Persistent Problem: Global Challenges to Managing PCBs.

Polychlorinated biphenyls (PCBs), "famous" as persistent organic pollutants (POPs), have been managed nationally since the 1970s and globally under the Stockholm Convention on POPs since 2004, requiring environmentally sound management (ESM) of PCBs by 2028. At most, 30% of countries are on track to achieve ESM by 2028. Globally over 10 million tonnes of PCB-containing materials remain, mostly in countries lacking the ability to manage PCB waste. Canada (Ontario) and Czechia, both parties to the Stockholm Convention, are close to achieving the 2028 goal, having reduced their stocks of pure PCBs by 99% in the past 10 years. In contrast, the USA, not a party to the Stockholm Convention, continues to have a substantial but poorly inventoried stock of PCBs and only ∼3% decrease in mass of PCBs since 2006. PCB management, which depends on Stockholm Convention support and national compliance, portends major challenges for POP management. The failure to manage global PCB stocks >30 years after the end of production highlights the urgent need to prioritize reducing production and use of newer, more widely distributed POPs such as chlorinated paraffins and per- and polyfluorinated alkyl substances, as these management challenges are unlikely to be resolved in the coming decades.

A Cumulative Framework for Identifying Overburdened Populations under the Toxic Substances Control Act: Formaldehyde Case Study.

Extensive scholarship has demonstrated that communities of color, low-income communities, and Indigenous communities face greater environmental and health hazards compared to communities with more White or affluent people. Low-income, Indigenous, Black, and/or other populations of color are also more likely to lack access to health care facilities, healthy food, and adequate formal education opportunities. Despite the mountains of evidence that demonstrate the existence and significance of the elevated toxic social and environmental exposures experienced by these communities, the inclusion of these factors into chemical evaluations has been scarce. In this paper, we demonstrate a process built with publicly available data and simple geospatial techniques that could be utilized by the U.S. Environmental Protection Agency (USEPA) to incorporate cumulative approaches into risk assessments under the Toxic Substances Control Act. The use of these approaches, particularly as they relate to identifying potentially exposed and susceptible subpopulations, would help USEPA develop appropriate risk estimates and mitigation strategies to protect disproportionately burdened populations from the adverse effects of chemical exposures. By utilizing such approaches to inform risk evaluation and mitigation, USEPA can identify and protect those most burdened and impacted by toxic chemicals, and finally begin to close the gap of environmental health inequities.

Assessment of Methylene Chloride-Related Fatalities in the United States, 1980-2018.

Importance: Methylene chloride is a halogenated organic solvent widely used in paint strippers, cleaners, adhesives, and sealants. Despite label warnings and occupational standards, methylene chloride-related fatalities continue to occur in the United States. Objective: To identify and analyze methylene chloride-related fatalities in the US. Design, Setting, and Participants: For this case series, we conducted systematic searches of sources, including PubMed and government databases, for unintentional fatalities in the US that were associated with exposure to methylene chloride or products containing methylene chloride between 1980 and 2018. We reviewed all available information, including inspection reports, autopsy reports, and medical records; data analyses were conducted from August 2018 to August 2020. Cases were categorized as those occurring in the home (consumer deaths) or at work (occupational deaths). Exposures: Methylene chloride or products containing methylene chloride. Main Outcomes and Measures: To determine characteristics of the methylene chloride-related fatalities, we recorded demographic information; the setting; circumstances, including information on safety measures used, if available; and products used. Where medical records were available, we recorded toxicology results and autopsy findings. We also obtained data about nonfatal methylene chloride cases from the American Association of Poison Control Centers. Results: From 1980 to 2018, 85 methylene chloride-related fatalities were identified in the US, including 74 (87%) in occupational settings; of those who died, 75 (94%) were men, and for the 70 cases with available information, the median (interquartile range) age of the decedents was 31 (24-46) years. Paint strippers were the most common products involved in methylene chloride-related fatalities (n = 60). The proportion of occupational fatalities related to paint stripping increased from 22 (55%) before 2000 to 30 (88%) after 2000. Similarly, occupational fatalities associated with bathtub or paint stripping in bathrooms increased from 2 (5%) before 2000 to 21 (62%) after 2000. From 1985 to 2017, the American Association of Poison Control Centers documented 37 201 nonfatal methylene chloride cases, with a decrease in the annual number of cases starting in the late 1990s. Conclusions and Relevance: Results of this case series demonstrated that despite regulations to address the toxic effects of methylene chloride use for consumers and workers, there are continuing fatalities in the US, particularly in occupational settings. Prevention of fatalities associated with methylene chloride exposure should emphasize the use of safer substitutes, rather than hazard warnings or reliance on personal protective equipment.

