Targeted Use of Sustainable Aviation Fuel to Maximize Climate Benefits.

Sustainable aviation fuel (SAF) can reduce aviation's CO2 and non-CO2 impacts. We quantify the change in contrail properties and climate forcing in the North Atlantic resulting from different blending ratios of SAF and demonstrate that intelligently allocating the limited SAF supply could multiply its overall climate benefit by factors of 9-15. A fleetwide adoption of 100% SAF increases contrail occurrence (+5%), but lower nonvolatile particle emissions (-52%) reduce the annual mean contrail net radiative forcing (-44%), adding to climate gains from reduced life cycle CO2 emissions. However, in the short term, SAF supply will be constrained. SAF blended at a 1% ratio and uniformly distributed to all transatlantic flights would reduce both the annual contrail energy forcing (EFcontrail) and the total energy forcing (EFtotal, contrails + change in CO2 life cycle emissions) by ∼0.6%. Instead, targeting the same quantity of SAF at a 50% blend ratio to ∼2% of flights responsible for the most highly warming contrails reduces EFcontrail and EFtotal by ∼10 and ∼6%, respectively. Acknowledging forecasting uncertainties, SAF blended at lower ratios (10%) and distributed to more flights (∼9%) still reduces EFcontrail (∼5%) and EFtotal (∼3%). Both strategies deploy SAF on flights with engine particle emissions exceeding 1012 m-1, at night-time, and in winter.

Impact of Alternative Jet Fuels on Engine Exhaust Composition During the 2015 ECLIF Ground-Based Measurements Campaign.

The application of fuels from renewable sources ("alternative fuels") in aviation is important for the reduction of anthropogenic carbon dioxide emissions, but may also attribute to reduced release of particles from jet engines. The present experiment describes ground-based measurements in the framework of the ECLIF (Emission and Climate Impact of Alternative Fuels) campaign using an Airbus A320 (V2527-A5 engines) burning six fuels of chemically different composition. Two reference Jet A-1 with slightly different chemical parameters were applied and further used in combination with a Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK) to prepare three semi synthetic jet fuels (SSJF) of different aromatic content. In addition, one commercially available fully synthetic jet fuel (FSJF) featured the lowest aromatic content of the fuel selection. Neither the release of nitrogen oxide or carbon monoxide was significantly affected by the different fuel composition. The measured particle emission indices showed a reduction up to 50% (number) and 70% (mass) for two alternative jet fuels (FSJF, SSJF2) at low power settings in comparison to the reference fuels. The reduction is less pronounced at higher operating conditions but the release of particle number and particle mass is still significantly lower for the alternative fuels than for both reference fuels. The observed correlation between emitted particle mass and fuel aromatics is not strict. Here, the H/C ratio is a better indicator for soot emission.

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.

A permeation-controlled formaldehyde reference source for application in environmental test chambers.

In a wide range of indoor air pollutants, formaldehyde is one of the most-used and best-known substances. In order to protect human health, many countries have established threshold values for the release of formaldehyde from miscellaneous products and revise them constantly. Compliance with these regulations is usually assessed by emission test chamber measurements or derived methods. To control and improve the mechanisms of an emission test chamber, a reliable reference source with sample mimicking emission properties is required but not available so far. This study describes a permeation-controlled reference source based on the application of paraformaldehyde as formaldehyde releasing polymeric compound. Interactions between the formaldehyde release of the source and the governing chamber parameters temperature, relative humidity and air velocity were investigated in 1 m3 emission chambers. Depending on the conditions, constant formaldehyde concentrations between approximately 10 ppb and 150 ppb can be adjusted for up to 600 h. A linear correlation between the logarithm of the chamber concentration and the reciprocal temperature was found. The results support the feasibility of the source for validation of emission test chamber performance.

Linking a dermal permeation and an inhalation model to a simple pharmacokinetic model to study airborne exposure to di(n-butyl) phthalate.

