Long-term prediction of the effects of climate change on indoor climate and air quality.

Limiting the negative impact of climate change on nature and humans is one of the most pressing issues of the 21st century. Meanwhile, people in modern society spend most of the day indoors. It is therefore surprising that comparatively little attention has been paid to indoor human exposure in relation to climate change. Heat action plans have now been designed in many regions to protect people from thermal stress in their private homes and in public buildings. However, in order to be able to plan effectively for the future, reliable information is required about the long-term effects of climate change on indoor air quality and climate. The Indoor Air Quality Climate Change (IAQCC) model is an expediant tool for estimating the influence of climate change on indoor air quality. The model follows a holistic approach in which building physics, emissions, chemical reactions, mold growth and exposure are combined with the fundamental parameters of temperature and humidity. The features of the model have already been presented in an earlier publication, and it is now used for the expected climatic conditions in Central Europe, taking into account various shared socioeconomic pathway (SSP) scenarios up to the year 2100. For the test house examined in this study, the concentrations of pollutants in the indoor air will continue to rise. At the same time, the risk of mold growth also increases (the mold index rose from 0 to 4 in the worst case for very sensitive material). The biggest problem, however, is protection against heat and humidity. Massive structural improvements are needed here, including insulation, ventilation, and direct sun protection. Otherwise, the occupants will be exposed to increasing thermal discomfort, which can also lead to severe heat stress indoors.

Analytical chemistry of carbonyl compounds in indoor air.

Carbonyl compounds are ubiquitous in outdoor and indoor air. Due to the high electronegativity of the oxygen atom, they are polar in nature and the CO group opens possibilities for many types of chemical reactions. Their physical and chemical properties are additionally influenced by substituents and conjugated double bonds. The concentration ranges are also highly variable. Formaldehyde can reach 100 ppb or more in indoor air, but reaction products such as 4-oxopentanal (4-OPA) are in the lower ppb range or even below 1 ppb. Another point concerns the dynamics of carbonyls. When examining the emission of formaldehyde in test chambers, an equilibrium concentration is usually established, so that changes over time can be neglected during the measurement. On the other hand, many substances and scenarios are subject to strong fluctuations in concentration over short time periods. The analysis is also made more difficult by the fact that different methods are often required for saturated carbonyls, unsaturated carbonyls and dicarbonyls. This work focuses on aprotic carbonyl compounds such as aldehydes, ketones, lactams and pyrones with relevance for the indoor environment that do not contain any other reactive groups. The range of interesting compounds has grown significantly in recent years, notably through the derivation of health-based guide values, as well as through investigations into new products, human activities and human emissions from the skin and respiratory gas. Classical and modern analysis methods are discussed, which can be considered for the respective research question. Many small molecules require derivatization as a first step, followed by separation via gas chromatography or HPLC. Substance-specific detection without chromatographic separation is routinely used for formaldehyde. With some limitations, the identification of carbonyls in multicomponent mixtures is possible using online mass spectrometry. In particular, proton-transfer-reaction mass spectrometry (PTR-MS) has established as a method with high sensitivity and high time resolution.

The acute vapour inhalation toxicity of 2-butoxyethanol. Points considered when designing and conducting a study in Guinea pigs and evaluating existing inhalation toxicity data on low volatility solvents.

This publication reports the outcome of an acute inhalation toxicity study with guinea pigs by nose-only exposure to the substance 2-butoxyethanol at exposures close to the maximum attainable saturation vapour concentration. We describe the methods used to ensure exposure only to saturation vapour at a level as high as could be practically achieved whilst avoiding aerosol formation. We consider the practical difficulties and implications of testing substances at or close to their saturation vapour concentration and the criteria that should be used to critically assess such studies, especially with reference to the GHS (Globally Harmonised System) for classification and labelling, where a clear differentiation between gases, vapours and dust and mists applies. Guinea pigs showed no adverse effects when exposed for 4 h to the maximum attainable concentration of pure 2-butoxyethanol vapour. If guinea pigs are regarded as the most appropriate species to assess short term toxicity to humans from exposure to 2-butoxyethanol, because they are like humans not sensitive to haemolysis of red blood cells caused by exposure to the substance, then the data from this study shows that 2-butoxyethanol presents a low acute inhalation toxicity hazard.

