Background
Although cigarette smoking decreased in Thailand between 1991 and 2007 from 12.2 million to 10.86 million smokers, it has increased among younger men (aged approx. 18 years) and women (aged approx. 22 years). Moreover, in low education, urban and eastern parts of the country, cigarette smoking has increased from 9.66 to 10.26 cigarettes per smoker per day [1]. Light and self-rolling cigarettes are generally used everywhere, especially in northern regions such as Chiang Mai province. Cigarette smoke contains an abundance of free radicals and prooxidant species known to negatively influence human health [2]. Increased production of free radicals from tobacco is recognized because of the more than 4,000 chemical substances found in tobacco [3]. Previous reports have noted that the levels of protein carbonyl [4] and the lipid peroxidation product malondialdehyde [5,6] are higher in smokers than non-smokers. Therefore, cigarette smoking related ill-health and disease may be mechanistically linked to increased production of free radicals. Aside from monitoring bloodborne biomarkers of oxidized molecules, evaluation of oxidative stress from smoking can be determined from exhaled hydrogen peroxide (H2O2) or carbon monoxide (CO). Nicotine in smoke is known to release neuroendocrine substances, such as beta-endorphin (β-end) [7], found in women smokers with either high doses of nicotine cigarettes or with heavy smoking [8,9]. Moreover, a previous report showed that nicotine stimulates the pituitary release of the pro-opiomelanocortin (POMC) which contains the precursor for β-end [10].