In the lewis and clark expedition in 1804 members of the expedition commonly used mercury as a treatment for parasites and to prevent illness while on there journey across america , recently scientist followed there route and found high levels of mercury in the soil at each of there camp sites ,which tells me that mercury has a very long half life ,way longer than 30 years which we have been led to believe , the scientist are still getting high mercury levels from over 200 years ago , which tells me that ALL sources of mercury must be removed and properly detoxed from the body to regain your health and to remain healthy