Exposure to DDT and HCH congeners and associated potential health risks through khat (Catha edulis) consumption among adults in South Wollo, Ethiopia

Abstract

Khat (Catha edulis) chewing is widespread in the region of East Africa. Even low levels of organochlorine pesticides (OCPs) in khat could induce public health concern. In a market-based study, from five popular khat varieties, a total of 35 composite khat samples were analyzed for dichlorodiphenyltrichloroethane (DDT) and its main transformation products, and four hexachlorocyclohexane (HCH) isomers. Extraction was carried out by quick, easy, cheap, effective, rugged and safe method (QuEChERS). OCP concentrations were determined by head space solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS). Every sample contained β-HCH above the maximum residue limit set by the European Commission. For total DDT, this was the case for 25.7% of the samples. The ratios of (p,p'-DDD + p,p'-DDE) to p,p'-DDT were less than one for 85% of khat samples, demonstrating recent use of DDT in khat farmlands. Conversely, the ratio of β-HCH to total HCH varied from 0.56 to 0.96, implying historical input of technical HCH. Assuming a daily chewable portion of 100 g, dietary intakes of p,p'-DDT, total DDT and total HCH by adults ranged from 3.12 to 57.9, 6.49 to 80.2 and 39.2 to 51.9 ng (kg body weight)^-1 day^-1, respectively. These levels are below acceptable levels suggested by international organizations. Chewing khat showed lower non-cancer health risk, but showed relatively higher cancer risk in terms of OCPs. Because khat is chewed without being subjected to any treatment, uncertainties associated with estimated intakes and health risks should be low. Therefore, this practice is of great concern.

Keywords: Dichlorodiphenyltrichloroethane; Ethiopia; Gas chromatography–mass spectrometry; Hexachlorocyclohexane; Khat; Organochlorine pesticides; Solid phase microextraction.

Fig. 1

Scatter plot of p,p′-DDT concentration [µg kg⁻¹] and ratio between transformation products of and p,p′-DDT itself for five different khat varieties including an exponential fit indicating the dependence of the TPs from the parent compound

Fig. 2

Scatter plot of γ-HCH concentration [µg kg⁻¹] and ratio of the most persistent isomer (β-HCH) to the other less persistent isomers (α- and γ-HCH). Rising ratios indicate the elapsing time since application. With increasing time, β-HCH becomes the most prominent isomer, whereas the γ-HCH concentration slowly diminishes

Fig. 3

Cancer risk values for p,p'-DDT, β-HCH, δ-HCH and γ-HCH through the consumption of 100 g fresh khat leaves (low-end consumption probability) for five khat varieties at P₅₀ and P₉₅ concentrations