While it says in the tweet "in 1986" there are no more than 100 deaths expected from chernobyl. Around 50 were killed at the accident, and around a dozen more in the years after. As of 2005 fewer than 50 deaths were directly linked to the radiation exposure.from the accident itself.

Dr. Geraldine Thomas explained this pretty good in "The Rational Veiw"-Podcast, linked above. If we hat the same cancer-incidence by radioactivity related exclusion zones but with particulate matter, half the cities of europe would have to be closed off in summer.