Challenges to environmental litigation posed by emerging contaminants and possible strategies

ENVIRONMENTAL LITIGATION CASES INVOLVING EMERGING CONTAMINANTS

In environmental litigation cases, technical means and professional activities - namely environmental damage assessment^[1], environmental forensics^[2], and environmental judicial appraisal^[3] - are essential. In recent decades, emerging contaminants (ECs) have become increasingly involved in environmental litigation. Some ECs that attracted attention at the end of the last century, such as methyl tertiary butyl ether^[4] and polybrominated diphenyl ethers^[2], are now widely regulated. Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are probably among the most concerning ECs at present. At least 25 environmental conflicts concerning PFAS were recorded by February 2025^[5], some of which became environmental litigation cases. As a recent typical case, DuPont/Chemours agreed to pay $2 billion for the PFAS-induced drinking water pollution case in New Jersey on August 4, 2025^[6]. This amount is second only to the compensation paid by Minnesota Mining and Manufacturing Company (3M) to U.S. public water suppliers ($10.3 billion), also related to PFAS contamination^[7]. In the U.S., groundwater, which serves as a drinking water source for 71 to 95 million people, is supposed to be widely affected by PFAS pollution^[8].

Microplastics, another widely discussed EC, have been involved in environmental litigation. On July 24, 2025, Sri Lankan Supreme Court fined $1 billion for the losses caused by the sinking accident of container vessel X-Press Pearl in 2021^[9]. On-site records, including photographs collected by the United Nations Environment Programme (UNEP)^[10], supported the conclusion that marine ecological damage caused by this incident was at least partially related to plastic nurdles.

Furthermore, according to a case report in China Judgements Online^[11], brominated dioxins, an endocrine disruptor, were suspected to be generated in a metal smelting plant, with public welfare compensation of 0.5 million RMB (Renminbi)^[12].

REQUIREMENTS FROM ENVIRONMENTAL LITIGATION AND THE CHALLENGES CAUSED BY EC

Environmental litigation often requires detailed information during the damage assessment process [Figure 1]. Table 1 summarizes the challenges encountered at each key step of environmental damage assessment for ECs, including the lack of critical information. Generally, cases originate from different types of clues: (i) suspected discharge activity or incident from a contaminant source; (ii) suspected contaminants from unknown sources; or (iii) suspected environmental damage. Regardless of the starting point, the entire damage assessment process involves many uncertainties, particularly when dealing with ECs. For instance, source identification (tracing or apportioning the source) is especially difficult for clue type (ii). The presence of certain contaminants in the target, along with similar substances in nearby suspicious sources, does not necessarily prove that the contaminants migrated from these specific sources to the target. Consequently, in 2023, the United States Court of Appeals for the Sixth Circuit dismissed a plaintiff’s claim that 3M caused PFAS pollution and related health damage^[13]. Only five types of PFAS were detected in his body, and the plaintiff failed to establish their traceability. In other words, they could not provide evidence that the PFAS entered the environment or his body from the defendant’s product, nor could they exclude the possibility that the PFAS originated from other sources. This limitation is attributed to insufficient information on ECs in the targets (e.g., the body) and the migration characteristics of specific ECs (e.g., each type of PFAS). Moreover, interactions between ECs and other contaminants can alter their environmental behavior and effects. In the X-Press Pearl case, microplastics were believed to act as carriers for hazardous materials (such as nitric acid and oil^[10]) that simultaneously entered the sea during the accident. This should not be considered an isolated case, as plastic waste and hazardous chemicals frequently co-occur in shipwreck incidents^[14]. Additionally, events such as wildfires can further influence contaminant migration^[15]. Consequently, extensive research data on ECs should be collected to support practical cases.

Figure 1. Framework diagram for key steps in environmental damage assessment involving contamination. The figure is produced with Microsoft PowerPoint. Three symbols (i), (ii), and (iii) represent the types of clues mentioned in the main text.

When only clues (i) and/or (iii) are found, contaminant screening is complicated. The toxic effects of various ECs are still being investigated. This situation is analogous to a “menu with only dish names” - you cannot determine which EC is responsible for the observed effect; sometimes it is even worse, as the specific effect of interest is unknown when only suspected sources are present. Moreover, appraisers or judges dealing with traditional contaminants often focus on which contaminants surpass the baseline (i.e., environmental background value) and/or the standard values/criteria (i.e., officially recognized or toxicologically recommended allowable ranges), as well as the degree of exceedance. However, historical baseline data for ECs only occasionally cover the relevant area; ECs are not yet widely regulated, so there are usually no standard values available; and with limited toxicological data, the criteria for many ECs have not yet been established. Therefore, it is difficult to quantify the damage caused by ECs.

Another challenge in the assessment of EC contamination is timeliness. The fixation of evidence, including contaminant screening/identification and quantitative evaluation of the levels and ranges of contamination, requires timeliness. However, the wide variety of ECs and the lack of related knowledge/data mean that investigation plans for ECs in the environment may be exceptionally complex and time-consuming. Owing to timeliness constraints, the damage assessors in the case concerning brominated dioxins failed to directly collect samples of the toxic gas. Instead, they relied on existing literature data on brominated dioxins produced from the incineration of circuit board waste to conduct simulations^[12]. This approach can only be applied to cases involving small quantities, given its limited evidentiary capability.

