Multimedia Fate Model Research Articles

Air toxics matter to more than just air

The U.S. EPA regulates hazardous air pollution under the Clean Air Act, designating 188 substances as ‘air toxics’. Despite this designation, air pollutants may partition to other environmental compartments and present risks through exposure routes other than inhalation. We use the USEtox multi-media fate model to determine which exposure routes contribute to overall intake fraction and disease risk for 60 air toxics that are present in the model. Inhalation was the dominant exposure route for intake fraction for the majority of air toxics considered, but for 13 cases (>20%), ingestion was dominant, particularly through consumption of above-ground produce. Disease risk showed similar patterns, with a contribution from inhalation of higher than 90% for approximately half of the air toxics considered and higher than 50% for another quarter, but with a dominant contribution from ingestion for the remaining quarter of substances. The results emphasize the continued need for careful communication of chemical risks that reflects complex partitioning and multiple potential exposure routes.

Can next generation ecological risk assessment decisions be made today?―A case study of regulatory risk assessment in the United States

We examined the need for new in vivo avian toxicity testing for three common industrial chemicals (1,2 dichloropropane, 1,1,2-trichloroethane and triphenyl phosphate) based on estimated avian exposures using fugacity and multimedia fate models for current conditions of use compared to hazard information including existing in vivo test data for the chemicals and analogs, interspecies correlation estimates and results from hundreds of acute avian dietary toxicity studies. The data indicated that acute avian toxicity is not likely to be observed below 10 ppm in the diet for any chemical with the exception of those with a specific mode of toxic action. Modeling indicated low exposure potential for terrestrial birds to any of the three chemicals, with estimated dietary concentration of less than 0.001 ppm. Despite uncertainty associated with the underlying data sources, the four order of magnitude gap between potential exposure and a minimum hazard threshold suggests that additional avian in vivo testing would not generate valuable data. However, a weight of evidence approach for integrating data is necessary to engender greater confidence among government decision-makers in cases where data from a particular in vivo study is not expected to improve risk decision-making and an existing data gap can remain unfilled.

Cadmium accumulation in farmlands through irrigation: evidence from multimedia fate modeling and scenario simulations

The studies of heavy metal input and output fluxes from farmland soils will contribute to sustainable agricultural practices. However, debate on the primary pollution to crops has not resulted in the emergence of practical remediation strategies. Hence, the flux should be identified with precision for targeted pollution control. In this study, a catchment downstream of a metal mining area was selected for investigation of Cadmium pollution in the topsoil of farmlands, including the input and output fluxes in different environmental media. The results showed that irrigation was the main input source of Cd to soil, accounting for more than 75%, in which the contribution of dissolved Cd in water was 1–2 orders of magnitude higher than that of Cd adsorbed on suspended particles. Crop harvesting, surface runoff, and leaching were the main Cd output pathways from this area. The dynamic prediction results under different scenarios showed that Cd in farmland soil would be in a cumulative state in the following years by 2050. Straw removing could significantly reduce Cd accumulation in farmland soil. In addition, the substantial increase of crop yield in the future would increase the Cd output flux. This work revealed the accumulation pattern of Cd in farmland soils, and will aid in the development of remediation strategies for cadmium contamination of agricultural soils.

Microplastic aquatic impacts included in Life Cycle Assessment

Although Life Cycle Impact Assessment (LCIA) methods assess a wide range of environmental impacts, ecological impacts of plastic pollution are not commonly included. Here, characterization factors of Polypropylene (PP), Low density polyethylene (LDPE) and Polyethylene Terephthalate (PET) microplastics were assessed. Fate was assessed through the multimedia fate model Simplebox4Plastics. Ecological effects were based on species sensitivity distributions. Macroplastic impacts were included though a conversion fraction. The characterization factors were included in ReCipe2016 method and applied to two consumer packaging films to show the relevance of including plastic pollution in LCAs. Plastic losses were assessed using material flow analysis. The freshwater and marine ecotoxicity midpoint indicators were dominated by plastic pollution impacts, whilst these impacts were limited on ecosystem quality as endpoint. Extending this methodology to additional polymers and additional methodological developments will help to obtain a more complete picture of plastic pollution in LCA and to identify effective mitigation options.

