Low-temperature, low-pressure gas plasma application on Aspergillus brasiliensis, Escherichia coli and pistachios

AIM

The aim of this study was to investigate the effect of plasma-enhanced chemical vapour deposition (PECVD) treatment on selected bacteria and spores and to contribute to the understanding of the synergistic effect of UV-directed plasma.

METHODS AND RESULTS

The experiments were conducted on pure cultures of Aspergillus brasiliensis and Escherichia coli and on naturally contaminated pistachios that were exposed to pure oxygen-, pure argon- and to a mixture of oxygen-argon-generated plasma for different treatment times and at different micro-organism concentrations. Optical emission spectroscopy (OES) measurements were performed to observe the active species in the plasma. After exposure, the effectiveness of decontamination was assessed through microbiological techniques by calculating the growth reduction on a logarithmic scale. A treatment time of 30 min resulted in a 3·5 log reduction of A. brasiliensis using pure oxygen or argon, while treatment times of 5 min, 1 min and 15 s resulted in a 5·4 log reduction using a mixture of argon and oxygen (10 : 1 v/v). Treatment times of 1 min and 30 s resulted in a 4 log reduction of E. coli with oxygen and argon, respectively, which led to a complete elimination of the micro-organisms. Two-log reductions of fungi were achieved for pistachios after a treatment time of 1 min.

CONCLUSIONS

These results suggest that this newly designed plasma reactor offers good potential applications for the reduction in micro-organisms on heat-sensitive materials, such as foods. The plasma that was generated with Ar/O2 was more effective than that which was generated with pure oxygen and pure argon.

SIGNIFICANCE AND IMPACT OF THE STUDY

An improvement in the knowledge about PECVD mechanisms was acquired from the chemical and biological points of view, and the suitability of the method for treating dry food surfaces was demonstrated.

Formation of N-(2-hydroxyethyl)valine due to exposure to ethylene oxide via tobacco smoke: A risk factor for onset of cancer

Human exposure to ethylene oxide (EtO) occurs mainly through inhalation of occupational polluted air and tobacco smoke. EtO is able to react with DNA and proteins producing some molecular adducts. One of these, resulting from reaction between EtO and valine in hemoglobin, is N-(2-hydroxyethyl) valine (HOEtVal). This adduct represents a biological effective dose marker, the level of which correlates linearly with the alkylating activity occurring in DNA. The aim of the present study was to measure HOEtVal in 146 urbanized adult and healthy subjects, nonoccupationally exposed to EtO, and to correlate it with smoke habits. HOEtVal showed a direct positive relationship to tobacco smoke exposure quantified by questionnaire, urinary cotinine (r=0.64509), and the number of cigarettes (r=0. 6308) actively or passively smoked. Results relative to HOEtVal and urinary cotinine in adults distinguish well between active and passive smokers but do not allow distinguishment between passive smokers and nonsmokers. Nevertheless, several authors demonstrated a very good capacity of cotinine to discriminate inside groups of adolescents passive smokers. Therefore, the future objective of the present study is a closer inspection of the two biomarkers with respect to passive exposure to tobacco smoke considering a large group of adolescents. Finally, the correlation between urinary cotinine and HOEtVal increases knowledge about early steps of the carcinogenic process due to active exposure to tobacco smoke.

Effects of tobacco smoke exposure on lung growth in adolescents

A longitudinal study on exposure to tobacco smoke among adolescents was carried out in Turin (North-Western Italy) in January-February 1992 and in January-February 1993. In 1992, 394 schoolchildren aged 14-16 years were enrolled in a study protocol which consisted in answering a standardized questionnaire, measurement of urinary cotinine and testing of lung function (flow-volume curve--[FVC] and forced expiratory volume in I sec.--[FEV1]). In 1993, 333 schoolchildren from the same group repeated the survey. By comparison to urinary cotinine, findings obtained showed a reduction of increase, from 1992 to 1993, of -0.57% (p = 0.082) for FVC, and -0.66% (p = 0.05) for FEV1. Assuming that the systematic selection bias did not seem to have occurred, findings, obtained from a multiple regression analysis, showed that active and passive exposure to tobacco smoke, as measured by urinary cotinine, had a significant effect on lung growth (as measured by FEV1) in adolescents; this effect, though small, was dose-related.

Tobacco smoke habits in a group of adolescents: responsibility of the cohabitants in the active and passive exposure

Several studies in adults demonstrated a positive relationship between the number of cigarettes smoked and the urinary cotinine. The aim of this work was to analyze the passive and active smoking exposure of 333 sixteen-year-old students, demonstrated by their urinary cotinine, in comparison with the smoking habits of all the cohabitants. This last information was obtained from a questionnaire and urinary cotinine in mothers. The second purpose of this work was to observe whether the smoking habits of parents can promote the voluntary active exposure to tobacco smoke in children. The considered students represent a particular group of people (16 years old) having a life-style still strictly bound to the smoking habit of parents. In fact, the nonactive smokers show urinary cotinine levels described by the following means: 28.81, 39.35, 39.62, and 57.67 ng/mL. This finding demonstrates a trend of exposure from no exposure to a maximum level of passive exposure. Similar results can be observed by considering the urinary cotinine of mothers. Finally, the active smoking habit potentially acquired by the adolescents seems to be induced also by emulation of the smoking habits of fathers. This possibility is demonstrated by a light positive and statistically significative correlation with the number of cigarettes actively smoked and, consequently, with urinary cotinine.