Quantifying the impact of PFOA exposure on B-cell development and antibody production

Integrated PBPK Modelling for PFOA Exposure and Risk Assessment

Per- and polyfluoroalkyl substances (PFASs) pose significant public health concerns due to their environmental persistence, bioaccumulation, and ubiquitous presence in human biomonitoring (HBM) data, despite regulatory restrictions. This study establishes a deterministic pharmacokinetic model for perfluorooctanoic acid (PFOA), enabling the estimation of PFOA concentrations in major human organs, even at low doses. The model integrates accumulation and recirculation mechanisms of PFOA in hepatic and renal tissues, leveraging publicly available HBM datasets (e.g., HBM4EU, NHANES, literature) to reconstruct bodyweight-normalized intake levels. Importantly, due to the extremely low urinary excretion concentrations of PFOA, most datasets were derived from blood-based measurements, particularly serum while confirming urine as unreliable biomarker of exposure. The analysis underscores the effectiveness of regulatory efforts in reducing PFOA exposures, as evidenced by declining time-trends in estimated exposure levels in recent studies. Risk characterization ratios were calculated based on recommended limits set by the European Food Safety Authority (EFSA), the United States, and Australia. While EFSA's tolerable weekly intake (TWI) indicated a high risk, other regulatory limits suggested less concern about risk at these intake levels. These findings highlight the need for continuous re-evaluation of exposures and targeted studies to identify key determinants of PFOA exposure, informing future regulatory measures. The study emphasizes the critical role of physiologically based pharmacokinetic (PBPK) modeling, HBM data, and exposure reconstruction in advancing chemical risk assessment. These tools form a science-based framework integral to the Chemical Strategy for Sustainability (CSS), enabling accurate predictions of internal exposure levels, empirical validation of models, and robust assessments of real-world exposure scenarios. The integration of these approaches supports the CSS goals of minimizing chemical risks while promoting innovation, ultimately contributing to a sustainable and protective regulatory landscape for human health and the environment.

In vitro approaches to investigate the effect of chemicals on antibody production: the case study of PFASs

The increasing variety and quantity of new chemical substances have raised concerns about their potential immunotoxic effects, making it essential to assess their impact on human health. One key concern is the reduction of antibody production, as seen with per- and poly-fluoroalkyl substances (PFASs), commonly known as "forever chemicals." Both in vivo and epidemiological data show that PFASs have immunosuppressive effects, leading to reduced antibody responses, particularly following vaccination. In animal studies, the T cell-dependent (TD) antibody response is the gold standard for assessing chemical effects on immune function. This study utilized two in vitro approaches to investigate the effects of chemicals on antibody production using human peripheral blood mononuclear cells. Initial tests used unstimulated, negative (vehicle), and positive (rapamycin) controls to confirm the robustness of the models. Subsequently, four long-chain PFASs (PFOA, PFOS, PFNA, and PFHxS) were tested. Keyhole limpet hemocyanin (KLH) was used to mimic the TD response, while a TLR9 agonist and IL-2 activated B cells for T cell-independent (TI) immunoglobulin production. The results demonstrated the ability to reproduce TD and TI responses in vitro with robust, reproducible outcomes across a cohort of 20 human donors. The data, consistent with existing literature, showed a significant reduction in anti-KLH IgM production, especially for PFOA in male donors. Similar trends were observed for all PFASs in suppressing total TI IgG and IgM production. These methods closely replicated in vivo conditions, offering a potential alternative to animal models in immunotoxicity assessments.

