Environmental impact and human health risk assessment of polycyclic aromatic hydrocarbons (pahs) in raw milk from free-ranging cattles in northwest nigeria

Polycyclic aromatic hydrocarbons (PAHs) were determined in raw milk from Northwest Nigerian cattle (cow, goat and sheep) as indicators in assessing the current pollution status of the region. In Northwest Nigeria, most animals are free rangers with the likelihood that PAHs have been taken up by these animals on the process of drinking PAHs contaminated surface waters, eating road-side grasses, and soils. A total of 42 composite milk samples were collected by milking 3-5 animals. PAHs were extracted after saponification of the milk fats through sonication using dichloromethane/hexane mixture and the five ascertained most abundant PAHs are: Phe > BaP > Chr > Fla. > Pyr using gas chromatography-flame ionization detector (GC-FID). The diagnostic ratios showed that combustion is the major pathway of PAHs emission in the study area which judging from the economic level of the area, could be attributed to vehicular exhaust emission, use of firewood, industrial fumes, waste incineration and bush burning at the beginning of the farming season. The values of PAHs showed no significant variations (p > 0.05), either between the milk types (cow, goat and sheep) or between the seven states' milk samples, indicating a similar source of the PAHs. The European Food Safety Authority set 2 mu g/kg w/w BaP as a marker for the occurrence of PAHs contamination and assessment of likely effect of carcinogenic PAH in foodstuffs, the value of BaP obtained was however much higher even though raw milk is about 80% water. Most PAHs have carcinogenic effects on humans and induce various cancers. Therefore there should be a reduction in the bush burning at the beginning of the farming season, use of firewood and other pronounced sources of PAHs in the region.