Conceptual Framework To Extend Life Cycle Assessment Using Near-Field Human Exposure Modeling and High-Throughput Tools for Chemicals.

Life Cycle Assessment (LCA) is a decision-making tool that accounts for multiple impacts across the life cycle of a product or service. This paper presents a conceptual framework to integrate human health impact assessment with risk screening approaches to extend LCA to include near-field chemical sources (e.g., those originating from consumer products and building materials) that have traditionally been excluded from LCA. A new generation of rapid human exposure modeling and high-throughput toxicity testing is transforming chemical risk prioritization and provides an opportunity for integration of screening-level risk assessment (RA) with LCA. The combined LCA and RA approach considers environmental impacts of products alongside risks to human health, which is consistent with regulatory frameworks addressing RA within a sustainability mindset. A case study is presented to juxtapose LCA and risk screening approaches for a chemical used in a consumer product. The case study demonstrates how these new risk screening tools can be used to inform toxicity impact estimates in LCA and highlights needs for future research. The framework provides a basis for developing tools and methods to support decision making on the use of chemicals in products.

Defining Product Intake Fraction to Quantify and Compare Exposure to Consumer Products.

There is a growing consciousness that exposure studies need to better cover near-field exposure associated with products use. To consistently and quantitatively compare human exposure to chemicals in consumer products, we introduce the concept of product intake fraction, as the fraction of a chemical within a product that is eventually taken in by the human population. This metric enables consistent comparison of exposures during consumer product use for different product-chemical combinations, exposure duration, exposure routes and pathways and for other life cycle stages. We present example applications of the product intake fraction concept, for two chemicals in two personal care products and two chemicals encapsulated in two articles, showing how intakes of these chemicals can primarily occur during product use. We demonstrate the utility of the product intake fraction and its application modalities within life cycle assessment and risk assessment contexts. The product intake fraction helps to provide a clear interface between the life cycle inventory and impact assessment phases, to identify best suited sentinel products and to calculate overall exposure to chemicals in consumer products, or back-calculate maximum allowable concentrations of substances inside products.

Risk-Based High-Throughput Chemical Screening and Prioritization using Exposure Models and in Vitro Bioactivity Assays.

We present a risk-based high-throughput screening (HTS) method to identify chemicals for potential health concerns or for which additional information is needed. The method is applied to 180 organic chemicals as a case study. We first obtain information on how the chemical is used and identify relevant use scenarios (e.g., dermal application, indoor emissions). For each chemical and use scenario, exposure models are then used to calculate a chemical intake fraction, or a product intake fraction, accounting for chemical properties and the exposed population. We then combine these intake fractions with use scenario-specific estimates of chemical quantity to calculate daily intake rates (iR; mg/kg/day). These intake rates are compared to oral equivalent doses (OED; mg/kg/day), calculated from a suite of ToxCast in vitro bioactivity assays using in vitro-to-in vivo extrapolation and reverse dosimetry. Bioactivity quotients (BQs) are calculated as iR/OED to obtain estimates of potential impact associated with each relevant use scenario. Of the 180 chemicals considered, 38 had maximum iRs exceeding minimum OEDs (i.e., BQs > 1). For most of these compounds, exposures are associated with direct intake, food/oral contact, or dermal exposure. The method provides high-throughput estimates of exposure and important input for decision makers to identify chemicals of concern for further evaluation with additional information or more refined models.

The magnitude and spatial range of current-use urban PCB and PBDE emissions estimated using a coupled multimedia and air transport model.

