Arsenic toxicity in rice with special reference to speciation in Indian grain and its implication on human health

Rice is a potentially important route of human exposure to arsenic, especially in populations with rice-based diets. However, arsenic toxicity varies greatly with species. The initial purpose of the present study was to evaluate arsenic speciation in rice.

It appeared very clear from the present study that inorganic arsenic shared maximum arsenic load in rice straw while in grains it is considerably low. As species recovered from rice grain and straw are principally As(III) and As(V) with a small amount of dimethylarsenic acid (DMA) and almost non-detectable monomethylarsonic acid (MMA) and arsenobetain (AsB). Discussion of the health risk of As in rice has largely been based on its inorganic arsenic content because these species have generally been considered to be more toxic than MMA and DMA and can be directly compared to As in drinking water, assuming equal bioavailability of inorganic As in the rice matrix and in water. The maximum dietary risk of exposure to inorganic arsenic through transplanted boro paddy in the present experiment was calculated to be almost 1706% of the provisional tolerable weekly intake for an adult of 60 kg body weight.

As species recovered from boro rice grain and straw are principally As(III) and As(V) with a small amount of DMA and almost non-detectable MMA and AsB. Reductions in total As load through organic amendments in boro rice grain and straw samples were manifested predominately through reduced accumulations of inorganic As species [As(III) and As(V)], between which As(V) accounted for the larger share.