Volatile methyl siloxanes (VMS) are ubiquitous in indoor environments due to their use in personal care products. This paper builds on previous work identifying sources of VMS by synthesizing time-resolved proton-transfer reaction time-of-flight mass spectrometer VMS concentration measurements from four multiweek indoor air campaigns to elucidate emission sources and removal processes. Temporal patterns of VMS emissions display both continuous and episodic behavior, with the relative importance varying among species. We find that the cyclic siloxane D5 is consistently the most abundant VMS species, mainly attributable to personal care product use. Two other cyclic siloxanes, D3 and D4, are emitted from oven and personal care product use, with continuous sources also apparent. Two linear siloxanes, L4 and L5, are also emitted from personal care product use, with apparent additional continuous sources. We report measurements for three other organosilicon compounds found in personal care products. The primary air removal pathway of the species examined in this paper is ventilation to the outdoors, which has implications for atmospheric chemistry. The net removal rate is slower for linear siloxanes, which persist for days indoors after episodic release events. This work highlights the diversity in sources of organosilicon species and their persistence indoors.

Abstract We performed a cross-sectional survey of 2143 female students in a university in Tianjin, China regarding perceived air quality (PAQ) and sick building syndrome (SBS) symptoms in the student dormitory. The prevalence of general, mucosal, and skin symptoms was 22.1%, 21.9%, and 26.3%, respectively. The three most prevalent PAQ complaints were ?dry air? (48.9% often), ?stuffy odor? (18.2%), and ?other unpleasant odors? (5.1%), and they were significant risk factors for 11?12 out of 12 SBS symptoms (adjusted odds ratios [AOR]: 1.6?5.8). Survey data of 1471 undergraduates, whose dorms were of uniform layout and furnishing, were used to further investigate the influences of occupancy level and occupant behaviors on PAQ and SBS symptoms. Frequent use of air freshener/perfume was a significant risk factor for ?dry air,? less frequent room cleaning and higher occupancy density were significant risk factors for ?stuffy odor,? and less natural ventilation was a significant risk factor for both ?stuffy odor? and ?pungent odor.? These factors were also significantly associated with some SBS symptoms. In particular, the use of air freshener/perfume exhibited a significant dose?response pattern with ?fatigue? (sometimes: AOR 1.3; often: AOR 2.0) and with ?irritated, stuffy, or runny nose? (sometimes: AOR 1.6; often: AOR 2.2).

Indoor air is a complicated matrix. There are various volatile organic compounds (VVOCs) such as formaldehyde and volatile organic compounds (VOCs) such as benzene, toluene, and xylene in indoor air. They are of low concentration and have different polarities. This chapter first introduces the sampling methods, sample treatment, and analysis of VVOCs (mainly carbonyls and ketones) in indoor air. The 2,4-dinitrophenyl-hydrazine (DNPH) derivatization – high-performance liquid chromatography (HPLC) method – is the most commonly used for the determination of VVOCs. Then four sampling methods for VOCs, including active sampling, passive sampling, whole-air sampling, and solid-phase microextraction (SPME), are introduced. Thermal desorption and solvent extraction are two commonly used methods to pretreat the samples for further analysis. GC combined with MS, FID, ECD, or BID is frequently used for the VVOCs, VOCs, quantitation.

More than 8 million people fly on commercial aircraft each day with approximately 5% having a pre-existing respiratory disease. Thus it is necessary to provide high air quality in aircraft to protect public health. Volatile organic compounds (VOCs) present in aircraft cabins are suspected to contribute to the reported complaints. We investigated concentrations of VOCs, air temperature, relative humidity, and CO2 concentrations in a total of 46 flights, including 26 Chinese domestic flights and 20 international flights. We focused on the data from the cruising phase without meal serving in which the air supply and air recirculation were steady. A total of 284 passengers (i.e., 101 on international flights and 183 on Chinese domestic flights) were invited to participate in questionnaire surveys in this phase. We performed a linear mixed model analysis by controlling for potential confounders (age, gender, smoke habits, and history of allergy) to study associations between VOCs exposures and passengers' complaints. Xylene was significantly associated with irritations of the eyes, nose, and throat on both international and domestic flights, with antilog beta values from 1.12 to 1.28 (p < 0.05). The association of some aldehydes (i.e., nonanal, decanal, and heptanal), which are potential oxidation products with ozone, with passengers' sensory irritations was also significant, especially during international flights (antilog beta values: 1.19–1.22). It indicates that VOCs, especially xylene and aldehydes, in aircraft cabins may influence the perceived indoor air quality and complaints among passengers.

