How Long it Might Take for PFOA Blood Levels to Decline Assumes a 3-year half-life (Micrograms per Liter) 100 Average PFOA Levels in Blood (Micrograms per Liter) 3M Workers, Decatur, AL 1,125 This figure estimates a 3-year haif-life of PFOA levels in blood at different starting levels of exposure. PFOA levels decrease by about half every two to four years 90 Dupont Workers, Parkersburg. WV 410 80 C8 Study: Little Hecking. OH 228 A holf-ate is the amount of time it takes for PFOA levels in blood to be reduced C8 Study Lubeck, WV 92 70 by haif C8 Study: Tuppers Plains, OH I 42 Hoosick Falls area, NY I 23.5* The level shown for PFOA in blood for the Hoosick Falls area is the geometric mean and is based on test results for 2,081 participants including people using Village water, people using private wells, people who work in the area, and former residents. 60 C8 Study: Mason County. WV I 16 50 U.S. Population| 2 Geometric means are a way of calculating the middle level. They are used in science to prevent the highest and lowest values from distorting the average when rest of the data are close together. 40 30 20 Assume the elimination of PFOA from the human blood stream is a 1st order reaction. 10 at 3 yrs. at 6 yrs. at 9 yrs. at 12 yrs. at 15 yrs. Level of PFOA in blood at 3-year intervals Bortell SM, Colofot AM, Lyu C, et al 2010. Rate of dectne in serum PFOA concentrations after granular octivated carbon fitrotion at two pubic water systems in Oho and West Virginia. Environ Health Perspect 2 222-8 To follow the PFAS action plan, the EPA created an advisory level of 70ppt (parts per trillion) of the sum of PFOA and PFOS in drinking water. From the given information: 1. Calculate the numbers of years it will take 3M workers in Decatur Alabama's PFOA level in blood to reach the same level as the average US population assuming first order reaction with respect to PFOAS. 2. From the graph above, the half -life of PFOA blood levels is estimated at 3 years, other sources claim it is as high as 5.12 years. Compare the concentration of PFOA in blood after 15 years. Assuming a half-life of 3 years and 5.12 years for a patient with 100 mg/L starting PFOA blood level. Starting level of PFOA in blood