| Background and Objective Cadmium(Cd)is a heavy metal that exists widely in the nature and harmful to the human body,it enters the body through a variety of ways such as the digestive tract,respiratory tract and skin contact.Diet is the main source of exposure for non-smokers.Cd has a long biological half-life up to 10-35 years,so it is difficult to completely metabolism after entering the human body,it can cause harm by accumulating in the human kidneys,liver and bones.Its harm effects include:liver and kidney damage,neurotoxicity in children,Itai Itai disease,kidney stones,osteoporosis,lung cancer and even death.With the development of social economy,the health hazards of Cd on the population has become more and more serious,and the health standard of cadmium is more and more strict.In 1988,the health standard value for a provisional tolerable weekly intake of Cd was set at 7 μg/kg bw by the Joint FAO/WHO Expert Committee on Food Additives(JECFA).However,in 2010,this standard was withdrawal,and a more stringent standard for a monthly tolerable intake of 25 μg/kg bw was proposed.In 2011,a more stringent standard for a tolerable weekly intake of 2.5 μg/kg bw was reconfirmed by European Food Safety Authority(EFSA).At the same time dietary exposure assessment models has developed rapidly,long-term dietary exposure assessment model has developed from traditional deterministic model into probabilistic model,and the probabilistic model has been applied within the scope of some developed countries.China has applied probabilistic model in heavy metal exposure assessment currently,however,the input data requirement,calculation accuracy of this model,and rationality of the model applied in the assessment of Chinese population need to be verified.At the same time,the heavy metal dietary exposure estimates are limited to the use of a single season to estimate the exposure for a lifetime in the worldwide;the model cannot estimate the exposure change with seasons.In this study,24-hour diet recall method was applied to obtain the food consumption data on four on-consecutive days in Jiangsu Province in 2012.The consumption data were combined with the Cd concentration data from the national pollutant-monitoring program,and the latest data simulation method by using short-term data to generate longitudinal data with flexible numbers of subjects and days was applied,to simulate different input data scenarios.The accuracy and the influence on exposure calculated by fully probabilistic Betabinomial-Normal(BBN)model of the different scenarios were explored.The usual intake of Cd exposure was estimated by long-term dietary probabilistic model based on population in Jiangsu Province,meanwhile,the regional and seasonal effects,the potential non-carcinogenic and carcinogenic effect of the dietary Cd exposure on human were also analyzed.Content and Methods(1)Based on the consumption data covering four seasons a year in Jiangsu Province in 2012 and the Cd concentration data from the national pollutant monitoring program,the mixed effects model was constructed,and the correlation coefficient of the model was calculated.The total variation of the population was separated into between person variance and within person variance and random sampling was carried out in the corresponding standard normal distribution to generate longitudinal data with flexible numbers of subjects and days.Bootstrap method of 200 times was applied in the uncertainty analysis.The 95%confidence intervals of mean and ICC were calculated for both simulation data and raw data.The 95%confidence intervals were compared to determine similarity.Means and ICC were recalculated when different numbers of subjects and days were used.(2)Exposure data of 365 subjects and 1000 days were simulated,and calculate the average daily exposure of this population.Five different scenarios including consecutive three days,and non-consecutive two days,non-consecutive three days,non-consecutive four days and non-consecutive seven days were randomized selected from the simulation data.The 95%confidence interval of each scenario exposure was calculated.Simulation subjects were set at 300,500,1000 and 5000.Analyzing the impact of different sample size on exposure distribution.(3)Fully-probabilistic BBN model was applied to estimate the diary Cd exposure distribution by combining the consumption data on non-consecutive four days covering four seasons a year in Jiangsu Province in 2012 and the Cd concentration data from the national pollutant-monitoring program.The area and seasonal effects wear analyzed.Target hazard quotient(THQ)was applied to evaluate the non-cancer effect.The potential cancer effect was evaluated by calculating the annual excess lifetime cancer risk(AELCR).The contribution of dietary Cd exposure of population from different areas and in different seasons in Jiangsu province was analyzed.Bootstrap method was used to analyze the uncertainty of exposure calculation.Results(1)The mean and ICC of the raw data were 0.40 μg/kg bw/day and 0.46.The mean and the 95%CI of the simulation data with 1000 subjects and 365 days were 0.40(0.39-0.42)μg/kg bw/day.The ICC and its 95%CI were 0.48(0.45-0.50).The 95%CI of the mean and ICC of the simulation data covered the general parameters.