Quantum Chemical Calculation and Evaluation of Partition Coefficients for Classical and Emerging Environmentally Relevant Organic Compounds.

Octanol/water (KOW), octanol/air (KOA), and hexadecane/air (KHdA) partition coefficients are calculated for 67 organic compounds of environmental concern using computational chemistry. The extended CRENSO workflow applied here includes the calculation of extensive conformer ensembles with semiempirical methods and refinement through density functional theory, taking into account solvation models, especially COSMO-RS, and thermostatistical contributions. This approach is particularly advantageous for describing large and nonrigid molecules. With regard to KOW and KHdA, one can refer to many experimental data from direct and indirect measurement methods, and very good matches with results from our quantum chemical workflow are evident. In the case of the KOA values, however, good matches are only obtained for the experimentally determined values. Larger systematic deviations between data computed here and available, nonexperimental quantitative structure-activity relationship literature data occur in particular for phthalic acid esters and organophosphate esters. From a critical analysis of the coefficients calculated in this work and comparison with available literature data, we conclude that the presented quantum chemical composite approach is the most powerful so far for calculating reliable partition coefficients because all physical contributions to the conformational free energy are considered and the structure ensembles for the two phases are generated independently and consistently.

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.

Effectiveness of air-purifying devices and measures to reduce the exposure to bioaerosols in school classrooms.

The SARS-CoV-2 pandemic, which suddenly appeared at the beginning of 2020, revealed our knowledge deficits in terms of ventilation and air pollution control. It took many weeks to realize that aerosols are the main route of transmission. The initial attempt to hold back these aerosols through textile masks seemed almost helpless, although there is sufficient knowledge about the retention capacity of fabric filters for aerosols. In the absence of a sufficient number of permanently installed heating, ventilation, and air conditioning systems, three main approaches are pursued: (a) increasing the air exchange rate by supplying fresh air, (b) using mobile air purifiers, and (c) disinfection by introducing active substances into the room air. This article discusses the feasibility of these different approaches critically. It also provides experimental results of air exchange measurements in a school classroom that is equipped with a built-in fan for supplying fresh air. With such a fan and a window tilted at the appropriate distance, an air exchange rate of 5/h can be set at a low power level and without any significant noise pollution. Heat balance calculations show that no additional heat exchanger is necessary in a normal classroom with outside temperatures above 10°C. Furthermore, a commercial mobile air purifier is studied in a chamber and a test room setup in order to examine and evaluate the efficiency of such devices against viable viruses under controlled and realistic conditions. For this purpose, bacteriophages of the type MS2 are used. Both window ventilation and air purifiers were found to be suitable to reduce the concentration of phages in the room.

A holistic modeling framework for estimating the influence of climate change on indoor air quality.

The IPCC 2021 report predicts rising global temperatures and more frequent extreme weather events in the future, which will have different effects on the regional climate and concentrations of ambient air pollutants. Consequently, changes in heat and mass transfer between the inside and outside of buildings will also have an increasing impact on indoor air quality. It is therefore surprising that indoor spaces and occupant well-being still play a subordinate role in the studies of climate change. To increase awareness for this topic, the Indoor Air Quality Climate Change (IAQCC) model system was developed, which allows short and long-term predictions of the indoor climate with respect to outdoor conditions. The IAQCC is a holistic model that combines different scenarios in the form of submodels: building physics, indoor emissions, chemical-physical reaction and transformation, mold growth, and indoor exposure. IAQCC allows simulation of indoor gas and particle concentrations with outdoor influences, indoor materials and activity emissions, particle deposition and coagulation, gas reactions, and SVOC partitioning. These key processes are fundamentally linked to temperature and relative humidity. With the aid of the building physics model, the indoor temperature and humidity, and pollutant transport in building zones can be simulated. The exposure model refers to the calculated concentrations and provides evaluations of indoor thermal comfort and exposure to gaseous, particulate, and microbial pollutants.

Formaldehyde, aliphatic aldehydes (C2 -C11 ), furfural, and benzaldehyde in the residential indoor air of children and adolescents during the German Environmental Survey 2014-2017 (GerES V).

