Assessment of Toxic Metals in Dairy Milk and Animal Feed in Peshawar, Pakistan

Abstract

Assessment of Toxic Metals in Dairy Milk and Animal Feed in Peshawar, Pakistan Aims: To assess the concentration of toxic heavy metals [Cadmium, Copper, Lead and Nickle] in dairy milk and animal feed of urban and rural areas and correlate them. Study Design: It was a cross-sectional comparative study. Place and Duration of Study: The study was conducted on the dairy milk and animal feed in milk farms of Peshawar. The samples were collected during June – July of 2010. Methodology: The study area was divided into two zones: urban area which was located in the centre of the city and rural area comprising of peri urban villages. Fifty milk samples were collected, 30 from urban and 20 from rural areas. Feed samples were also collected. Milk and feed samples were prepared by wet digestion method using HNO3 and H2O2 as described by Association of Official Analytical Chemists (AOAC) of North America, 1990. This was followed by analysis on Atomic Absorption Spectrometer. Results: The results showed that the mean concentration of toxic heavy metals under study namely Cadmium, Copper, Lead and Nickle were greater in dairy milk than the maximum residue limits (MRLs) of these elements as given by Joint Expert Committee on Food and Agriculture and World Health Organization. In comparison of urban and rural areas it was found that higher concentration of Cadmium, Copper, and Nickle was found in dairy milk samples from urban areas than rural areas but there was no significant difference in Lead concentration of the two areas. Their concentration in urban and rural samples were respectively Cadmium 0.69 and 0.037 with P-value <0.001, Copper 1.40 and 0.09 with P-value 0.001, Nickel 0.806 and 0.024 with P-value <0.001, Lead 2.243 and 2.082 with P -value 0.026. However in this study all these elements were within the permissible limits in animal feed except for copper in cotton khal which was 83.3mg kg-1 against the MRL of 10 mg kg-1 given by National Research Council, NRC, 2005. Also there was no significant difference in the concentration of these elements in feed of urban and rural areas. Correlation study between the concentration of these elements in milk and feed showed positive pearson’s correlation coefficient between the two particularly for copper (0.451) in sugarcane khal  and (0.341) in wheat grain, Nickle (0.342) in maize, and (0.30) in wheat bran and cotton khal. Conclusion: The concentrations of toxic metals were higher than the maximum residue limits in milk but were within their normal limits in animal feed suggesting that milk is being contaminated by various other sources but not farm feed. Comparison between urban and rural areas showed higher concentration in urban milk samples as compared to rural except for lead probably because urban farms are located in polluted areas in the centre of the city. However no significant difference was found in animal feed of urban and rural areas because it is supplied from common source.