Six males clad only in shorts were exposed to high levels of airborne di(n-butyl) phthalate (DnBP) and diethyl phthalate (DEP) in chamber experiments conducted in 2014. In two 6 h sessions, the subjects were exposed only dermally while breathing clean air from a hood, and both dermally and via inhalation when exposed without a hood. Full urine samples were taken before, during, and for 48 h after leaving the chamber and measured for key DnBP and DEP metabolites. The data clearly demonstrated high levels of DnBP and DEP metabolite excretions while in the chamber and during the first 24 h once leaving the chamber under both conditions. The data for DnBP were used in a modeling exercise linking dose models for inhalation and transdermal permeation with a simple pharmacokinetic model that predicted timing and mass of metabolite excretions. These models were developed and calibrated independent of these experiments. Tests included modeling of the "hood-on" (transdermal penetration only), "hood-off" (both inhalation and transdermal) scenarios, and a derived "inhalation-only" scenario. Results showed that the linked model tended to duplicate the pattern of excretion with regard to timing of peaks, decline of concentrations over time, and the ratio of DnBP metabolites. However, the transdermal model tended to overpredict penetration of DnBP such that predictions of metabolite excretions were between 1.1 and 4.5 times higher than the cumulative excretion of DnBP metabolites over the 54 h of the simulation. A similar overprediction was not seen for the "inhalation-only" simulations. Possible explanations and model refinements for these overpredictions are discussed. In a demonstration of the linked model designed to characterize general population exposures to typical airborne indoor concentrations of DnBP in the United States, it was estimated that up to one-quarter of total exposures could be due to inhalation and dermal uptake.

Children's well-being at schools: Impact of climatic conditions and air pollution.

Human civilization is currently facing two particular challenges: population growth with a strong trend towards urbanization and climate change. The latter is now no longer seriously questioned. The primary concern is to limit anthropogenic climate change and to adapt our societies to its effects. Schools are a key part of the structure of our societies. If future generations are to take control of the manifold global problems, we have to offer our children the best possible infrastructure for their education: not only in terms of the didactic concepts, but also with regard to the climatic conditions in the school environment. Between the ages of 6 and 19, children spend up to 8h a day in classrooms. The conditions are, however, often inacceptable and regardless of the geographic situation, all the current studies report similar problems: classrooms being too small for the high number of school children, poor ventilation concepts, considerable outdoor air pollution and strong sources of indoor air pollution. There have been discussions about a beneficial and healthy air quality in classrooms for many years now and in recent years extensive studies have been carried out worldwide. The problems have been clearly outlined on a scientific level and there are prudent and feasible concepts to improve the situation. The growing number of publications also highlights the importance of this subject. High carbon dioxide concentrations in classrooms, which indicate poor ventilation conditions, and the increasing particle matter in urban outdoor air have, in particular, been identified as primary causes of poor indoor air quality in schools. Despite this, the conditions in most schools continue to be in need of improvement. There are many reasons for this. In some cases, the local administrative bodies do not have the budgets required to address such concerns, in other cases regulations and laws stand in contradiction to the demands for better indoor air quality, and sometimes the problems are simply ignored. This review summarizes the current results and knowledge gained from the scientific literature on air quality in classrooms. Possible scenarios for the future are discussed and guideline values proposed which can serve to help authorities, government organizations and commissions improve the situation on a global level.

Role of clothing in both accelerating and impeding dermal absorption of airborne SVOCs.

To assess the influence of clothing on dermal uptake of semi-volatile organic compounds (SVOCs), we measured uptake of selected airborne phthalates for an individual wearing clean clothes or air-exposed clothes and compared these results with dermal uptake for bare-skinned individuals under otherwise identical experimental conditions. Using a breathing hood to isolate dermal from inhalation uptake, we measured urinary metabolites of diethylphthalate (DEP) and di-n-butylphthalate (DnBP) from an individual exposed to known concentrations of these compounds for 6 h in an experimental chamber. The individual wore either clean (fresh) cotton clothes or cotton clothes that had been exposed to the same chamber air concentrations for 9 days. For a 6-h exposure, the net amounts of DEP and DnBP absorbed when wearing fresh clothes were, respectively, 0.017 and 0.007 µg/kg/(µg/m(3)); for exposed clothes the results were 0.178 and 0.261 µg/kg/(µg/m(3)), respectively (values normalized by air concentration and body mass). When compared against the average results for bare-skinned participants, clean clothes were protective, whereas exposed clothes increased dermal uptake for DEP and DnBP by factors of 3.3 and 6.5, respectively. Even for non-occupational environments, wearing clothing that has adsorbed/absorbed indoor air pollutants can increase dermal uptake of SVOCs by substantial amounts relative to bare skin.

