Impact of Cleaning on Concentrations of Volatile and Semivolatile Organic Compounds in A Normally-Occupied Residence
Nathan Sweet,
CU ANYL 1st year

The use of cleaning products alters the chemical composition of indoor air. Utilizing data from detailed observational monitoring conducted over multiple months, we explore the influence of cleaning activities in a normally occupied single-family house. To study emissions and chemistry, we quantified more than 200 VOCs using a proton-transfer reaction time-of-flight mass spectrometer and 52 SVOCs using semivolatile thermal-desorption gas chromatography. During regular professional home cleaning, we observed concentration enhancements in ~60% of observed VOCs and ~80% of reported SVOCs. Most of these concentration enhancements were not clearly linked to either primary emission from cleaning products or secondary formation through reactive chemistry. Instead, shifts in the sorptive properties of indoor surfaces may account for these observations. Individual concentrations of four chlorinated compounds, including dichloramine, increased by up to 0.8 ppb during bleach cleaning. Most cleaning-associated compounds returned to pre-event concentrations within a few hours, with some VOCs and lower volatility SVOCs persisting more than 5 hours, longer than would be expected for removal by ventilation alone. Concentrations of ultrafine particles also increased during professional cleaning, likely from nucleation events associated with bleach cleaning. Use of carpet cleaner was associated with emission of hexanediol, which persisted at elevated concentrations for days after the initial event. We infer that surface sorption dynamics influence the composition of indoor air after cleaning a home. Cleaning events can affect indoor air quality long after the cleaning is completed.

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Using Caulobacter crescentus as a Model to Probe the Reactivity of Silver Nanoparticles
Maddie Farber,
CU ANYL 1st year

Silver nanoparticles (AgNPs) are an increasingly common environmental pollutant with antimicrobial and antibacterial properties. The elucidation of their interaction with cellular membranes and subsequent mechanisms of toxicity are critical areas of research that need to be better understood in order to manage potential adverse environmental effects. This work investigates the interaction of AgNPs with large unilamellar vesicles (LUVs) as a model membrane system. Similar studies conducted by others in this field have largely been conducted with uncoated AgNPs, ignoring the effect of environmental conditions on the formation of an eco-corona on AgNPs. Thus, in this study, the spent medium (SM) of a relevant environmental bacterium, Caulobacter crescentus, was used to form a complex eco-corona. We hypothesized that the eco-corona would mediate the in vivo reactivity of AgNPs, specifically through distinct interactions at the cell membrane. The differential reactivity of AgNPs and SM-AgNPs is shown through an in vivo toxicity study using C. crescentus. Model membranes were analyzed using dynamic light scattering (DLS), in which AgNP and LUV size and charge are characterized, and fluorescence anisotropy, where changes to LUV membrane fluidity and dynamics are interrogated. Results of the in vivo study are presented in tandem with model membrane studies in order to correlate toxicity effects seen in vivo with potential mechanisms of reactivity at the cell membrane.