Carcinogens in Products: Inadequate Protections Raise Cancer Risks.

Evidence shows, that over their life cycle, chemicals used in everyday products contribute to raising cancer risks, especially for vulnerable populations such as children and communities of color. This article outlines how US policies have not yet incorporated current science in relation to environmental carcinogenesis and recommends improvements to protect public health.

Population susceptibility: A vital consideration in chemical risk evaluation under the Lautenberg Toxic Substances Control Act.

The 2016 Frank Lautenberg Chemical Safety for the 21st Century Act (Lautenberg TSCA) amended the 1976 Toxic Substances Control Act (TSCA) to mandate protection of susceptible and highly exposed populations. Program implementation entails a myriad of choices that can lead to different degrees of public health protections. Well-documented exposures to multiple industrial chemicals occur from air, soil, water, food, and products in our workplaces, schools, and homes. Many hazardous chemicals are associated with or known to cause health risks; for other industrial chemicals, no data exist to confirm their safety because of flaws in 1976 TSCA. Under the 2016 Lautenberg amendments, the United States Environmental Protection Agency (EPA) must evaluate chemicals against risk-based safety standards under enforceable deadlines, with an explicit mandate to identify and assess risks to susceptible and highly exposed populations. Effective public health protection requires EPA to implement the Lautenberg TSCA requirements by incorporating intrinsic and extrinsic factors that affect susceptibility, adequately assessing exposure among vulnerable groups, and accurately identifying highly exposed groups. We recommend key scientific and risk assessment principles to inform health-protective chemical policy such as consideration of aggregate exposures from all pathways and, when data are lacking, the use of health-protective defaults.

Organophosphate Ester Flame Retardants: Are They a Regrettable Substitution for Polybrominated Diphenyl Ethers?

As the use of polybrominated diphenyl ethers (PBDEs), and the entire class of organohalogen flame retardants, is declining, the use of organophosphate esters flame retardants (OPFRs) is increasing. In this paper, we ask whether OPFRs are a better choice than PBDEs. To address this question, we compared OPFRs with PBDEs for a wide range of properties. OPFRs exposure is ubiquitous in people and in outdoor and indoor environments, and are now often found at higher levels compared to PBDE peak exposure levels. Furthermore, data from toxicity testing, epidemiological studies, and risk assessments all suggest that there are health concerns at current exposure levels for both halogenated and non-halogenated OPFRs. Obtaining the scientific evidence needed for regulation of OPFRs can take many years. Given the large number of OPFRs in use, manufacturers can move towards healthier and safer products by developing innovative ways to reduce fire hazard for electronics enclosures, upholstered furniture, building materials and other consumer products without adding flame retardant chemicals.

Reducing chemical exposures at home: opportunities for action.

Indoor environments can influence human environmental chemical exposures and, ultimately, public health. Furniture, electronics, personal care and cleaning products, floor coverings and other consumer products contain chemicals that can end up in the indoor air and settled dust. Consumer product chemicals such as phthalates, phenols, flame retardants and per- and polyfluorinated alkyl substances are widely detected in the US general population, including vulnerable populations, and are associated with adverse health effects such as reproductive and endocrine toxicity. We discuss the implications of our recent meta-analysis describing the patterns of chemical exposures and the ubiquity of multiple chemicals in indoor environments. To reduce the likelihood of exposures to these toxic chemicals, we then discuss approaches for exposure mitigation: targeting individual behaviour change, household maintenance and purchasing decisions, consumer advocacy and corporate responsibility in consumer markets, and regulatory action via state/federal policies. There is a need to further develop evidence-based strategies for chemical exposure reduction in each of these areas, given the multi-factorial nature of the problem. Further identifying those at greatest risk; understanding the individual, household and community factors that influence indoor chemical exposures; and developing options for mitigation may substantially improve individuals' exposures and health.

Using yeast to determine the functional consequences of mutations in the human p53 tumor suppressor gene: An introductory course-based undergraduate research experience in molecular and cell biology.

