Analysis of Organochlorine Pesticide Residues in Cow's Milk from Different Parts of Laikipia West Region




Taking into account the special place that milk and its derivative products have in the human diet, it is important to know whether the milk being consumed in the area is fit for human consumption and therefore, this work reports on a preliminary study carried out in Laikipia west district to build a profile of the contamination of cow's milk with 17 organochlorine pesticides and make recommendations based on the findings.


On November 2011, milk samples were collected from six different sites in the region. The samples were analyzed for residues of α-HCH, β-HCH, γ-HCH, δ-HCH, aldrin, dieldrin, endrin, heptachlor, methoxychlor, heptachlor epoxide, endosulfan I,endrin aldehyde, endosulfan II, endosulfan sulfate and the principal metabolites of p,p’-DDT (p,p’-DDE, and p,p’-DDD). The sequence steps in pesticide residues analysis are sampling, sample preparation, extraction, clean- up using a column packed with alumina, and the quantities of the residues were determined using Varian CP-3800 gas chromatography equipped with electron capture detector and statistical data was analyzed using Microsoft excel and statistical programme for social tools (SPSS). Various physical parameters such pH, moisture content, Total solid were carried out according to AOAC (2000)’s method while Total fat was determined by the standard method (Bligh and Dyer).


The findings showed that 12 different pesticides were found to be pollutant in all the six milk samples  these include (α-HCH, β-HCH, γ-HCH, δ-HCH, Aldrin, Endosulfan 1, Dieldrin, Endosulfan 2, p,p’-DDD, p,p’-DDT, Methoxychlor and Endrin aldehyde). The pesticides residues in milk varied from below detection limit to 19.28 ng/ml. Milk from Rumuruti Town had the highest sum of 17 organochlorine pesticide at 42.63 ng/ml while the other five sites had lower concentration which were 15.8 ng/ml in Ngano, 23.44 ng/ml in Shabaa, 24.7 ng/ml in African Location, 27.18 ng/ml in GG Secondary, and 32.32 ng/ml in Katutura. Presence of OCPs residues in milk implies that the consumer of milk and it is products are in dangers since pesticides are toxic and carcinogenic. Therefore, other animal products need to be studied to give a comparative contamination levels in these products.


Key words: organochlorine pesticides, cow milk, gas chromatography (GC), electron capture Detector (ECD)

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