SO-MUM, a coupled atmospheric transport and multimedia urban model, was used to estimate spatially resolved (5 × 5 km(2)) air emissions and chemical fate based on measured air concentrations and chemical mass inventories within Toronto, Canada. Approximately 95% and 70% of Σ5PCBs (CB-28, -52, -101, -153, and -180) and Σ5PBDEs (BDE-28, -47, -100, -154, and -183) emissions of 17 (2-36) and 18 (3-42) kg y(-1), respectively, undergo atmospheric transport from the city, which is partly over Lake Ontario. The urban air plume was found to reach about 50 km for PCBs and PBDEs, in the direction of prevailing winds which is almost twice the distance of the wind-independent plume. The distance traveled by the plume is a function of prevailing wind velocity, the geographic distribution of the chemical inventory, and gas-particle partitioning. Soil wash-off of historically accumulated Σ5PCBs to surface water contributed ∼ 0.4 kg y(-1) (of mainly higher congeners) to near-shore Lake Ontario compared with volatilization of ∼ 6 kg y(-1) of mainly lighter congeners. Atmospheric emissions from primary sources followed by deposition to surface films and subsequent wash-off to surface water contributed ∼ 1 kg y(-1) and was the main route of Σ5PBDE loadings to near-shore Lake Ontario which acts as a net PBDE sink. Secondary emissions of PCBs and PBDEs from at least a ∼ 900,000 km(2) rural land area would be needed to produce the equivalent primary emissions as Toronto (∼ 640 km(2)). These results provide clear support for reducing inventories of these POPs.

From the city to the Lake: loadings of PCBs, PBDEs, PAHs and PCMs from Toronto to Lake Ontario.

Loadings from Toronto, Canada to Lake Ontario were quantified and major sources and pathways were identified, with the goal of informing opportunities for loading reductions. The contaminants were polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs) and polycyclic musks (PCMs). Loadings were calculated from measured concentrations for three major pathways: atmospheric processes, tributary runoff, and wastewater treatment plant (WWTP) effluents. Although atmospheric deposition to the Great Lakes has received the greatest attention, this was the dominant loading pathway for PCBs only (17 ± 5.3 kg/y or 66% of total loadings). PCB loadings reflected elevated urban PCB air concentrations due to, predominantly, primary emissions. These loadings contribute to consumption advisories for nearshore fish. PBDE loadings to the lake, again from mainly primary emissions, were 48% (9.1 ± 1.3 kg/y) and 42% (8.0 ± 5.7 kg/y) via tributaries and WWTPs, respectively, consistent with emissions deposited and subsequently washed-off of urban surfaces and emissions to the sewage system. PAHs loadings of 1600 ± 280 kg/y (71%) from tributaries were strongly associated with vehicle transportation and impervious surfaces. PCM loadings were 83% (±140 kg/y) from WWTP final effluent, reflecting their use in personal care products. Opportunities for source reduction lie in reducing the current inventories of in-use PCBs and PBDE-containing products, reducing vehicle emissions of PAHs and use of PAHs in the transportation network (e.g., pavement sealants), and improving wastewater treatment technology.

SO-MUM: a coupled atmospheric transport and multimedia model used to predict intraurban-scale PCB and PBDE emissions and fate.

A spatially resolved, dynamic version of the Multimedia Urban Model (MUM) and the boundary layer forecast and air pollution transport model BLFMAPS were coupled to build Spatially Oriented MUM (SO-MUM), to estimate emissions and fate of POPs in an urban area on a 5 × 5 km(2) cell resolution. SO-MUM was used to back-calculate emissions from spatially resolved measured air concentrations of PCBs and PBDEs in Toronto, Canada. Estimated emissions of Σ(88)PCBs were 230 (40-480) kg y(-1), 280 (50-580) g y(-1) km(-2), or 90 (16-190) mg y(-1) capita(-1), and Σ(26)PBDEs were 28 (6-63) kg y(-1), 34 (7-77) g y(-1) km(-2), or 11 (2-25) mg y(-1) capita(-1). A mass inventory of penta- and octa-BDEs in Toronto was estimated to be 200 tonnes (90-1000 tonnes) or 80 (40-400) g capita(-1). Using this estimate and that of 440 (280-800) tonnes of PCBs, estimated emissions of Σ(88)PCBs and Σ(26)PBDEs per mass of chemical inventory in Toronto were 0.5 (0.05-1.6) and 0.1 (0.01-0.7) g y(-1) kg(-1), respectively. The results suggest annual emission rates of 0.04% and 0.01% from the mass inventories with downtown accounting for 30% and 16% of Toronto's chemical inventory and emissions of PCBs and PBDEs, respectively. Since total PBDE emissions are a function of mass inventory, which is proportional to building volume, we conclude that building volume can be used as a proxy to predict emissions. Per mass inventory emission rates were negatively related to vapor pressure within a compound class, but not consistently when considering all compound congeners.

