A market-based probabilistic risk assessment of As concentration in raw and cooked rice in Bangkok

Abstract

Rice is a staple food of human and can be a main source of arsenic (As) exposure. This study was conducted to i) investigate the concentrations of total, inorganic and bioaccessible of As in raw rice, ii) investigate the effects of rice processing before human consumption on the concentrations of As in rice, and iii) evaluate the potential health impacts of As exposure through rice consumption. A total of 208 polished and non-polished samples sold in the local markets of Bangkok were collected. The total As concentrations in polished (0.0878 to 0.2949 mg kg-1, n = 154) and non-polished (0.1187 to 0.51722 mg kg-1, n = 54) were determined. The percentages of inorganic As to total As in rice were 58% and 52% in polished and non-polished rice, respectively. Approximately 25% of total As in 8% DOP rice grain were significantly reduced compared to the total As in non-polished rice (0% DOP) (p < 0.01). Only 3-time washing could significantly decrease total As concentration in polished rice (p < 0.05) by approximately 29%. Washing did not effectively remove As from non-polished rice grain. Rice washed for 3 times and then cooked with the traditional and modern cooking method using an aluminum pot and an electric rice cooker, respectively, had approximately 60% and 21% of total As reduction comparing to the raw rice. Cooked rice from both cooking methods had significantly lower As bioaccessibility than the raw rice. The deterministic and probabilistic risk assessment results of bioaccessible As exposure through the consumption of modern cooked rice indicated a negligible non-carcinogenic effects in the majority of children, adolescents, and adults as the hazard quotients in all groups were less than 1. Adults were susceptible population to carcinogenic effects especially from the non-polished rice consumption. The average cancer risk which was approximately 1.12×10-4 exceeded the acceptable cancer risk of 1×10-4. Three important factors affecting the health risk levels were rice ingestion rate, individual body weight, and As concentration in cooked rice.