Transdermal Uptake of Diethyl Phthalate and Di(n-butyl) Phthalate Directly from Air: Experimental Verification.

BACKGROUND: Fundamental considerations indicate that, for certain phthalate esters, dermal absorption from air is an uptake pathway that is comparable to or greater than inhalation. Yet this pathway has not been experimentally evaluated and has been largely overlooked when assessing uptake of phthalate esters. OBJECTIVES: This study investigated transdermal uptake, directly from air, of diethyl phthalate (DEP) and di(n-butyl) phthalate (DnBP) in humans. METHODS: In a series of experiments, six human participants were exposed for 6 hr in a chamber containing deliberately elevated air concentrations of DEP and DnBP. The participants either wore a hood and breathed air with phthalate concentrations substantially below those in the chamber or did not wear a hood and breathed chamber air. All urinations were collected from initiation of exposure until 54 hr later. Metabolites of DEP and DnBP were measured in these samples and extrapolated to parent phthalate intakes, corrected for background and hood air exposures. RESULTS: For DEP, the median dermal uptake directly from air was 4.0 µg/(µg/m(3) in air) compared with an inhalation intake of 3.8 µg/(µg/m(3) in air). For DnBP, the median dermal uptake from air was 3.1 µg/(µg/m(3) in air) compared with an inhalation intake of 3.9 µg/(µg/m(3) in air). CONCLUSIONS: This study shows that dermal uptake directly from air can be a meaningful exposure pathway for DEP and DnBP. For other semivolatile organic compounds (SVOCs) whose molecular weight and lipid/air partition coefficient are in the appropriate range, direct absorption from air is also anticipated to be significant.

Latex paint as a delivery vehicle for diethylphthalate and di-n-butylphthalate: predictable boundary layer concentrations and emission rates.

The description of emission processes of volatile and semi-volatile organic compounds (VOCs and SVOCs) from building products requires a detailed understanding of the material and the air flow conditions at the surface boundary. The mass flux between the surface of the material and air depends on the mass transfer coefficient (hm) through the boundary layer, the gas phase concentration of the target compound immediately adjacent to the material (y0), and the gas-phase concentration in bulk air (y(t)). In the present study emission experiments were performed in two chambers of quite different sizes (0.25 m(3) and 55 m(3)), and, in the larger chamber, at two different temperatures (23°C and 30°C). The emitting material was latex wall paint that had been doped with two plasticizers, diethylphthalate (DEP) and di-n-butylphthalate (DnBP). The phthalate content in the paint was varied in the small chamber experiment to evaluate the impact of the initial concentration in the bulk material (C0) on the emission rate. Boundary layer theory was applied to calculate hm for the specific phthalates from the Sherwood number (Sh) and the diffusion coefficient (Dair). Then y0 was determined based on the bulk gas-phase concentration at steady state (y¯). For both, DEP and DnBP, the y0 obtained was lower than the respective saturation vapor pressure (Ps). Furthermore, for both phthalates in latex paint, the material/air partition coefficient (C0/y0) was close in value to the octanol/air partition coefficient (KOA). This study provides a basis for designing phthalate emitting reference materials that mimic the emission behavior of common building materials.

Chamber studies on nonvented decorative fireplaces using liquid or gelled ethanol fuel.

Decorative ethanol fireplaces are becoming more and more commonly used in many different countries. These fireplaces are constructed such that they have no fume extraction system, and so all of the gases from combustion, volatile organic compounds, and particulate emissions are released into the room. In order to determine the release behavior and the chemical composition of the emissions, a variety of combinations of ethanol fireplaces and fuels were examined in a 48 m(3) emission test chamber under typical living room environmental conditions. Four ethanol fireplaces with 8 different fuels (3 liquid samples, 5 gel-type samples) were tested. The ventilation conditions were set up corresponding to the manufacturers' recommendations and DIN 4734-1. The air concentrations in the chamber were evaluated based on guideline values for indoor air. Of the combustion gases examined, the quantity of carbon dioxide and nitrogen dioxide in particular were close to or even above the guideline values in many cases. A release of components of the fuel (e.g., the denaturing substances) was also detected in the chamber air. In two experiments, a benzene concentration of over 12 ppb and an increased formaldehyde concentration (>0.1 ppm) were identified in the chamber air. The ethanol fireplaces were--irrespective of the type of fuel used--strong sources of fine and ultrafine particles. Overall, ethanol fireplaces have a considerable influence on the quality of the indoor air due to the lack of ventilation. This aspect should--in addition to fire protection--be properly considered when using such devices.

