As a result of a tragic industrial accident, a highly alkaline red mud sludge inundated settlements and agricultural areas near Ajka, Hungary on October 4, 2010. One of the major concerns about the aftermaths of the accident is the potential health effects of vast amounts of fugitive dust from red mud sediment. Thus, we studied the chemical and physical properties of particles of red mud and its respirable fugitive dust, and performed toxicity measurements. Under unfavorable meteorological conditions dry red mud sediment could emit very high amounts of respirable alkaline particles into the air. The number size distribution of fugitive dust peaks above 1 μm aerodynamic diameter; therefore, its inhalation is unlikely to affect the deep regions of the lungs. No significant mineralogical or elemental fractionation was observed between the sediment and dust, with the major minerals being hematite, cancrinite, calcite, and hydrogarnet. Although the high resuspension potential and alkalinity might pose some problems such as the irritation of the upper respiratory tract and eyes, based on its size distribution and composition red mud dust appears to be less hazardous to human health than urban particulate matter.

Abstract. In addition to its mass concentration, the health effects of urban particulate matter may depend on its particle size distribution and chemical composition. Yet air pollution regulations rely on exclusively bulk PM 10 concentration measurements, without regard to their potentially different health effects under different conditions. Aerosols from various sources are well known to contain a plethora of toxic, carcinogenic, mutagenic or teratogenic constituents such as heavy metals and polycyclic aromatic hydrocarbons. Extensive public health studies established the link between mass concentrations of PM 2.5 / PM 10 and health problems within the population. However, little is known about the relative importance of PM from different sources and the effect of seasonality on the toxicity. Here we present the application of a simple and sensitive method for the direct assessment of the overall ecotoxicity of various PM 2.5 / PM 10 samples collected on filters. The method is based on the Vibrio fischeri bioluminescence inhibition bioassay that has been standardized for solid samples, representing a relevant biological exposure route. Direct emission samples proved to be significantly more ecotoxic than photochemically processed aerosol, thus marked differences were observed between the ecotoxicities of urban PM 10 in summer and winter. These effects of urban PM 10 may be useful supplementary indicators besides the mass concentrations of PM 2.5 / PM 10 in cities.

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In addition to its mass concentration, the health effects of urban particulate matter may depend on its particle size distribution and chemical composition. Yet air pollution regulations rely on exclusively bulk PM₁₀ concentration measurements, without regard to their potentially different health effects under different conditions. Aerosols from various sources are well known to contain a plethora of toxic, carcinogenic, mutagenic or teratogenic constituents such as heavy metals and polycyclic aromatic hydrocarbons. In spite of the fact that tremendous efforts have been put to establish links between aerosol pollution and human health or mortality, the potential acute effects of PM_2.5/PM₁₀ have never been assessed for lack of adequate methodology. Here we present the application of a simple and sensitive method for the direct assessment of the overall ecotoxicity of various PM_2.5/PM₁₀ samples collected on filters. The method is based on the <i>Vibrio fischeri</i> bioluminescence inhibition bioassay that has been standardized for solid samples, representing a relevant biological exposure route. Direct emission samples proved to be significantly more ecotoxic than photochemically processed aerosol, thus marked differences were observed between the ecotoxicities of urban PM₁₀ in summer and winter. The previously overlooked acute effects of urban PM₁₀ may add to the established effects of gaseous primary pollutants aggravating health problems during severe air pollution episodes