Determination of Heavy Metals in Citrus Peels and Seeds: Implications for Food Safety and Waste Valorization

The concentrations of heavy metals—Chromium (Cr), Copper (Cu), Cadmium (Cd), Nickel (Ni), Iron (Fe), Lead (Pb), and Zinc (Zn)—were determined in the peels and seeds of sweet orange (Citrus sinensis) and lemon (Citrus limon) obtained from Kawo market, Kaduna State, Nigeria. The samples were digested using a mixture of nitric and per chloric acids and analyzed with an Atomic Absorption Spectrophotometer (AAS). Results showed that the metal concentrations were generally higher in the seeds than in the corresponding peels. In the peels, the concentrations of Cu, Cd, and Fe exceeded the permissible limits set by the World Health Organization (WHO), while Ni and Cr were within limits, and Zn was below the recommended value. In contrast, the seeds exhibited exceedances for Cu, Ni, Pb, and Cd above WHO limits; the concentration of Cr was well below the acceptable limit. This study indicates potential health risks associated with the consumption of citrus seeds and, to a lesser extent, peels, highlighting the need for monitoring heavy metals in agricultural produce.