Study of the Transition Pattern of Heavy Metal Absorption in a Rice-Related Matrix

Abstract

Exposure to heavy metals, including arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg), is a major health hazard. The toxic effects of these heavy metals can exist in a latent state. These metals may accumulate through persistent exposure, causing adverse effects after several years to decades. Heavy metals are found in rice, the main staple food in East Asia. We studied the ecological effects of heavy metals on rice plant roots, straws, and seeds, and the soil and water used for rice cultivation. Food-grade rice grains were also analyzed. The toxicity level of As changed with the chemical form; therefore, species separation analysis of As was conducted. The concentrations of Pb, Cd, and As were analyzed by inductively coupled plasma - mass spectrometry (ICP-MS). The Pb concentration was the highest in soil (59.32 x 10(2) mu g/kg), whereas Cd and As concentrations were the highest in rice roots at 52.36 and 20.65 x 10(2) mu g/kg, respectively. In all samples, Hg was below the detection limit of the employed instrumentation. None of the heavy metal concentrations in the samples exceeded the Korean safety guideline levels. The heavy metal concentrations in the rice samples were the highest near the soil and decreased with distance, particularly As. The concentration of inorganic As was analyzed by high-performance liquid chromatography coupled with ICP-MS. The separation of As species in rice, consumed as food, showed the concentration of inorganic As was 69.51 mu g/kg, which is below the Korean safety guideline levels.