Heavy metals in foods – Part 4

Arsenic in rice

Exposure to heavy metals such as arsenic (As), lead (Pb), and cadmium (Cd) in either the short or the long term can cause cancers in humans. Dietary intake and consumption of rice (Oryza sativa L.) is increasing in Iran, and several studies on the concentration of heavy metals in rice have been carried out in this country in recent years. In this perspective, the main objective of the present study was to investigate, even via a meta-analysis of the existing literature, the presence of As and Pb in rice from many geographical areas in Iran, as well as to estimate the carcinogenic risk of these heavy metals in rice consumers. The results of the present ten years-spanning systematic review indicate that 21 reports, collecting a total of 2088 samples, were performed between 2008 and October 2017. The minimum and maximum concentration of As was observed in the Golestan area (0.01 ± 0.01 mg/kg d.w) and the Gillan region (3 mg/kg d.w); and Pb in the Shahrekord (0.07 ± 0.02 mg/kg d.w) and Mazandaran (35 mg/kg d.w). The meta-analysis of data showed that pooled concentration of As in the rice was 0.04 (95%CI: 0.02–0.06 mg/kg d.w), which resulted lower than the National Standard (NS) limits. However, the pooled concentration of Pb in the rice was 0.38 (95%CI: 0.25–0.5 mg/kg d.w), i.e., higher than NS limits. The heterogeneity was significant between As (I2 = 63%, P value = .003) and Pb (I2 = 96%, P value < .001) studies. The carcinogenic risk assessment showed that minimum and maximum incremental lifetime cancer risk (ILCR) of As was in the 45–54 (4.53 × 10−2) and 15–24 (5.50 × 10−2) year age groups consumers; and Pb, 45–54 (2.442 × 10−3) and 15–24 (2.96 × 10−3), respectively. The overall carcinogenesis risk of As (4.864 × 10−2) was 18.5 times higher than Pb (2.623 × 10−3). All age groups consumers of rice content of As and Pb are at considerable carcinogenesis risk (ILCR > 10−3). Therefore a decreased level of heavy metals in rice cultivation should be encouraged and performed in next planning.

Toxicity level of different species of arsenic

Toxicity level of different species of arsenic