Evaluating PFAS-Induced modulation of peripheral blood mononuclear cells (PBMCs) immune response to SARS-CoV-2 spike in COVID-19 Vaccinees

The persistent nature of the environmental contaminants per- and polyfluoroalkyl substances (PFAS) has recently received considerable attention, particularly because of their adverse effects on immune system functionality in the context of vaccine responses to infectious diseases. Following COVID-19 vaccination, some studies have shown a significant negative correlation between serum PFAS concentrations and the humoral immune response to the SARS-CoV-2 spike protein vaccination. However, the influence of PFAS on the cell-mediated immune response to SARS-CoV-2 spike protein post-COVID-19 vaccination remains underexplored. In the present study, we investigated the impact of a human blood-relevant PFAS mixture, containing perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA) on innate (monocytes and NK cells), cell-mediated (T cells) and B cells adaptive immune responses in COVID-19-vaccinated female and male healthy donors. Human peripheral blood mononuclear cells (PBMCs) were exposed to a mixture of the six PFAS at real life concentrations and subsequently stimulated with the SARS-CoV-2 spike peptide. We report a significant upregulation of IFNγ production in T and NK cells, particularly among male donors exposed to high concentrations of the PFAS mixture. Conversely, we observed a decrease in the total B-cell population, particularly among female donors. A significant reduction in the secretion of the pro-inflammatory chemokines MIP-1α (CCL3) and MIP-3α (CCL20) was observed at high PFAS mixture concentrations. Overall, these findings suggest that high PFAS exposure may differentially affect immune responses in a sex-specific manner, with a potential impact on vaccine efficacy.

Mode of action Criteria for selection of the critical effect and safe dose range for PFOA by the Alliance for risk assessment

In response to the current disparity in risk assessment values for PFOA from different agencies and countries, an international effort facilitated by the Alliance for Risk Assessment (ARA) was recently undertaken to characterize the range of scientifically supportable safe dose estimates. In this assessment (Burgoon et al., 2023), an evaluation of the evidence regarding the potential modes of action (MOA) for PFOA toxicity was performed first, so that it could be used to inform subsequent decisions regarding potential critical effects and studies. This review describes the evidence considered in the MOA evaluations that were performed as part of the ARA effort. The overall conclusions of this evaluation are that the available mechanistic data do not support any conclusion that reported epidemiological associations of blood concentrations of PFOA as low as 10 ng/mL with various health effects should be considered causal. It is more likely that the reported associations may instead reflect reverse causality/pharmacokinetic confounding. These conclusions are consistent with the opinions of the World Health Organization (WHO, 2022).

Binary and quaternary mixtures of perfluoroalkyl substances (PFAS) differentially affect the immune response to influenza A virus infection

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic organofluorine compounds that persist indefinitely in the environment and bioaccumulate throughout all trophic levels. Biomonitoring efforts have detected multiple PFAS in the serum of most people. Immune suppression has been among the most consistent effects of exposure to PFAS. PFAS often co-occur as mixtures in the environment, however, few studies have examined immunosuppression of PFAS mixtures or determined whether PFAS exposure affects immune function in the context of infection. In this study, mixtures containing two or four different PFAS and a mouse model of infection with influenza A virus (IAV) were used to assess immunotoxicity of PFAS mixtures. PFAS were administered via the drinking water as either a binary mixture of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) or quaternary mixture of PFOS, PFOA, perfluorohexane sulfonate (PFHxS), and perfluorononanoic acid (PFNA). The results indicated that the binary mixture affected the T-cell response, while the quaternary mixture affected the B-cell response to infection. These findings indicate that the immunomodulatory effects of PFAS mixtures are not simply additive, and that the sensitivity of immune responses to PFAS varies by cell type and mixture. The study also demonstrates the importance of studying adverse health effects of PFAS mixtures.

Per- and polyfluoroalkyl substances alter innate immune function: evidence and data gaps

Per- and polyfluoroalkyl substances (PFASs) are a large class of compounds used in a variety of processes and consumer products. Their unique chemical properties make them ubiquitous and persistent environmental contaminants while also making them economically viable and socially convenient. To date, several reviews have been published to synthesize information regarding the immunotoxic effects of PFASs on the adaptive immune system. However, these reviews often do not include data on the impact of these compounds on innate immunity. Here, current literature is reviewed to identify and incorporate data regarding the effects of PFASs on innate immunity in humans, experimental models, and wildlife. Known mechanisms by which PFASs modulate innate immune function are also reviewed, including disruption of cell signaling, metabolism, and tissue-level effects. For PFASs where innate immune data are available, results are equivocal, raising additional questions about common mechanisms or pathways of toxicity, but highlighting that the innate immune system within several species can be perturbed by exposure to PFASs. Recommendations are provided for future research to inform hazard identification, risk assessment, and risk management practices for PFASs to protect the immune systems of exposed organisms as well as environmental health.

