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IGERT Trainees Study Human Exposure to Harmful Chemical Found in Moth Repellents and Deodorizers
Achievement/Results
The National Science Foundation’s (NSF) Integrative Graduate Education and Research Traineeship (IGERT) program in Indoor Environmental Science and Engineering at The University of Texas (UT) has allowed two trainees to team to study human exposure to p-dichlorobenzene (DCB), a toxic chemical found in moth repellants and deodorizers. Trainee Diana Hun (Architectural Engineering), a third year IGERT student, is studying human exposure to toxic air contaminants in low-income housing. She has found important associations between risks of exposure to specific toxic air contaminants in households characterized by socio-economic status and race.
Diana is analyzing data from the multi-city Relationships between Indoor, Outdoor, and Personal Air (RIOPA) study, and she is also assisting with a large filed study in Houston entitled the Houston Exposure to Air Toxics Study (HEATS). Her work indicates that in homes that contain sources of DCB, e.g., moth repellants, toilet deodorizers and some air “fresheners”, this contaminant tends to dominate overall cancer risks. Within the Mexican American community in Houston, the median cancer risk associated with indoor exposure to DCB in the RIOPA data set is over 150 in a million, an order of magnitude greater than the median risk in white households. The 75th percentile cancer risk was over 2,000 in a million for Mexican American exposures to DCB, with some individual risks in excess of 10,000 in a million. Such risks are alarming in so much that they dwarf most cancer risks associated with human exposure to environmental contaminants, typically in the range of 1 to 10 in a million.
In response to these findings, Priscilla Guerrero (Environmental Engineering), a first-year IGERT trainee, has embarked on a study to better understand the processes that affect human exposure to DCB. She has started by completing a detailed experimental analysis of DCB emission rates (mg/hr) from three of the most common consumer products that emit DCB in homes, and is also assessing the factors that affect DCB emissions from these products. Her analysis includes not only environmental conditions such as temperature and air speed over products, but also the effects of product design, e.g., casing, on emissions. She has used her experimental results as inputs to mathematical models to predict indoor DCB concentrations and human exposures and risks. Her findings generally agree with field measurements related to the RIOPA study.
Priscilla will next study the effects of adsorption of DCB to indoor materials, human clothing, human hair and skin. These new experiments will be intended to understand the role of materials in reducing exposures when a source is emitting, and also prolonging the actual exposure period due to desorption from such materials. Diana and Priscilla are currently developing two journal papers that will soon be submitted for review, and have presented their work at two recent conferences.
Address Goals
Diana Hun’s and Priscilla Guerrero’s collective research efforts are novel on several fronts, and therefore advancing the frontiers of knowledge related to human inhalation exposure to toxic chemicals. Their findings are unique in that they explore risks associated to a toxic air contaminant, p-dichlorobenzene (DCB), and how those risks differ between socio-economic classes and race (discovery). Importantly, Diana is studying the reasons for these differences in terms of the nature of consumer products used by lower-income populations, activity patterns, location of housing, nature of housing (attached garage, etc.) and operation of housing. Priscilla is focusing her attention on factors that affect DCB emissions and how adsorption processes affect human exposure to DCB. Since Diana is an engineering student with a strong building science background, her efforts will also lead to insights related to how to solve high exposure scenarios in lower-income households (discovery).
Diana Hun’s participation in HEATS is made possible because of our NSF-funded IGERT program, and is a prime example of how funding from NSF has allowed a Ph.D. student in Architectural Engineering to work alongside health scientists on a novel and important study that benefits from the synergy of interdisciplinary teamwork. This goes to the strategic goal of learning, and the fact that interdisciplinary collaboration lends “value added” to the learning process for all committed participants.
Priscilla Guerrero’s participation in this study was made possible by the flexibility afforded by the IGERT program. She became aware of Diana’s work while attending an annual meeting of our program and hearing a presentation made by Diana on her results. Priscilla’s own research then evolved based on her interest in Diana’s findings. This goes to the strategic goal of learning, and shows how IGERT programs can catalyze research sequences that address important societal problems.
