fig4

Figure 4. Principal component analysis score plot for OPEs concentrations in the tree bark and human hair samples collected in Weifang (A) and Yantai (B), Shandong Province, China. (A) Eight tree bark samples (WB1-WB8) and twenty-six hair samples (WH1-WH26) are included. WH1-WH8: The Weifang hair samples of people aged < 20 years. (B) Nine tree bark samples (YB1-YB9) and thirty-three hair samples (YH1-YH33) are included. YH1-YH9: The Yantai hair samples of people aged < 20 years. WB: the tree bark samples collected in Weifang; WH: the human hair samples collected in Weifang; YB: the tree bark samples collected in Yantai; YH: the human hair samples collected in Yantai.