Impact of operating wood-burning fireplace ovens on indoor air quality.

The use of combustion heat sources like wood-burning fireplaces has regained popularity in the past years due to increasing energy costs. While the outdoor emissions from wood ovens are strictly regulated in Germany, the indoor release of combustion products is rarely considered. Seven wood burning fireplaces were tested in private homes between November 2012 and March 2013. The indoor air quality was monitored before, during and after operation. The following parameters were measured: ultra-fine particles (5.6-560 nm), fine particles (0.3-20 µm), PM2.5, NOx, CO, CO2, formaldehyde, acetaldehyde, volatile organic compounds (VOCs) and benzo[a]pyrene (BaP). Most ovens were significant sources of particulate matter. In some cases, an increase of benzene and BaP concentrations was observed in the indoor air. The results illustrate that wood-burning fireplaces are potential sources of indoor air contaminants, especially ultra-fine particles. Under the aspect of lowering indoor air exchange rates and increasing the use of fuels with a net zero-carbon footprint, indoor combustion sources are an important topic for the future. With regards to consumer safety, product development and inspection should consider indoor air quality in addition to the present fire protection requirements.

Aerosols generated by hardcopy devices and other electrical appliances.

In recent years the pollution of indoor air with ultrafine particles has been an object of intensive research. Several studies have concurred in demonstrating that outdoor air makes only a limited contribution to polluting indoor air with ultrafine particles, provided significant sources in the immediate neighborhood are absent. Nowadays, electrical devices operated in homes and offices are identified as particle emission sources. A comparison of the emission rates can be made by calculating the total number of particles released with respect to the operating time. The identified particles are condensed semi-volatile organic compounds with a low percentage of non-volatile inorganic components. To characterize the indoor exposure to airborne particles, an algorithm has been developed which permits a realistic calculation of the particle intake and deposition in the human respiratory tract from measured size and time resolved particle number concentrations following the model of the International Commission on Radiological Protection.

Beyond phthalates: gas phase concentrations and modeled gas/particle distribution of modern plasticizers.

The ongoing health debate about polymer plasticizers based on the esters of phthalic acid, especially di(2-ethylhexyl) phthalate (DEHP), has caused a trend towards using phthalates of lower volatility such as diisononyl phthalate (DINP) and towards other acid esters, such as adipates, terephthalates, citrates, etc. Probably the most important of these so-called "alternative" plasticizers is diisononyl cyclohexane-1,2-dicarboxylate (DINCH). In the indoor environment, the continuously growing market share of this compound since its launch in 2002 is inter alia apparent from the increasing concentration of DINCH in settled house dust. From the epidemiological point of view there is considerable interest in identifying how semi-volatile organic compounds (SVOCs) distribute in the indoor environment, especially in air, airborne particles and sedimented house dust. This, however, requires reliable experimental concentration data for the different media and good measurements or estimates of their physical and chemical properties. This paper reports on air concentrations for DINP, DINCH, diisobutyl phthalate (DIBP), diisobutyl adipate (DIBA), diisobutyl succinate (DIBS) and diisobutyl glutarate (DIBG) from emission studies in the Field and Laboratory Emission Cell (FLEC). For DINP and DINCH it took about 50 days to reach the steady-state value: for four months no decay in the concentration could be observed. Moreover, vapor pressures p(0) and octanol-air partitioning coefficients K(OA) were obtained for 37 phthalate and non-phthalate plasticizers from two different algorithms: EPI Suite and SPARC. It is shown that calculated gas/particle partition coefficients K(p) and fractions can widely differ due to the uncertainty in the predicted p(0) and K(OA) values. For most of the investigated compounds reliable experimental vapor pressures are not available. Rough estimates can be obtained from the measured emission rate of the pure compound in a microchamber as is shown for di-n-butyl phthalate (DnBP), di(2-ethylhexyl) adipate(DEHA), tri(octyl) trimellitate (TOTM) and DEHP.