Indoor air concentrations of formaldehyde, furfural, benzaldehyde, and 11 aliphatic aldehydes (C2 -C11 ) were measured in residences of 639 participants in the German Environmental Survey for Children and Adolescents 2014-2017 (GerES V). Sampling was conducted using passive samplers over periods of approximately seven days for each participant. The most abundant compounds were formaldehyde and hexanal with median concentrations of 24.9 µg m-3 and 10.9 µg m-3 , respectively. Formaldehyde concentrations exceeded the Guide Value I recommended by the German Committee on Indoor Guide Values (Ausschuss für Innenraumrichtwerte - AIR) (0.10 mg m-3 ) for 0.3% of the participating residences. The sum of aliphatic n-aldehydes between C4 (butanal) and C11 (undecanal) exceeded their Guide Value (0.10 mg m-3 ) for 2.0% of the residences. The geometric mean concentrations of most aldehydes were lower than in the earlier GerES IV (2003-2006) study. Formaldehyde and hexanal concentrations, however, were comparable in both studies and showed no significant difference. Indoor aldehyde concentrations did not exhibit significant correlations with factors collected in questionnaires, such as the age of the participants, their socio-economic status, the location of the residence (former East/West Germany), migration background, tobacco exposure, and the type of furniture used. The validity of the passive sampler measurements was verified against active sampling techniques in a test chamber experiment.

A multi-layered strategy for COVID-19 infection prophylaxis in schools: A review of the evidence for masks, distancing, and ventilation.

Implications for the academic and interpersonal development of children and adolescents underpin a global political consensus to maintain in-classroom teaching during the ongoing COVID-19 pandemic. In support of this aim, the WHO and UNICEF have called for schools around the globe to be made safer from the risk of COVID-19 transmission. Detailed guidance is needed on how this goal can be successfully implemented in a wide variety of educational settings in order to effectively mitigate impacts on the health of students, staff, their families, and society. This review provides a comprehensive synthesis of current scientific evidence and emerging standards in relation to the use of layered prevention strategies (involving masks, distancing, and ventilation), setting out the basis for their implementation in the school environment. In the presence of increasingly infectious SARS-Cov-2 variants, in-classroom teaching can only be safely maintained through a layered strategy combining multiple protective measures. The precise measures that are needed at any point in time depend upon a number of dynamic factors, including the specific threat-level posed by the circulating variant, the level of community infection, and the political acceptability of the resultant risk. By consistently implementing appropriate prophylaxis measures, evidence shows that the risk of infection from in-classroom teaching can be dramatically reduced. Current studies indicate that wearing high-quality masks and regular testing are amongst the most important measures in preventing infection transmission; whilst effective natural and mechanical ventilation systems have been shown to reduce infection risks in classrooms by over 80%.

Microplastics and their Additives in the Indoor Environment.

Analyses of air and house dust have shown that pollution of the indoor environment with microplastics could pose a fundamental hygienic problem. Indoor microplastics can result from abrasion, microplastic beads are frequently added to household products and microplastic granules can be found in artificial turf for sports activities and in synthetic admixtures in equestrian hall litter. In this context, the question arose as to what extent particulate emissions of thermoplastic materials from 3D printing should be at least partially classified as microplastics or nanoplastics. The discussion about textiles as a possible source of indoor microplastics has also been intensified. This Minireview gives an overview of the current exposure of residents to microplastics. Trends can be identified from the results and preventive measures can be derived if necessary. It is recommended that microplastics and their additives be given greater consideration in indoor environmental surveys in the future.

Sensory Perception of Non-Deuterated and Deuterated Organic Compounds.

The chemical background of olfactory perception has been subject of intensive research, but no available model can fully explain the sense of smell. There are also inconsistent results on the role of the isotopology of molecules. In experiments with human subjects it was found that the isotope effect is weak with acetone and D6 -acetone. In contrast, clear differences were observed in the perception of octanoic acid and D15 -octanoic acid. Furthermore, a trained sniffer dog was initially able to distinguish between these isotopologues of octanoic acid. In chromatographic measurements, the respective deuterated molecule showed weaker interaction with a non-polar liquid phase. Quantum chemical calculations give evidence that deuterated octanoic acid binds more strongly to a model receptor than non-deuterated. In contrast, the binding of the non-deuterated molecule is stronger with acetone. The isotope effect is calculated in the framework of statistical mechanics. It results from a complicated interplay between various thermostatistical contributions to the non-covalent free binding energies and it turns out to be very molecule-specific. The vibrational terms including non-classical zero-point energies play about the same role as rotational/translational contributions and are larger than bond length effects for the differential isotope perception of odor for which general rules cannot be derived.

