Impact of Heavy Metals Toxicity on Children and Adults from Local Rice Varieties of Northern Nigeria

The current study aimed to investigate the levels of heavy metals [cadmium (Cd), zinc (Zn), arsenic (As), lead (Pb), and mercury (Hg)] in local rice varieties named Jamila (JM), Santana (STN), Kwandala (KW), and Sipi (SP) collected from Danbatta town of Kano State, Northwestern Nigeria. The samples of local rice varieties were digested using HNO3 and HCl as digestion acids in a ratio of 2:1 (v/v). The digested samples were later analyzed for heavy metals using atomic absorption spectrophotometer. Moreover, the health risk assessment of heavy metals by the consumption of local rice varieties among local children and adults was also estimated based on estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TCR). The concentrations of Cd, Zn, and Pb dry weight basis observed in the range of 0.002- 0.06, 0.02-20.0, and 1.16-14.2mg/kg, respectively. Hg was detected only in SP rice variety with a concentration of 0.022 mg/kg. Whereas, As was detected in STN (0.086 mg/kg), KW (0.006 mg/kg), and SP (0.028 mg/kg). The resulting data showed that Cd, Zn, Hg, and As were within the maximum permissible limits set by regulatory bodies. The EDI values ranged from 1.21E-5 - 1.21E-1 and 5.0E-6 – 5.0E-2 for children (24 kg body weight) and adults (70 kg body weight), respectively. The data of the non-carcinogenic risk assessment indicated that the THQ values of Cd, Hg, and As were less than the maximum permissible limit of 1.00 for both children and adults. The HI data showed the potentially high possible health risk of the heavy metals by the consumption of the studied local rice varieties, with Pb being the major contributor. Similarly, resulting data of TCR for Cd and Pb showed high cancer risk upon the consumption of the studied local rice varieties over a long time.