(2)Scenario analysis of simulated exposure:For the mean level,the 95%confidence interval of each scenario contained the true value.With the gradual increase of the number of repeated measures,the width of the 95%confidence interval was gradually reduced.From the P95 point of view,with the increase of the number of repeated measurements,the degree of dispersion of the exposure was gradually reduced.Meanwhile,the 95%confidence interval was gradually close to the true value.All the assessment of the consecutive three days scenario did not include the true value.50%of the results of non-consecutive four days scenario included the true value.75%of the results of the non-consecutive seven days scenario in the seasonal group included the true value,and all the results in the whole study population included the true value.The width of each 95%confidence interval was gradually reduced with the increase of the number of simulations.(3)Scenario analysis of actual exposure:the mean,P90 and P95 of the Cd exposure from the 3 consecutive scenario in 2011 were 0.208,0.364 and 0.444 μg/kg bw/day.The relative value from the 4 non-consecutive scenario in 2012 were 0.210,0.312 and 0.357 μg/kg bw/day。The means of the two scenarios were comparable,the P95 of the the latter was lower than that of the former,this result was in agreement with the simulation results.(4)The uncertainty analysis and exposure estimation of fully probabilistic BBN model:The mean level of the Cd exposure of the population in Jinhu,Yangzhou and Suzhou were 0.196,0.178 and 0.269 μg/kg bw/day.The exposure value in four seasons were 0.206,0.208,0.213 and 0.243 μg/kg bw/day.For P95 level,The Cd exposure in all subgroups were ranged from 0.290 to 0.439 pg/kg bw/day,the percentage accounted for PTMId were from 34.9%to 52.9%.The 95%CI of mean exposure of the population in Jinhu,Yangzhou,Suzhou and overall population were 0.17-0.3 μg/kg bw/day,0.14-0.29 pg/kg bw/day,0.21-0.61 μg/kg bw/day and 0.18-0.41 pg/kg bw/day.The 95%CI of P99 were 0.36-0.76 μg/kg bw/day,0.30-0.74 μg/kg bw/day,0.45-1.58μg/kg bw/day and 0.41-1.33μg/kg bw/day.The 95%CI of mean exposure of the population in four seasons were 0.17-0.38 μg/kg bw/day,0.17-0.40 pg/kg bw/day,0.17-0.43 pg/kg bw/day and 0.20-0.43 μg/kg bw/day.The 95%CI of P99 were 0.40-1.22 μg/kg bw/day,0.39-1.31 μg/kg bw/day,0.40-1.38 μg/kg bw/day and 0.46-1.39 μg/kg bw/day.(5)Contribution analysis:the food group with high contribution in all the subgroups were rice,seafood,pak-choi,wheat flour,leafy vegetables and pig meat;these food groups accounted more than 60%.The major contributors in Jinhu were rice(29.4%),pak-choi(15.4%)and seaweed(11.1%).The major contributors in Yangzhou were rice(22.7%),pak-choi(10.6%)and wheat flour(10.3%).In Suzhou,rice(18.9%),pak-choi(11.8%)and kidney(11.5%)had high contribution.In spring,rice(20.1%),kidney(17.7%)and pak-choi(10.8%)had high contribution.In summer,rice(27.8%),seaweed(14.1%)and wheat flour(8.6%)had high contribution.In autumn,rice(26.0%),pak-choi(13.7%)and kidney(8.7%)had high contribution.In winter,rice(21%),pak-choi(17.3%)and wheat flour(9%)had high contribution.(6)Risk evaluation:the means THQ of population in each city and season were all 0.2P95 of THQ ranged from 0.3-0.4.The means AELCR in each city and season ranged from 1.5×10-5～2.16×10-5 a-1.P95 of AELCR ranged from 2.46×10-5～3.56×10-5a-1.Conclusion The 95%IC of the mean and ICC of the simulation data with 1000 subjects and 365 days cover the overall parameters of the raw data.The mean and ICC of the simulation data were unstable when the number of subjects was below 500,and with the increase in the number of subjects,the mean and ICC became gradually stabilized.In the case of a sample size of 1000,the number of days of simulation has little impact on the stability of the simulation data.The validation study showed that if the dietary assessment did not take into account the seasonal effect,the survey of non-consecutive two days could be used instead of the survey of consecutive three days.For the high-end percentile(such as P95),non-consecutive four days scenario was better than the consecutive three days scenario,non-consecutive seven days scenario was better than the non-consecutive four days scenario.The scenarios of non-consecutive four and seven days could also evaluate the seasonal effect of dietary exposure.Therefore,compared with the consecutive three days survey,the non-consecutive four days survey method could not only assess the seasonal effect of dietary exposure,but also the results were more accurate than consecutive three days method.The actual data exposure scenario analysis showed that the mean of the exposure of the two scenarios(consecutive 3 days and non-consecutive 4 days)were comparable.Because the ICC of the 3 consecutive days scenario was 1.7 times than that of the non-consecutive 4 days scenario,so the discrete degree of the exposure of the former scenario is higher than the latter.In Jiangsu Province,the mean and P95 of exposure were lower than PTMId in all subgroups in 2012.The exposure in autumn and winter was higher than that of the spring and summer.The exposure of Suzhou area was significantly higher than that of Jinhu and Yangzhou,the difference was statistically significant.The major contributors of the total Cd exposure were rice,seafood,vegetables,wheat flour,leafy vegetables and pig meat.In Jiangsu Province,both the dietary Cd carcinogenic and non-carcinogenic effects of the population were unlikely to happen after a lifetime’s exposure to dietary Cd,however,attention should be paid to the cancer effect of the population of Suzhou and the high-end exposed population(P99)in winter. |
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