Spatial modeling framework for aquatic exposure assessments of chemicals disposed down the drain: Case studies for China and Japan.

A modeling framework was created for the development of spatially explicit aquatic exposure models for any region or country of interest for chemicals disposed of down the drain. The framework relies on globally available data sets for river flow and population, and locally available data sets for wastewater treatment infrastructure and domestic water use, and leverages the iSTREEM® chemical routing algorithm. The framework was applied to China and Japan as case study countries. Spatially explicit population data were obtained from WorldPop. River flows covering the spatial extent of the two countries were derived from a high-resolution surface runoff gridded data set that was based on the Curve Number approach and combined with the hydrology network for catchments and rivers from HydroBASINS and HydroSHEDS data sets. Publicly available data from government sources were used for estimating per capita water use and wastewater treatment infrastructure. To demonstrate the framework, the China model was used to predict the levels of the antifungal agent climbazole in rivers across the country, and the Japan model was used to predict river concentrations of linear alkylbenzene sulfonate. For both chemicals, the comparison of measured to modeled values showed good agreement, using linear regression analysis (R2 ≥ 0.96). The framework presented in this study provides a systematic and robust approach to develop spatially resolved exposure models that can be extrapolated to any country or region, allowing more accurate risk assessment of chemicals disposed down the drain by leveraging concentration distributions generated by the model. Integr Environ Assess Manag 2022;18:722-733. © 2021 SETAC.

Freshwater Environmental Risk Assessment of Down-the-Drain Octinoxate Emissions in the United States.

Organic ultraviolet (UV) filters are used in a variety of cosmetic and personal care products (CPCPs), including sunscreens, due to their ability to absorb solar radiation. These UV filters can be washed down the drain through bathing, cleansing, or the laundering of clothing, therefore UV filters can enter the freshwater environment via wastewater treatment plant effluent, and so a freshwater risk assessment is necessary to establish the environmentally safe use of these important CPCP ingredients. In the present study, an environmental safety assessment for a UV filter of regulatory concern, octinoxate, was conducted. An established risk assessment framework designed specifically for CPCPs released to the freshwater environment in the United States was used for the assessment. A distribution of predicted environmental concentrations (PECs) representative of conditions across the region was calculated using the spatially resolved probabilistic exposure model iSTREEM. A review of available hazard data was conducted to derive a predicted no-effect concentration (PNEC). The safety assessment was conducted by comparing the PEC distribution to the PNEC. A substantial margin of safety was found between the 90th percentile PEC, which is representative of the reasonable worst-case environmental exposure, and the PNEC. Owing to this finding of negligible risk, further refinement of the risk assessment through the generation of experimental data or refinement of conservative assumptions is not prioritized. These results are critical for demonstrating the environmental safety of UV filters in the US freshwater environment and will help guide future work. Environ Toxicol Chem 2022;41:3116-3124. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

National scale down-the-drain environmental risk assessment of oxybenzone in the United States.

Organic ultraviolet (UV) filters are used in cosmetic and personal care products (CPCPs) and over-the-counter (OTC) sunscreens, due to their ability to absorb solar radiation. When OTC and CPCP ingredients are washed down the drain, they can then enter freshwaters that receive wastewater treatment plant effluents. This paper presents a freshwater environmental safety assessment of a key UV filter, oxybenzone, used in OTC sunscreens and CPCPs in the United States. Exposure was characterized using iSTREEM® , a spatially resolved aquatic exposure model developed for chemicals disposed of down the drain. iSTREEM® provides a comprehensive exposure assessment of oxybenzone concentrations in United States receiving waters through predicted environmental concentration (PEC) distributions representative of conditions across the region. A review of available hazard data was used to derive a predicted no-effect concentration (PNEC) using aquatic toxicity data and assessment factors. A safety assessment was conducted by comparing the PEC distribution with the PNEC. The results indicate that oxybenzone is of low concern and there is a significant margin of safety as the 90th percentile PEC is two orders of magnitude below the PNEC. These results are instrumental in demonstrating the environmental safety of key organic UV filters in the U.S. freshwater environment and will help prioritize future work. Integr Environ Assess Manag 2021;17:951-960. © 2021 Personal Care Products Council. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Stochastic modeling of near-field exposure to parabens in personal care products.

