Exposure and toxicity characterization of chemical emissions and chemicals in products: global recommendations and implementation in USEtox

Abstract

Purpose Reducing chemical pressure on human and environmental health is an integral part of the global sustainability agenda. Guidelines for deriving globally applicable, life cycle–based indicators are required to consistently quantify toxicity impacts from chemical emissions as well as from chemicals in consumer products. In response, we elaborate the methodological framework and present recommendations for advancing near-field/far-field exposure and toxicity characterization, and for implementing these recommendations into the scientific consensus model USEtox. Methods An expert taskforce was convened by the Life Cycle Initiative hosted by UN Environment to expand existing guidance for evaluating human toxicity impacts from exposure to chemical substances. This taskforce evaluated scientific advances since the original release of USEtox and identified two major aspects that required refinement, namely integrating near-field and far-field exposure, and improving human dose-response modeling. Dedicated efforts have led to a set of recommendations to address these aspects in an update of USEtox, while ensuring consistency with the boundary conditions for characterizing life cycle toxicity impacts and being aligned with recommendations from agencies that regulate chemical exposure. The proposed updated USEtox framework was tested in an illustrative rice production and consumption case study. Results and discussion On the exposure side, a matrix system is proposed and recommended to integrate far-field exposure from environmental emissions with near-field exposure from chemicals in various consumer product types. Consumer exposure is addressed via sub-models for each product type to account for product type-specific characteristics and exposure settings. Case study results illustrate that product use–related exposure dominates overall life cycle exposure. On the effect side, a probabilistic dose-response approach combined with a decision tree for identifying reliable points of departure is proposed for non-cancer effects, following recent guidance from the World Health Organization. This approach allows for explicitly considering both uncertainty and human variability in toxicity effect factors. Factors reflecting disease severity are proposed to distinguish cancer from non-cancer effects and within the latter to discriminate reproductive/developmental and other non-cancer effects. All proposed aspects have been consistently implemented into the original USEtox framework. Conclusions The recommended methodological advancements address several key limitations in earlier approaches. Next steps are to test the new characterization framework in additional case studies and to close remaining research gaps. Our framework is applicable for evaluating chemical emissions and product-related exposure in life cycle assessment, chemical alternatives assessment and chemical substitution, consumer exposure and risk screening, and high-throughput chemical prioritization.

Addressing the importance of microplastic particles as vectors for long-range transport of chemical contaminants: perspective in relation to prioritizing research and regulatory actions

“…Estimates of indoor concentrations of PACs, for instance, have been derived through the application of multimedia environmental fate models [112]. When coupled with assumptions of indoor-outdoor airexchange fluxes, the far-field exposure of PACs, such as phthalates and flame retardants [3,[118][119][120], can be estimated when coupled with models of emissions for indoor environments.…”

“…Assessing exposure is the process of estimating or measuring the magnitude, frequency and duration of exposure to a stressor, which ideally includes characterization of the sources, pathways, routes and the associated uncertainties [1,2]. Recognizing that all physical and chemical stressors have the potential to cause harm to human and ecological healthactions aimed at reducing the magnitude, frequency and duration of their exposure represents an aspirational goal within any global sustainability agenda [3].…”

Improved plant bioconcentration modeling of pesticides: The role of periderm dynamics

“…Such a tool could be further incorporated into existing plant uptake models to help reduce human exposure to pesticide residues in edible crop components as well as to evaluate the influence of food processing (e.g. peeling) on the magnitude of residue‐related exposures 10–15,30–36 . To address this gap, it is the aim of the present study to propose a modeling approach that treats the potato periderm as a separate compartment to quantify the influence of the periderm on the uptake of pesticides into edible potato tubers and related residues.…”

“…peeling) on the magnitude of residue‐related exposures. 10 , 11 , 12 , 13 , 14 , 15 , 30 , 31 , 32 , 33 , 34 , 35 , 36 To address this gap, it is the aim of the present study to propose a modeling approach that treats the potato periderm as a separate compartment to quantify the influence of the periderm on the uptake of pesticides into edible potato tubers and related residues. To achieve this aim, we defined three specific objectives: (i) to develop a model for pesticide uptake into potato tubers that explicitly considers the periderm (periderm model) and compare results with uptake without considering the periderm (nonperiderm model); (ii) to parameterize the periderm model for inclusion into existing plant uptake models applied for human exposure and health impact assessments; and (iii) to identify the key input variables that drive modeled pesticide uptake into potato tubers as input for further refining the model.…”

Human Chemical Exposure from Background Emissions in the United States and the Implication for Quantifying Risks from Marginal Emission Increase

“…Such a slope is often derived from toxicological endpoints measured at high doses with high responses. Typical endpoints include the median effective dose (ED 50 ) that corresponds to the population incidence response level of 50%, and, more recently, the 10% effective dose (ED 10 ) recommended by the latest version of the life cycle impact assessment scientific consensus model USEtox [9]. Underlying this practice is an assumption of the linear dose-response relationship, in which the health effect (response) is independent of the exposure rate (dose) without a safe dosage (threshold).…”