Dust comprises small particles (about 50 microns or smaller in diameter) of sediment or soil which are suspended in the atmosphere and transported by the wind. While these small airborne particles may seem benign, they pose a significant threat to human and environmental health, transportation safety, and the global economy.
A recent study in Reviews of Geophysics explores the costly effects of dust in the Western Hemisphere, where scientific understanding is fragmented. We asked some of the authors to give an overview of airborne soil dust, its health and safety impacts, and what important questions remain.
What are the most common sources of dust, and how does it travel around?
On Earth, dust most commonly originates in semiarid to arid regions where there are loose sediments and flat, poorly vegetated land prone to wind erosion. These include many global deserts (dry lake beds in deserts are a potent dust source) and some agricultural lands.
Dust travels around on all scales, from small puffs blown only meters by local wind gusts, to huge dust clouds that move across oceans between continents, such as the Saharan Air Layer that transports African dust to the Americas.
There are other kinds of dust, such as dust erupted from volcanoes and cosmic dust deposited from space, but we focus on windblown soil particles, which is called “aeolian” dust.
What are some under-appreciated ways that dust impacts human and ecosystem health?
Hundreds of studies show dust’s connection to respiratory diseases, such as asthma and bronchitis, as well as cardiovascular disease, but there are other ways that dust impacts health, many of them under-appreciated. Here are a few examples:
The Western Hemisphere faces a unique dust-related health challenge, the disease coccidioidomycosis, better known as Valley fever, which results from exposure to a soil-dwelling fungus endemic to the Americas. Although most cases are mild, some are disabling or even fatal, not only in humans but also in other animals. The exact role of airborne dust in the transmission of coccidioidomycosis is still not clear, but it appears to be a factor when the fungal spores ride along on currents of air with soil particles.
Airborne dust that settles on the blossoms of some food crops such as tomatoes, cucumbers, and apples, immediately before the blossoms set, can transfer dustborne bacteria such as Salmonella into the flesh of the growing fruit- and no amount of washing removes it. Some outbreaks of foodborne illness may be caused by this transmission pathway.
Dust clouds crossing roadways are first and foremost a huge safety hazard for drivers, causing numerous crashes, some fatal, when drivers are blinded by the sudden loss of visibility. This was tragically reinforced on 1 May 2023, when dust from agricultural fields crossing highway I-55 in Illinois, USA caused multiple vehicle crashes involving over 70 vehicles, killing 8 persons at last count, and injuring at least 36 more.
What are some of the socioeconomic impacts of dust?
Dust represents soil loss from its source areas, including valuable organic matter and nutrients: and the dust emission process damages plants, especially seedlings. Dust can contaminate crops, e.g., compromise ‘organic’ agricultural practice, and spread plant and animal pathogens into areas far downwind.
As renewable energy increases its contribution to global electricity generation, dust’s effects grow with them. Drylands are favorable for photovoltaic development but are also often dust hotspots. Dust coating solar panels (“soiling”) not only decreases the panels’ efficiency at absorbing sunlight but can also cause overheating and damage to the panels themselves.
Dust can significantly increase the cost of aircraft maintenance. The high operating temperatures of modern jet engines melt engine-ingested mineral dusts onto engine components, increasing engine maintenance and replacement costs—with potentially catastrophic consequences if ignored.
Highways closed by dust hazards delay delivery of goods and services, increase costs for public safety agencies, and cause damage to secondary roads when motorists seek other routes to bypass a closed section of highway.
How might climate change and human activities impact future dust levels?
Within and around many global drylands, dust, drought, and water availability are closely related. As the climate warms, precipitation patterns will change and drought in many regions is expected to expand the arid landscape and become more frequent and/or intense, causing a cascade of effects that lead to dust production through reduction in land cover.
Climate change is often attributed as the cause of shrub encroachment into semi-arid grasslands. Shrublands are characterized by bare soil surfaces between the scattered plant canopies. Due to the increased bare soil surfaces in these invasive shrub communities, they are often much more dust-emissive than the grasslands they replaced.
As water resources diminish with drought, and human populations grow, demand for water for both urban and rural use will increase. Dryland rivers and lakes shrink and disappear as their waters are diverted, and their exposed beds become potent dust sources. We saw this in the last century in places such as Owens Lake (California, USA) and the Aral Sea (former USSR). This is happening now at the Great Salt Lake (Utah, USA), Lake Urmia (Iran), and elsewhere.
In other areas, climate change will result in wetter conditions, likely reducing overall dust levels through increasing land cover and soil moisture. However, short-term, intense “flash droughts” in temperate regions can quickly dry the soil and may make it vulnerable to wind erosion. The recent dust emissions from fields in the normally humid region of Illinois, USA may be a consequence of a developing “flash drought.”
How are models used to predict dust events?
Dust events are controlled by both weather conditions, such as high winds, and land surface conditions, such as vegetation cover and soil moisture. To predict dust events, climate and weather models are often used to predict weather and land changes that determine the occurrence and severity of these events. In addition to numerical models, satellite and ground observations increasingly are used to constrain models or provide more realistic initial weather or land conditions.