Largely limited by measurement technique, dynamics of semivolatile organic compounds (SVOCs) in the indoor air is not well understood. This study reports time-resolved measurements of airborne concentration of di-2-ethylhexyl phthalate (DEHP) in an office, using semivolatile thermal desorption aerosol gas chromatography (SV-TAG). The measurements were conducted in two separate periods during the summer-to-fall transition in 2020, each for more than 10 days. The indoor gas-plus-particle DEHP concentration varied by more than one order of magnitude in each observation period, and the temporal pattern exhibited possible influences of the indoor temperature, particle mass concentration, and outdoor DEHP concentrations. Further analysis focusing on window-closed conditions (i.e., with less outdoor contribution) reveals that the DEHP dynamics was primarily driven by variations in the indoor temperature (R2 = 0.85) during the first, warmer period (24–29 °C), and by variations in the particle mass concentration (R2 = 0.83) during the subsequent cooler period (20–23 °C). The unexpected transition of the key driving factor with change of the temperature was qualitatively justified by a simplified mechanistic model. Moreover, the particle fraction of DEHP was measured during the latter, cooler period, and it exhibited strong dependence on particle concentration, which can be fitted assuming gas-particle equilibrium partitioning, with a best-fit apparent partitioning coefficient of 0.053 ± 0.006 m3/$μ$g at 20 ± 1 °C. Overall, these results improve our understanding of real-world SVOC dynamics.

Many manmade organic air pollutants are semivolatile and primarily used and exposed indoors. It remains unclear how indoor environmental parameters affect indoor air dynamics of semivolatile organic compounds (SVOCs) in real-world indoor conditions, which directly relates to human exposure. By making time-resolved SVOC measurements over multiple weeks in an office, we characterized the indoor air dynamics of six representative SVOCs which were mainly present in the gas phase and of indoor origins, and investigated the effects of the temperature and ventilation rate. The six species include di-isobutyl phthalate and di-n-butyl phthalate, as well as two n-alkanes and two siloxanes. Airborne concentrations of all six SVOCs responded strongly and quickly to changes in the indoor temperature. The temperature dependence of individual species can be well fitted in the form of the van't Hoff equation, and explained 65–86% of the observed variation in the logarithm-transformed concentrations. In contrast, increasing the ventilation rate by a factor of 3–5 for hours at a constant temperature had no discernible influence on the SVOC concentrations. Further kinetic modeling analysis suggests that the observed fast temperature response and indiscernible ventilation effect are both associated with SVOC sorption onto indoor surfaces, which dramatically slows the response of SVOC concentration to changes in the ventilation rate and speeds up the response to changes in the temperature. These results highlight the importance of sorption reservoirs on regulating indoor SVOC dynamics and also have important implications for controlling and assessing indoor air exposure to SVOCs.

Abstract We present OH observations made in Amazonas, Brazil during the Green Ocean Amazon campaign (GoAmazon2014/5) from February to March of 2014. The average diurnal variation of OH peaked with a midday (10:00?15:00) average of 1.0 ? 106 (±0.6 ? 106) molecules cm?3. This was substantially lower than previously reported in other tropical forest photochemical environments (2?5 ? 106 molecules cm?3) while the simulated OH reactivity was lower. The observational data set was used to constrain a box model to examine how well current photochemical reaction mechanisms can simulate observed OH. We used one near-explicit mechanism (MCM v3.3.1) and four condensed mechanisms (i.e., RACM2, MOZART-T1, CB05, CB6r2) to simulate OH. A total of 14 days of analysis shows that all five chemical mechanisms were able to explain the measured OH within instrumental uncertainty of 40% during the campaign in the Amazonian rainforest environment. Future studies are required using more reliable NOx and VOC measurements to further investigate discrepancies in our understanding of the radical chemistry in the tropical rainforest.