Chemical contaminants and plastics are pervasive in lakes, streams, and rivers, and threaten environmental and human health. Mass-balance models, which simulate the transport and transformation of contaminants across multiple environmental compartments, are essential for understanding chemical and plastic pollution in freshwater systems. However, many existing models neglect the spatial and temporal variability of particle transport processes driven by variable flow velocities, which is key for hydrophobic chemical contaminants and plastic. In this study, we develop a generic parameterization of particle dynamics as a function of flow velocity for contaminant mass-balance models of freshwater systems that is parsimonious in that it does not increase data demands over current modeling approaches. We demonstrate our parameterization using the open-source Full Multi framework by replicating the classic Hjulström diagram and by validating against a shear stress baseline. Model performance evaluated by simulating suspended solid concentrations in the non-tidal River Thames from 2009 to 2017 yielded strong positive Pearson correlations (P < 0.01) and low root-mean-square errors between simulations and observations. Extrapolating the parameterization from natural sediments to plastic particles with a broad range of sizes, densities, and weathering states allowed us to map plastic dynamics under varying flow conditions. This parsimonious parameterization represents a significant advance in process-fidelity for particle dynamics in contaminant mass-balance models, and will improve assessments of plastic and particle-associated chemical contaminants in freshwater systems.

The occurrence and burden of per- and polyfluoroalkyl substances (PFAS) in adipose tissue of humans and wildlife represent an underexamined dimension of PFAS exposure. While most PFAS research has focused on ionic substances that accumulate in tissues such as liver and blood, there is growing evidence that a distinct and diverse suite of neutral PFAS bioaccumulate in adipose tissue. This Perspective synthesizes recent data illustrating the substantial contribution of some adipose-associated PFAS to overall body burdens, applies quantum chemical modeling to exemplify additional PFAS likely to partition into adipose tissue, and examines analytical blindspots that have limited their detection to date. We show that certain neutral PFAS possess partitioning properties comparable to legacy persistent organic pollutants, which, provided that they are sufficiently persistent, can lead to bioaccumulation in adipose tissue. We further outline the analytical challenge of extracting, detecting, and quantifying neutral PFAS in matrices rich in storage lipids and discuss the implications for exposure assessment, toxicology, and environmental surveillance. Finally, we identify key research needs and call for expanded monitoring strategies that capture the full chemical space of PFAS bioaccumulation.

Discovering hazardous pollutants currently relies on the tedious and often inaccurate structural identification step, required for further toxicity and exposure studies. Here, we propose and validate a workflow for prioritizing the detected features prior to structural elucidation. The proposed approach relies on the priority score (environmental concentration divided by lethal concentration) serving as a proxy of the risk and is deduced solely from mass spectrometric data. The workflow integrates two machine learning approaches, MS2Tox and MS2Quant, that predict toxicity and ionizability of unidentified molecular features, respectively, and the relative risk-based ranking of detected features does not require any additional standards to be measured in the same run, allowing the application to digitally frozen data. Validation by using priority score for classifying 23 chemicals with available risk quotient values into high and low risk categories yielded recall value of 0.33 to 0.81, precision of 0.08 to 0.50, and accuracy of 0.52 to 0.81, depending on the acquisition mode and fish species. Applying the developed workflow to wastewater effluent prioritized 13–19% of features with predicted fingerprints as “precautionary risk features” with a risk quotient ≥1 based on the lower limit of the 95% prediction interval. All prioritized features were subject to spectral library matching, with 12% of the features yielding level 2 identification. Features categorized as high-risk were further subject to structural annotation using in silico identification tools SIRIUS+CSI:FingerID and MetFrag. While plausible candidates were suggested, the in silico tools disagreed in the top 10 suggested structures, highlighting structural assignment as a bottleneck in risk estimation. This work investigates the usefulness of applying data-driven feature prioritization prior to identification.

