well each person is very different which means that each human body has different levels of tolerance. for example one person's body may be able to handle the 30% burns easier than others. the body could go into shock from any traumatic experience such as a burn or being exposed to mercury. the amount that the body can handle before going into shock is different for each person. you also have to take into consideration the health of the person. for example someone with healthy lungs usually has no complications recovering from bronchitis while someone with a condition such as asthma may have several complications because it is harder for the body to heal itself.
how can so little damage or so little of something cause mortality? . how can so little of something or so small a percentage of damage cause something as severe as mortality? for example dying from as little as 30% burns on your body (not from something more common sense -to me- like 50% or higher) or having 7% plaque blocking your arteries or even ingesting as little as 100 micrograms of mercury would kill you.