Contamination and health risk assessment of instant noodles by heavy metals from commercial outlets in Windhoek, Namibia

With growing international trade, food safety has emerged as an important global human health issue. One of the pathways by which extraneous contaminants such as toxic heavy metals access the human system is through food ingestion. At above permissible levels, these metals pose serious danger to human health. Cultivated farm produce on contaminated soil has the propensity to uptake and accumulate such contaminants. In this study, the prevalence and possible human health risks of toxic heavy metals such as Zinc, Cadmium, Copper, Lead, and Arsenic (Zn, Cd, Cu, Pb and As) in selected Instant Noodle Brands (INBs) from commercial outlets in Windhoek, Namibia was carried out. Different brands of instant noodle samples were purchased from four different commercial outlets for four periods with one-month interval. A total of 48 samples were collected and analysed for the level of heavy metals using mineral acid digestion method. Quantification of analysed metals in digested samples was done using Inductive Coupled Plasma -Optical Emission Spectrometer (ICP-OES). The mean concentration of heavy metals in the digested instant noodle samples across the sampling periods ranged from 13.1 – 17.9 mg/kg with overall mean concentration of 14.6mg/kg; 0.05 – 0.5mg/kg with overall mean level of 0.15 mg/kg; 1.5 – 2.4 mg/kg with overall mean concentration of 1.9 mg/kg; ND – 1.3 mg/kg with overall mean level of 0.4 mg/kg and 2.3 – 3.8 mg/kg with overall mean concentration of 1.4 mg/kg for Zn, Cd, Cu, Pb and As, respectively. A strong correlation (r = 0.99) was obtained between Zn and Cd levels but average correlation (r = 0.56) between Cd and Cu as well as between Cu and As (r= 0.55). Target Hazard Quotient (THQ) values greater than 1 (one) was obtained for Pb (1.7) and As (7.3). In addition, Carcinogenic Risk Index (CRI) values of 0.71 and 0.02 were also obtained for Pb and As, respectively. Of great concerns are the potential development of non-carcinogenic health effects and carcinogenic health risks with respect to these two toxic metals. Both metals are of no physiological benefits to the human system and very toxic at low levels. Hence, proper quality assurance protocol and monitoring of the level of toxic heavy metals in instant noodles products is recommended.