ABSTRACT

1
Effects of Dust Flux on Human Health
Carlie Bulen ES473 Environmental Geology
ABSTRACT One field of study in medical geology
examines the effects of atmospheric dust on human
health. These effects can have significant health
consequences, but are not widely recognized in
the literature. Dust inhalation and lung
accumulation is known to cause long term chronic
health conditions. Sources in the atmosphere
include wind deflation, burning of vegetation,
volcanic eruptions, and anthropogenic
disturbance. Classic locations associated with
dust-related lung complications include the great
dry lands of the northern hemisphere, the U.S.
Great Basin, and southern hemisphere arid regions
of Australia, South America and southern Africa.
These locations are notoriously associated with
high rates of silicosis and asbestosis, and
attendant lung disease. Factors that influence
the severity of these conditions include duration
of exposure, the size of particles inhaled, and
the toxicity of minerals comprising the
particles. One detrimental element found in dust
particles that is linked to a significant number
of these conditions is silica. Although
dust-related lung disease is a significant
problem in underdeveloped countries and desert
regions, few public health actions are being
implemented to mitigate harmful effects of dust
inhalation. This paper presents an overview of
the geological influences on global dust flux and
case examples of chronic health effects
associated with excessive inhalation.

• Health Connection
• How up taken- Inhaled coarse mineral particles
  are commonly lodged in the upper respiratory
  tract and are rejected by expectoration, but they
  may constitute a health risk if the mineralogy is
  toxic. Inhalation of the finer mineral dust
  eventually leads to deposition in the pulmonary
  alveoli where chronic lung disease is initiated.
  Some types of inhaled particulates are degraded
  by macrophages, but many are highly resistant to
  this process and persist in the lungs. The
  fraction of dust that penetrates more deeply into
  the finer lung passages may cause silicosis,
  asbestosis, and other lung conditions.
• What effects on the body- factors include
  size, shape, chemical and mineral composition of
  dust particles, length of exposure, and certain
  lung functions.
• Lung Conditions- Pneumoconiosis, silicosis,
  fibrosis, asbestosis.

Figure 3. Long-term dust storm frequency, showing
a distribution of major sources closely similar
to other data sources. Sources occur in all
continents except Europe and Antarctica. Figure
4. Before and during a Mongolian dust pall over
Beijing, April 2003.

• Introduction
• Loess and Dust-Loess is windblown silt.
  Characteristic properties of loess include high
  porosity and collapsibility on wetting. Dust
  aerosols include gases, liquids and solid
  particles suspended in the atmosphere for varying
  lengths of time. Solid aerosols include particles
  injected into the atmosphere such as mineral dust
  and sea salt, and those that form within the
  atmosphere, such as sulfates. Other contributors
  to dust hazards are smoke plumes from natural and
  man-made fires, and biomass burning, producing
  black carbon.
• Mineral components- Loess mineralogy consists
  of angular, blade-shaped, quartz grains, with
  minor feldspars, micas and carbonates.
• Where found- High Asia, China, U.S. Great
  Basin, North Africa, Middle East, Australia,
  South Africa, and South America.

Figure 2. Some essential links in the direct and
indirect pathways from dust sources to human
inhalation and ingestion.
Figure 4. Lungs with Silicosis vs. normal lungs.

• Case Examples
• A radiographic study of 54 Bedouin people in the
  Negev Desert strongly suggested that the
  incidence of fibrosis is age related, with
  progression more notable in women (13 out of 22)
  than in men (only 4 out of 32), perhaps related
  to greater exposure in and around the family
  tents.
• In Ladakh dust storms are frequent, mineral dust
  found on the wooden beam rooftop of Ladakhi
  houses is all finer than 15 µm, more than 25 by
  weight being finer than 1 µm. The silica content
  gt60. Study of necropsy lung tissue samples from
  villagers revealed heavy dust deposition with
  abundant hard 1-3mm nodules and a lymph node
  largely replaced by hyaline collegenous nodules,
  a classis feature of silicosis.
• Mineral dust finer than 3 µm found in lung tissue
  form one Chinese postmortem subject made up about
  75 by weight of the total dust burden in the
  lungs.

Summary Dust and loess accumulation can
have very deleterious effects on human health
when inhaled. The mineral compound, duration of
exposure, and particle size and shape can
influence these effects and cause such lung
complications as silicosis, asbestosis,
pneumoconiosis, and fibrosis. The Worlds dry
lands are a major source of dust and are
associated with many cases of these and other
lung complications and diseases.
Figure 1. Sketch showing the two modes of aeolian
dust transport and deposition, based on a
transect from the Chinese dry lands to the Loess
Plateau and the North Pacific Ocean.

• Geological Process
• Why dust amount is higher in certain areas of
  the world
• 1-High Asia- one of the worlds most efficient
  producers of loess due to the combination of the
  highest known uplift rates, rapid river incision,
  unstable slopes, glaciations and widespread rock
  breakup by crystal growth during freezing, and by
  hydration of salts.
• 2-North Africa and China- dried out former lake
  beds, deserts. In parts of North China loess
  formation exceeds 300m in thickness.

References Cited Derbyshire, E., Natural Dust and
Pneumoconiosis in High Asia, p.
15-18. Derbyshire, E., 2005, Natural Aerosolic
and Mineral Dusts and Human Health Elsevier
Inc., p. 459-480. Derbyshire, E., 2007, Natural
Minerogenic Dust and Human Health Royal Swedish
Academy of Sciences, p. 73-77.