Influenza Virus Infectivity Is Retained in Aerosols and Droplets Independent of Relative Humidity.

Pandemic and seasonal influenza viruses can be transmitted through aerosols and droplets, in which viruses must remain stable and infectious across a wide range of environmental conditions. Using humidity-controlled chambers, we studied the impact of relative humidity on the stability of 2009 pandemic influenza A(H1N1) virus in suspended aerosols and stationary droplets. Contrary to the prevailing paradigm that humidity modulates the stability of respiratory viruses in aerosols, we found that viruses supplemented with material from the apical surface of differentiated primary human airway epithelial cells remained equally infectious for 1 hour at all relative humidities tested. This sustained infectivity was observed in both fine aerosols and stationary droplets. Our data suggest, for the first time, that influenza viruses remain highly stable and infectious in aerosols across a wide range of relative humidities. These results have significant implications for understanding the mechanisms of transmission of influenza and its seasonality.

C60 fullerenes from combustion of common fuels.

Releases of C60 fullerenes to the environment will increase with the growth of nanotechnology. Assessing the potential risks of manufactured C60 requires an understanding of how its prevalence in the environment compares to that of natural and incidental C60. This work describes the characterization of incidental C60 present in aerosols generated by combustion of five common fuels: coal, firewood, diesel, gasoline, and propane. C60 was found in exhaust generated by all five fuels; the highest concentrations in terms of mass of C60 per mass of particulate matter were associated with diesel and coal. Individual aerosols from these combustion processes were examined by transmission electron microscopy. No relationship was found between C60 content and either the separation of graphitic layers (lamellae) within the particles, nor the curvature of those lamellae. Estimated global emissions of incidental C60 to the atmosphere from coal and diesel combustion range from 1.6 to 6.3 t yr(-1), depending upon combustion conditions. These emissions may be similar in magnitude to the total amount of manufactured C60 produced on an annual basis. Consequent loading of incidental C60 to the environment may be several orders of magnitude higher than has previously been modeled for manufactured C60.

Oxidation of c60 aerosols by atmospherically relevant levels of o3.

Atmospheric processing of carbonaceous nanoparticles (CNPs) may play an important role in determining their fate and environmental impacts. This work investigates the reaction between aerosolized C60 and atmospherically relevant mixing ratios of O3 at differing levels of humidity. Results indicate that C60 is oxidized by O3 and forms a variety of oxygen-containing functional groups on the aerosol surface, including C60O, C60O2, and C60O3. The pseudo-first-order reaction rate between C60 and O3 ranges from 9 × 10(-6) to 2 × 10(-5) s(-1). The reaction is likely to be limited to the aerosol surface. Exposure to O3 increases the oxidative stress exerted by the C60 aerosols as measured by the dichlorofluorescein acellular assay but not by the uric acid, ascorbic acid, glutathione, or dithiothreitol assays. The initial prevalence of C60O and C60O2 as intermediate products is enhanced at higher humidity, as is the surface oxygen content of the aerosols. These results show that C60 can be oxidized when exposed to O3 under ambient conditions, such as those found in environmental, laboratory, and industrial settings.

The role of atmospheric transformations in determining environmental impacts of carbonaceous nanoparticles.

In studies that have explored the potential environmental impacts of manufactured nanomaterials, the atmosphere has largely been viewed as an inert setting that acts merely as a route for inhalation exposure. Manufactured nanomaterials will enter the atmosphere during production, use, and disposal, and rather than simply being transported, airborne nanoparticles are in fact subject to physical and chemical transformations that could modify their fate, transport, bioavailability, and toxicity once they deposit to aqueous and terrestrial ecosystems. The objective of this paper is to review the factors affecting carbonaceous nanomaterials' behavior in the environment and to show that atmospheric transformations, often overlooked, have the potential to alter nanoparticles' physical and chemical properties and thus influence their environmental fate and impact. Atmospheric processing of naturally occurring and incidental nanoparticles takes place through coagulation, condensation, and oxidation; these phenomena are expected to affect manufactured nanoparticles as well. It is likely that carbonaceous nanomaterials in the atmosphere will be oxidized, effectively functionalizing them. By influencing size, shape, and surface chemistry, atmospheric transformations have the potential to affect a variety of nanoparticle-environment interactions, including solubility, interaction with natural surfactants, deposition to porous media, and ecotoxicity. Potential directions for future research are suggested to address the current lack of information surrounding atmospheric transformations of engineered nanomaterials.