Batch equilibrium experiments and modeling reveal weak temperature dependence of cyclic volatile methylsiloxane sorption in soil/sediment organic carbon-water systems

The organic carbon normalized partition coefficient, KOC, describes the equilibrium distribution of a chemical between water and organic carbon in soil or sediment. It is a key parameter in evaluating chemical persistence, mass distribution, and transport using multimedia fate and transport models. Considerable uncertainty remains about the KOC values of cyclic volatile methylsiloxane (cVMS) compounds, and in particular the dependence of KOC on temperature. In this study, we used a batch equilibrium (BE) method to measure KOC values and their temperature dependence between ∼5 and 25 °C for octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) with soil and sediments. Approximate log KOC values at 25 °C were 4.5–5.0 for D4 and 5.5–6.1 for D5 with different sorbents, and decreased by 0.3 log units or less at 4–5 °C. Enthalpies of sorption, ΔHOC, obtained for the different sorbents ranged from +7.2 to +16 kJ mol−1, with average values of +7.9 and +13 kJ mol−1 for D4 and D5, respectively. These values differ in magnitude and direction from those reported elsewhere based on KOC values determined by a novel dynamic purge-and-trap (PnT) method, but are consistent with predictions based on their solvation properties. A new fugacity-based multimedia model incorporating sorption/desorption kinetics was developed and used to predict concentrations in the phases of BE and PnT systems during desorption of cVMS under different experimental and ideal conditions. Model simulations suggested that KOC values for cVMS compounds derived from the PnT systems could be influenced by sorption disequilibrium between water and solids controlled by desorption rates from the particle phase to water, and subsequent losses due to volatilization and degradation. This has the potential to result in overestimation of KOC values when fitting the experimental data of cVMS mass remaining in a PnT system over time, which could explain the observed differences between the methods.

An integrated multimedia fate modeling framework for identifying mitigation strategy of antibiotic ecological risks: A case study in a peri-urban river

Antibiotics have been heavily used over the past decades, resulting in their frequent detections in rivers and increasing ecological risks. Recognizing characteristics of antibiotic ecological risks (AERs) and making effective strategies to mitigate the AERs are essential to ensure the safety of aquatic ecosystem and public health. In this study, an integrated technological framework has been proposed toward identifying management options for reducing AERs by jointly utilizing multimedia fugacity modelling and ecotoxicological risk assessment, and applied to characterize the AERs in a peri-urban river in Beijing. Specifically, a level III fugacity model has been successfully established to simulate the fate of antibiotics in the environment, and the manageable parameters have been screened out via sensitivity analysis of the model. Then the validated fugacity model has been used for scenario modellings to optimize mitigation strategies of AERs. Results show most of the antibiotics considered are frequently detected in the river, and pose medium or high risks to aquatic organisms. Relatively, the macrolides and fluoroquinolones present higher ecotoxicological risks than sulfonamides and tetracyclines. Furthermore, the mixture risk quotient and predictive equation of concentration addition suggest joint and synergistic/antagonistic effects of AERs for multiple or binary antibiotics in the environment. Largely, the concentrations of antibiotics in the river are determined by the source emissions into water and soil. Scenario modellings show the improvement of antibiotic removal rates would be considered preferentially to mitigate the AERs. Also, controlling human consumption is conducive to reducing the risks posed by tetracyclines, macrolides and trimethoprim, while controlling animal consumption would benefit the reduction for sulfonamides. Overall, the joint strategy presents the greatest reduction of AERs by reducing antibiotic consumption and together improving sewage treatment rate and antibiotic removal rate. The study provides us a useful guideline to make ecological risk-based mitigation strategy for reducing AERs in environment.