The dose-response relationship is an important basis for causation judgment and damage assessment. However, the effects of ECs on humans, other living organisms, and the ecological system are complex. Taking the interference of endocrine disruptors with metabolism as an example, there are 12 key factors^[16]. However, there is a lack of appropriate guidelines (similar to those for clinical diagnosis published by official institutions or academic organizations) on how to quickly identify key items for each type of EC. Moreover, some effects of ECs can currently only be demonstrated by observational evidence (such as the relationship between endocrine-disrupting chemicals and adverse effects shown in statistical data^[17]), making it difficult to determine causation among various confounding factors. Epidemiological evidence is another type of evidence used for causation judgment. However, in some cases, the transitional period between exposure to endocrine disruptors and the manifestation of adverse effects^[16] hinder the collection of epidemiological evidence.

In the clearance sector, the lack of knowledge about ECs’ toxicological mechanisms also negatively affects pollution control. The substitution of bisphenol A with bisphenol S is an example of an unsuccessful mitigation approach^[16].

In addition to the specific issues caused by ECs [Table 1], there are some general issues affecting damage assessment involving all types of contaminants. These may be perceived as more problematic in the context of ECs due to the paucity of data and limited experience. The first and foremost issue is the contradiction between funding and time in most cases. Sometimes, significant differences between cases make it necessary to obtain specific data for each case^[18]. Case-by-case studies are not designed to address broad issues and are not suitable for supporting fundamental research. They are unlikely to generate profits and may even yield unfavorable evidence for enterprises, complicating the acquisition of long-term financial support. The unpredictable occurrence of similar cases does not incentivize government- or self-funded preliminary research. Damage appraisers often receive sufficient funding only in cases involving severe or widespread pollution to conduct these extensive studies. However, in such instances, both governmental bodies and the public impose strong demands regarding fairness and strict time constraints. As a consequence, appraisers often hesitate to use new technological methods or models that lack broad acceptance or to allocate additional time for large-scale on-site experiments.

POSSIBLE STRATEGIES

It should be pointed out that the strategies presented here are not specific to particular types of ECs. The following are some possible strategies [Figure 2].

Figure 2. Four types of possible strategies to deal with challenges in environmental damage assessment involving ECs. The figure is produced with Microsoft PowerPoint. ECs: Emerging contaminants.

(1) Fundamental research is the cornerstone. Any reliable model requires sufficient and accurate data, such as the environmental behavior characteristics and toxicological data of ECs. Understanding the background knowledge concerning EC-related sources and potential targets is also a prerequisite for establishing traceability methods.

(2) Datasets and models should be made publicly accessible on information platforms that offer public recognition. Given the wide variety of ECs and the numerous receptors and endpoints in the environment, there is a massive demand for environmental behavior characteristics and toxicological data. Effective models should be applied to efficiently fill these data needs. Multiple models have been used to simulate several basic physicochemical parameters of compounds^[19], while new tools, such as machine learning and artificial intelligence (AI), have been applied to improve toxicity prediction models^[20-22]. For environmental litigation, it is crucial that the data are publicly recognized. Establishing a platform that includes publicly shared datasets and the associated models responsible for generating these data, along with continuous updates of both, appears to be a viable approach. KAshinhou Tool for Ecotoxicity (current version: KATE2025 version 1.1), a quantitative structure-activity relationship (QSAR)-based tool maintained by the National Institute for Environmental Studies of Japan, exemplifies a typical application in this domain. Furthermore, it is imperative that additional information, such as comprehensive lists of potential sources for typical ECs, be provided and regularly updated. This is important given rapid industrial advancements and evolving applications of various compounds.

(3) Advanced methods for the screening, identification, and quantification of ECs should be introduced and standardized. Standardized monitoring methods are available for many ECs. For example, PFAS can be monitored with ISO 21675:2019 (International Organization for Standardization), and pharmaceuticals and personal care products can be monitored with U.S. Environmental Protection Agency (USEPA) Method 1694. However, these methods are mainly targeted for specific ECs and are time-consuming and labor-intensive. Non-target screening methods should be developed. Moreover, the sensitivity and resolution of existing methods often cannot meet the information requirements for environmental damage identification^[23]. More detailed information from traceability methods, such as refined fingerprint spectra, biomarkers, or element isotope characteristic signals, is needed to show similarities/distinctions between potential sources and target matrices. Meanwhile, rapid detection equipment can maximize the timeliness of quantification.

(4) Special regulations and financial resources are essential for the analysis and dissemination of typical case studies. In emerging fields such as those involving ECs, there is significant demand for guidance from exemplary case documents, including judicial records, damage assessment reports, and remediation plans. It is imperative to establish legal assurances for these cases, permitting extended time limits and facilitating research activities such as simulation experiments. Governmental financial support or dedicated funds from industry associations should be allocated to these cases.