Exposure assessment is a key step in determining risks to chemicals in consumer goods, including personal care products (PCPs). Exposure models can be used to estimate exposures to chemicals in the absence of biomonitoring data and as tools in chemical risk prioritization and screening. We apply a PCP exposure model based on the product intake fraction (PiF), which is defined as the fraction of chemical in a product that is taken in by the exposed population, to estimate chemical intake based on physicochemical properties and PCP usage characteristics. The PiF can be used to estimate route and pathway-specific exposures during both the use and disposal stages of a product. As a case study, we stochastically quantified population level exposures to parabens in PCPs, and compared estimates with biomarker values. We estimated exposure based on the usage of PCPs in the female US population, taking into account population variability, product usage characteristics, paraben occurrence in PCPs and the PiF. Intakes were converted to urine levels and compared with National Health and Nutrition Examination Survey (NHANES) biomonitoring data. Results suggest that for parabens, chemical exposure during product use is substantially larger than environmentally mediated exposure after product disposal. Modeled urine concentrations reflect well the NHANES variation of three orders of magnitude across parabens for the 50th, 75th, 90th, and 95th percentiles and were generally in good agreement with measurements, when taking uncertainty into account. This study presents an approach to estimate multi-pathway exposure to chemicals in PCPs and can be used as a tool within exposure-based screening of chemicals as well in higher tier exposure estimates.

A review of models for near-field exposure pathways of chemicals in consumer products.

Exposure to chemicals in consumer products has been gaining increasing attention, with multiple studies showing that near-field exposures from products is high compared to far-field exposures. Regarding the numerous chemical-product combinations, there is a need for an overarching review of models able to quantify the multiple transfers of chemicals from products used near-field to humans. The present review therefore aims at an in-depth overview of modeling approaches for near-field chemical release and human exposure pathways associated with consumer products. It focuses on lower-tier, mechanistic models suitable for life cycle assessments (LCA), chemical alternative assessment (CAA) and high-throughput screening risk assessment (HTS). Chemicals in a product enter the near-field via a defined "compartment of entry", are transformed or transferred to adjacent compartments, and eventually end in a "human receptor compartment". We first focus on models of physical mass transfers from the product to 'near-field' compartments. For transfers of chemicals from article interior, adequate modeling of in-article diffusion and of partitioning between article surface and air/skin/food is key. Modeling volatilization and subsequent transfer to the outdoor is crucial for transfers of chemicals used in the inner space of appliances, on object surfaces or directly emitted to indoor air. For transfers from skin surface, models need to reflect the competition between dermal permeation, volatilization and fraction washed-off. We then focus on transfers from the 'near-field' to 'human' compartments, defined as respiratory tract, gastrointestinal tract and epidermis, for which good estimates of air concentrations, non-dietary ingestion parameters and skin permeation are essential, respectively. We critically characterize for each exposure pathway the ability of models to estimate near-field transfers and to best inform LCA, CAA and HTS, summarizing the main characteristics of the potentially best-suited models. This review identifies large knowledge gaps for several near-field pathways and suggests research needs and future directions.

Coupled near-field and far-field exposure assessment framework for chemicals in consumer products.

