Exposure Of DDTs To Scalp Hair From General Population In Qingyuan And Guangzhou Areas

Assessing the adverse effects on human health of persistent organic pollutants(POPs) and the impact of policies aiming to reduce human exposure to POPs warrants monitoring POPs burdens of targeted populations. Identifying an ideal material to make human exposure risk assessment of persistent organic pollutants(POP) easy and reliable has been one of the most important tasks. Compared to traditional human samples like blood and breast milk, human hair as a biomarker to estimate human exposure to POPs began much later. However, the use of hair in human POPs biomonitoring has gained increasing attention, for its obvious advantages in sampling. But there are still a lot of problems to be solved concerning hair analysis indicating human POPs exposure. For example, only a few studies have investigated the correlation between human hair and internal tissues for levels of contaminants, or the contribution of internal and external exposure to hair.This study collected human hair and blood samples as well as indoor dust samples from city(Guangzhou City), town(Yuantan Town, Qingyuan County) and rural(three villages in Longtang Town, Qingyuan County) regions of Guangdong Province to analyze a class of widespread POPs, DDT pesticide, which was often the main contributor of organochlorine pesticides in analyzed human samples. Blood and indoor dust samples were used as internal and external sources of hair contaminants separately. To evaluate the validity of hair samples in reflecting human exposure to DDTs, we investigated the correlation between concentrations of DDTs in matched blood and hair samples. Besides, compositions of DDTs in different kinds of samples were also compared to explore the contribution of internal and external routes to hair DDTs.Median concentrations of ΣDDTs in human scalp hair samples from Guangzhou, Yuantan and Longtang were 14.6ng/g, 21.8 ng/g and 23 ng/g, respectively; p,p′-DDE in serum samples were 797 ng/g lipid, 841 ng/g lipid and 622 ng/g lipid. Accordingly, indoor dust from these regions possessed median ΣDDTs level of 78 ng/g, 99 ng/g and 120 ng/g respectively. No significant differences were found for any kind of samples between regions. However, the highest concentrations in three kinds of samples were all collected from Longtang.Concentrations of ΣDDTs in both human hair and blood samples were positively correlated with ages(hair ΣDDTs level and ages: r = 0.40, p < 0.001; blood p,p′-DDE levels and ages: r = 0.25, p < 0.05). When gender was considered, females contained significantly higher hair levels of p,p′-DDE, p,p′-DDT and ΣDDTs than males. Moreover, values of p,p′-DDT/p,p′-DDE ratios were also significantly higher for females(mean value, 1.7) than for males(mean value, 1.2).Whereas blood samples didn’t present such gender difference. These findings implied that external exposure might play an important role in the gender difference in hair DDTs contamination.Significant positive correlation was found for p,p′-DDE levels between matched hair and blood samples(p < 0.05), with or without gender differentiating. Given that p,p′-DDE was the prevailing compound of DDTs in serum samples of this study, serum p,p′-DDE was also used to represent ΣDDTs. Only male hair ΣDDTs levels positively correlated with serum p,p′-DDE levels. Maybe the male hair samples verily reflected DDTs from the body, while the female hair samples gained higher impact of external DDTs exposure. Hence, hair samples can effectively indicate human body burden of p,p′-DDE, while more attention should be paid when it comes to other compounds.The compositions of DDTs in human hair and blood samples were very different. We supposed that external exposure played an important role in DDTs pollution in hair, especially for woman. With the values of ratio p,p′-DDT to p,p′-DDE, the contribution of external exposure to hair samples from Guangzhou males, Longtang males and Longtang females were estimated to be 9.6%, 29% and 61%, respectively. Higher contribution of external exposure to female hair DDTs emphasized the importance of obeying a sampling standard while using hair samples to indicate human body burden of POPs.