Establishment And Application Of Models For Long-Term Dietary Exposure For Arsenic

Objective:(1) To establish and compare four models for evaluation of long-term dietary exposure for arsenic(As) for Chinese population; (2) To conduct risk assessment for As and inorganic As exposure for Chinese population and compare the results with the total diet study; (3) To compare the exposure for As of different age groups, different districts and different years.Methods:(1) The study established the point estimate model, observed individual means model, semi-probabilistic model and fully probabilistic model to calculate the As exposure for Chinese population of different age groups, districts and years through integrating the As contamination data and consumption data. As contamination data were obtained from the national food contamination monitoring programme during 2001-2006 and 66 commodities were included. Food consumption data were gathered from National Diet and Nutrition Survey in 2002 over three consecutive days by the 24-h recall method including 65915 subjects aged more than two years old in China. This study calculated inorganic As exposure through the analysis of food contribution for As dietary exposure and the conversion rate between As and inorganic As in different food categories. The tolerable daily maximum intake (TDMI) of 50ug/kg"’bw and provisional tolerable weekly intake (PTWI) of 0.015mg/kg bw were used in the risk assessment to evaluate Chinese population’s safety; (2) The study compared the results from the probabilistic model with the total diet study and validated its reasonableness.Results:(1) The point estimate model:the results showed that children’s dietary exposure for As was 2.2μg/kg bw/day (4.4% of TDMI), which was more than teenagers and adults. The dietary exposure for As decreased with the age increasing. The dietary exposure for As for rural population was higher than urban population, which was 1.15μg/kg bw/day (2.3% of TDMI). The dietary exposure for As also decreased with the years increasing; (2) The observed individual means model:the results showed that higher percentages of dietary exposure for different age groups were all lower than 20% of TDMI. According to the conservative principles in risk assessment, the dietary exposure for As for Chinese population was safe; (3)The semi-probabilistic model:the results showed that the exposure for As in P99 percentage was 5.26μg/kg bw/day (10.5% of TDMI). For the upper tail (5%) of children, rice(50.99%), marine fishes(22.19%), crab and lobster(6.41%), mollusc animal(5.88%) and wheat(3.24%) contributed to more than 85% of total As intake. The dietary exposure for inorganic As for Chinese children was the highest. The exposure in P99 percentage was 70.2%of PTWI; (4) The fully probabilistic model:the results showed that the dietary exposure for As for children in P99 percentages was 10.29μg/kg bw/day(20.6% of TDMI); (5)The total diet study in 2002 showed that dietary exposure for As for Chinese standard people was 4.38μg/kg bw/day(8.8% of TDMI). Dietary exposure for inorganic As was 8.82μg/kg bw(58.6% of PTWI). This study showed dietary exposures for general population for As and inorganic As were 1.23μg/kg bw/day (2.5%of TDMI) and 2.48μg/kg bw/week(16.5% of PTWI), respectively.Conclusion:The point estimate model calculates the exposures in mean level and the results are rough, which can be used for screening. The results from observed individual means model can provide more conservative reference. The semi-probabilistic model eliminates the within-person variation and keeps the between-person variation to represent the long-term dietary exposure, which is a preferred model. The fully probabilistic model has higher variation than semi-probabilistic model, which can provide more elaborate evaluation. When semi-probabilistic model suggest dietary exposures in high percentages don’t exceed the health limit, the more conservative fully probabilistic model should be used to conduct the risk assessment. Dietary exposures for As and inorganic As for Chinese population were lower than health limit, however, children’s exposure for inorganic As needs a public concern.