Distribution of five SVOCs in a model room: effect of vacuuming and air cleaning measures

Lessons from the COVID-19 pandemic for ventilation and indoor air quality

The rapid global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the beginning of 2020 presented the world with its greatest health challenge in decades. It soon became clear that governments were unprepared to respond appropriately to this crisis. National and international public health authorities were confused about the transmission routes of the virus and the control measures required to protect against it. In particular, the need to reduce the risk of infection through sufficient and effective ventilation of indoor spaces was given little attention. In this review, we discuss insights and key lessons learned from the COVID-19 pandemic regarding the role of ventilation as an effective means against airborne transmission of pathogens and, more broadly, for supporting good indoor air quality.

Nanocluster Aerosols from Ozone-Human Chemistry Are Dominated by Squalene-Ozone Reactions

Nanocluster aerosols (NCAs, <3 nm particles) are associated with climate feedbacks and potentially with human health. Our recent study revealed NCA formation owing to the reaction of ozone with human surfaces. However, the underlying mechanisms driving NCA emissions remain unexplored. Squalene is the most abundant compound in human skin lipids that reacts with ozone, followed by unsaturated fatty acids. This study aims to examine the contribution of the squalene-ozone reaction to NCA formation and the influence of ozone and ammonia (NH3) levels. In a climate-controlled chamber, we painted squalene and 6-hexadecenoic acid (C16:1n6) on glass plates to facilitate their reactions with ozone. The squalene-ozone reaction was further investigated at different ozone levels (15 and 90 ppb) and NH3 levels (0 and 375 ppb). The results demonstrate that the ozonolysis of human skin lipid compounds contributes to NCA formation. With a typical squalene-C16:1n6 ratio found in human skin lipids (4:1), squalene generated 40 times more NCAs than did C16:1n6 and, thus, dominated NCA formation. More NCAs were generated with increased ozone levels, whereas increased NH3 levels were associated with the stronger generation of larger NCAs but fewer of the smallest ones. This study experimentally confirms that NCAs are primarily formed from squalene-ozone reactions in ozone-human chemistry.

Associations of urinary phthalate metabolites with household environments among mothers and their preschool-age children

Phthalates have become a matter of public health concern due to their extensive use worldwide and negative health effects. The evaluation of potential sources of phthalate exposure is crucial to design prevention strategies, especially for vulnerable populations. This study included 528 mother-child pairs in the Taiwan Mother Infant Cohort Study who were followed up at ages 3-6 years between 2016 and 2020. Each mother was interviewed by using a structured questionnaire containing questions on demographic characteristics and household environment factors, such as the use of plastic food packaging, residential visible mold, insecticide sprays, and electric mosquito repellents. Eleven phthalate metabolites were analyzed in urine samples simultaneously collected from the mother-child pairs. The phthalate metabolite urinary concentrations were higher among the children than among their mothers, except those of mono-ethyl phthalate (MEP) and mono-2-ethylhexyl phthalate (MEHP). Multiple linear regression analyses showed that urine samples collected during the summer showed higher concentrations of phthalate metabolites than those collected during the winter. Family income levels had negative associations with the concentrations of MnBP and metabolites of di-2-ethylhexyl phthalate (DEHP) in children. The use of plastic food packaging was positively associated with mono-n-butyl phthalate (MnBP) and metabolites of DEHP in mothers. Residential visible mold or mold stains were significantly associated with higher MnBP and DEHP metabolite concentrations in children. The use of insecticide sprays was positively associated with MnBP concentrations in children. Significant associations between household environmental factors and phthalate exposure were mostly found in children, potentially indicating different exposure pathways between mothers and their children. Findings from this study provide additional information for the design of prevention strategies to protect the health of children and women.

