Environmental exposures play an important role in the development of diseases [...]

Benzene is a ubiquitous environmental pollutant that induces blood cancers via its complex metabolism. Since cancer risks to the general public involve toxic benzene metabolites derived from the inhalation of benzene at ppb air concentrations, questions remain regarding low-dose metabolism. Using previously published data from 389 Chinese workers, we fit Michaelis–Menten-like models to predict urinary concentrations of E,E-muconic acid (the most discriminating urinary metabolite) as functions of urinary benzene levels between 0.0001 μM and 54 μM, equivalent to benzene air concentrations between 0.1 ppb and more than 100 ppm. When we compared models having either one or two metabolic pathways, weights of evidence favoring two pathways were essentially 100 percent for nonsmoking males and females and 58 percent for smoking males. At ppb exposure levels, metabolic rates for the high-affinity pathway were 43-fold greater than those for the low-affinity pathway in nonsmoking males, 6.5-fold greater in nonsmoking females, and 4.9-fold greater in smoking males. Thus, the high-affinity pathway is most efficient in nonsmoking males and is inhibited by smoking. The characteristics of the two-pathway model implicate lung metabolism of benzene via CYP2A13 and/or CYP2F1 at ppb air levels and liver metabolism by CYP2E1 above one ppm. Since ambient benzene concentrations are typically less than 10 ppb, blood-cancer risks predicted from workers exposed to above 1 ppm likely underestimate risks to the general public by many fold, and these risks may be modulated by smoking. Also, since the lung is the site of initial metabolism upon inhalation, the respiratory bioactivation of benzene could contribute to lung-cancer incidence, including that for lung adenomas in never smokers.

Nearly one fourth of lung cancers occur among never-smokers and are predominately lung adenocarcinomas (LUADs) that are distinct from smoking-related cancers. Causal links between LUADs in never-smokers have been attributed to reactive oxygen species (ROS) arising from airborne fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs). These effects are pronounced among East Asian women who experience massive exposures to PM2.5 and PAHs and have the highest incidence of LUADs in the world. We employed untargeted adductomics to establish ROS adduct signatures in human serum albumin (HSA) from lung cancer cases and controls from never-smokers in the Shanghai Women’s Health Study. Forty-seven HSA adducts were quantified by mass spectrometry, nine of which were selected for association with lung cancer, including Cys34 sulfoxidation products and disulfides of cysteine and homocysteine and two modifications to Lys525. Associated adducts include constituents of redox biology and one-carbon metabolism (OCM), which are pathways associated with lung cancer. Differences in adduct abundance between cases and controls and correlations of adducts with urinary PAHs and dietary factors provide additional evidence linking air pollutants, OCM, and redox biology with lung cancer in never-smokers.

The key characteristics (KCs) of carcinogens are the properties common to known human carcinogens that can be used to search for, organize, and evaluate mechanistic data in support of hazard identification. A limiting factor in this approach is that relevant in vitro and in vivo assays, as well as corresponding biomarkers and endpoints, have been only partially documented for each of the 10 KCs (Smith MT, Guyton KZ, Kleinstreuer N et al. The key characteristics of carcinogens: relationship to the hallmarks of cancer, relevant biomarkers, and assays to measure them. Cancer Epidemiol Biomarkers Prev 2020;29:1887-903. https://doi.org/10.1158/1055-9965.EPI-19-1346). To address this limitation, a comprehensive database is described that catalogues these previously described methods and endpoints/biomarkers pertinent to the 10 KCs of carcinogens as well as those referenced as supporting evidence for each KC in the International Agency of Research on Cancer Monograph Volumes 112-131. Our comprehensive mapping of KCs to assays and endpoints can be used to facilitate mechanistic data searches, presents a useful tool for searching for assays and endpoints relevant to the 10 KCs, and can be used to create a roadmap for utilizing data to evaluate the strength of the evidence for each KC. The KC-Assay database is available to the public on the web at https://kcad.cchem.berkeley.edu and acts as a 'living document', with the ability to be updated and refined. Database URL: https://kcad.cchem.berkeley.edu.

