system
Given the following post, respond as if you're commenting on Reddit:
human
Why is Bismuth so non-lethal, compared to other heavy metals?  Especially considering its neighbors are Thallium, Mercury, Lead, and Polonium.

Specifically, why can we ingest it via pepto-bismol?  Is it the element itself which is safe, or the way it's bonded in the compound?  If it is the former, what makes Bismuth safer for us?  If the latter, why is pepto safe, yet various lead compounds are not?
gpt
One property of bismuth that separates it from other heavy metals is that it does not accumulate in an organism. This process is called bioaccumulation, and is the reason why its neighboring elements are so much more toxic. With lead, for example, if an organism ingests it, the rate of absorption of lead in the body will be greater than the rate of removal from the body. With bismuth, the body removes it so quickly following ingestion that there is no time for absorption. The half life of bismuth when it is inside an organism is five days. 

This is not to say that bismuth is safe though, so dont go off and eat a tuna and bismuth sandwich just yet. Even though it may not stay in your body as long as other heavy metals, bismuth poisoning does exist and can  harm  the kidneys, liver, and bladder. Also, one of its main suppliers, Alfa Aesar, notes that it can cause skin, eye, and GI irritation.