Levels of Nitrates, Nitrites and Selected Toxic Metals in Brands of Infant Formula Milk from Nairobi County, Kenya
Odhiambo, Vincent Otieno
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Infant formula milk has been increasingly used as a breast milk substitute as a result of maternal occupation, death and illness. This happens despite the United Nations, World Health Organization (WHO), international and national health agencies recommending exclusive breast feeding during the first six months of infancy. Following this, infant formula milk is increasingly being associated with infant health complications and even infant deaths due to its contamination during processing and contamination of its raw materials. In 2008, contamination of infant formula milk with melanine in China lead to serious illness in more than 300,000 children and death of at least six babies. Exposure of infants to high levels of nitrates and nitrites can lead to methemoglobinemia while metals such as aluminium, cadmium, lead, nickel, and zinc have adverse effects to the kidney, brain development as well as causing nausea and loss of appetite to an infant. The WHO and Food and Agricultural Organisation (FAO) have set maximum levels of concentration of these ions and metals in infant formula milk and levels of provisional tolerable weekly intake (PTWI) of these ions and metals by infants. The Kenya Bureau of Standards (KEBS) too has set the maximum level of concentration of Pb in infant formula milk. There is no information on the levels of these nitrates, nitrites and metals in infant formula milk marketed in Nairobi County, Kenya. This study determined concentration of NO3-, NO2-, Al, Cd, Pb, Ni and Zn, in seven brands of purposively selected infant formula milk sold in Nairobi County for feeding infants aged 0-6 months. The techniques used were Ion selective electrode (ISE) and atomic absorption spectroscopy (AAS) while analysis of variance (ANOVA) was used for data analysis. Except for NO 2- and Cd, NO3-, Al, Pb, Ni and Zn were detected in all the brands of infant formula milk. The mean (n=9) levels (μg/mg) of the nitrate and metals ranged as follows; NO 3-: 0.022±0.004 (brand code U) – 0.035±0.004 (brand code Z); Al: 1.054±0.085 (brand code T) – 2.156±0.423 (brand code X); Pb: 0.018±0.002 (brand code T) – 0.059±0.002 (brand code W); Ni: 0.022±0.001 (brand code X) – 0.032±0.002 (brand code V) and Zn: 24.00±0.52 (brand code T) – 32.04±0.74 (brand code U). There was significant difference in the levels of the ions and metals in the different brands of infant formula milk. The levels were found to be below the limits set by WHO/FAO. However, the concentration of Pb was found to be higher than the limits set by KEBS in all the brands except brand codes T and V. The levels of Zn were below those indicated in the labels of infant formula milk. The estimated weekly intake (EWI) of the ions and metals was found to be below Provisional Tolerable Weekly Intake (PTWI) showing safety of the infant formula milk. However, there is a risk of bioaccumulation.