Quantifying Historical Human Exposure to Indoor Air Pollutants Through Building Material Forensics Combined with Inverse Diffusion ModelingEPA Grant Number: FP917121
Title: Quantifying Historical Human Exposure to Indoor Air Pollutants Through Building Material Forensics Combined with Inverse Diffusion Modeling
Investigators: McKinney, Jonathan Lewis
Institution: Missouri University of Science and Technology
EPA Project Officer: Michaud, Jayne
Project Period: August 23, 2010 through August 21, 2012
Project Amount: $74,000
RFA: STAR Graduate Fellowships (2010) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Fellowship - Human Health: Risk Assessment and Decision Making
Health scientists believe that VOCs in indoor air may lead to a variety of adverse health effects, which occur long after the occupant was actually exposed to the chemical. Current air sampling methods only allow for quantification of air quality at the present time, and not the past, which leads to uncertain conclusions from studies regarding which VOC exposures lead to adverse health effects. This project’s goal is to generate sampling and data analysis methods for health scientists to use in the field that significantly improve their understanding of historical occupant exposure. The goal may be achieved by forensically analyzing VOCs that have transported into building materials via diffusion, such as toluene in walls or foam cushions, and then using inverse diffusion analysis to determine what historical exposure may have led to the present samples of the building material.
Health scientists believe that VOCs in indoor air lead to many adverse health effects, which occur long after occupant exposure. Studies regarding historical exposures and their health effects are often uncertain due to limitations in air sampling methods. This project’s goal is to quantify historical occupant exposure by sampling chemical concentrations in building materials, such as walls, then using mass transport models to back-calculate historical exposures.
We will use a three-phase approach to meet research objectives. Sampling methods for chemical concentrations in building materials using Solid Phase Micro-Extraction (SPME), methods for forward diffusion analysis, and a system to simulate and allow sampling of diffusion through building materials in the laboratory were previously generated during undergraduate research. First, we will create inverse diffusion analysis methods, and use the existing laboratory system to verify both the existing forward analysis and new inverse analysis methods. Second, we will perform parameter sensitivity analyses using the laboratory system, and modify the diffusion models and analysis methods to match realistic field situations, rather than laboratory conditions. Last, we will field-test all sampling and analysis methods that were developed.
The expected result of this research is to provide health scientists with a new toolbox that allows them to better understand historical occupant exposure to VOCs in indoor environments. As a result, the health scientists may be able to draw more concise conclusions about which VOC exposures lead to which health problems. We expect limitations to how sampling and analysis methods can be used in the field based on uncertainties such as temperature/humidity fluctuations and unknown historical gas phase chemistry in buildings. Uncertainty propagation is inherent in inverse diffusion analysis. The further back in time we try to “see,” our “snapshot of the past” will get fuzzier in the background, but stay clear in the foreground. The most critical results of this research are clear guidelines to health scientists about what is feasible, and not feasible, with this new toolbox in the field.
Potential to Further Environmental/Human Health Protection:
If scientists are able to use our methods to show certain VOCs are harmful, then there will be a direct positive impact on human health and society. Knowledge of which VOCs at which doses are harmful would develop, opening a regulatory path to better protect human health and society in the future, including regulation of chemicals released by consumer products that are typically used indoors, such as air fresheners and cleaning solvents. Our methods also have other applications, such as predicting future exposure rates in new homes that were previously contaminated.