How does alpha decay affect humans?
Radiations from radioactive materials – alpha , beta and gamma radiation – are all ionizing radiations which can damage living cells.
Alpha particles are unable to penetrate the outer layer of dead skin cells, but are but are capable if an Alpha emitting substance is ingested in food or air, causing living cells to die or become cancerous. DNA can also be affected by radiation, causing mutations.
Alexander Litvinenko is a famous example. He was poisoned by Polonium-210, an Alpha emmiter, in his tea.