Household selection procedures and survey designs went through a vital iterative process of revision before and after piloting in one of the study sites.
Mean concentrations of chlorpyrifos residues detected in the lettuce samples after subjecting them to the various household treatment procedures and that of the control at all the three (3) different stages of growth are presented in Table 1.
The within-cluster referral process presents the potential for bias, as respondents may not have always referred to the nearest household; referral procedures and small clusters size may have attenuated within-cluster similarities and the associated design effect.
In Ghana, pesticide residues including that of chlorpyrifos have been found at concentrations above the acceptable limits in lettuce (Amoah et al., 2006), shallots (Kotey et al., 2008) and tomatoes (Essumang et al., 2008) that have not been subjected to any household treatment procedures.
Pre-household treatment procedures are used commercially and in the home to reduce pesticide residues concentrations to levels below the MRL value.
But information on household treatment procedure on chlorpyrifos residue in vegetables such as lettuce is very scarce.
The results also showed that, all the pre-household treatment procedures caused significant reduction in residues levels of chlorpyrifos on the crop.
The objectives of the study were to measure chlorpyrifos residue levels in lettuce and examine the effect of pre-household treatment procedures on the residues.
A comparison of the effects of different pre-household treatment procedures on the levels of chlorpyrifos in the lettuce samples, indicated that levels of chlorpyrifos residues were reduced significantly by washing with salt solution and 1 % detergent solution.
Pre-household treatment procedures used in this study were washing under running tap water (Treatment 2), dipping in salt water for 2 min (Treatment 3) and dipping in 1 % detergent solution for 2 min (Treatment 4).
The effectiveness of washing as a household treatment procedure to remove pesticide residues on the surface of a vegetable varies but depends on the physicochemical properties of the compound, age of residue, surface area of leave and nature and thickness of the cuticle.
