There is nothing wrong in mixing a bleach with a bleach, although why it would be needed unless you had run out of one bottle is beyond me. It is when cleaning chemicals of different types are mixed that the trouble starts, so it's better not to do it at all.
Many things contain chemicals that are harmful. Our homes are one chemical-filled melting-pot of carcinogens. It's in cleaning products, plastics, our food, you name it. You'd think we would be safer outside, but the air is polluted, there's the risk of being murdered, and of course you take your life in your hands.
Ultimately you are not safe indoors or outdoors, and if you over-think it this leaves suicide as possibly the only course of action, were it not for the fact that death was what we were trying to avoid in the first place.
Someone once told me that we are dying from the day we are born, and I live by that.