Effects of surface material, ventilation, and human behavior on indirect contact transmission risk of respiratory infection.

Infectious particles can be deposited on surfaces. Susceptible persons who contacted these contaminated surfaces may transfer the pathogens to their mucous membranes via hands, leading to a risk of respiratory infection. The exposure and infection risk contributed by this transmission route depend on indoor surface material, ventilation, and human behavior. In this study, quantitative infection risk assessments were used to compare the significances of these factors. The risks of three pathogens, influenza A virus, respiratory syncytial virus (RSV), and rhinovirus, in an aircraft cabin and in a hospital ward were assessed. Results showed that reducing the contact rate is relatively more effective than increasing the ventilation rate to lower the infection risk. Nonfabric surface materials were found to be much more favorable in the indirect contact transmission for RSV and rhinovirus than fabric surface materials. In the cases considered in this study, halving the ventilation rate and doubling the hand contact rate to surfaces and the hand contact rate to mucous membranes would increase the risk by 3.7-16.2%, 34.4-94.2%, and 24.1-117.7%, respectively. Contacting contaminated nonfabric surfaces may pose an indirect contact risk up to three orders of magnitude higher than that of contacting contaminated fabric surfaces. These findings provide more consideration for infection control and building environmental design.

A multilevel antimicrobial coating based on polymer-encapsulated ClO(2).

A multilevel antimicrobial coating with "release-killing", "contact-killing" and "anti-adhesion" properties was prepared from polymer-encapsulated chlorine dioxide (ClO(2)), water-in-oil-in-water (w/o/w) double emulsion. A slow sustained release of gaseous ClO(2) at a rate sufficient to inhibit bacterial growth (approximately 1300 microg of ClO(2).g(-1).day(-1)) was demonstrated for a prolonged period of time (i.e., 28 days). Touch and infectious droplets triggered an increased release of the biocides at the sites of contamination, resulting in rapid disinfection. Zinc chloride (i.e., 30 ppm) was added to provide "contact-killing" properties, while bacterial adhesion was prevented by the Pluronic polymer used to encapsulate ClO(2). The new antimicrobial coating is effective against Gram positive and Gram negative bacteria, including Bacillus subtilis , Staphylococcus aureus , and Escherichia coli. A greater than 5 log (i.e., >or= 99.999%) reduction of viable bacteria was obtained at a short contact time of 10 min.

Application of vitamin E to antagonize SWCNTs-induced exacerbation of allergic asthma.

The aggravating effects of zero-dimensional, particle-shaped nanomaterials on allergic asthma have been previously investigated, but similar possible effects of one-dimensional shaped nanomaterials have not been reported. More importantly, there are no available means to counteract the adverse nanomaterial effects to allow for their safe use. In this study, an ovalbumin (OVA)-sensitized rat asthma model was established to investigate whether single walled carbon nanotubes (SWCNTs) aggravate allergic asthma. The results showed that SWCNTs in rats exacerbated OVA-induced allergic asthma and that this exacerbation was counteracted by concurrent administration vitamin E. A mechanism involving the elimination of reactive oxygen species, downregulation of Th2 responses, reduced Ig production, and the relief of allergic asthma symptoms was proposed to explain the antagonistic effects of vitamin E. This work could provide a universal strategy to effectively protect people with allergic asthma from SWCNTs or similar nanomaterial-induced aggravating effects.