Abstract Introduction Occupational exposure to formaldehyde (FA) has been linked to hematopoietic and nasopharyngeal cancers. Methods To further evaluate the biological effects of exposure to FA in humans, we used comprehensive untargeted liquid chromatography with high resolution mass spectrometry (LC-HRMS) to characterize the plasma metabolome of workers (n=43) exposed to relatively high levels of FA [median 8-h time-weighted air level average exposure: 1.3 parts-per-million (ppm) of air] and comparable controls (n=51). Metabolite features associated with FA exposure were identified using a metabolome- wide association study that tested for relationships between metabolite feature intensity and occupational exposure to FA. Results and discussion Metabolic pathway enrichment analysis highlighted multiple pathways associated with FA exposure, with significant changes in the carnitine shuttle and in arachidonic acid, fatty acid, nucleic acid, amino acid, steroid, and prostaglandin metabolism. These results suggest possible changes or perturbations from FA exposure in fatty acid uptake, oxidative stress, and pathways related to mitochondrial dysfunction, immune system disorders, and altered cell proliferation, several of which are consistent with previous experimental and human studies. Taken together, our results suggest that occupational exposure to FA was associated with alterations in a number of systemic metabolic processes. Conclusion Further study is needed with larger sample sizes to replicate and extend these findings.

Supplementary Figure S4A and S4B: Comparison of Designs 0/1A/1B and Designs 0/3A/3B

In June, 2023, a Working Group of 25 scientists from 12 countries met at the International Agency for Research on Cancer (IARC) in Lyon, France, to finalise their evaluation of the carcinogenicity of aspartame, methyleugenol, and isoeugenol. Aspartame was classified as "possibly carcinogenic to humans" (Group 2B) based on "limited" evidence for cancer in humans. There was also "limited" evidence for cancer in experimental animals and "limited" mechanistic evidence. Methyleugenol was classified as "probably carcinogenic to humans" (Group 2A) based on "sufficient" evidence for cancer in experimental animals and "strong" mechanistic evidence, including studies in humanised mice and supported by mechanistic studies in exposed humans.

Glyphosate was classified as a probable human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC) partially due to strong mechanistic evidence in 2015. Since then, numerous studies of glyphosate and its formulations (GBF) have emerged. These studies can be evaluated for cancer hazard identification with the newly described ten key characteristics (KC) of carcinogens approach. Our objective was to assess all in vivo, ex vivo, and in vitro mechanistic studies of human and experimental animals (mammals) that compared exposure to glyphosate/GBF with low/no exposure counterparts for evidence of the ten KCs. A protocol with our methods adhering to PRISMA guidelines was registered a priori (INPLASY202180045). Two blinded reviewers screened all in vivo, ex vivo, and in vitro studies of glyphosate/GBF exposure in humans/mammals reporting any KC-related outcome available in PubMed before August 2021. Studies that met inclusion criteria underwent data extraction conducted in duplicate for each KC outcome reported along with key aspects of internal/external validity, results, and reference information. These data were used to construct a matrix that was subsequently analyzed in the program R to conduct strength of evidence and quality assessments. Of the 2537 articles screened, 175 articles met inclusion criteria, from which we extracted >50,000 data points related to KC outcomes. Data analysis revealed strong evidence for KC2, KC4, KC5, KC6, KC8, limited evidence for KC1 and KC3, and inadequate evidence for KC7, KC9, and KC10. Notably, our in-depth quality analyses of genotoxicity (KC2) and endocrine disruption (KC8) revealed strong and consistent positive findings. For KC2, we found: 1) studies conducted in humans and human cells provided stronger positive evidence than counterpart animal models; 2) GBF elicited a stronger effect in both human and animal systems when compared to glyphosate alone; and 3) the highest quality studies in humans and human cells consistently revealed strong evidence of genotoxicity. Our analysis of KC8 indicated that glyphosate's ability to modulate hormone levels and estrogen receptor activity is sensitive to both exposure concentration and formulation. The modulations observed provide clear evidence that glyphosate interacts with receptors, alters receptor activation, and modulates the levels and effects of endogenous ligands (including hormones). Our findings strengthen the mechanistic evidence that glyphosate is a probable human carcinogen and provide biological plausibility for previously reported cancer associations in humans, such as non-Hodgkin lymphoma. We identified potential molecular interactions and subsequent key events that were used to generate a probable pathway to lymphomagenesis.