Humans can be exposed to chemicals in consumer products through product use and environmental emissions over the product life cycle. Exposure pathways are often complex, where chemicals can transfer directly from products to humans during use or exchange between various indoor and outdoor compartments until sub-fractions reach humans. To consistently evaluate exposure pathways along product life cycles, a flexible mass balance-based assessment framework is presented structuring multimedia chemical transfers in a matrix of direct inter-compartmental transfer fractions. By matrix inversion, we quantify cumulative multimedia transfer fractions and exposure pathway-specific product intake fractions defined as chemical mass taken in by humans per unit mass of chemical in a product. Combining product intake fractions with chemical mass in the product yields intake estimates for use in life cycle impact assessment and chemical alternatives assessment, or daily intake doses for use in risk-based assessment and high-throughput screening. Two illustrative examples of chemicals used in personal care products and flooring materials demonstrate how this matrix-based framework offers a consistent and efficient way to rapidly compare exposure pathways for adult and child users and for the general population. This framework constitutes a user-friendly approach to develop, compare and interpret multiple human exposure scenarios in a coupled system of near-field ('user' environment), far-field and human intake compartments, and helps understand the contribution of individual pathways to overall human exposure in various product application contexts to inform decisions in different science-policy fields for which exposure quantification is relevant.

Multi-pathway exposure modeling of chemicals in cosmetics with application to shampoo.

We present a novel multi-pathway, mass balance based, fate and exposure model compatible with life cycle and high-throughput screening assessments of chemicals in cosmetic products. The exposures through product use as well as post-use emissions and environmental media were quantified based on the chemical mass originally applied via a product, multiplied by the product intake fractions (PiF, the fraction of a chemical in a product that is taken in by exposed persons) to yield intake rates. The average PiFs for the evaluated chemicals in shampoo ranged from 3×10(-4) up to 0.3 for rapidly absorbed ingredients. Average intake rates ranged between nano- and micrograms per kilogram bodyweight per day; the order of chemical prioritization was strongly affected by the ingredient concentration in shampoo. Dermal intake and inhalation (for 20% of the evaluated chemicals) during use dominated exposure, while the skin permeation coefficient dominated the estimated uncertainties. The fraction of chemical taken in by a shampoo user often exceeded, by orders of magnitude, the aggregated fraction taken in by the population through post-use environmental emissions. Chemicals with relatively high octanol-water partitioning and/or volatility, and low molecular weight tended to have higher use stage exposure. Chemicals with low intakes during use (<1%) and subsequent high post-use emissions, however, may yield comparable intake for a member of the general population. The presented PiF based framework offers a novel and critical advancement for life cycle assessments and high-throughput exposure screening of chemicals in cosmetic products demonstrating the importance of consistent consideration of near- and far-field multi-pathway exposures.

High-throughput exposure modeling to support prioritization of chemicals in personal care products.

We demonstrate the application of a high-throughput modeling framework to estimate exposure to chemicals used in personal care products (PCPs). As a basis for estimating exposure, we use the product intake fraction (PiF), defined as the mass of chemical taken by an individual or population per mass of a given chemical used in a product. We calculated use- and disposal- stage PiFs for 518 chemicals for five PCP archetypes. Across all product archetypes the use- and disposal- stage PiFs ranged from 10(-5) to 1 and 0 to 10(-3), respectively. There is a distinction between the use-stage PiF for leave-on and wash-off products which had median PiFs of 0.5 and 0.02 across the 518 chemicals, respectively. The PiF is a function of product characteristics and physico-chemical properties and is maximized when skin permeability is high and volatility is low such that there is no competition between skin and air losses from the applied product. PCP chemical contents (i.e. concentrations) were available for 325 chemicals and were combined with PCP usage characteristics and PiF yielding intakes summed across a demonstrative set of products ranging from 10(-8)-30 mg/kg/d, with a median of 0.1 mg/kg/d. The highest intakes were associated with body lotion. Bioactive doses derived from high-throughput in vitro toxicity data were combined with the estimated PiFs to demonstrate an approach to estimate bioactive equivalent chemical content and to screen chemicals for risk.

Modeling urban films using a dynamic multimedia fugacity model.

