Residues of Chlorfenvinphos and 2,4-dichloroacetophenone in cow milk in Western Kenya

Abstract

A survey of the literature revealed that livestock production ranks second to cereals, provides employment and helps in alleviating poverty especially in the rural areas of Western Kenya; that a number of acaricides are available of which Steladone 300EC is the most commonly used for the control of tick-borne diseases such as East Coast Fever in grazing cattle in the area; that chronic or acute exposure to these acaricides can have serious health effects on man; and that no comprehensive research had been carried out determine the fate and potential accumulation of these chemicals in cows' milk. A study was therefore conducted in which one hundred samples of cows' milk were collected from individual farms and several delivery centres in the districts of Bungoma and Trans Nzoia in Western Kenya at different periods of the year. The objective was to determine the fate and residual effect of chlorfenvinphos, the active ingradient in Steladone 300EC, as affected by season, butterfat content and method of acaricide application (whether by dipping or hand spraying). Samples.were subjected to 'chlorfenvinphos analysis by' high pressure liquid chromatography and a combined gas chromatography mass spectometric technique following the mandatory li9uid extraction and clean-up operations. Results were based on butterfat content which was determined gravimetrically after 'extraction into hexane. Concentrations of chlorfenvinphos varied between 0.52 and 3.90 pg/kg in the dry season; and from 1.58 to 10.96 g/kg in the samples collected during the wet season. Dipped cows gave milk which was significantly higher (P<0.05) in the acaricide content than hand-sprayed animals. The chlorfenvinphos degradation product, 2,4- dichloroacetophenone was detected in only 12 % of the samples, at concentrations ranging from 3 276 ~g/kg. Concentrations of both the acaricide and it's metabolite were positively correlated with the content of butterfat in the milk. Reference to the 1993 Codex Alimentarius showed that the acaricide residue concentrations all fell below the recommended critical level of 8 ug/kg, suggesting that health risks arising from dietary exposure by the adult residents in the study area may not be serious. However, for infants, the danger may be significant since the accepted daily intake was exceeded by between 7 - 15 times. It is suggested that monitoring programes be initiated to generate data on pesticide residues on a regular basis. Educational programmes to sensitize the farm-workers and dip manangers on the hazards posed by poor acaricide handling and careless spillages will be an added advantage. Nursing mothers should be encouraged whenever possible to breastfeed their young to reduce exposure to acaricides through intake of cow's milk.