Supplementary Figure S2A and S2B: miR qPCR Assay Comparison

Background: Impairment of the hematopoietic system is one of the primary adverse health effects from exposure to benzene. We previously have shown that exposure to benzene at low levels (<1 ppm) affects the blood forming system and that these effects were proportionally stronger at lower versus higher levels of benzene exposure. This observation is potentially explained by saturation of enzymatic systems. Methods: Here we extend these analyses by detailed modeling of the exposure response association of benzene and its major metabolites (i.e. catechol, muconic acid, phenol, and hydroquinone) on peripheral white blood cell (WBC) counts and its major cell-subtypes (i.e. granulocytes, lymphocytes, and monocytes) using two previously published cross-sectional studies among occupationally exposed Chinese workers. Results: Supra-linear exposure response associations were observed between air benzene concentrations (range similar to 0.1 - 100 ppm) and WBC counts and its cell-subtypes, with a larger than proportional decrease in cell counts at lower than at higher levels of benzene exposure. The hematotoxicity associations were largely similar in shape when the analyses were repeated with benzene urinary metabolites suggesting that enzymatic saturation is not a full explanation of the observed non-linearity with WBC endpoints. Discussion: We hypothesize that the flattening of the exposure response curve especially at higher benzene exposure levels may reflect a response by the bone marrow to maintain hematopoietic homeostasis. Toxicity to the bone marrow and an induced hyper-proliferative response could both contribute to risk of subsequently developing a hematopoietic malignancy. Additional work is needed to explore this hypothesis.

BACKGROUND:The ability to induce chronic inflammation and immunosuppression are two key characteristics of carcinogens and important forms of immunotoxicity. The National Toxicology Program (NTP) evaluated the immunotoxicity of two per- and polyfluoroalkyl substances (PFASs), PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate), in 2016. However, the potential pro-inflammatory and immunosuppressive effects of other PFASs remain largely uncharacterized.METHODS:We developed an expanded set of search terms pertaining to the chronic inflammatory and immunosuppressive effects of PFASs based on those of the International Agency for Research on Cancer (IARC) and NTP. To confirm searching effectiveness and scope, we compared our search term results with those of IARC and NTP for both PFASs and two other known carcinogens, chromium (VI) and benzene. Systematic evidence maps (SEMs) were also produced using Tableau to visualize the distribution of study numbers and types reporting immunotoxic effects and specific biomarkers elicited by PFAS exposures.RESULTS:In total, 1155 PFAS studies were retrieved, of which 321 qualified for inclusion in our dataset. Using our search terms, we identified a greater number of relevant studies than those obtained using IARC and NTP's search terms. From the SEM findings, increased cytokine production strengthened an association between PFAS exposure and chronic inflammation, and decreased B-cell activation and altered levels of T-cell subtypes and immunoglobulins confirmed PFAS-induced immunosuppression.CONCLUSION:Our SEM findings confirm that several PFASs commonly found in both in the environment, including those that are lesser-known, may induce immunosuppression and chronic inflammation, two key characteristics of carcinogens. This approach, including development of search terms, study screening process, data coding, and evidence mapping visualizations, can be applied to other key characteristics of chemical carcinogens.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical

Supplementary Legends for Figures S1-S4

Supplementary Figure S1A and S1B: miR Extraction Methods Comparison

Supplementary Methods for miR Extraction, qPCR, and statistical analysis

Supplementary Table 1 from Chromosome 12p Deletions in TEL-AML1 Childhood Acute Lymphoblastic Leukemia Are Associated with Retrotransposon Elements and Occur Postnatally

Supplementary Figure S3A-S3C: Cumulative Distributions including 95% Confidence Intervals