Characterizing Bioaerosol
Risk from Environmental
Sampling
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Abstract
In the aftermath of a release of microbiological agents,
environmental
sampling must be conducted to characterize the release sufficiently
so that mathematical models can then be used to predict the subsequent
dispersion and human health risks. Because both the dose–response
and environmental transport of aerosolized microbiological agents
are functions of the effective aerodynamic diameter of the particles,
environmental assessments should consider not only the total amount
of agents but also the size distributions of the aerosolized particles.
However, typical surface sampling cannot readily distinguish among
different size particles. This study evaluates different approaches
to estimating risk from measurements of microorganisms deposited on
surfaces after an aerosol release. For various combinations of sampling
surfaces, size fractions, HVAC operating conditions, size distributions
of release spores, uncertainties in surface measurements, and the
accuracy of model predictions are tested in order to assess how much
detail can realistically be identified from surface sampling results.
The recommended modeling and sampling scheme is one choosing 3, 5,
and 10 μm diameter particles as identification targets and taking
samples from untracked floor, wall, and the HVAC filter. This scheme
provides reasonably accurate, but somewhat conservative, estimates
of risk across a range of different scenarios. Performance of the
recommended sampling scheme is tested by using data from a large-scale
field test as a case study. Sample sizes of 10–25 in each homogeneously
mixed environmental compartment are sufficient to develop order of
magnitude estimates of risk. Larger sample sizes have little benefit
unless uncertainties in sample recoveries can be reduced