A thin film coats impervious urban surfaces that can act as a source or sink of organic pollutants to the greater environment. We review recent developments in the understanding of film and film-associated pollutant behavior and incorporate them into an unsteady-state version of the fugacity based Multimedia Urban Model (MUM), focusing on detailed considerations of surface film dynamics. The model is used to explore the conditions under which these atmospherically-derived films act as a temporary source of chemicals to the air and/or storm water. Assuming film growth of 2.1 nm d(-1) (Wu et al., 2008a), PCB congeners 28 and 180 reach air-film equilibrium within hours and days, respectively. The model results suggest that the film acts as a temporary sink of chemicals from air during dry and cool weather, as a source to air in warmer weather, and as a source to storm water and soil during rain events. Using the downtown area of the City of Toronto Canada, as a case study, the model estimates that nearly 1 g d(-1) of ∑(5)PCBs are transferred from air to film to storm water.

Aquivalence revisited--new model formulation and application to assess environmental fate of ionic pharmaceuticals in Hamilton Harbour, Lake Ontario.

A model formulation based on "aquivalence", as defined in terms of activity is presented to estimate the multimedia fate of ionizing chemicals. The aquivalence approach is analogous to fugacity but aquivalence is applicable to neutral and ionizing compounds, and has been applied previously to speciating chemicals, notably metals. The new aquivalence-based mass-balance model treats ionizing organic compounds that exist as interconverting neutral and ionic species which are subject to fate processes at differing rates. The model is illustrated by application to four ionizing pharmaceuticals in Hamilton Harbour, Lake Ontario. At the system pH of 7.9-8.5, ibuprofen, gemfibrozil, and naproxen are expected to be almost entirely ionic and triclosan split between ionic and neutral forms. Measured seasonal surface water concentrations, which were 2-10 times lower in the late summer and fall than during spring, were used to solve for unknown values of chemical half-life in the water column due to degradation (photo- and bio-) of the ionizing and neutral forms and secondarily, ionic sorption coefficients of the ionizing forms. Model estimates of half-lives in the habour's water ranged from 11 to 77, 11 to 147 and 10 to 37 for ionic ibuprofen, gemfibrozil, and naproxen, respectively; and 4-22 days and 2-9 days for ionic and neutral triclosan, respectively, with the shortest half-lives in spring and the longest in summer.

Estimation of PCB stocks, emissions, and urban fate: will our policies reduce concentrations and exposure?

PCBs, used to manage risks from the flammability of dielectric fluids and to increase the durability of elastic sealants, had declining environmental concentrations after legislation banning new production was passed during the 1970s and 1980s in Europe and North America. To answer why PCB temporal trends are now nearly stable and if current policies will further reduce concentrations and our exposure, we estimated PCB stocks in Toronto, Canada (population of approximately 2.5 million) of 437 (282-796) tonnes, of which 97 and 3% are in closed sources and building sealants, respectively. The greatest geographic density of PCBs is downtown, specifically in commercial, electricity-intensive skyscrapers. An unknown stock is within now-buried landfills and other waste-handling facilities as well as diffuse sources such as electrical wiring and paints. Using the Multimedia Urban Model, we estimated city-wide emissions of approximately 0.14-1.4 mg m(-2) y(-1) or 35-350 mg capita(-1) y(-1) of SigmaPCB(70), which is approximately 0.01-0.3% annually of total documented stocks. Canada, as one of 159 signatories of the Stockholm Convention and the 35 parties that have reported progress toward environmentally sound management of their PCB inventories by 2028, has passed national legislation with a timetable of inventory reductions. It is unclear whether this legislation will successfully reduce concentrations and exposures, however the analysis should inform our management of other contaminants.

Continuing sources of PCBs: the significance of building sealants.

To investigate the significance of building sealants as a remaining source of PCBs to the environment a combined measurement campaign and GIS-based stock estimation were undertaken for Toronto, Canada. This showed that 14% of buildings measured had detectable quantities of PCBs present in sealants, with concentrations from 0.57 mg/g to 82 mg/g (n=95). We then constructed a GIS-based database of remaining PCB-containing sealants in Toronto. This showed that there is an estimated 13 t still present in the city. Mass balance calculations showed that up to 9% had been lost via volatilization alone. This potentially has important implications for both human exposure and the continued presence of PCBs in the environment.