Why have the Americas received less attention in dust health effects studies?
Most of Earth’s dust originates in “the Global Dust Belt,” which stretches from the westernmost Sahara Desert across Africa, the Arabian Peninsula and parts of the Middle East, into South Asia and the drylands of Mongolia and China.
Its heavy loads of dust regularly impact many large metropolitan areas within and beyond the Dust Belt, including portions of Europe, and other parts of Asia.
Therefore, it’s no surprise that most population-level and clinical studies of mineral dust’s health effects have been done in that part of the globe where dust is more acutely and frequently felt.
In comparison, there’s less dust in the Western Hemisphere, and fewer of its major human population centers are impacted by dust storms. That’s not to say that dust wouldn’t have health impacts, including unique ones, in the Americas, as we have documented in our article.
What are some data gaps in the dust record, and their consequences?
Aerosol monitors are often located in major cities to associate with human health effects or in national parks and wilderness areas to detect impacts on visibility and ecosystems. However, dust sources and transport pathways often fall in the geospatial gaps between them. Particulate monitoring networks should include more sites in dusty areas, especially to address disparities in health, safety and environmental services, and areas suspected of harmful soil content. These areas, generally rural, lack sufficient observations to better document particulate matter concentrations and chemical composition, to better understand dust’s health and safety effects and better model dust transport.
More and better observations will help correct misunderstandings of how dusty weather conditions are recorded and understood in meteorological and public safety datasets. “Blowing dust” and “dust storm” are separate phenomena with different definitions, but sometimes are misunderstood or misrecorded, and different agencies define “dust storm” differently. In addition, dust events are sometimes recorded as “haze” by weather observers or automated sensors. These cause data quality issues and potential inaccuracies in dust health, safety and economic effects studies based on those datasets. Transportation and law enforcement records sometimes list dust-related vehicle crashes as associated with “windstorm” or “thunderstorm” instead, causing underestimation of the actual impact of dust on highway safety.
What are some measures that can be taken to mitigate the harmful effects of dust?
In terms of regulated air pollutants, aeolian dust is more strongly associated with coarse aerosol (PM10) than fine particles (PM2.5), which are considered to have greater health effects. However, dust storms can result in high levels of both PM10 and PM2.5, and the health effects of coarse particles are becoming more evident. Explanations to the public should not imply that “natural,” large particles are harmless. Public education should advise precautions to avoid exposure when dust blows, just as with any other strong air pollution episode.
Modern soil conservation science began in North America as a result of its greatest dust-related disaster, the Dust Bowl of the 1930s. Soil conservation measures must always be in mind in wind-erodible agricultural lands. Wind erosion and dust emissions degrade otherwise productive agricultural lands and result in losses of nutrients that must be replaced at great cost to the farmer. Less obvious is the loss of the fine fractions of mineral soil and soil carbon that are responsible for soil water retention between rain events. During the fallow season of the year, standing crop residues provide the greatest protection of soil surfaces from wind-induced erosion and resultant fugitive dust. In addition to leaving standing residues, cover crops planted to cover bare fields and build soil health are also effective dust limiting measures. Both of these cropping system management methods are commonly known components of conservation agriculture.
Hundreds of millions of dollars have been spent in recent years in the USA on engineering modifications of highways and roadsides to mitigate transportation safety hazards associated with blowing dust. Public awareness campaigns, such as Arizona’s “Pull Aside, Stay Alive” program (pullasidestayalive.org), are also crucial to reduce dust-related casualties.
What are some of the knowledge gaps where additional research, data, or modeling of dust are needed?
One of the most pressing knowledge gaps is a lack of process-level understanding of linkages between dust and its health endpoints, including prevalence of Valley fever and other dust-associated infectious diseases among humans and animals. Enhanced disease surveillance to keep up with advances in dust science will have great benefit. Not all of the US states where Valley fever is endemic report cases to a national record; all states should comply in order to understand the true extent and character (for example, preferred soil type) of the disease and how climate change may affect other population sectors.
Operational links between dust predictions, dust observations, and public health/safety advisories and endpoints are still missing in many parts of the Western Hemisphere, especially in South America.
Another problem in predicting and mitigating dust hazards is the inability of satellites, models, and surface-based monitoring networks to observe and predict small-scale dust events that are responsible for many fatal accidents and attendant societal costs. Airborne microplastics have become an important research topic in recent years, and much more needs to be known about their associations with dust and their potential role in dust’s adverse effects.
To address these and many other challenges, it is important to advance dust research through observations, modeling, laboratory analyses, clinical and epidemiological health effects studies, and to implement mitigation measures that emerge from research.
—Thomas E. Gill (email@example.com; 0000-0001-9011-4105), University of Texas at El Paso, USA; Daniel Tong (0000-0002-4255-4568), George Mason University, USA; William Sprigg (0000-0002-3316-3442), University of Arizona, USA; and R. Scott Van Pelt (0000-0002-7036-4032) , USDA-ARS, USA
Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.