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.

Human exposure to air contaminants in sports environments.

The aim of this review was to investigate human exposure to relevant indoor air contaminants, predictors affecting the levels, and the means to reduce the harmful exposure in indoor sports facilities. Our study revealed that the contaminants of primary concern are the following: particulate matter in indoor climbing, golf, and horse riding facilities; carbon dioxide and particulate matter in fitness centers, gymnasiums, and sports halls; Staphylococci on gymnasium surfaces; nitrogen dioxide and carbon monoxide in ice hockey arenas; carbon monoxide, nitrogen oxide(s), and particulate matter in motor sports arenas; and disinfection by-products in indoor chlorinated swimming pools. Means to reduce human exposure to indoor contaminants include the following: adequate mechanical ventilation with filters, suitable cleaning practices, a limited number of occupants in fitness centers and gymnasiums, the use of electric resurfacers instead of the engine powered resurfacers in ice hockey arenas, carefully regulated chlorine and temperature levels in indoor swimming pools, properly ventilated pools, and good personal hygiene. Because of the large number of susceptible people in these facilities, as well as all active people having an increased respiratory rate and airflow velocity, strict air quality requirements in indoor sports facilities should be maintained.

Review of the characteristics and possible health effects of particles emitted from laser printing devices.

Many studies have shown that the use of laser printing devices (LPDs) contributes to the release of particles into the indoor environment. However, after more than two decades of research, the physicochemical properties of LPD-emitted particles and the possible health effects from exposure to particles are still heavily debated. We therefore carried out a critical review of the published studies around emissions and health effects of LPD-emitted particles, aiming at elucidating the nature of these particles and their potential health risks. Realizing the varying methodologies of the studies, a classification of the reviewed studies is adopted, resulting in three categories of emission studies (chamber experiment, office/room measurement, and photocopy shop measurement), and three types of health studies (in vitro/animal studies, human studies in the real world, and human studies in controlled settings). The strengths and limitations of each type of study are discussed in-depth, which in turn helps to understand the cause of divergent results. Overall, LPD-emitted particles are mainly condensed or secondary-formed semi-volatile organic compounds (SVOCs), while solid toner particles account for a very small fraction. The health risk from exposure to LPD-emitted particles is small compared with the health risk from exposure to ambient particles.

Predicting the Gas/Particle Distribution of SVOCs in the Indoor Environment Using Poly Parameter Linear Free Energy Relationships.

Understanding the partitioning of semi volatile organic compounds (SVOCs) between gas phase and particle phase is essential for exposure analysis and risk assessment in the indoor environment. Numerous attempts have been made to calculate gas/particle partitioning coefficients Kip. Single-parameter adsorption and absorption models, which relate Kip to the vapor pressure Ps or the octanol/air distribution coefficient KOA are usually applied. In this work we use poly parameter Linear Free Energy Relationships (pp-LFER) to describe the partitioning behavior of 14 SVOCs with high relevance for the indoor environment. The pp-LFER concept is based on Abraham descriptors and considers interactions between molecule and particle by separate parameters. van der Waals interactions can be approximated by the logarithm of the hexadecane/air partitioning coefficient (log KHdA = L), which is a key parameter for the 14 polar but nonionizable organic esters being studied here. For many of the examined compounds experimentally determined L-values were not available and had to be measured using gas chromatography. It is shown that the pp-LFER method is a strong alternative to single-parameter approaches and gives reliable coefficients for gas/particle distribution in the indoor environment.

Analytical procedure for the determination of very volatile organic compounds (C3-C6) in indoor air.