Relationship Between Perfluoroalkyl Acids in Human Serum and Sjogren's Syndrome: A Case-Control Study of Populations in Hangzhou, China

Exposure to perfluoroalkyl acids (PFAAs) has been found to elicit a range of detrimental effects on human health. However, limited research has investigated the impact of PFAAs on immunity and immune disorders such as Sjogren's syndrome, with existing studies yielding inconsistent results. This study was conducted in Hangzhou, China, with an initial cohort comprising 156 healthy individuals and 162 patients diagnosed with Sjogren's syndrome. We quantified serum levels of PFAAs and examined associations between PFAAs and both susceptibilities to the development of Sjogren's syndrome and immune marker concentrations. Nine PFAAs were frequently detected in the serum, with perfluorooctanoate (PFOA) exhibiting the highest concentration, followed by perfluorooctanesulfonate (PFOS). Exposure to PFOA and perfluorotridecanoate (PFTrDA) was inversely associated with the disease. Furthermore, a negative correlation between PFOA and C-reactive protein (CRP) was observed. These findings suggest that exposure to specific PFAAs may impact the immune system and potentially influence the development of Sjogren's syndrome.

Guardians under Siege: Exploring Pollution's Effects on Human Immunity

Chemical pollution poses a significant threat to human health, with detrimental effects on various physiological systems, including the respiratory, cardiovascular, mental, and perinatal domains. While the impact of pollution on these systems has been extensively studied, the intricate relationship between chemical pollution and immunity remains a critical area of investigation. The focus of this study is to elucidate the relationship between chemical pollution and human immunity. To accomplish this task, this study presents a comprehensive review that encompasses in vitro, ex vivo, and in vivo studies, shedding light on the ways in which chemical pollution can modulate human immunity. Our aim is to unveil the complex mechanisms by which environmental contaminants compromise the delicate balance of the body's defense systems going beyond the well-established associations with defense systems and delving into the less-explored link between chemical exposure and various immune disorders, adding urgency to our understanding of the underlying mechanisms and their implications for public health.

Altered Transcriptome Response in PBMCs of Czech Adults Linked to Multiple PFAS Exposure: B Cell Development as a Target of PFAS Immunotoxicity

While the immunomodulation effects of per- and polyfluoroalkyl substances (PFASs) are described on the level of clinical signs in epidemiological studies (e.g., suppressed antibody response after vaccination), the underlying mechanism has still not been fully elucidated. To reveal mechanisms of PFAS exposure on immunity, we investigated the genome-wide transcriptomic changes of peripheral blood mononuclear cells (PBMCs) responding to PFAS exposure (specifically, exposure to PFPA, PFOA, PFNA, PFDA, PFUnDA, PFHxS, and PFOS). Blood samples and the chemical load in the blood were analyzed under the cross-sectional CELSPAC: Young Adults study. The overall aim of the study was to identify sensitive gene sets and cellular pathways conserved for multiple PFAS chemicals. Transcriptome networks related to adaptive immunity were perturbed by multiple PFAS exposure (i.e., blood levels of at least four PFASs). Specifically, processes tightly connected with late B cell development, such as B cell receptor signaling, germinal center reactions, and plasma cell development, were shown to be affected. Our comprehensive transcriptome analysis identified the disruption of B cell development, specifically the impact on the maturation of antibody-secreting cells, as a potential mechanism underlying PFAS immunotoxicity.