Study On Vegetable Heavy Metals Risk Assessment In Guangdong Province

Vegetable that is a large proportion of dietary consumption for Chinese is an important agricultural product in China. Guangdong Province is a big province, which products, trades and consumes agricultural products. Currently, industry and economy are developing quickly. However, the'three'wastes caused by industrial factories brings heavy metal contaminations to surrounding soil. Since vegetable is consumed hugely and affects human health greatly, it has been caught our attention. The study of heavy metals' risk assessment in vegetable may be a guide of safe vegetable consumption. Meanwhile, the study can perhaps promote the development of vegetable industry, expand international vegetable trades and offer scientific method for risk management. This research selected ten cities, which products or consumes vegetable most hugely in Guangdong Province. Five heavy metals including lead (Pb), cadmium (Cd), arsenic (As), mercury (Hg) and chromium (Cr) in1117samples at representative12vegetables had been collected and analyzed. Based on the typical condition and character of vegetable consumed by different group residents, through Monte Carlo simulation and Bootstrap sampling in@risk risk assessment software the non-parametric probability of heavy metals'exposed quantity and risk in vegetable had been evaluated. According to the assessment results, Shaoguan City that is polluted most heavily and extensively had been focused on. The resources of heavy metal pollution in this city had been analyzed. Furthermore, the theoretical suggestion how to build up the limit standard of heavy metals in vegetable in China had been given. The main results and innovations are as follows.1. The content and distribution character of heavy metals in vegetable in Guangdong Province had been analyzed and studied comprehensively. The results indicate that the mean value of Pb, Cd, As, Hg and Cr are0.147mg,0.0766mg,0.0303mg/kg,0.00233mg/kg and0.0750mg/kg, respectively. In light of current national standards, the exceeding rate is19.7%,21.2%,17.8%,3.50%and1.40%separately. Cd contamination occupies most seriously all around China. Hg and Cr pollution should also be paid attention. The polluted level of Cr is closely relevant to the condition of city development. The contaminated condition in individual city differs from each other almost completely. In Shaoguan City Pb and Cd pollutions in vegetable are the most serious. The contents of Cr in Dongguan City and Shenzhen City are clearly higher than in other cities. Vegetable in Huizhou City contains the smallest amount of Pb, Cd, Hg and Cr. The least amount of As in Chaozhou City appears. Water Spinach (Ipomoea aquatica) has been impacted mostly by Pb, As and Cr pollution. Cd in baby bokchi(Brassica chinensis L.) and celery (Apium graveolens), Pb in both leaf and stem lettuce (Lactuca sativa) as well as Hg in luffa (Luffa cylindrica) and baby bokchi(Brassica chinensis L.) have shown higher. On the contrary, Cowpea (Vigna unguiculata) and tomato(Solanum lycopersicum) are polluted relatively less. The distribution character of heavy metal pollutes in different vegetable is directly related to vegetable's biological property.2. The study stated the advanced analytical method. The risk assessment of heavy metals in vegetable in Guangdong Province has been investigated. In Guangdong Province Pb's estimated daily intake (EDI) from vegetable by children, young adults and elder residents are1.34E-03mg/(kg·d),8.66E-04mg/(kg·d) and9.07E-04mg/(kg·d). From vegetable Cd's EDI by those group residents are6.99E-04mg/(kg·d),4.51E-04mg/(kg·d) and4.73E-04mg/(kg·d). From vegetable As's EDI are2.76E-04mg/(kg·d),1.78E-04mg/(kg·d) and1.87E-04mg/(kg·d). Vegetable Hg's EDI are2.12E-05mg/(kg·d),1.37E-05mg/(kg·d) and1.44E-05mg/(kg·d). Vegetable Cr's EDI are6.84E-04mg/(kg·d),4.42E-04mg/(kg·d) and4.63E-04mg/(kg·d). The exposure level of Cr is significant and the exposure of Pb is serious. The exposure quantity of As is on average. The exposure amount of Cr depends on the development of industry. Hg pollution in vegetable gets less attention. The declining order of exposure amount among different age people is children, elder adults and young adults. Children's EDI is1.55times of young adults and1.48times of elder adults. Children and the elder who live in variable area have different exposure amount, and the deceasing sequence is rural area, county, suburban and city. The young lived in individual region expose the descending amount of rural area, suburban, county and city.3. The heavy metal risk in vegetable in Guangdong Province had been described by using non-parametric probability assessment. The results are shown that target hazard quotients (THQs) of Pb, Cd, As, Hg and Cr in Guangdong Province are less than1. The descendent sequence of THQ is Cd>Pb>>s>Cr> Hg. There is higher risk of Pb and Cd in some regions. Among children's, the elder's and the young's THQ, children has the highest THQ and the young has the lowest THQ. Children's average THQ is1.61times of the young and1.54times of the elder. The elder's average THQ is about1.05times of the young. Children are the most sensitive group against heavy metals. However, the sensitivity of the young to heavy metals does not have big difference with the elder. Children's accumulated THQ is1.52, which means that heavy metal hazard among children may be caused by vegetable intake. The elder and the young should also pay attention to the heavy metal accumulation in vegetable, although two groups'THQs are0.944and0.990(nearly1). Different heavy metal contributes less hazard to human health as the order, Cd> Pb>> As> Cr> Hg. The accumulated contribution rates of Cd and Pb reach85%. In Guangdong Province Cd and Pb are at higher risk than other elements in vegetable. As, Hg and Cr have less risk.4. In this research, the relationship of heavy metal contents in soil, vegetable and irrigation water had been analyzed. In Shaoguan City heavy metal pollution is seriously. Four areas (three industry area and one control area) in Shaoguan City had been selected. The heavy metal contents in vegetable, soil and irrigation water sampled from those four areas had been analyzed and compared. Pb and Cd in vegetable and soil appear direct relationship (P<0.001). The phenomenon of As has been found as well. However, apart from Hg in rape (Brassica chinensis L.)(P<0.05) and stem lettuce (Lactuca sativa)(P<0.001), there is no significant relationship between vegetable and corresponding soils. Cr contents in all tested vegetable and soils do not have obvious relationship. Pb, Cd, As, Hg and Cr in vegetable tested and irrigation water do not show direct relationship.5. This investigation recommended reasonably the scientific limit standard content of heavy metals in vegetable. By using the risk assessment models established in this study, the safe threshold of heavy metals can be calculated reversely through hazard of heavy metals in edible vegetable. According to 'National Food Safety Standard:Limit Value of Contaminations in Food (draft)'in State Ministry of Health GB2762, the limit standard of heavy metals in vegetable has been discussed. From the discussion, we can see that the limit standard of Pb, Hg and Cr required by the draft national standard is within the safety value for children, young adults and elder adults. The limit standard of As is nearly close the safety value. But the limit standard of Cd content in vegetable may impact certain sensitive group residents. As long as human health is protected under the framework of safe threshold, the limit standards of Pb, Cd and Cr in vegetable may be lower. Oppositely, the limit standards of Cd and As are strongly recommended to be discussed and modified further.