Novel entities are diverse and complex; hence, defining their Planetary Boundary through control variables, indicators, and acceptable limits is challenging. Here, we highlight shortcomings of the current quantitative boundary, which applies a purely precautionary interpretation of safety that defines the safe operating space as zero novel entities that are not fully characterized. In practice, the zero limit is unattainable and undesirable for human societies that rely on services provided by novel entities. Furthermore, it is not operational within the framework of other boundaries, which have risk-based thresholds. We therefore propose a reboot of the Planetary Boundary for Novel Entities and recommend governance and monitoring strategies based on: (a) clarification of the “safe operating space” for novel entities, distinguishing pure precaution (“safe from the unknown”) from operational precaution that tolerates a workable, non-zero level of uncertainty; (b) complementary, multilayer control variables spanning pressures, states, and impacts; (c) extensions to existing monitoring systems to provide quantitative indicators of distribution, accumulation, exposure, and impacts for subsets of novel entities to communicate the status and trends of stress from novel entities on the Earth system; and (d) recognition of regulatory and policy-related success stories that illustrate comprehensive, protective, and operational governance of novel entities.

High-altitude terrain may intersect the upper atmospheric boundary layer and exhibit distinct environmental dynamics. We investigated the anthropogenic pollutants polychlorinated alkanes (PCAs, also known as chlorinated paraffins) in surface soils along a transect from the La Paz-El Alto metropolitan area in Bolivia (3200–4100 masl) to the upper slopes of Mount Chacaltaya (>5200 masl), around 16 km away. Concentrations of PCAs in urban soils (750–5,230 ng/g organic carbon [OC]) decreased exponentially with increasing distance from the urban boundary, declining to ∼150 ng/g OC at elevations below 4,700 masl. Beyond 4,700 masl concentrations increased again, reaching levels comparable to those in the urban area, 1,670–4,300 ng/g OC, above 5,000 masl. Given that pollutant concentrations typically decline with distance from their source, this altitudinal trend, together with a pronounced shift in PCA forensic fingerprints near 4,700 masl, strongly suggests contributions from sources beyond the local metropolitan area. Carbon and nitrogen isotope signatures in organic carbon further support long-range transport as a source, consistent with previous modeling and observations that the upper slopes of Mount Chacaltaya predominantly receive air masses and organic carbon from distant regions via transport in the free troposphere. Our observation that pollutant levels in high-altitude areas are comparable to those in the metropolis of 1.8-million inhabitants underscores the efficiency of long-range atmospheric transport.

Plastic agricultural films (PAFs) are widely used to enhance crop productivity, with global use projected to reach 9–14 million tonnes (Mt) per year by 2030. However, their use has led to contamination of soils with microplastics (MPs), nanoplastics and associated chemical additives. In this Review, we synthesize evidence on the global use of PAFs, their environmental fate and strategies to enhance their sustainable application. PAFs deliver substantial agronomic benefits, enhancing crop yields by 7–48% and soil water retention by 9–25%. However, films fragment and degrade under physical erosion, elevated ultraviolet radiation, temperature, humidity, and microbial and faunal activity. As a result, PAF use generates 3–5 Mt yr⁻¹ of largely unmanaged waste, contributing to widespread plastic pollution in agricultural soils. For example, MP concentrations can reach ~13,000 items per kilogram, with PAFs accounting for 10–30%. Conventional polyethylene films degrade slowly and primarily undergo physical fragmentation, whereas biodegradable films fragment more rapidly, with cases of ~30% converted to MPs within 2 years. However, complete mineralization remains limited even for biodegradable materials. Additives in PAFs, including poorly characterized non-intentionally added substances, further increase environmental and toxicological risks, and their release varies substantially with environmental conditions and film type. MPs and additives affect soil health, crop yields and nutrient cycles. Mitigation strategies include substitution with safer additives, developing biodegradable waste-derived bio-based polymers, and conventional film recycling. Future work should improve field monitoring, develop a global database of PAF use and composition, and implement policy innovations to support sustainable PAF systems.

The United Nations Outer Space Treaty states that the exploration of celestial bodies must avoid “harmful contamination” which may impede scientific exploration by other parties to the treaty. To guide treaty compliance, Planetary Protection regulations promulgated by the Committee on Space Research set limits for microbial contamination of celestial bodies, particularly those that may harbor extant life (e.g., Mars). However, anthropogenically introduced chemicals and materials are not regulated but may cause “harmful contamination” and thus pose a potential threat to scientific exploration. On Earth, threats from anthropogenic chemicals and materials are often managed by considering both potential exposure to the substances and their hazardous properties. The lack of knowledge around hazards to possible extant life on Mars means that chemicals and materials should be designed and used so that their exposure concentrations are minimized. Here, we review possible emission, partitioning, persistence, and transport processes on Mars for anthropogenically introduced chemicals and materials and identify key knowledge gaps. We highlight difficulties and lessons learned from pollution policy development on Earth that could inform interplanetary chemical and material management. This work aims to support the expansion of the Planetary Protection guidelines to include a “No- or Low-Exposure by Design” approach to chemicals and materials on Mars.

