Nusrat Jung

Humans spend most of their time indoors (Strøm-Tejsen et al. 2016; Mullan 2019). Reports from the National Human Activity Pattern Survey in the U.S. show that people spend 68% of their time at home...

Heat-based hair styling activities, such as straightening, curling, and waving, emit volatile and semivolatile chemicals when used with hair care products like creams, lotions, and serums. This study investigates the formation of airborne nanoparticles (6-500 nm) during such activities as a previously unrecognized source of indoor air pollution. Experiments conducted in the Purdue zEDGE Test House revealed that hair styling at temperatures above 300 °F produced indoor nanoparticle concentrations ranging from 10,000 to over 100,000 particles cm^-3, with sub-100 nm particles typically accounting for more than 95% of total number concentrations at temperatures exceeding 360 °F. The primary mechanism for nanoparticle formation was heat-driven volatilization of cyclic siloxanes and various low-volatility constituents in hair care products, followed by nanoparticle nucleation and subsequent growth via condensation and coagulation. Ozonolysis of fragrance additives served as a secondary formation pathway. Respiratory tract deposition modeling indicated that more than 10 billion nanoparticles could deposit in the respiratory system during a single hair styling session, with the highest dose occurring in the pulmonary region. These findings identify heat-based hair styling as a significant indoor source of airborne nanoparticles and highlight previously underestimated exposure risks. This work advances our understanding of the physical and chemical processes underlying emissions from personal care product use and underscores the need for mitigation strategies to reduce exposure in residential environments.

Scented wax melts are being popularized as a safer, nontoxic alternative to traditional candles and incense for indoor aromatherapy. We performed field measurements in a residential test house to investigate atmospheric nanoparticle formation from scented wax melt use. We employed a high-resolution particle size magnifier-scanning mobility particle sizer (PSMPS) and a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) for real-time monitoring of indoor atmospheric nanoparticle size distributions and terpene mixing ratios, respectively. Our findings reveal that terpenes released from scented wax melts react with indoor atmospheric ozone (O₃) to initiate new particle formation (NPF) events, resulting in significant indoor atmospheric nanoparticle concentrations (>10⁶ cm^-3) comparable to those emitted by combustion-based scented candles, gas stoves, diesel engines, and natural gas engines. We show that scented wax melt-initiated NPF events can result in significant respiratory exposures, with nanoparticle respiratory tract deposited dose rates similar to those determined for combustion-based sources. Our results challenge the perception of scented wax melts as a safer alternative to combustion-based aromatherapy, highlighting the need for further research on the toxicological properties of the newly formed nanoparticles to better understand their environmental health implications.

Cured-in-place-pipe (CIPP) technology has begun to be adopted for drinking water pipe repairs, and limited information exists about its drinking water quality impacts. CIPP involves the manufacture of a new plastic pipe inside a buried damaged pipe. In this study, the chemical composition of the raw materials and CIPP water quality impacts were examined. Numerous (47) VOCs and SVOCs were found in the resin and two hardeners were studied. TGA results indicated that new CIPPs contained about 3.2–4.8 wt% VOC. A controlled static headspace analysis using PTR-TOF-MS detected eight protonated ions (m/z < 114) with mixing ratios above 1 ppb and phenol was identified as the most abundant VOC released into air. The analytical methods were unable to identify 99.9% of the extractable VOC mass. A 5% shorter curing duration had no impact on the chemical residual left in the CIPPs, but a 5% hardener reduction prompted an increase in the amount of monomer remaining. Both normal drying and quick drying formulations released similar amounts of 2-EHGE and BPA into drinking water. Laboratory results scaled to 4–36 in. diameter pipes indicated only 4 in. diameter CIPPs would cause BPA levels to exceed a U.S. state drinking water standard, EU, and WHO drinking water limits. Flushing and drinking water VOC and SVOC testing should be conducted before use. Additional studies of resins, manufacturing conditions, and wastes generated, are recommended. At present, the limited information available about these materials has shifted the burden of potential health and financial costs to the users.