Aim to get unwaxed whenever you can - lemons, after sorting according to color, washing and coating with a fungicide and a thin layer of wax are stored (cured) until ready for shipping, so don't buy an ordinary lemon and slice it and chuck into your G & T or usee the rind for zesting as there are lots of nasties you could be ingesting. . . .
Oh, and if you thought your food was always fresh from the supermarket? Little light extract about the lemon: Generally, lemons are cured at 56� to 58� F (13.33�-14.4� C)and 85-90% relative humidity. Green fruits may be held for 4 months or more, while the peel becomes yellow and thinner, the pulp juicier (6-80%) and the proportion of soluble solids higher (7-24%). Sometimes the degreening process is hastened by exposing the fruit to ethylene gas, ethephon, or silane, but this practice tends to stimulate decay, mainly through the shedding of the "button" (stem stub), the absence of which allows entry of Diplodia natalensis, Phomopsis citri, or Alternaria mycelium. Various auxins have been studied to determine which can be applied before storage to prevent button loss without delaying degreening. In 1982, Israeli investigators reported that decay losses from degreening procedures can be greatly reduced (from over 50% to 6.3%) by packaging the fruits in 10 micrometer-thick high-density polyethylene. This treatment makes it possible to store lemons with minimum damage for as long as 6 months.