Temperature and indoor environments

From the thermodynamic perspective, the term temperature is clearly defined for ideal physical systems: A unique temperature can be assigned to each black body via its radiation spectrum, and the temperature of an ideal gas is given by the velocity distribution of the molecules. While the indoor environment is not an ideal system, fundamental physical and chemical processes, such as diffusion, partitioning equilibria, and chemical reactions, are predictably temperature-dependent. For example, the logarithm of reaction rate and equilibria constants are proportional to the reciprocal of the absolute temperature. It is therefore possible to have non-linear, very steep changes in chemical phenomena over a relatively small temperature range. On the contrary, transport processes are more influenced by spatial temperature, momentum, and pressure gradients as well as by the density, porosity, and composition of indoor materials. Consequently, emergent phenomena, such as emission rates or dynamic air concentrations, can be the result of complex temperature-dependent relationships that require a more empirical approach. Indoor environmental conditions are further influenced by the thermal comfort needs of occupants. Not only do occupants have to create thermal conditions that serve to maintain their core body temperature, which is usually accomplished by wearing appropriate clothing, but also the surroundings must be adapted so that they feel comfortable. This includes the interaction of the living space with the ambient environment, which can vary greatly by region and season. Design of houses, apartments, commercial buildings, and schools is generally utility and comfort driven, requiring an appropriate energy balance, sometimes considering ventilation but rarely including the impact of temperature on indoor contaminant levels. In our article, we start with a review of fundamental thermodynamic variables and discuss their influence on typical indoor processes. Then, we describe the heat balance of people in their thermal environment. An extensive literature study is devoted to the thermal conditions in buildings, the temperature-dependent release of indoor pollutants from materials and their distribution in the various interior compartments as well as aspects of indoor chemistry. Finally, we assess the need to consider temperature holistically with regard to the changes to be expected as a result of global emergencies such as climate change.

Cardiorespiratory responses in healthy young adults with exposure to indoor airborne PAEs: A randomized, crossover trial of air purification

BACKGROUND

Phthalic acid esters (PAEs) are widely used as plasticizers in industrial process and consumer products. Nowadays, PAEs are ubiquitous in the environment and are reported to be associated with cardiorespiratory diseases. However, studies about the association between indoor airborne PAEs exposure and cardiorespiratory health were limited, and the potential biological mechanism remains under-recognized.

METHODS

A randomized crossover trial was conducted on 57 healthy young adults in Beijing. Repeated health measurements were performed under real and sham indoor air purification with a washout interval of at least 2 weeks. The concentration of indoor airborne PAEs were determined by gas chromatography-orbit ion trap mass spectrometry. Health indicators including blood pressure, lung function, airway inflammation, and circulating biomarkers reflecting blood coagulation and systematic oxidative stress were measured. Linear mixed-effect model was used to examine the between-treatment differences in health indicators, and three models including single-constituent, constituent-fine particulate matter (PM_2.5) joint, and single-constituent residual model were used to estimate the association between indoor airborne PAEs and health indicators.

RESULTS

The indoor airborne PAEs were reduced effectively under real air purification. The total indoor airborne di-2-ethylhexyl phthalate (DEHP), bis (4-Methyl-2-pentyl) phthalate (DMPP), diphenyl phthalate (DPP), and diethyl phthalate (DEP) were identified to be most significantly associated with the increase of blood pressure and airway inflammation, and decrease of lung function. A doubling increase in DEHP, DMPP, DPP, DEP was associated with the increase of 17.2% (95% CI: 3.9%, 32.2%), 11.7% (95% CI: 3.5%, 20.6%), 7.0% (95% CI: 2.4%, 11.8%), 6.0% (95% CI: 1.8%, 10.4%) in FeNO, respectively, in single-constituent residual model. Significant associations between specific total indoor airborne PAEs and increased levels of health biomarkers including oxidized low-density lipoprotein (ox-LDL), 8-isoprostane (8-isoPGF2α), and soluble P-selectin (sP-selectin) were observed.

CONCLUSION

Indoor airborne PAEs may cause adverse cardiorespiratory health effects in young healthy adults, and indoor air purification could ameliorate the adverse cardiorespiratory effects.

