the human brain is a very fragile thing, there is a. delicate circuitry equipped to handle the natural world, but lead is not natural
its about as natural as oil, like yeah its naturally occurring but its not naturally all over the place, lead isn't something that is normally in soluble compounds, it was never in the food or soil. perhaps we would have evolved a system to deal with it if it were- but then we wouldn't be we, would we.
Evolution is a fierce gauntlet, genetic drift, specialization and natural selection happen over vast timescales and they require that organisms do not reproduce for the selection to happen. so if we needed to dispense with calcium gated ion channels in the brain- i do not know what would have happened
there is more to say on this and all things lead, and i regret not starting on this earlier. but its never too late to start something good. whether it be a new diet, career, way of life or ridding yourself of lead. the best time to start was a year ago, the second best time is today.