Bay leaves have been used in entomology as the active ingredient in killing jars. The crushed, fresh, young leaves are put into the jar under a layer of paper. The vapours they release kill insects slowly but effectively, and keep the specimens relaxed and easy to mount. The leaves discourage the growth of molds. They are not effective for killing large beetles and similar specimens, but insects that have been killed in a cyanide killing jar can be transferred to a laurel jar to await mounting.[7] It is not clear to what extent the effect is due to cyanide released by the crushed leaves. quoted from wiki. In addition to pesticide and insecticide, cyanide is contained in tobacco smoke, smoke from building fires and some foods, like almonds, apricot kernel, cassava, yucca, manioc, and apple seeds. Vitamin B12 in the form of hydroxycobalamin, or hydroxocobalamin, may reduce the negative effects of chronic exposure, and a deficiency can lead to negative health effects following exposure.[4]
Exposure to lower levels of cyanide over a long period (e.g., after use of cassava roots as a primary food source in tropical Africa) results in increased blood cyanide levels, which can result in weakness and a variety of symptoms, including permanent paralysis, nervous lesions,[5][6][7] hypothyroidism,[6] and miscarriages.[8][9] Other effects include mild liver and kidney damage. http://en.wikipedia.org/wiki/Cyanide_poisoning#Chronic_exposure