Assessing Human Exposure to SVOCs in Materials, Products, and Articles: A Modular Mechanistic Framework

A critical review of the current state of knowledge of chemical emissions from indoor sources, partitioning among indoor compartments, and the ensuing indoor exposure leads to a proposal for a modular mechanistic framework for predicting human exposure to semivolatile organic compounds (SVOCs). Mechanistically consistent source emission categories include solid, soft, frequent contact, applied, sprayed, and high temperature sources. Environmental compartments are the gas phase, airborne particles, settled dust, indoor surfaces, and clothing. Identified research needs are the development of dynamic emission models for several of the source emission categories and of estimation strategies for critical model parameters. The modular structure of the framework facilitates subsequent inclusion of new knowledge, other chemical classes of indoor pollutants, and additional mechanistic processes relevant to human exposure indoors. The framework may serve as the foundation for developing an open-source community model to better support collaborative research and improve access for application by stakeholders. Combining exposure estimates derived using this framework with toxicity data for different end points and toxicokinetic mechanisms will accelerate chemical risk prioritization, advance effective chemical management decisions, and protect public health.

Disappearance kinetics of 56 toxic semi-volatile organic compounds under common storage conditions

Synthetic semi-volatile organic compounds (SVOCs) are widely distributed in the environment due to their ever expanding uses. But because some are hazardous, their presence in matrices such as indoor air, wastewater, fish tissue and marine sediment samples (where they could adversely impact public health and the environment) is carefully monitored. To do so, samples are collected, stabilized for transport to laboratories (which are often off-site) and purified for analysis. In-between purification and analysis, the stability of SVOCs in storage is largely assumed. In this study, we test this assumption by assessing the collective stability of 56 SVOCs (amines, halo ethers, nitrobenzenes, phenols, phthalate esters, polycyclic aromatic hydrocarbons and chlorinated compounds) in mixtures stored at -20 °C, 4 °C or 22 °C over a 53 day period. Results show that (i) SVOCs are stable in darkened Amber vials, (ii) that constant temperature is more important than fluctuating temperature in maintaining the integrity of samples in storage, and (iii) that the collective disappearance of SVOCs in colorless 1 mL vials follow first-order kinetics with half-lives (in days) of 28 ± 8, 26 ± 3 and 31 ± 7 at -20 °C, 4 °C or 22 °C, respectively. PAHs (and phthalate esters) were mostly stable with dibenz[a,h]anthracene, indeno[1,2,3-cd]pyrene and 1,12-benzoperylene showing the longest half-lives (57 ± 2 days at -20 °C and 65 ± 6 days at 4 °C, respectively). The degree of substitution on phenols by deactivating groups appears to introduce stability differences. While mono-substituted phenols (chloro and nitro) were sensitive to temperature changes, di- and tri-substituted phenols (dinitro, dichloro and trichloro) were not. Overall, light was found to be the most important factor in the disappearance of SVOCs in colorless vials.

Ten questions concerning the implications of carpet on indoor chemistry and microbiology

Carpet and rugs currently represent about half of the United States flooring market and offer many benefits as a flooring type. How carpets influence our exposure to both microorganisms and chemicals in indoor environments has important health implications but is not well understood. The goal of this manuscript is to consolidate what is known about how carpet impacts indoor chemistry and microbiology, as well as to identify the important research gaps that remain. After describing the current use of carpet indoors, questions focus on five specific areas: 1) indoor chemistry, 2) indoor microbiology, 3) resuspension and exposure, 4) current practices and future needs, and 5) sustainability. Overall, it is clear that carpet can influence our exposures to particles and volatile compounds in the indoor environment by acting as a direct source, as a reservoir of environmental contaminants, and as a surface supporting chemical and biological transformations. However, the health implications of these processes are not well known, nor how cleaning practices could be optimized to minimize potential negative impacts. Current standards and recommendations focus largely on carpets as a primary source of chemicals and on limiting moisture that would support microbial growth. Future research should consider enhancing knowledge related to the impact of carpet in the indoor environment and how we might improve the design and maintenance of this common material to reduce our exposure to harmful contaminants while retaining the benefits to consumers.