Introduction to a Special Issue of Aeolian Research Airborne mineral dust contaminants: Impacts on human health and the environment.

Aeolian research focuses primarily on the fundamental processes of dust emissions and transport (Ravi et al., 2011) but this scientific focus is also particularly relevant for the related consequences of the emissions of airborne mineral dust contaminants (Csavina et al., 2012), which have important implications for human health and the environment. Linking from “dust to dose” is particularly important in the context of human health (Whicker et al., 2006). However, expertise in the relevant research areas tends to be fragmented, with researchers looking at different spatial and temporal scales related to the processes, often with insufficient integration (Field et al., 2010; Ravi et al., 2011; Csavina et al., 2012). To help foster interdisciplinary interactions, a conference sponsored with support from the US National Environmental Institute of Health Sciences was held in Tucson, AZ in the USA in May 2013 with the goal “to stimulate interaction among different research communities interested in dust and to promote better integration of research on airborne mineral dust from emissions to environmental exposure” (http://www.superfund.pharmacy.arizona.edu/content/airborne-mineral-dust-contaminants-conference-report). Linking from dust emissions to contaminant transport through atmospheric processes and to toxicological and epidemiological relevance is complex and requires multidisciplinary perspectives and initiatives. Here we summarize the main points of the papers in this special issue in the context of a previous framework linking potential for dust emissions, potential contaminant concentration in dust, and potential risk to human health and the environment (Fig. 1, modified from Csavina et al., 2012). We also listed future needs identified in a survey from the meeting. Fig. 1 Natural and anthropogenic sources of dust associated with potential emission rates, contaminant concentration, and risk to human health and the environment (modified from Csavina et al., 2012). Papers in this special issue are related to airborne mineral ... A first section of papers emphasize basic processes and modeling of dust emissions and transport that are relevant for airborne mineral dust contaminants. Belnap et al. (2014) present a large data set evaluating threshold friction velocities as a function of soil type and surface type for two southwestern US deserts. Their results highlight the importance of soil surface conditions and their sensitivity to disturbances. Judger et al. (2014) quantify increases in dust concentrations during dust events in Mongolia as function of health-relevant particle sizes (PM10 and PM2.5), documenting increases of more than an order of magnitude in some cases. Merino-Martin et al. (2014) focus on “background” conditions that do not include very windy periods but do include brief gusts; these periods, while less windy, are the most common, and the results highlight an interplay between spatial and temporal scale of measurement from different sampler types and particle size. Many field measurement methods capture horizontal dust flux using samplers such as the Big Spring Number Eight (BSNE) collector, but these horizontal fluxes are not equivalent to vertical fluxes relevant for dust emission suspension and transport; Whicker et al. (2014) consider previous formulations for horizontal and vertical fluxes based on theoretical, empirical and risk-based perspectives, yielding several potential relationships between horizontal and vertical fluxes that can serve as hypotheses for future testing. Sprigg et al. (2014) highlight improved dust emission forecasting approaches for dust avoidance, which is particularly relevant for Valley Fever. Stovern et al. (2014) highlight advances in modeling of dust and contaminant transport; importantly they also highlight how management of surface conditions can aid in controlling dust emissions. A second section of the special issue focuses more directly on contaminant emissions, transport and risks related to toxicology and/or epidemiology. Kim et al. (2014) quantify surface enrichment of arsenic in mine tailings environments due to windborne transport and the bioaccessibility of arsenic in fine-grained tailings through the inhalation pathway. Xiao et al. (2014) evaluates characteristics of toxicity of emissions, which is directly relevant to human health risks. And Taylor et al. (2014) highlight issues related to the public health impacts in mining and smelting communities affected by the transport of metal-rich dust and aerosol contaminants, and to associated regulatory relationships. A survey of participants at the conference highlighted the following gaps in the field (http://www.superfund.pharmacy.arizona.edu/content/airborne-mineral-dust-contaminants-conference-report): Stronger links needed between the dust community and epidemiologists. More specific information needed on the health impacts of dust (moving beyond generic PM2.5 and PM10; immune system suppression; biological responses of various human organs). Needed improvements in dust modeling (forecast severity of dust storms; quantitative dust fluxes; verification of model predictions). Improved information on effects of dust storms on public safety (highways, airports). We also note other challenges highlighted in pulling together this special section. These include issues of scaling (e.g. from small source patches of dust up through large urban area impacts) (Ravi et al., 2011); issues related to climate change (Field et al., 2011) as well as land use change (Ravi et al., 2011); the relative roles of background conditions with gusts vs. windy periods vs. dust storms; consideration of longer term processes and environmental disturbances (Breshears et al., 2012); and the need to link studies of dust and contaminant emission and transport processes more directly to epidemiology studies, including more integration with the medical community to evaluate causality of emissions. The papers in this issue reveal the value of interdisciplinary collaboration and integration spanning from source terms to human health and ecological consequences. Collectively, these papers serve as an important baseline for further advancing aeolian research in the context of airborne mineral dust contaminants, which is likely to become as increasingly important issue under pressures of future population growth, urbanization, land use change and climate change.