Environmental Engineering Reference
In-Depth Information
SBS-type symptoms. The term, “dust,” includes a broad range of particulate-
phase materials, which vary in size, chemical composition, type, and source.
Airborne dust concentrations may be reported as total suspended par-
ticles (TSP), respirable suspended particles (RSP), ultraviolet particulate mat-
ter (UVPM), particle numbers, or concentrations of specific particle fractions
such as man-made mineral fibers. TSP particles represent the largest range
of particle sizes measured, including those that are respirable (<3.0
µ
m, RSP),
inhalable (<10.0
m). Respirable suspended
particles are generally considered to have the greatest biological significance
since they can be deposited in lung tissue. Larger particles (3 to 10
µ
m), and not inhalable (10 to 100
µ
m) tend
to be deposited in the upper respiratory passages where they have the
potential to cause irritation or allergic/inflammatory responses. Though
UVPM particles are in the respirable size range, they differ somewhat from
RSP concentrations since the measurement technique is dependent on light
scattering/absorption properties of particulate matter.
Cross-sectional epidemiological studies to determine whether relation-
ships between exposure to airborne dust and SBS-type symptoms exist have
reported mixed results. Several studies have shown significant relationships
between symptoms and airborne dust concentrations measured as TSP and
RSP. Indirect evidence to demonstrate a causal relationship is available from
breathing-zone filtration studies, which have shown decreases in workplace
symptoms with decreases in airborne dust concentrations.
A number of studies have observed significant relationships between
SBS-type symptoms and surface dust concentrations. Building cleaning stud-
ies have shown significant reductions in SBS symptom prevalence rates after
the implementation of major, systematic building surface cleaning efforts.
Surface dusts may cause symptoms on resuspension as a result of toxic
effects, irritation, or immunological (allergenic) mechanisms. Potential toxic
or irritation effects may be increased as a result of the adsorption of gases
or vapors. Personal exposure measurements indicate that individual air-
borne dust exposure may be 3 to 5 times greater than those predicted from
area sampling (used in most systematic epidemiological studies). It appears
that individuals create their own “dust cloud” as surface dust is resuspended
during activities. Indoor activities increase airborne concentrations in the
very coarse (12.5 to 25
µ
µ
m) and very fine (0.05 to 0.4
µ
m) size ranges; particles
in the 0.8 to 6.4
m range appear to be least affected.
The effect of human activities on airborne particle concentrations can be
seen in day-care center studies. Day-care centers subject to significant floor
and surface dust cleaning had average airborne particle concentrations of
59
µ
µ
g/m
3
(range 32 to 98
µ
g/m
3
) compared to 96
µ
g/m
3
in control day-care
centers (range 42 to 204
g/m
3
). Notably, in both experimental and control
cases, supply air concentrations were <20
µ
g/m
3
.
These studies indicate that a large percentage of airborne dust may be asso-
ciated with resuspension of surface dust by human activity; increased clean-
ing reduces airborne dust concentrations.
µ
g/m
3
and averaged 5 to 6
µ
