancer cases, most of which are caused by the sun, would dwarf that number.