Study On Dietary Exposure And Body Load Of Dioxins In Chinese Residents

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are ubiquitous, bioaccumulative, toxic and persistent lipophilic chemicals. They are unwanted by-products derived from manufacture of certain chemicals and incomplete combustion as well as industrial PCB products. Due to their severe toxic effects, including carcinogenicity, immunotoxicity and adverse effects on reproduction and development, and bioaccumulation/biomagnification in the food chain, the occurrence of these chemicals in foods and dietary exposure, human burden as well as potential health risk has been a matter of great concern in the world.In this study, with the urgent necessity of assessment of the exposure to dioxin like compounds as well as health risk assessment in China and evaluating the performance of the "Stockholm Convention", and through the breast-monitoring and total diet study recommended by WHO, a study was carried out to evaluate the human exposure and human body burden. Data of external exposure (dietary exposure) and internal exposure (human body burden) of typical general population of Chinese were obtained. And the distribution of dietary exposure to PCDD/Fs and dl-PCBs of individuals as well as time trend of external and internal exposure in China was analyzed for the first time.1. Occurrence of dioxin like compounds in typical food samples from China and assessment of dietary exposureConcentrations of17PCDD/Fs congeners and12dl-PCBs congeners were measured in256composite food samples from eight food groups, including aquatic foods, meat and meat products, egg and egg products, milk and dairy products, cereals, legume and nuts, potatoes, and vegetables, from the4th TDS in2007and5th TDS in2009-2011.12provinces were involved in2007, and20provinces were included in2009-2011. The highest level of dioxin like compounds were detected in aquatic samples, mean concentration was0.38and030pg TEQ/g fw from4th TDS and5th TDS, respectively, followed by milk and dairy products, mean concentration was0.17and0.13pg TEQ/g fw from4th TDS and5th TDS, respectively. The concentrations of dioxin like compounds in meats and eggs were comparable to each other. And relatively lower level of dioxin like compounds was detected in other plant origin foods. Levels of dioxin like compounds in eggs, milk, cereals, legumes and nut showed downward trends from2007-2011, and uptrend of dioxin like compounds levels were detected in potatoes and vegetables. Time trends of pollution levels in aquatic food and meat were different among various regions.Subsequently, dietary exposure of residents to PCDD/Fs and dl-PCBs was calculated in china, and potential health risk was also evaluated. The average dietary exposure of residents (adult male) was19.9pg TEQ/kg bw/month within the range of4.6-44.0pg TEQ/kg bw/month in2007. And the dietary exposure of residents (adult male) was20.2pg TEQ/kg bw/month within the range of4.3-53.8.0pg TEQ/kg bw/month in2009-2011. These values were all below the PTMI,70pg TEQ/kg bw/month, recommended by JECFA in2001, indicating relatively low health risk caused by dietary exposure to dioxin like compounds. Animal origin foods such as meat and meat products and aquatic foods made the major percentage contribution to total dioxin like compounds dietary intake. By comparison of the dietary exposure from the same region all involved in4th TDS and5th TDS, the average of dietary exposure from5th TDS in2009-2011was slightly lower than that from4th in2007, but there was no statistical difference. By analysis of the distribution of dietary exposure of individuals, dietary exposure for average (median) and high (P95) consumers was17.5and69.3pg TEQ/kg bw/month, respectively, indicating that dietary exposure for the majority of Chinese below the PTMI and the potential health risk is relatively low. Considering from the influence of age on the dietary exposure, with an assumption of constant dietary habits, about2.5%of total population in China might get high exposure, reach or higher than the PTMI, through their life, with an assumption of constant dietary habits. Due to huge population in China, this might mean serious health risk and disease burden.2. Levels of PCDD/Fs and dl-PCBs in human breast milk and assessment of exposure for mothers and infants in China.According to the guideline from WHO, human milk samples were collected in various provinces where China TDS was also conducted. In every province, on urban sites and two rural sited were selected, and milk samples from urban and rural area were pooled, respectively. With rare exceptions, almost all congeners of PCDD/Fs and dl-PCBs were detected in human milk samples. The most abundant congeners of PCDD/Fs and dl-PCBs were OCDD, and PCB-118,105,157, respectively. For the TEQ of total dioxin like compounds, the percentage contribution of PCDD/Fs was3times higher than that of dl-PCBs. The level of total TEQ was6.31±2.70pg TEQ/g fat in human breast milk from China. The average level of total TEQ in human milk from urban area and rural area was6.63and5.99pg TEQ/g fat, respectively. The residue level of PCDD/Fs and dl-PCBs in breast milk samples from urban regions was slightly higher than that from rural regions, but there is no statistical difference found. In general, higher levels of PCDD/Fs and dl-PCBs were detected in human milk samples from relatively developed regions with higher industrialization like Shanghai rather than economic less-developed regions like Qinghai and Neimenggu. There was significant correlation between human burden of PCDD/Fs and dl-PCBs in2011and calculated dietary exposure from5th TDS in2009-2011and4th TDS in2007(r=078, p<0.01; r=0.75,p<0.01, respectively). By comparison of the human body burden from the same province included in2007national breast-monitoring and2011national breast-monitoring, there was a notable uptrend of human body burden from2007-2011. The levels of total TEQ in human milk samples in2011was significantly higher than that in2007, and the mean was6.76and5.42pg TEQ/g fat, respectively. The dietary exposure for0-6month breast-feeding infants was39.3±18.5pg TEQ/kg bw/day, within a range of13.1～82.6pg TEQ/kg bw/day, which was more higher than the ADI recommended by WHO, TWI recommended by EU SCF, and PTMI recommended by JECFA, indicating relative higher health risk. Thus, it is necessary to carry out breast-monitoring program continual in China.3. Research prospectsAlthough a slight decrease in average dietary exposure was found from2007- 2011, higher consumer of China population was still reach or excess the PTMI, and notable increase was found in human body burden of PCDD/Fs and dl-PCBs. Thus, it is necessary to strengthen and continue the national monitoring program of residual levels of PCDD/Fs and dl-PCBs in typical foods, dietary exposure and human body burden. Due to higher exposure for breast-feeding infants and potential health risk, it is necessary to study the relationship between exposure in early life like in utero and lactation and health outcomes in future, and strengthen legislation and supervision to reduce the pollution level of PCDD/Fs and dl-PCBs in environment, and reduce the dietary exposure and human body burden, finally, to protect human health and environment.