If the dose of radiation exceeds a certain threshold level, then it can produce acute effects, such as skin redness, hair loss, radiation burns, and acute radiation syndrome (ARS1).

Within a month, Ferreira's wife, his 6-year-old niece and two of his employees had died from acute radiation syndrome.

Radiation sickness (or acute radiation syndrome) usually sets in after a whole-body dose of three sieverts-3,000 times the recommended public dose limit per year, Langhorst says.