***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : Although millions of people are using  electronic cigarettes ( ECs ) and research on this topic has intensified in recent years , the pattern of EC use has not been systematic ally studied . Additionally , no comparative measure of exposure and nicotine delivery between EC and tobacco cigarette or nicotine replacement therapy ( NRTs ) has been established . This is important , especially in the context of the proposal for a new Tobacco Product Directive issued by the European Commission . Methods : A second generation EC device , consisting of a higher capacity battery and tank atomiser design compared to smaller cigarette-like batteries and cartomizers , and a 9 mg/mL nicotine-concentration liquid were used in this study . Eighty subjects were recruited ; 45 experienced EC users and 35 smokers .  EC users were video-recorded when using the device ( ECIG group ) , while smokers were recorded when smoking ( SM-S group ) and when using the EC ( SM-E group ) in a r and omized cross-over design . Puff , inhalation and exhalation duration were measured . Additionally , the amount of EC liquid consumed by experienced EC users was measured at 5 min ( similar to the time needed to smoke one tobacco cigarette ) and at 20 min ( similar to the time needed for a nicotine inhaler to deliver 4 mg nicotine ) . Results : Puff duration was significantly higher in ECIG ( 4.2 ± 0.7 s ) compared to SM-S ( 2.1 ± 0.4 s ) and SM-E ( 2.3 ± 0.5 s ) , while inhalation time was lower ( 1.3 ± 0.4 , 2.1 ± 0.4 and 2.1 ± 0.4 respectively ) . No difference was observed in exhalation duration . EC users took 13 puffs and consumed 62 ± 16 mg liquid in 5 min ; they took 43 puffs and consumed 219 ± 56 mg liquid in 20 min . Nicotine delivery was estimated at 0.46 ± 0.12 mg after 5 min and 1.63 ± 0.41 mg after 20 min of use . Therefore , 20.8 mg/mL and 23.8 mg/mL nicotine-containing liquids would deliver 1 mg of nicotine in 5 min and 4 mg nicotine in 20 min , respectively . Since the ISO method significantly underestimates nicotine delivery by tobacco cigarettes , it seems that liquids with even higher than 24 mg/mL nicotine concentration would be comparable to one tobacco cigarette . Conclusions : EC use topography is significantly different compared to smoking . Four-second puffs with 20–30 s interpuff interval should be used when assessing EC effects in laboratory experiments , provided that the equipment used does not get overheated . Based on the characteristics of the device used in this study , a 20 mg/mL nicotine concentration liquid would be needed in order to deliver nicotine at amounts similar to the maximum allowable content of one tobacco cigarette ( as measured by the ISO 3308 method ) . The results of this study do not support the statement of the European Commission Tobacco Product Directive that liquids with nicotine concentration of 4 mg/mL are comparable to NRTs in the amount of nicotine delivered to the user Abstract Context : Electronic cigarettes ( e-cigarettes ) are becoming increasingly popular yet their effects on health remain unknown . Objective : To conduct the first comprehensive and st and ardized assessment of the acute impact of active and passive e-cigarette smoking on serum cotinine and lung function , as compared to active and passive tobacco cigarette smoking . Material s and methods : Fifteen smokers ( ≥15 cigarettes/day ; seven females ; eight males ) and 15 never-smokers ( seven females ; eight males ) completed this repeated- measures controlled study . Smokers underwent a control session , an active tobacco cigarette ( their favorite br and ) smoking session and an active e-cigarette smoking session .  Never-smokers underwent a control session , a passive tobacco cigarette smoking session and a passive e-cigarette smoking session . Serum cotinine , lung function , exhaled carbon monoxide and nitric oxide were assessed . The level of significance was set at p ≤ 0.001 to adjust for multiple comparisons . Results : e-Cigarettes and tobacco cigarettes generated similar ( p > 0.001 ) effects on serum cotinine levels after active ( 60.6 ± 34.3 versus 61.3 ± 36.6 ng/ml ) and passive ( 2.4 ± 0.9 versus 2.6 ± 0.6 ng/ml ) smoking . Neither a brief session of active e-cigarette smoking ( indicative : 3 % reduction in FEV1/FVC ) nor a 1 h passive e-cigarette smoking ( indicative : 2.3 % reduction in FEV1/FVC ) significantly affected the lung function ( p > 0.001 ) . In contrast , active ( indicative : 7.2 % reduction in FEV1/FVC ; p < 0.001 ) but not passive ( indicative : 3.4 % reduction in FEV1/FVC ; p = 0.005 ) tobacco cigarette smoking undermined lung function . Conclusion : Regarding short-term usage , the studied e-cigarettes generate smaller changes in lung function but similar nicotinergic impact to tobacco cigarettes . Future research should target the health effects of long-term e-cigarette usage , including the effects of nicotine dosage Despite the recent popularity of e-cigarettes , to date only limited data is available on their safety for both users and secondh and smokers . The present study reports a comprehensive inner and outer exposure assessment of e-cigarette emissions in terms of particulate matter ( PM ) , particle number concentrations ( PNC ) , volatile organic compounds ( VOC ) , polycyclic aromatic hydrocarbons ( PAH ) , carbonyls , and metals . In six vaping sessions nine volunteers consumed e-cigarettes with and without nicotine in a thoroughly ventilated room for two hours . We analyzed the levels of e-cigarette pollutants in indoor air and monitored effects on FeNO release and urinary metabolite profile of the subjects . For comparison , the components of the e-cigarette solutions ( liquids ) were additionally analyzed . During the vaping sessions substantial amounts of 1,2-propanediol , glycerine and nicotine were found in the gas-phase , as well as high concentrations of PM2.5 ( mean 197 μg/m(3 ) ) . The concentration of putative carcinogenic PAH in indoor air increased by 20 % to 147 ng/m(3 ) , and aluminum showed a 2.4-fold increase . PNC ranged from 48,620 to 88,386 particles/cm(3 ) ( median ) , with peaks at diameters 24 - 36 nm . FeNO increased in 7 of 9 individuals . The nicotine content of the liquids varied and was 1.2-fold higher than cl aim ed by the manufacturer . Our data confirm that e-cigarettes are not emission-free and their pollutants could be of health concern for users and secondh and smokers . In particular , ultrafine particles formed from supersaturated 1,2-propanediol vapor can be deposited in the lung , and aerosolized nicotine seems capable of increasing the release of the inflammatory signaling molecule NO upon inhalation . In view of consumer safety , e-cigarettes and nicotine liquids should be officially regulated and labeled with appropriate warnings of potential health effects , particularly of toxicity risk in children 
    Output:
    
The majority of studies determined that passive exposure to EC vapour may pose a health risk to byst and ers .
Our review found that the absolute impact from passive exposure to EC vapour has the potential to lead to adverse health effects .
The risk from being passively exposed to EC vapour is likely to be less than the risk from passive exposure to conventional cigarette smoke