Sunblocks often have chemicals that leach into the brain/blood with alarming effects... and more people suffer from Vitamin D deficiency than skin cancer from prolonged exposure...
Well, Vitamin D deficiency is easy to treat with supplements instead. And I would say skin cancer is rather more serious than Vitamin D deficiency. I don't think the goal should be to have skin cancer and Vitamin D deficiency be equally common.
You're saying that sunblock enters the blood stream through the skin and that some of the ingredients can cross the blood brain barrier? Titanium dioxide and Zinc oxide are generally recognized as safe by the FDA. The ingredients that are somewhat questionable aren't sold in the US or Europe.