Wania and McLachlan (1) continue a discussion about the work of the Stockholm Convention (SC) on Persistent Organic Pollutants (POPs). This is useful because some of the issues raised surrounding the implementation of the SC warrant concerted action to safeguard the effectiveness of the SC. However, several of their statements are unsubstantiated or factually incorrect and could mislead the discussion about the future work of the SC. Here, we first respond to some of their general statements about the functioning of the SC and then to their specific criticism of the nomination of UV-328.

According to the authors, “a large increase in the number of chemicals that fulfill the screening requirements could lead to a considerable expansion in the number of chemicals being eligible for nomination and listing.” They see this as a problem, primarily because the capacity of countries to implement SC decisions may be exceeded. However, contrary to the authors’ insinuation that a high number of nominations is a problem, the nominations show that the SC works well and addresses exactly the concern for which it was established, namely to protect human health and the environment from POPs. If there is a concern about too high a burden from implementing the SC, the logical response is to strengthen the implementation process, not to throttle the nomination process.

Polymers are the main constituents of many materials and products in our modern world. However, their environmental safety is not assessed with the same level of detail as done for non-polymeric chemical substances. Moreover, the fundamentals of contemporary regulatory approaches for polymers were developed in the early 1990s, with little change occurring since then. Currently, the European Commission is working on a proposal to initiate registration of polymers under the European Union's (EU) chemicals legislation REACH. This provides a unique opportunity for regulation to catch up on recent scientific advances. To inform this process, we here critically appraise the suggested regulatory approaches to the environmental assessment and management of polymers against the latest scientific findings regarding their environmental fate, exposure, and effects, and identify the remaining critical knowledge gaps. While we use the EU draft proposal as an example, our findings are broadly applicable to other polymer legislations worldwide, due to the similarity of polymer assessment criteria being used. We emphasize four major aspects that require more attention in the regulation of polymers: (i) increased transparency about chemical identities, physical characteristics and grouping approaches for in-use polymers; (ii) improved understanding of the environmental fate of polymers and materials composed of polymers across size and density categories and exposure profiles; (iii) comprehensive assessment of the environmental hazards of polymers, considering the effects of degradation and weathering and taking into account the actual uptake, long-term toxicity, and geophysical impacts; and (iv) consideration of the production volume and use/release patterns in determining regulatory data and testing requirements. Transitioning toward a toxic-free and sustainable circular economy will likely require additional policy instruments that will reduce the overall complexity and diversity of in-use polymers and polymeric materials.

Polar regions should be given greater consideration with respect to the monitoring, risk assessment, and management of potentially harmful chemicals, consistent with requirements of the precautionary principle. Protecting the vulnerable polar environments requires (i) raising political and public awareness and (ii) restricting and preventing global emissions of harmful chemicals at their sources. The Berlin Statement is the outcome of an international workshop with representatives of the European Commission, the Arctic Council, the Antarctic Treaty Consultative Meeting, the Stockholm Convention on Persistent Organic Pollutants (POPs), environmental specimen banks, and data centers, as well as scientists from various international research institutions. The statement addresses urgent chemical pollution issues in the polar regions and provides recommendations for improving screening, monitoring, risk assessment, research cooperation, and open data sharing to provide environmental policy makers and chemicals management decision-makers with relevant and reliable contaminant data to better protect the polar environments. The consensus reached at the workshop can be summarized in just two words: “Act now!”

Specifically, “Act now!” to reduce the presence and impact of anthropogenic chemical pollution in polar regions by.

•Establishing participatory co-development frameworks in a permanent multi-disciplinary platform for Arctic-Antarctic collaborations and establishing exchanges between the Arctic Monitoring and Assessment Program (AMAP) of the Arctic Council and the Antarctic Monitoring and Assessment Program (AnMAP) of the Scientific Committee on Antarctic Research (SCAR) to increase the visibility and exchange of contaminant data and to support the development of harmonized monitoring programs.

•Integrating environmental specimen banking, innovative screening approaches and archiving systems, to provide opportunities for improved assessment of contaminants to protect polar regions.