Coupled multimedia fate and bioaccumulation models for predicting fate of florfenicol and fluoroquinolones in water and fish organs in the seasonal ice-sealed reservoir

Ice formation in reservoirs could promote the accumulation of antibiotics in fish, potentially leading to elevated concentrations in fish muscles, kidneys, and livers. However, for the seasonal ice-sealed reservoirs, antibiotic sampling and detecting conditions in water and fish are normally limited by the ice cover. Additionally, previous studies on the prediction of antibiotics accumulated in seasonal ice-sealed reservoir fish are scarce. This study presents a coupled model incorporating a multimedia fate model and a bioaccumulation model to predict antibiotic fate in water and the muscles, kidneys, and livers of fish in seasonal ice-sealed reservoirs. Prediction concentrations of florfenicol were higher than those of ofloxacin and norfloxacin in both water and fish from the seasonal ice-sealed reservoir. Log bioaccumulation factors of antibiotics in Cyprinus carpio and Hypophthalmichthys nobilis in January 2021 were higher than those in October 2020 by 21.5% and 12.6%, respectively. Antibiotics mean transfer fluxes from water to fish muscles, kidneys, and livers increased owing to the reservoir ice-cover formation date advancing by 13.0%, 77.1%, and 61.0%, respectively. This work provides a modeling tool for investigating the fate and mass transfer flux of antibiotics in biological and environmental phases in seasonal ice-sealed reservoirs.

Predicting the contribution of a local emission source in mid-range transport of DDT and its deposition in terrestrial and aquatic ecosystems in Northern Italy

A recently developed dynamic multiple box multimedia fate model (Gridded-SoilPlusVeg, or GSPV) was developed and implemented to account for the environmental variation and the effect of directional advective transport of chemicals towards different compartments and geographical locations. A chemical plant located in Pieve Vergonte in Ossola Valley produced and emitted DDTs for around 50 years. In the previous study the fate and transport of p,p’-DDT emitted from the chemical plant were evaluated in nearby areas (up to 12 km). In this paper, the GSPV model was run for p,p’-DDT from its production period and decades after the production stop in 1996 (a total of 100 years) for a much larger study area (40,000 km2) in order to evaluate the contribution of a local source on a larger scale. Additionally, the deposition fluxes into the lakes were calculated and were used as input into a dynamic fugacity-based aquatic model to calculate DDT concentration in water and sediments of three Prealpine lakes: Lake Maggiore, Lake Como and Lake Lugano. The results of the simulations were compared with the monitoring and literature data. The results obtained from GSPV allowed to estimate the atmospheric deposition fluxes and identify the role of this source for the regional scale contamination in terrestrial and aquatic ecosystems.

Optimizing the multimedia fate model for characterizing environmental risks of florfenicol in seasonally ice-covered reservoirs

Seasonally ice-covered reservoirs have both freeze-thaw and artificial regulation characteristics which could cause the accumulation of antibiotics. Florfenicol, one of the most widely used veterinary antibiotics, with an environmental persistence due to its fluorinated substituents has been detected in the suburban drinking water source reservoirs. In this study, a four-level fugacity model that is appropriate for ice-water-sediment systems was developed to predict the fate of florfenicol and assess its ecological risk in seasonally ice-covered reservoirs. The effects of freeze-thaw and artificial regulation processes on the volume variation of ice and water were considered by the model. The simulation accuracies in ice and water in the model were improved by 3.9% and 17.7%, respectively, compared with the traditional model. The results of mass transfer analysis showed that the inflow of florfenicol in tributaries and the volume variation of ice and water were the major factors influencing the concentration variation of florfenicol in the seasonally ice-covered reservoir. Additionally, ecological risk analysis showed that the values of risk quotients ranged from 0.019 to 0.038 which was consistently at a low ecological risk level. Our findings provide a modeling tool for predicting the fate of antibiotics with persistence and assessing their ecological risks in seasonally freeze-thaw reservoirs in cold regions.

A method for simulating spatial fates of chemicals in flowing lake systems: Application to phthalates in a lake

In order to describe spatio-temporal distribution of chemicals in flowing lake systems, a dynamic multimedia fate model of chemicals with spatial differentiation was constructed by coupling the level IV fugacity model with lake hydrodynamics. It was successfully applied to four phthalates (PAEs) in a lake recharged by reclaimed water and its accuracy was verified. Results show that under the long-term influence of flow field, the distributions of PAEs in both lake water and sediment have significant spatial heterogeneity of 2∼5 orders of magnitude, but present different distribution rules, which was explained by analysis of PAE transfer fluxes. The spatial distribution of PAEs in the water column depends on hydrodynamic conditions and whether the primary source is reclaimed water or atmospheric input. Slow water exchange and flow speed promote the migration of PAEs from water to sediment, causing them to always accumulate in sediments far away from the recharging inlet. Uncertainty and sensitivity analysis show that the PAE concentrations in water phase are mainly affected by emission and physicochemical parameters, while those in sediment phase are also sensitive to environmental parameters. The model can provide important information and accurate data support for the scientific management of chemicals in flowing lake systems.

