Analysis Of Cadmium Contamination And Health Risk Assessment In Rice Locally Pruduced In Chongqing City

Objective:With the rapid economical development,anthropogenic and natural factors are leading to more serious heavy metals pollution. Cadmium(Cd) is one of the most toxic nonessential heavy metal elements, especially to which humans could be exposed at work or in environment, leading to more serious damages. Cd can enter food chains from contaminated paddy fields. Cd in soils can be taken up by crops and pose a severe threat to human health through food chain.Cd could be easilly accumulated in rice because of its properties.Incidents of the cadmium pollution happened in many regions have caused widespread concern in the worldand.The staple food in Chongqing city is rice, rice is the main source of exposure to Cd in the population of Chongqing city.The study is to investigate the concentration of Cd in rice produced locally in chongqing city.The detection data is analyzed to understand the the Cd level of rice produced locally in Chongqing City.Health risk on Cd exposure through dietary rice intake of local residents in Chongqing city could be assessed. The measure of controlling cadmium concentration in food also could be proposed to provide the scientific basis for the local food safety supervision.Method:Chongqing Citywas divied into four areas according to the administrative division(the main city zone, the other districts of "a circle", the northeast region and the southeast region).Total districts of rice pruduced locally in Chongqing city was randomly sampled from November 2013 to May 2014. The monthly sampling number of the main city zone, the other districts of "a circle", the northeast region and the southeast region was 1,2,2 and 1 respectively.The samples of rice were covered 34 districts in 7 months in Chognqing city. All rice mill factories of collected districts were included. Four rice samples locally produced were extracted in each rice mill factory each time in accordance with national standards. Collected rice samples will be pretreated and digested by microwave dissolver.The graphite urnace atomic absorption spectrometry(GFAAS) was using to detect the concentration of Cd in rice produced locally in chongqing city according to national standard GB/T 5009-2003.The standard curve range and recovery rate are required to meet the experimental standard.Health risk assessment model was carried out to evaluated local residents of different districts according to the detected concentration of Cd in rice of different districts.These final test datas will be processed and analyzed.Results:①The 1020 rice samples were detected.The detection range from 0.001 to 0.231 mg/kg.The average value is 0.025 mg/kg at a lower level. There are 7 rice samples exceeding the Cd concentration allowable limit. The qualified rate was highly 99.31%;②The Cd concentrations was mostly in a range from 0 to 0.040mg/kg, which had a ratio of 88.04% in all rice samples. Only 0.69% rice samples were higher than the Cd concentration allowable limit(0.2mg/kg).The less rice samples exceeding showed most of the Cd concentration of rice samples in the lower range;③To observe the Cd concentration in rice samples of different districts,the low average Cd concentration value in different district ranged from 0.012 mg/kg to 0.047mg/kg.Tongnan,Pengshui and Dazu were found a few exceeding Cd concentration in rice samples,but exceeding standard rate is low. The low average Cd concentration value of rice were within the defined limit in remaining 31 districts.In comparison to the average value and median in Tongnan,Pengshui and Dazu,medians were lower than the average value in three districts. Cd concentrations in different district were statistically significant (P<0.01).The exceeding standard rate in different district were also statistically significant (P< 0.01);④To observe the Cd concentration in rice samples of different regions, Cd concentrations in different region were statistically significant(P<0.01). The main city zone and the northeast region of Chognqing city were no exceeding Cd concentration allowable limit.The exceeding standard rate in southeast region was highest,which is no statistically significant compared with the main city zone and other districts of "a circle"(P>0.05), higher than the northeast region(P< 0.01);⑤Health risk assessment was carried out to evaluated Cd exposure by rice of local residents in Chongqing city. Daily intake (DI) of Cd via rice locally produced was far less than the allowable limit value 72μg/(mg·day). There were a very small amount of rice samples exceeding standard DI.The DI average values of Cd were within limits in all districts.Target hazard quotients (THQ) of Cd via rice locally produced was far less than the allowable limit value 1.There also were a very small amount of rice samples exceeding standard THQ.The THQ average values of Cd were within a safe level in all districts.Conclusion:The study showed the qualified rate of concentration of Cd in rice produced locally cadmium content was high in Chongqing city. The overall level of concentration of Cd and risk of Cd exposure are both at a lower level. Cd intake of local residents of via rice is in safe range. Cd in rice exposure was no pose a threat to human.There were differences of Cd concentrations in different district,which may due to the different soil environment,experimental factors caused by man-made and seasonal factors and limited sample numbers, so it can only represent the cadmium level of sampling rice produced locally at that time.The specific reason still needed further investigation.The farmland soil work testing in all districts could be suggested to investigate the local pollution of heavy metals.