The chemistry that happens indoors is relevant to human health due to the proximity to human occupants, and risk for exposure because of long periods spent indoors. There is a lot of diversity in chemical compounds present in the built environment, emission from materials, chemical interactions (e.g., adsorption, absorption) with materials, and local environmental conditions such as ventilation rate and temperature, all of which can alter chemical reactivity. This complexity makes it difficult to understand how indoor chemistry affects biological life.
Di-2-ethylhexyl phthalate (DEHP), a known endocrine-disrupting chemical, DEHP has been associated with increased reports of children’s asthma during warmer seasons, and its byproducts or metabolites can likewise be hazardous to human health. DEHP is commonly used in consumer goods and building materials, especially vinyl floor. It becomes a concern when it leaches from these materials into dust, water, or soil, as it can then be inhaled, absorbed, or ingested by building occupants. DEHP concentration is significantly higher in settled (i.e., surface) dust in homes with polyvinyl flooring. It is also found in HVAC filters, indicating that DEHP in dust easily moves from the floor to the air.
Little research has been done to elucidate the relationships between phthalate composition and the effects on microbial communities in dust. This pilot study investigated whether dust which accumulated DEHP emitted from polyvinyl chloride flooring would affect the bacterial communities in dust gathered from homes.
This was the first first-authored research paper by former undergraduate mentees of mine at the University of Oregon; Samantha Velazquez and Susie Nunez.
Velazquez, S., Bi, C., Kline, J., Nunez, S., Corsi, R., Xu, Y., Ishaq, S.L. 2019. Accumulation of di-2-ethylhexyl phthalate from polyvinyl chloride flooring into settled house dust and the effect on the bacterial community. PeerJ 7:e8147. Impact 2.353. Article.
Di-2-ethylhexyl phthalate (DEHP) is a plasticizer used in consumer products and building materials, including polyvinyl chloride flooring material. DEHP adsorbs from material and leaches into soil, water, or dust, and presents an exposure risk to building occupants by inhalation, ingestion, or absorption. A number of bacterial isolates are demonstrated to degrade DEHP in culture, but bacteria may be susceptible to it as well, thus this study examined the relation of DEHP to bacterial communities in dust. Polyvinyl chloride flooring was seeded with homogenized house dust and incubated for up to 14 days, and bacterial communities in dust were identified at days 1, 7, and 14 using the V3-V4 regions of the bacterial 16S rRNA gene. DEHP concentration in dust increased over time, as expected, and bacterial richness and Shannon diversity were negatively correlated with DEHP concentration. Some sequence variants of Bacillus, Corynebacterium jeddahense, Streptococcus, and Peptoniphilus were relatively more abundant at low concentrations of DEHP, while some Sphingomonas, Chryseobacterium, and a member of the Enterobacteriaceae family were relatively more abundant at higher concentrations. The built environment is known to host lower microbial diversity and biomass than natural environments, and DEHP or other chemicals indoors may contribute to this paucity.
Featured Image: Examples of seeded dust on the vinyl flooring materials. Image courtesy of Dr. Chenyang Bi.