The opportunity to engage in scientific research is an important, but often neglected, component of undergraduate training in biology. We describe the curriculum for an innovative, course-based undergraduate research experience (CURE) appropriate for a large, introductory cell and molecular biology laboratory class that leverages students' high level of interest in cancer. The course is highly collaborative and emphasizes the analysis and interpretation of original scientific data. During the course, students work in teams to characterize a collection of mutations in the human p53 tumor suppressor gene via expression and analysis in yeast. Initially, student pairs use both qualitative and quantitative assays to assess the ability of their p53 mutant to activate expression of reporter genes, and they localize their mutation within the p53 structure. Through facilitated discussion, students suggest possible molecular explanations for the transactivation defects displayed by their p53 mutants and propose experiments to test these hypotheses that they execute during the second part of the course. They use a western blot to determine whether mutant p53 levels are reduced, a DNA-binding assay to test whether recognition of any of three p53 target sequences is compromised, and fluorescence microscopy to assay nuclear localization. Students studying the same p53 mutant periodically convene to discuss and interpret their combined data. The course culminates in a poster session during which students present their findings to peers, instructors, and the greater biosciences community. Based on our experience, we provide recommendations for the development of similar large introductory lab courses. © 2016 by The International Union of Biochemistry and Molecular Biology, 45(2):161-178, 2017.

Consumer Product Chemicals in Indoor Dust: A Quantitative Meta-analysis of U.S. Studies.

Indoor dust is a reservoir for commercial consumer product chemicals, including many compounds with known or suspected health effects. However, most dust exposure studies measure few chemicals in small samples. We systematically searched the U.S. indoor dust literature on phthalates, replacement flame retardants (RFRs), perfluoroalkyl substances (PFASs), synthetic fragrances, and environmental phenols and estimated pooled geometric means (GMs) and 95% confidence intervals for 45 chemicals measured in ≥3 data sets. In order to rank and contextualize these results, we used the pooled GMs to calculate residential intake from dust ingestion, inhalation, and dermal uptake from air, and then identified hazard traits from the Safer Consumer Products Candidate Chemical List. Our results indicate that U.S. indoor dust consistently contains chemicals from multiple classes. Phthalates occurred in the highest concentrations, followed by phenols, RFRs, fragrance, and PFASs. Several phthalates and RFRs had the highest residential intakes. We also found that many chemicals in dust share hazard traits such as reproductive and endocrine toxicity. We offer recommendations to maximize comparability of studies and advance indoor exposure science. This information is critical in shaping future exposure and health studies, especially related to cumulative exposures, and in providing evidence for intervention development and public policy.

A high-enrollment course-based undergraduate research experience improves student conceptions of scientific thinking and ability to interpret data.

We present an innovative course-based undergraduate research experience curriculum focused on the characterization of single point mutations in p53, a tumor suppressor gene that is mutated in more than 50% of human cancers. This course is required of all introductory biology students, so all biology majors engage in a research project as part of their training. Using a set of open-ended written prompts, we found that the course shifts student conceptions of what it means to think like a scientist from novice to more expert-like. Students at the end of the course identified experimental repetition, data analysis, and collaboration as important elements of thinking like a scientist. Course exams revealed that students showed gains in their ability to analyze and interpret data. These data indicate that this course-embedded research experience has a positive impact on the development of students' conceptions and practice of scientific thinking.

The ciliogenic protein Oral-Facial-Digital 1 regulates the neuronal differentiation of embryonic stem cells.

Oral-Facial-Digital 1 (OFD1) Syndrome is an X-linked developmental disorder caused by mutations in the gene Ofd1. OFD1 syndrome involves malformation of the face, oral cavity, and digits and may be characterized by cystic kidneys and mental retardation. Deletion or missense mutations in Ofd1 also result in loss of primary cilia, a microtubule-based cellular projection that mediates multiple signaling pathways. Ofd1 mutant mice display pleiotropic developmental phenotypes, including neural, skeletal, and cardiac defects. To address how loss of Ofd1 and loss of primary cilia affect early differentiation decisions, we analyzed embryoid bodies (EBs) derived from Ofd1 mutant embryonic stem (ES) cells. Ofd1 mutant EBs do not form primary cilia and display defects in Hedgehog and Wnt signaling. Additionally, we show that ES cells lacking Ofd1 display an increased capacity to differentiate into neurons. Nevertheless, neurons derived from Ofd1 mutant ES cells fail to differentiate into V3 interneurons, a cell type dependent on ciliary function and Hedgehog signaling. Thus, loss of Ofd1 affects ES cell interpretation of developmental cues and reveals that EBs model some aspects of ciliopathies, providing insights into the developmental origins of OFD1 syndrome and functions of cilia.

Ofd1, a human disease gene, regulates the length and distal structure of centrioles.