Octanol/Air Partition Coefficient─A General-Purpose Fragment Model to Predict Log Koa from Molecular Structure.

The octanol/air partition coefficient Koa is important for assessing the bioconcentration of airborne xenobiotics in foliage and in air-breathing organisms. Moreover, Koa informs about compound partitioning to aerosols and indoor dust, and complements the octanol/water partition coefficient Kow and the air/water partition coefficient Kaw for multimedia fate modeling. Experimental log Koa at 25 °C has been collected from literature for 2161 compounds with molecular weights from 16 to 959 Da. The curated data set covers 18.2 log units (from -1.0 to 17.2). A newly developed fragment model for predicting log Koa from molecular structure outperforms COSMOtherm, EPI-Suite KOAWIN, OPERA, and linear solvation energy relationships (LSERs) regarding the root-mean-squared error (rms) and the maximum negative and positive errors (mne and mpe) (rms: 0.57 vs 0.86 vs 1.09 vs 1.19 vs 1.05-1.53, mne: -2.55 vs -3.95 vs -7.51 vs -7.54 vs (-5.63) - (-7.34), mpe: 2.91 vs 5.97 vs 7.54 vs 4.24 vs 6.89-10.2 log units). The prediction capability, statistical robustness, and sound mechanistic basis are demonstrated through initial separation into a training and prediction set (80:20%), mutual leave-50%-out validation, and target value scrambling in terms of temporarily wrong compound-Koa allocations. The new general-purpose model is implemented in a fully automatized form in the ChemProp software available to the public. Regarding Koa indirectly determined through Kow and Kaw, a new approach is developed to convert from wet to dry octanol, enabling higher consistency in experimental (and thus also predicted) Koa.

Predicting the regional contamination evolution of DDT for 100-years with a new gridded spatial and dynamic multimedia fate model

In 1996 high dichlorodiphenyltrichloroethane (DDT) concentrations were found in Lake Maggiore (Italy) fish and sediments. DDT was produced by a chemical company located in a subalpine valley (Ossola valley, Piedmont Region, Italy), and ended up in the Toce River, a tributary of Lake Maggiore. In the area surrounding the chemical plant, high DDT concentrations in soil and vegetation were found after subsequent investigations. The quantification of the release from contaminated soil and the following migration toward downwind areas, deposition to the soil, and further evaporation plays an important role in understanding future DDT trends in soil and the atmosphere. To study this phenomenon, soil, and vegetation from Ossola Valley were monitored in 2001 and 2011. The concentration values obtained (soils: 0.05 to 1 μg/g; vegetation 2–100 ng/g), allowed to reconstruct the contamination gradient in the valley and were used to develop and calibrate a spatially resolved multimedia fugacity model. The model accounts for spatial and temporal dynamicity of environmental characteristics such as wind speed and direction, variable air compartment height etc., and simulates the fate and transport of chemicals on a local scale. The dynamic emission of DDT (about 13,000 kg for the 50 y production time) to the air was estimated and utilized for a 100-year simulation (from 1948 to 2048). The results obtained allowed to understand the temporal and spatial pattern of DDT contamination for a long period at a local scale as well as the potential contribution as a source potentially affecting sites at larger distances.

Environmental risk assessment for relevant ingredients in adhesives and sealants in commonplace industrial uses.

The Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals requires that the risks from the exposure to substances be controlled throughout the life cycle. This includes that conditions of safe use are established via risk assessments, documented and communicated to the downstream users of chemicals. This also applies to the environmental risks originating from downstream uses of chemicals, for instance, those from the industrial uses of adhesives and sealants. Upon application, these products form solid matrices with low emissions to the environment during the application. Hence, it is expected that environmental exposure is low, provided that good industrial practice is followed. To explore this, an environmental risk assessment for industrial uses of adhesives and sealants is performed for the environmentally most hazardous ingredients. These include several solvents, organotin catalysts, fillers, reactive resins, a pigment, and a preservative. Specific environmental release categories (SPERCs) developed by the Association of European Adhesives and Sealants Industries (FEICA) are used to derive emission estimates. In combination with multimedia fate modeling, the environmental risk in water, sediment, soil, and a sewage treatment plant is investigated. The assessment results indicate no environmental risk for any of the ingredients. The discussion evaluates the conservative nature of the assumed values of the use rates, the release factors, the fate modeling, and assessment factors. It concludes that their combination results in a sufficient degree of conservatism. In view of the conservative nature of the assessment and given that the worst‐case ingredients of adhesives and sealants are sufficiently controlled under the generically defined use conditions, it is concluded that the SPERCs used represent safe conditions for use, irrespective of the ingredient substances of adhesives and sealants. The essential SPERC information elements are identified for the purpose of communicating the conditions of safe use. The consolidation of this information in safety data sheets for adhesives and sealants is discussed. Environ Assess Manag 2022;18:1288–1296. © 2021 FEICA aisbl. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Evaluation of nano-silver concentrations using multi-media fate and transport models with different spatial resolutions.

Due to the complexity of the environmental matrix and the limitation of the detection level, it is important to use models to evaluate environmental exposure to nanomaterials. Based on this, this research established two multi-media fate and transport models of silver nanoparticles (AgNPs) with respective coarse and fine spatial resolutions. Using the case of the spatial distribution of AgNPs in the Xiangjiang River, China, we compared how the spatial resolution of a model impacts modeling results. The results show that the process of heterogeneous aggregation has the greatest impact on the modeled concentration of AgNPs in water, and the heterogeneous aggregation of free AgNPs with natural colloids and settling down to sediments is the dominant mechanism responsible for the loss of AgNPs. In addition, the use of different spatial resolutions gives similar trends in the modeled AgNPs concentration, despite the difference in absolute levels. Our work also shows that the reliability and accuracy of the rate constant of heterogeneous aggregation has a great influence on the modeled AgNPs concentrations.

Modeling multimedia fate and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the coastal regions of the Bohai and Yellow Seas

Using an improved multimedia fate model, this study simulated the spatial distributions, partitioning behaviors, and mass exchanges of PAH16 (16 species with priority by the USEPA) in multiple environmental compartments in the coastal regions of the Bohai and Yellow Seas, Northern China. The model predictions generally matched well with the measured results, as the deviations of most points were within one order of magnitude in the air, freshwater, and 3 soil compartments. The estimated concentrations of ΣPAH16 in the northern part were higher than those in the southern part, which was consistent with the emissions of each part. Approximately 97.6% of the ΣPAH16 mass was distributed in soils; therefore, soils served as the dominant sink of PAH16. The estimated net flux of ΣPAH16 from air to soil ranged from 0.4 to 10.7 mg/m2/year (an average of 3.2 mg/m2/year), and the estimated flux of deposition from air to soil fell in the range of 0.4–10.8 mg/m2/year (an average of 3.2 mg/m2/year), which served as the dominant process at the air-soil interface. The estimated net flux of ΣPAH16 from air to freshwater ranged from −15.3 to 9.4 mg/m2/year (an average of −0.3 mg/m2/year), and the reversed volatilization flux from freshwater to air ranged from 0.01 to 21.1 mg/m2/year (an average of 3.7 mg/m2/year). This situation indicated notable spatial variations and volatilization as the main process affecting the direction of net flux at the air-freshwater interface. Deterministic risk assessment and probabilistic risk assessment were conducted. The overall health risks of the studied regions were acceptable, while the excess lifetime cancer risk (ELCR) by air inhalation was greater than that by soil ingestion. CapsuleMultimedia fate model-predicted distributions and compositions of PAH16 in different compartments, compartmental exchange fluxes and directions, and deterministic and probabilistic ELCR via different exposure pathways were assessed.

Application of multimedia models for understanding the environmental behavior of volatile methylsiloxanes: Fate, transport, and bioaccumulation.

