The graphs above come from a 2005 study by the Toxic-Free Legacy Coalition and the Washington Toxics Coalition to identify chemical residues in the human body. Samples of hair, blood, and urine of ten Washingtonians were tested for a variety of toxins including mercury and DDT. Data for each individual (identified by initials) are shown for p-p' DDE (a breakdown product of DDT) and for mercury.

1. Identify the people with the highest and lowest levels of mercury and DDT.

2. Compare the levels of mercury and DDT in each study participant to the national median. Which study participants have levels of DDT and mercury that are at least twice the national median?

3. The EPA "safe dose" for mercury is 1100 ppb (parts per billion) for women in their childbearing years, as mercury levels above this value may impair neurological development in the fetus. Which participants are above this level and by how much? Is this a concern?

4. Who conducted this study and for what purpose? Based on this information, do you feel this data is reliable? Do you really know that and how could you be more confident in your answer?

5. The pesticide DDT has been banned in the United States since 1972. How might you explain the presence of DDT in 8 of the 10 study participants?

p, p'- DDE in blood (ppb) 14 12 10 00 6 4 2 0 DDT levels in 10 Washingtonians National median PD AR DA KB LB PT AS LV DH BF Subjects males Mercury in hair (ppb) 2500 2000 1500 1000 500 0 Mercury levels in 10 Washingtonians Jodl PD AR DA KB LB PT AS LV DH BF Subjects males National median range