Characterization of particle emission from household electrical appliances.

The release of ultra-fine particles from equipment of daily use is currently a topic of high public concern. The present study reports on the measurement of 12 household appliances such as toasters, grills, and hair dryers in an emission test chamber regarding the release of particles between 5.6 and 560 nm. The devices were new at the time experiments started and had never been used for their original purpose. For instance, toasters and sandwich-makers were tested without the presence of food or residues from prior usage. During the experiments the devices released aerosols with count mean diameters mainly below 100 nm. Within the operating phase high quantities of 10 nm particles are released which form larger particles by agglomeration. The origin of the particles can be attributed to the heated surfaces but cleaning these surfaces only had a minor influence on the emission strength. The released particles are evaporated in a thermodenuder between 150 °C and 200 °C. These findings indicate the particles to be formed from semi-volatile organic compounds. However, the compounds are not located on the heated surfaces and are not released as supersaturated vapor because emission is continuous over the operating phase of the device. Furthermore, the contribution of oxygen to the formation process can be neglected because the emission can also be detected in a nitrogen atmosphere. However, the presence of additional organic compounds in the surrounding air was found to be influencing the growth of the particles within the operating phase. All in all the tested household appliances were strong particle emission sources even when there was no contact with food or clothing.

Ultra-fine particles release from hardcopy devices: sources, real-room measurements and efficiency of filter accessories.

The release of ultra-fine particles (UFP, d < 0.1 microm) from hardcopy devices such as laser printers into the indoor environment is currently a topic of high concern. The general emission behavior of a printer can be examined by conducting emission test chamber measurements with particle-counting devices. Chamber experiments with modified laser printers operated without toner or paper also revealed UFP emissions. On the basis of these results we reasonably doubt the opinion that UFPs primarily originate from the toner. Instead, the high-temperature fuser unit is assumed to be one source for ultra-fine particle emission. UFP release typically follows the flow path of the cooling air which may leave the printer casing at various points (e.g. the paper tray). This limits the usability of the commercial filter systems available because the released particles could leave the printer without passing through the filter. Chamber measurements with various filter systems retrofitted to a laser printer demonstrate different efficiencies of UFP reduction. Complementary experiments were carried out in an office room. Here the decay of the particle concentration after a print job was about ten times slower than in the test chamber. A toxicological assessment of the emitted particles requires that their chemical composition be known. Due to the low mass of the released UFPs chemical analysis needs a prior enrichment on a feasible media. Experiments using electrostatic precipitation showed a flame retardant (tri-xylyl phosphate) whose concentration on the media was dependent on the number of pages printed. Whether this compound was particle-bound could not be determined.

Evaluation of ultrafine particle emissions from laser printers using emission test chambers.

It has now been recognized that some hardcopy devices emit ultrafine particles (d(p) < 100 nm) during their operation. As a consequence, the time-dependent characterization of particle release from laser printers is of high interest in order to evaluate the exposure of office workers to such emissions. The emission profiles of different printers can be compared in test chambers using a standardized test protocol and measuring devices with high time resolution. The extraction of meaningful and comparable data from the obtained data set is a complex procedure due to the different emission behavior patterns of the printers. The calculation of the unit specific emission rate (SERu) is of limited use because the emission profiles during the printing process ranged between short-term bursts and constant particle release. Therefore, other parameters such as the particle loss-rate coefficient, beta, which provides information about the testing conditions, and the area belowthe time vs concentration curve, F, which characterizes the particle release, allow for a comparison of the different printer tests. Variations in the emission behavior could not be associated with specific manufacturers or product lines. In addition, when performing several print jobs on the same device, with only short pauses between jobs, the emission rate was reduced in some cases. This further complicates the ability to determine the influence of printer construction and consumables, such as toner and paper, on the concentration of particles emitted.