This is actually a thing people are criticizing Musk for, he is being accused of sending people to Mars with insufficient shielding against cosmic rays.
In my opinion it's a bit silly argument, as there's a whole bunch of other risks and quality of life sacrifices made by the persons who are going to undertake that journey. Some raised chance of cancer is probably the least of their worries.
He can't send people to Mars yet so how are people accusing him of sending people to mars with insufficient shielding? There are limits to criticism of Musk one would think.
"NASA told Business Insider it estimates there’s a 1-in-276 chance the flight could be fatal and a 1-in-60 chance that some problem would cause the mission to fail (but not kill the crew)"
That's fairly low - feels like the age of sail would be far higher -- Columbus's second voyage alone had about 25 deaths just from scurvy. His first voyage was only about 90 crew.
But remember that life wasn't exactly easy on land either.
The Magellan Expedition left with 5 ships and ~270 men and returned with 1 ship and 18 men. People knew that going on long, overseas expeditions was very dangerous, but so was life in general in 1500. I imagine worrying about 50% increase in cancer risk by taking a voyage to fricking Mars, would seem very silly to those explorers.
A lot less than an astronaut has when going to Mars for sure. We at least know how far away Mars is exactly, and what obstacles lie in the way, and what inhabitants it has. They just got on a boat, and pray for fair wind and good weather so they might reach india, and thank god there was a whole other continent in between.
In my opinion it's a bit silly argument, as there's a whole bunch of other risks and quality of life sacrifices made by the persons who are going to undertake that journey. Some raised chance of cancer is probably the least of their worries.