Centrosomes and their component centrioles represent the principal microtubule organizing centers of animal cells. Here, we show that the gene underlying orofaciodigital syndrome 1, Ofd1, is a component of the distal centriole that controls centriole length. In the absence of Ofd1, distal regions of centrioles, but not procentrioles, elongate abnormally. These long centrioles are structurally similar to normal centrioles but contain destabilized microtubules with abnormal posttranslational modifications. Ofd1 is also important for centriole distal appendage formation and centriolar recruitment of the intraflagellar transport protein Ift88. To model OFD1 syndrome in embryonic stem cells, we replaced the Ofd1 gene with missense alleles from human OFD1 patients. Distinct disease-associated mutations cause different degrees of excessive or decreased centriole elongation, all of which are associated with diminished ciliogenesis. Our results indicate that Ofd1 acts at the distal centriole to build distal appendages, recruit Ift88, and stabilize centriolar microtubules at a defined length.

DNA damage drives an activin a-dependent induction of cyclooxygenase-2 in premalignant cells and lesions.

Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in the synthesis of prostaglandins. Its overexpression induces numerous tumor-promoting phenotypes and is associated with cancer metastasis and poor clinical outcome. Although COX-2 inhibitors are promising chemotherapeutic and chemopreventative agents for cancer, the risk of significant cardiovascular and gastrointestinal complications currently outweighs their potential benefits. Systemic complications of COX-2 inhibition could be avoided by specifically decreasing COX-2 expression in epithelial cells. To that end, we have investigated the signal transduction pathway regulating the COX-2 expression in response to DNA damage in breast epithelial cells. In variant human mammary epithelial cells that have silenced p16 (vHMEC), double-strand DNA damage or telomere malfunction results in a p53- and activin A-dependent induction of COX-2 and continued proliferation. In contrast, telomere malfunction in HMEC with an intact p16/Rb pathway induces cell cycle arrest. Importantly, in ductal carcinoma in situ lesions, high COX-2 expression is associated with high gammaH2AX, TRF2, activin A, and telomere malfunction. These data show that DNA damage and telomere malfunction can have both cell-autonomous and cell-nonautonomous consequences and can provide a novel mechanism for the propagation of tumorigenesis.

Floxin, a resource for genetically engineering mouse ESCs.

We describe a method for the highly efficient and precise targeted modification of gene trap loci in mouse embryonic stem cells (ESCs). Through the Floxin method, gene trap mutations were reverted and new DNA sequences inserted using Cre recombinase and a shuttle vector, pFloxin. Floxin technology is applicable to the existing collection of 24,149 compatible gene trap cell lines, which should enable high-throughput modification of many genes in mouse ESCs.

Kif3a constrains beta-catenin-dependent Wnt signalling through dual ciliary and non-ciliary mechanisms.

Primary cilia are microtubule-based organelles involved in signal transduction and project from the surface of most vertebrate cells. Proteins that can localize to the cilium, for example, Inversin and Bardet-Biedl syndrome (BBS) proteins, are implicated in both beta-catenin-dependent and -independent Wnt signalling. Given that Inversin and BBS proteins are found both at the cilium and elsewhere in the cell, the role of the cilium itself in Wnt signalling is not clear. Using three separate mutations that disrupt ciliogenesis (affecting Kif3a, Ift88 and Ofd1), we show in this study that the primary cilium restricts the activity of the canonical Wnt pathway in mouse embryos, primary fibroblasts, and embryonic stem cells. Interestingly, unciliated cells activate transcription only in response to Wnt stimulation, but do so much more robustly than ciliated cells. Loss of Kif3a, but not other ciliogenic genes, causes constitutive phosphorylation of Dishevelled (Dvl). Blocking the activity of casein kinase I (CKI) reverses this constitutive Dvl phosphorylation and abrogates pathway hyper-responsiveness. These results suggest that Kif3a restrains canonical Wnt signalling both by restricting the CKI-dependent phosphorylation of Dvl and through a separate ciliary mechanism. More generally, these findings reveal that, in contrast to its role in promoting Hedgehog (Hh) signalling, the cilium restrains canonical Wnt signalling.

The primary cilium as the cell's antenna: signaling at a sensory organelle.

Almost every vertebrate cell has a specialized cell surface projection called a primary cilium. Although these structures were first described more than a century ago, the full scope of their functions remains poorly understood. Here, we review emerging evidence that in addition to their well-established roles in sight, smell, and mechanosensation, primary cilia are key participants in intercellular signaling. This new appreciation of primary cilia as cellular antennae that sense a wide variety of signals could help explain why ciliary defects underlie such a wide range of human disorders, including retinal degeneration, polycystic kidney disease, Bardet-Biedl syndrome, and neural tube defects.