Multimedia fate and transport models (MFTMs) describe how chemicals behave in the environment based on their inherent properties and the characteristics of receiving systems. We critically review the use of MFTMs for understanding the behavior of volatile methylsiloxanes (VMS). MFTMs have been used to predict the fate of VMS in wastewater treatment, rivers, lakes, marine systems, and the atmosphere, and to assess bioaccumulation and trophic transfers. More widely, they have been used to assess the overall persistence, long‐range transport potential (LRTP), and the propensity for atmosphere–surface exchange. The application of MFTMs for VMS requires particularly careful selection of model inputs because the properties of VMS differ from those of most organic compounds. For example, although n‐octanol/water partition coefficient (K OW) values are high, air:water partition coefficient (K AW) values are also high and n‐octanol/air partition coefficient (K OA) values are relatively low. In addition, organic carbon/water partition coefficient (K OC) values are substantially lower than expectations based on K OW. This means that most empirical relationships between K OC and K OW are not appropriate. Good agreement between modeled and measured concentrations in air, sediment, and biota indicates that our understanding of environmental fate is reasonable. VMS compounds are “fliers” that principally partition to the atmosphere, implying high LRTP, although they have low redeposition potential. They are degraded in air (half‐lives 3–10 days) and, thus, have low overall persistence. In water, exposure can be limited by hydrolysis, volatilization, and partitioning to sediments (where degradation half‐lives are likely to be high). In food webs, they are influenced by metabolism in biota, which tends to drive trophic dilution (i.e., trophic magnification factors are often but not always <1). Key remaining uncertainties include the following: (i) the strength and direction of the temperature dependence for K OC; (ii) the fate of atmospheric reaction products; and (iii) the magnitude of emissions to wastewater. Integr Environ Assess Manag 2022;18:599–621. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Multimedia fate model and risk assessment of typical antibiotics in the integrated demonstration zone of the Yangtze River Delta, China

Due to the widespread consumption of antibiotics by humans and animals, antibiotic residues from human and animal excrements are released into the environment through domestic sewage and breeding wastewater, which ultimately affect the ecological environment and human health. In this study, the concentrations of 10 antibiotics in the air, water, soil, and sediment from 2013 to 2019 in Qingpu District of the integrated demonstration zone of the Yangtze River Delta were predicated by developing a dynamic Level IV fugacity model. The influence of seasonal environmental factors (e.g., temperature, rainfall) on the distribution and migration of antibiotics in multi-media was also explored. The simulation results show that the 10 antibiotics mainly existed in water and sediment. The concentrations of antibiotics in air, water, soil, and sediment were 0–7.629 × 10−14 ng/L, 1.187 × 10−10-16.793 ng/L, 1.042 × 10−14-3.500 × 10−11 ng/g and 8.015 × 10−12-14.188 ng/g, respectively. It was also found that the increase in temperature and rainfall can reduce the migration rate of some antibiotics into the water and sediment phases. The flux analysis of the cross-media migration and transformation of antibiotics in Qingpu District shows that advection was the prime input and output paths of antibiotics in the water. Moreover, the prime input and output paths of antibiotics in sediment were sedimentation from water to sediment and degradation. Sensitivity analysis shows that the characteristics of antibiotic emission, degradation rate, and Koc were the most influential parameters for target chemicals. The results of risk assessment based on Monte Carlo method reveal that the overall risk level of antibiotics in sediment was relatively risk-free, and the risk of antibiotics in water decreased in the order of tetracyclines > β-lactams > fluoroquinolones > macrolides > sulfonamides.

“Where do these chemicals come from?” Tracing-back chemical exposures to consumer products

