Association Between Polycyclic Aromatic Hydrocarbons And DNA Damage, Serum Levels Of P53 And P21 Proteins In Neonates From An E-waste Recycling Area

Background: Electronic and electric waste (e-waste) has become one of the most popular waste problems in the world with quick obsolescence and newer functionalities of electrical and electronic equipment. E-waste recycling operations have contributed to the release of numerous toxic materials including lead, chromium, cadmium and polycyclic aromatic hydrocarbons (PAHs), which posed a threat to environment and human. PAHs are mainly formed by incomplete combustion during e-waste recycling processing. A number of PAHs are known human mutagens and carcinogens. Although the detailed mechanism of action is still unknown, DNA damage and the response to genotoxic stress are critical events that have broad implications to cancer. Heightened fetal susceptibility to these carcinogens could result from higher rates of cell proliferation and differentiation, greater absorption or retention of xenobiotics, and/or less efficient detoxification, DNA repair, or apoptotic mechanisms. So the fetus may be more susceptible to DNA damage and that prenatal exposure to pollutants may increase carcinogenic risk. Guiyu, a town in Shantou, Guangdong Province, China, was one of e-waste recycling centers. The environment was polluted by PAHs due to the extremely simple and primitive e-waste"recycling''operations in Guiyu. However, no studies have reported on the effect of prenatal exposure to PAHs on DNA damage and the response to genotoxic stress in neonates from Guiyu.Objective: We aimed to determine the level of PAHs in umbilical cord blood (UCB), evaluate DNA damage in UCB lymphocytes and assess the UCB serum levels of P53 and P21 proteins in neonates from Guiyu, and explore the effect of prenatal exposure to PAHs on DNA damage and the serum levels of P53 and P21 proteins.Methods: In total 135 neonates born from 2009-2010 were studied, 88 from Guiyu and 47 from Chaoan. After informed consents were obtained from their parents or guardians, umbilical cord blood (UCB) samples were collected in all of neonates and questionnaires were administered to mothers. Questionnaires were addressed to collect information on potential routes of exposure to PAHs, as well as general demographic and health indicators. Sixteen priority United States Environmental Protection Agency (USEPA) PAHs were determined by Agilent 7890A gas chromatography coupled with 5975C mass spectrometry (GC-MS). The single cell gel electrophoresis was done to evaluate DNA damage of UCB lymphocytes. The UCB serum levels of P53 and P21 proteins were assessed by ELISA. The study protocol was approved by the Human Ethical Committee of Shantou University Medical College, China. Results:1. None of the mothers were reported smoking and drinking alcohol in the year prior to pregnancy and during the pregnancy. The mothers from Guiyu had lower educational levels and poor housing conditions than those from Chaoan. Neonates from Guiyu and Control did not differ in weight, gestational age, sex or Apgar (all P>0.05).2. Except for Fl, Chr, IP and BP, the rest twelve PAHs concentrations were all higher in UCB samples from Guiyu (P<0.05). The sum of 16 PAHs (∑16-PAHs) and 7 carcinogenic PAHs (∑7c-PAHs) were also higher in UCB samples from Guiyu than that from Chaoan (P<0.05). The distribution patterns of PAHs in UCB samples between Guiyu and Chaoan were similar, 3 rings, 5 rings and 6 rings PAHs were abundant.3. Compared with Chaoan group, there was more increased DNA damage of UCB lymphocytes in neonates from Guiyu. The tail length, tail DNA (%) and Olive tail moment (OTM) of UCB lymphocytes were all significantly higher in neonates from Guiyu (P<0.001). DNA of UCB lymphocytes in female neonates from Guiyu was more easily damaged than that in male neonates (P<0.05). Because of close correlation among tail length, tail DNA (%) and OTM (rs>0.95), OTM was selected to analysis the correlation between PAHs exposure and DNA damage. The results showed that DNA damage (OTM) was positively correlated with many PAHs exposure, including Ant, Phe, Fla, Pyr, BaA and Bap (P<0.05).4. The level of P53 protein was higher in UCB samples from Guiyu than that from Chaoan (P<0.05). No differences of P21 protein between the two groups were detected. When all subjects were divided into the group exposed to below-median level of∑16-PAHs and the group exposed to above-median level of∑16-PAHs, we found significantly higher level of P53 protein in the group exposed to below-median level of∑16-PAHs, however, the levels of P21 protein were still not different between the two groups. Compared with Chaoan group, there was higher UCB serum level of P53 protein in female neonates from Guiyu (P<0.05), however, there was lower UCB serum level of P21 protein (P<0.05). The UCB serum levels of P53 and P21 proteins in male neonates were not different between Guiyu and Chaoan. The P53 protein positively correlated with DNA damage (OTM), P21 protein and total PAHs exposure, especially positively correlated with three- and six-ring PAHs (P<0.05). The P21 protein only positively correlated with six-ring PAHs exposure. The P53 protein positively correlated with P21 protein and total PAHs exposure in male neonates (P<0.05), which was not seen in female neonates.Conclusions: Neonates born in Guiyu bad significant higher levels of PAHs. DNA was damaged to some extent and the UCB serum level of P53 protein increased in neonates from Guiyu, which were correlated with higher exposure to PAHs. The UCB serum level of P21 protein was not different, even decreased. In a word, our results suggest that prenatal exposure to PAHs may have posed genotoxic effect to neonates from Guiyu, especially for female neonates.