Preliminary investigation of pollution, impact on milk quality and health risk of potentially toxic elements in raw milk from free-ranging cattle bred in Northwestern Nigeria

Abstract

Potentially toxic elements (PTEs) were determined in raw milk from Nigerian cattles (cow, goat and sheep), to assess the environmental pollution, impact on milk quality and health risk. Nine composite samples were collected from five states in Northwest Nigeria, being the major cattle breeders. The samples were wet digested and PTEs determined using ICP-OES. 45 PTEs were ascertained of which Nitrogen (43754 mg/L) and Strontium, Sr (0.007 mg/L) recorded the highest and least mean concentration respectively. The mean concentration of other PTEs were: Selenium (0.253 ± 0.077), Cadmium (0.040 ± 0.0411), Mercury (0.048 ± 0.037), Silver (0.088 ± 0.013), Arsenic (0.044 ± 0.006), Boron (0.056 ± 0.005), Aluminium (0.014 ± 0.002), Tin (0.109 ± 0.019), Lead (0.018 ± 0.006), Gold (0.088 ± 0.048), Manganese (214.8 ± 18.754), Iron (473.9 ± 55.901), Zinc (247.9 ± 15.874), Copper (84.5 ± 12.905), Nickel (0.0031 ± 0.001), Molybdenum (0.459 ± 0.160), Cobalt (0.055 ± 0.020), Chromium (0.028 ± 0.008), Vanadium (0.185 ± 0.051), Calcium (24988 ± 16302), Magnesium (5733 ± 1460.8), Potassium (6555 ± 1199.6), Sodium (17.59 ± 2.914), Phosphorus (497.2 ± 90.38), Bismuth (0.055 ± 0.032), Cerium (0.048 ± 0.043), Argon (0.083 ± 0.011), Silicon (0.265 ± 0.110), Sulphur (0.087 ± 0.009), Titanium (0.073 ± 0.030) and Bromine (0.021 ± 0.005). Others are Platinum (0.021 ± 0.008), Antimony (0.088 ± 0.007), Iodine (0.16 ± 0.022), Caesium (0.374 ± 0.037), Barium (0.025 ± 0.009), Lanthanum (0.115 ± 0.182), Samarium (0.150 ± 0.095), Palladium (1.47 ± 0.991), Curium (0.042 ± 0.009), Fermium (0.036 ± 0.0098), Americium (0.826 ± 0.618) and Rubidium (0.048 ± 0.044). The Pearson’s correlation and paired sample t-test showed that most of the PTEs have similar origin at 0.05% significant level, and all the cattle had the same level of exposure to the PTEs respectively in the area. Raw milk is about 80% water and so, the determined PTEs concentrations are considered very high in the analyzed samples. The presence of Pb in the milk is a concern since Pb is a toxin at any concentration. The high content of PTEs in milk is attributed to the indiscriminate and artisanal mining activities in the region, and the fact that the animals are free rangers. The health risk factors were below unity (HR < 1) and so were not potential hazards. However, the environmental contaminations by these PTEs are very substantial and if this type of milk is taken raw or used for the production of dairy products like cheese and butter, then there may be a serious health condition on the consumer since they are not biodegradable.