Nicotine is a naturally-occurring alkaloid found primarily in tobacco. It is most commonly absorbed from cigarette smoke. A cigarette contains 10 to 15mg nicotine and delivers on average 1mg nicotine to the smoker. Nicotine is also available from smokeless tobacco (snuff, chewing tobacco), pipe and cigar tobacco, waterpipe tobacco, and a variety of smoking cessation medications. Nicotine is also present in some insecticides, which may be a source of accidental or intentional poisoning. About 17% of nicotine is excreted unchanged in urine, with rate of urinary excretion is pH-dependent, decreasing in alkaline urine. Nicotine is found in milk of lactating women; with concentrations that parallel those of plasma. But, approximately 80 to 90% of nicotine is metabolized by lung, liver, and kidney; the principle metabolite is cotinine, which has a plasma concentration that is 10-fold higher than nicotine. In fact, nicotine itself even has some benefits. For instance, author linked chewing nicotine gum with improved shortterm memory, and less likely to develop Parkinson's disease, reduce stress and anxiety, and stabilize mood. Nicotine is used as an insecticide since the 1690s, as tobacco extracts, but not commercially available in the US since 2014, and homemade pesticides are banned on organic
crops and not for small gardeners. Nicotine pesticides have been banned in the EU since 2009. Foods are imported from countries in which nicotine pesticides are allowed, such as China, but foods may not exceed maximum nicotine levels. Neonicotinoids derived from and structurally similar to nicotine, are widely used as agricultural and veterinary pesticides as of 2016.