Mathematical exposure modeling: Difference between revisions

Revision as of 07:12, 13 March 2012

Revision as of 21:03, 17 March 2012

Line 1:

{{nofootnotesno footnotes|date=June 2009}}

{{refimprove|date=June 2009}}

{{cleanup-confusing|article|date=June 2009}}

Line 7:

Mathematical modeling is commonly used to determine human exposure to indoor air pollution. Studies have shown that humans spend about 90% of their time indoors, and contaminant levels may be as high or higher inside than outside, due to the presence of multiple indoor contaminant sources, in combination with poor ventilation. Indoor air modeling requires information on a number of parameters including the air exchange rate, [[Deposition (Aerosol physics)|deposition rate]], source emission rate, and physical volume of the indoor setting. Indoor environments can basically be thought of as [[closed systems]], so models describing them are usually based on the "[[mass balance]]" equation. It is also assumed that a pollutant emitted into an indoor environment instantly spreads uniformly throughout the system, so that the concentration is the same at any point in space at any point in time. Mathematically, the total pollutant mass emitted inside a chamber during time T can be expressed as<br>

::G_source(T) = <math>\int_{0}^{T} g(t)\, dt</math><br>

:where<br>

::G_source(T) = total mass contributed by the source over time T (e.g., mg)<br>

::g(t) = emission flow rate as a function of time t (e.g., mg/min)

The total mass lost during time T can be expressed as<br>

::Q_lost(T) = <math>\int_{0}^{T} wx(t)\, dt</math><br>

:where<br>

::Q_lost(T) = total mass lost from the chamber over time T (e.g., mg)<br>

::x(t) = concentration of pollutant in the air exiting the chamber (e.g., mg/m³)<br>

::w = flow rate of air exiting the chamber (e.g., m³/min)

Line 25 ⟶ 24:

== Modeling human exposure to air pollution ==

There are two critical pieces of information that are needed to calculate human exposure. These include data on 1) the whereabouts of the individual or individuals being exposed and 2) the concentration of the pollutants in the different locations. This can be expressed mathematically as the sum of the products of time spent by a person in those different locations by the time-averaged [[air pollutant concentrations]] occurring in those locations.<br>

::E_''p'' = <math>\sum_{i=1}^m</math> C_''pi''T_''pi''<br>

:where<br>

::T_''pi'' is the time spent by person ''p'' in microenvironment ''i'', and C_''pi'' is the concentration of the air pollutant that person ''p'' experiences in microenvironment ''i'', E_''p'' is the integrated exposure for person ''p'' and ''m'' is the number of different microenvironments.

Line 35 ⟶ 34:

The Inside Story: A Guide to Indoor Air Quality. U.S. EPA (2009)

{{Uncategorized|date=March 2012}}