Not sure where you have picked that up. Carbon fiber has been around in cycling for 30 years and is perfectly safe. I've had carbon fiber bits and bobs on bikes for at least 10 years including handlebars on a mountain bike that i used to jump and generally hammer around mountain trails.
Carbon rods have been around angling circles for the same amount of time...me pals on his third, his pals on his second and tales of 6lb perch snapping 60lb breaking strain state of tbe art carbon abound.
https://reviews.mtbr.com/when-should-you-replace-your-carbon-handlebar
As for steel that would be my third choice, high end alloy frames are the best value for money by far - they are cheap, light and the tubes can be hydroformed so you get strength where you need it and bigger weld areas for strength. Carbon is the same but no welds and obs more expensive. Steel is heavier and you have to use straight tubes so the weld points are smaller weaker and you pay more for it.