PFOS, a type of PFAS chemical, doesn't just store in fat but also accumulates in the liver, blood, and kidneys. While it does build up in the kidneys, they aren't immediately damaged because the body can manage certain toxin levels over time, though long-term exposure can cause kidney problems. Regarding the brain, PFOS has limited ability to cross the blood-brain barrier, meaning its direct impact on the brain is minimal. However, its persistence in the body and potential long-term effects make it a concern for overall health.