I don't think you are understanding what a baseline test is. Those results are from a baseline test he's now getting every year. He hasn't had a fume event in years. So his "normal" levels are now established. There is some research that shows the stuff leaves your body in a a few days, or a week or two (if I remember correctly, and based on the quantity and other factors). But the damage/reaction your body has may or may not go away...that's where each individual reacts differently, and the cumulative measure isn't necessarily based on a specific amount of TCP in your system, but from damage each exposure, whether large or small, causes. So he wouldn't have permanently elevated levels. The reason behind getting a baseline test is not to see what your levels are, but to have something to compare it to right after you have an event. Then you can compare your recently exposed levels to non-exposed levels, which more easily links symptoms to the event, as opposed to other factors in life (old age, other health issues, etc.).