The substance group of very volatile organic compounds (VVOCs) is moving into the focus of indoor air analysis, facing ongoing regulations at international and European levels targeting on indoor air quality and human health. However, there exists at present no validated analysis for the identification and quantification of VVOCs in indoor air. Therefore, the present study targeted on the development of an analytical method in order to sample the maximum possible quantity of VVOCs in indoor air on solid sorbents with subsequent analysis by thermal desorption and coupled gas chromatography/mass spectrometry (TDS-GC/MS). For this purpose, it was necessary to investigate the performance of available sorbents and to optimize the parameters of GC/MS analysis. Stainless steel tubes filled with Carbograph 5TD were applied successfully for low-volume sampling (2-4 l) with minimal breakthrough (< 1%). With the developed method, VVOCs between C3 and C6 of different volatility and polarity  can be detected even in trace quantities with low limits of quantitation (LOQ; 1-3 µg m-3). Limitations occur for low molecular weight compounds ≤C3, especially for polar substances, such as carboxylic acids and for some aldehydes and alcohols. Consequently, established methods for the quantification of these compounds in indoor air cannot be fully substituted yet. At least three different analytical techniques are needed to cover the large spectrum of relevant VVOCs in indoor air. In addition, unexpected reaction products might occur and need to be taken into account to avoid misinterpretation of chromatographic signals. Graphical abstract Solid sorbent sampling of VVOCs (C3-C6) in indoor air with subsequent TDS-GC/MS analysis.

[Indoor air pollution-current fields of action]. / Schadstoffe im Innenraum ­ aktuelle Handlungsfelder.

People in Central Europe spend most of their time in private dwellings, offices, education centres or other public buildings. In these indoor places, they are exposed to a variety of gaseous or particulate pollutants that potentially exert adverse health effects. This work compiles current fields of action that are discussed in the public, among expert panels, and in the scientific community. These address ventilation in buildings, the impact of building product emissions and particulate matter sources on indoor air quality, the detection and prevention of mould as well as the assessment of indoor air quality using guidance values and the determination of the internal exposure by human biomonitoring. Indoor air quality appears as a dynamic field of action that has become more complex due to the interaction between new chemicals introduced into the indoor environment through a variety of products and the observed reduction of ventilation rates. Implications for human health have thus become less predictable.

Assessing Human Exposure to Organic Pollutants in the Indoor Environment.

There is an ongoing probing of the role of chemicals in the indoor environment. The majority of potential target substances are so-called very volatile, volatile, and semi-volatile organic compounds (VVOCs, VOCs, and SVOCs). Depending on their physical properties and the mass transfer conditions, they are distributed in or between the gas phase, particle phase, settled house dust, surface films, clothing, and other fabrics as well as the exposed skin and hair of the occupants themselves. Therefore, inhalation, ingestion, and dermal uptake all must be considered as relevant pathways for exposure assessment in human habitats. Exposure to VVOCs, VOCs, and SVOCs can be estimated by measuring their concentrations in relevant indoor compartments or by determining the amounts of the target compounds and/or their metabolites in urine and blood. Assessing the various routes of exposure often requires a combination of sophisticated and interdisciplinary theoretical background and experimental techniques. Consequently, close communication and collaboration between chemical and exposure scientists are needed to achieve a better understanding of human exposure to chemical substances in various indoor environments. Embedded in the toxicological context, this is the basis for assessing the corresponding health risks and for determining control strategies or approaches to limit such risks.

Dermal Uptake of Benzophenone-3 from Clothing.

Benzophenone-3 (also known as BP-3 or oxybenzone) is added to sunscreens, plastics, and some coatings to filter UV radiation. The suspected endocrine disruptor BP-3 has been detected in the air and settled dust of homes and is expected to redistribute from its original sources to other indoor compartments, including clothing. Given its physical and chemical properties, we hypothesized that dermal uptake from clothing could contribute to the body burden of this compound. First, cotton shirts were exposed to air at an elevated concentration of BP-3 for 32 days; the final air concentration was 4.4 µg/m3. Next, three participants wore the exposed shirts for 3 h. After 3 h of exposure, participants wore their usual clothing during the collection of urine samples for the next 48 h. Urine was analyzed for BP-3, a metabolite (BP-1), and six other UV filters. The rate of urinary excretion of the sum of BP-1 and BP-3 increased for all participants during and following the 3 h of exposure. The summed mass of BP-1 and BP-3 excreted during the first 24 h attributable to wearing exposed t-shirts were 12, 9.9, and 82 µg for participants 1, 2, and 3, respectively. Analysis of these results, coupled with predictions of steady-state models, suggest that dermal uptake of BP-3 from clothing could meaningfully contribute to overall body burden.