Editor’s note: SynergistNOW welcomes its newest contributor, Mike Jayjock. Mike will be posting from time to time on modeling, risk assessment, exposure assessment, toxicology, and more. Be sure to visit Mike's blog, Human Health Risk Assessment to Chemicals.

I have always thought that developing exposure and risk assessment tools is best done as a “public works” effort—that is, with public money for the public good, with costs and benefits shared equally. It is analogous to the need for people to cross a river. Individually they can wade or swim across. Some enterprising folks might finance and run a ferry; however, it could be argued that given enough need, a bridge built by the common government is the best answer. This is the way the EPA operated toward the end of the last century relative to exposure and risk assessment models, which they developed as PC-based programs.

Perhaps the best exposure assessment model EPA developed during this era was the Multi-Chamber Concentration and Exposure Model (MCCEM) version 1.2. It is a remarkable program in that it uses an extensive database of measured interzonal (between-room) and whole-house air flows and the single-zone well-mixed model for any room to calculate essentially any time-weighted concentration within that room.

EPA’s website has a thorough explanation of MCCEM, but here are a few highlights:

• Using a mass balance approach, it estimates average and peak indoor air concentrations of chemicals released from products or materials in residences. It can also be used to assess other indoor environments (such as schools and offices) as long as the user provides the proper inputs.
• It estimates inhalation exposures, calculated as single-day doses, chronic average daily doses, or lifetime average daily doses. (The dose estimates are potential doses; they do not acco​unt for actual absorption into the body.)
• It maintains a library of residences, containing data on zone or area volumes, interzonal air flows, and whole-house exchange rates.
• It allows you to tailor your analysis to a particular location, and to model air concentrations in as many as four zones for a given residence.
• It estimates exposure for periods ranging from 1 hour to 1 year, and develops seasonal or annual exposure profiles using a long-term model.
• It offers several options for dealing with “sinks”—a material such as carpeting or wallboard that can absorb chemicals from the air.

The only problem with MCCEM is that it was designed to run on Windows 95. It won’t run on new Windows 10 PCs. But Tom Armstrong, who has been a resource for the IH community for many years, has come to the rescue with an easy-to-follow two-page primer on what one can do for minimal cost to get this program and any other legacy Windows 95 or Windows XP program up and running.

That we have to go through this effort to use this excellent tool discloses just how little support the EPA has gotten in recent years. Indeed, in the last year the situation has gotten particularly acute. One can only hope that the future will bring a return of the agency’s support and the further development of these wonderful public works.​