BACKGROUND AND AIM: Non-targeted analysis has enabled us to screen biological samples for a broad spectrum of chemical compounds that would otherwise remain undetected with traditional targeted analytical techniques. While our previous studies have presented a number of man-made chemicals in human serum, the sources of many of these chemicals remain unknown. The aim of our study was to understand the sources of a group of chemicals, some of which are not actively biomonitored, (n=18; phenols, surfactants and per- and polyfluoroalkyl substances) identified and quantified in 300 maternal and 300 cord matched blood samples collected at delivery and analyzed with a non-targeted analysis workflow. METHODS: We matched measured concentrations in serum to questionnaire responses about participants’ use of consumer products in homes (n total = 148 questions) and evaluated their relationship using linear models. We also used an indoor environment multimedia fate model to test observed relationships by simulating concentrations of the chemicals in the carpets, furniture, dust and indoor air to evaluate the potential of exposure based on chemical mobility. RESULTS:We found strong positive correlations (r 0.5 and p-value 0.05) between concentrations in serum and carpets (installation and treatment), furniture (renovation and treatment), and floor (installation and treatment). One example where we measured widespread exposure in pregnant women is 4-nitrophenol. Our modeling calculations estimated that when 4-nitrophenol is emitted from carpets, it is expected to be resuspended and redeposited on vinyl floors and other surfaces leaving only a small fraction in the air available for inhalation (0.01 % of the total mass). Our modeling calculations also estimated that, due to its low volatility, the main route of exposure to 4-nitrophenol in the indoor environment is through dermal contact. CONCLUSIONS:Integrating non-targeted analysis with questionnaire data and multimedia modeling provided unique insights into the sources of environmental chemicals and pathways of exposure. KEYWORDS: exposome, non-targeted analysis, chemicals, exposure, modeling

Introducing a nested multimedia fate and transport model for organic contaminants (NEM).

Some organic contaminants, including the persistent organic pollutants (POPs), have achieved global distribution through long range atmospheric transport (LRAT). Regulatory efforts, monitoring programs and modelling studies address the LRAT of POPs on national, continental (e.g. Europe) and/or global scales. Whereas national and continental-scale models require estimates of the input of globally dispersed chemicals from outside of the model domain, existing global-scale models either have relatively coarse spatial resolution or are so computationally demanding that it limits their usefulness. Here we introduce the Nested Exposure Model (NEM), which is a multimedia fate and transport model that is global in scale yet can achieve high spatial resolution of a user-defined target region without huge computational demands. Evaluating NEM by comparing model predictions for PCB-153 in air with measurements at nine long-term monitoring sites of the European Monitoring and Evaluation Programme (EMEP) reveals that nested simulations at a resolution of 1°× 1° yield results within a factor of 1.5 of observations at sites in northern Europe. At this resolution, the model attributes more than 90% of the atmospheric burden within any of the grid cells containing an EMEP site to advective atmospheric transport from elsewhere. Deteriorating model performance with decreasing resolution (15°× 15°, 5°× 5° and 1°× 1°), manifested by overestimation of concentrations across most of northern Europe by more than a factor of 3, illustrates the effect of numerical diffusion. Finally, we apply the model to demonstrate how the choice of spatial resolution affect predictions of atmospheric deposition to the Baltic Sea. While we envisage that NEM may be used for a wide range of applications in the future, further evaluation will be required to delineate the boundaries of applicability towards chemicals with divergent fate properties as well as in environmental media other than air.

Simulating behavior of petroleum compounds during refinery effluent treatment using the SimpleTreat model

Distribution and elimination of petroleum products can be predicted in aerobic wastewater treatment plants (WWTPs) using models such as multimedia fate model SimpleTreat. An advantage of the SimpleTreat model is that it only requires a few basic properties of a chemical in wastewater to calculate partitioning, biodegradation and ultimately emissions to air, surface water and produced sludge. The SimpleTreat model structure reflects a WWTP scheme. However, refinery WWTPs typically incorporate more advanced treatment processes such as dissolved air flotation (DAF), a process that clarifies wastewaters by the removal of suspended matter such as oil or solids. The objective of this work was to develop a WWTP removal model that includes DAF treatment. To understand how including a DAF in the model affects the predicted concentrations of petroleum constituents in effluent, we replaced the primary sedimentation module in SimpleTreat with a module simulating DAF. Subsequently, we compared results from the WWTP-DAF model with results obtained with the original SimpleTreat model for a library of over 1500 representative hydrocarbon constituents. The increased air-water exchange in a WWTP-DAF unit resulted in higher predicted removal of volatile constituents. Predicted removal with DAF was on average 17% larger than removal with primary sedimentation. We compared modelled results with measured removal data from the literature, which supported that this model refinement continues to improve the technical basis of assessment of petroleum products.