Arsenic Speciation in Rice, Mechanisms and Associated Health Risk Through Rice Consumption in Various Districts of Khyber Pakhtunkhwa, Pakistan

Abstract

Arsenic (As) is one of the toxic metalloids, therefore, can cause health risk in the consumers through consumption of contaminated food and rice. The current study focused on As speciation in rice, bioavailability, mechanisms and its potential human health risk. For this purpose, rice and soil samples were collected from 16 different districts (non-mining and mining sites) of Khyber Pakhtunkhwa (Pakistan). Soil physicochemical characteristic such as texture, electrical conductivity (EC), organic matter (OM), pH, iron (Fe) and phosphorus (P) were determined. Total arsenic (AsT) concentrations were analyzed using ICP-MS, while the arsenite (As3+), arsenate (As5+), arsenobetine (BAs), dimethylarsenic (DMA) and monomethyl arsenic (MMA) were determined by HPLC–ICP-MS method. The highest AsT (0.28 mg/kg) was observed in the rice sample of DI Khan District and lowest (0.06 mg/kg) in Shangla District. However, these findings were found within the permissible limits set by various authorities. Furthermore, results showed higher concentrations of inorganic As (Asi) than organic As (Aso) species in rice. The estimated daily intake (EDI) and incremental lifetime cancer risk (ILTCR) were used to evaluate the potential human health risk for As consumption in rice. Results revealed that the rice samples collected from the district having mining activities had higher value of As (0.28 mg/kg of AsT) as compared to non-mining (0.072 mg/kg of AsT). The highest ILTCR value (0.00196) was observed for rice collected from mining districts. This study revealed that mining activities have great influence on the As contamination of soil and grown rice. This study recommends the use of geo-sorbents as soil amendments in districts having mining activities for the purpose to lower As availability in soil and its bioaccumulation in growing rice that will help to keep lower the potential risk.