The THEM Software Project


This page describes the Total Human Exposure Model (THEM) for exploring particle exposures in the San Francisco Bay Area. Please visit the [[A Total Human Exposure Model (THEM)|THEM Summary Page]] for a complete list of all the THEM project details.

The Total Human Exposure Model (THEM) program, version 1.0 was developed at Stanford University from July 1991 to April 1994 by Wayne R. Ott, Neil E. Klepeis, and Elena Tracy. THEM is written in MicroSoft Professional BASIC Development System version 7.1.

THEM is not currently being maintained, but questions can be directed to Dr. Neil E. Klepeis.

THEM is released under the GNU General Public License.

The current version calculates exposure to Respirable Suspended Particles (RSP) from Environmental Tobacco Smoke (ETS) and ambient sources. It uses the California Activity Pattern (CAP) Survey data from the California Air Resources Board (Sacramento, CA) and ambient RSP data from the Bay Area Air Quality Management District (David Fairley). The so-called Sequential Cigarette Exposure Model (SCEM), based on the mass balance equation, is used to determine concentrations of secondhand tobacco smoke for single cigarettes.

There is a scientific paper and a user's and programmer's manual.


A zipped archive is available containing all of the Microsoft Professional Basic source-code files, a variety of documentation files, and a Windows/DOS executable (themrsp3.exe).

[Download the THEM zipped archive]


The user interface to the program is fairly self-explanatory.

Execution of THEM for the calculation of exposures across populations requires the input of (1) activity pattern data, (2) mass balance parameters, (3) microenvironmental distributions, (4) activity, location, and calculation method reduced codes, and (5) ambient data (optional).

All parameters are specified using input data files, which have already been set at default values for the simulation of exposure to RSP from cigarettes and ambient sources for people living in the San Francisco Bay Area.

The documentation files in the software distribution contain more information on using THEM.

The main reference for THEM is the following AWMA conference paper:

Klepeis NE, Ott WR, Switzer P. A Total Human Exposure Model (THEM) for Respirable Suspended Particles (RSP), Presented at the 87th Annual Meeting and Exhibition of the Air and Waste Management Association, Cincinnati, OH, June 1994.

Please cite this paper if you use or describe THEM in any published research.

The THEM user's and programmer's manual contains a technical description of the program, including all the subprograms and variable declarations.

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