Background There is an exponential rise in the use of farming chemicals in agricultural practices ostensibly to increase food production. The chewing of fresh khat leaves and shoots has spread across the world from ancient khat producing regions in East Africa and the Arabian Peninsula. Khat is a well-established socialization substance with stimulating characteristics. In this work, we have reviewed the deleterious impacts of several heavy metals such as lead, cadmium, iron in the khat plant and their health impacts. Survey on the health complications of farming chemicals used in khat production is also presented. Main body of the abstract The toxic effects of heavy metals and farming chemicals in plant matter such as khat leaves are a serious health concern. Heavy metals including cadmium (Cd) and lead (Pb), for instance, bio-accumulate in the body and the food chain as precursors for disease. It has been established that blood that has lead levels of 40–60 ug/dL is a precursor for serious health illnesses such as cardiac arrest and cancer. On the other hand, cadmium is reported to bind itself onto metallothioneins hence forming cadmium–metallothionein complex that is transported to all body organs causing deleterious cell damage. The entry of farming chemical into the food chain especially via the chewing of contaminated khat has been known to contribute to health problems such as cancer, hypertension and liver cirrhosis. khat is branded a ‘substance of abuse’ by the World Health Organization (WHO) because of the adverse health risks it causes to humans. Relevant articles published between 2010 and 2021, and archived in PubMed, Google Scholar, Medley, Cochrane, and Web of Science were used in this review. Short conclusion The health implications of heavy metals and farming chemicals arising from the consumption of contaminated khat shoots are a serious concern to the khat chewing community. Consequently, there is need to develop better farming practices that may minimize the absorption of heavy metals and farming chemicals by the khat plant. Information presented in this review is also important in sensitizing policy makers to advance control measures towards safer khat farming practices.

In this study, an analysis of pesticide residues was performed using a gas chromatography/ electron impact mass spectrometer (GC/EI-MS) to qualitatively assess and characterize pesticide residues in khat leaves sampled from selected agricultural farms in Meru County, Kenya. A solid-phase microextraction (SPME) procedure followed by GC/EI-MS analysis led to the detection and identification of six pesticide compounds from the sample-ion chromatograms. They include cypermethrin, acephate, cyhalothrin, cyfluthrin, chlorpyrifos, and chlorfenvinphos. The prevalence rate of pesticide contamination was determined to be 54.5% of the sample size. Of the identified pesticide residues, 50% were compounds based on pyrethroids and the other 50% were based on organophosphate. Four of the six identified pesticides were chlorinated compounds. A quick, easy, cheap, effective, rugged, and safe UV-vis double beam spectrophotometric technique based on copper (II) chelation reactions leading to colored copper pesticide complexes was developed, validated, and applied to quantify and compare the levels of selected pesticide compounds found in the khat samples. UV-vis wavelength-scan measurements performed on pesticide compounds chelated with copper (II) ions revealed maximum absorption of Cu-cypermethrin and Cu-acephate at 321 and 207 nm, respectively. The standards calibration curves developed from the UV-Vis quantitation technique showed excellent linearity in the concentration range of 0.5-10.0 µg/L (R2 = 0.99) for both cypermethrin and acephate standards. The estimated limits of quantification (LOQ) were 0.25-0.26 µg/L, respectively. The UV-Vis quantitation results from the selected samples (in which residues were confirmed to be present) revealed that acephate (an organophosphate residue) occurred at higher concentration levels (range 2.897-7.978 µg/L) than cypermethrin (2.145 µg/L). For the pesticides quantitatively analysed in the selected samples, the levels were below the maximum residue limit (MRL). The hazard quotients (HQ) were in the range of between 0.247-0.797.