Systematic Review Methodologies and Endocrine Disrupting Chemicals: Improving Evaluations of the Plastic Monomer Bisphenol A

Towards a more effective REACH legislation in protecting human health

There is growing evidence indicating the substantial contribution of man-made products to an increase in the risk of diseases of civilization. In this article, the Belgian Scientific Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) Committee gives a critical view on the working of REACH. The current regulatory framework needs to further evolve taking into account data generated using modern science and technology. There is a need for improved assessment process not only before but also after entering the market. Objectivity, transparency, and the follow-up after market access can be optimized. Additionally, no guidance documents exist for regulation of mixture effects. Further, the lengthiness before regulatory action is a big concern. Decision-making often takes several years leading to uncertainties for both producers and end users. A first proposed improvement is the implementation of independent toxicity testing, to assure objectivity, transparency, and check and improve compliance. A "no data, no market" principle could prevent access of hazardous chemicals to the market. Additionally, the introduction of novel testing could improve information on endpoints such as endocrine disrupting abilities, neurotoxicity, and immunotoxicity. An adapted regulatory framework that integrates data from different sources and comparing the outputs with estimates of exposure is required. Fast toxicology battery testing and toxicokinetic testing could improve speed of decision-making. Hereby, several improvements have been proposed that could improve the current REACH legislation.

The Conflict between Regulatory Agencies over the 20,000-Fold Lowering of the Tolerable Daily Intake (TDI) for Bisphenol A (BPA) by the European Food Safety Authority (EFSA)

BACKGROUND

The European Food Safety Authority (EFSA) recommended lowering their estimated tolerable daily intake (TDI) for bisphenol A (BPA) 20,000-fold to 0.2  ng / kg  body weight  ( BW ) / day . BPA is an extensively studied high production volume endocrine disrupting chemical (EDC) associated with a vast array of diseases. Prior risk assessments of BPA by EFSA as well as the US Food and Drug Administration (FDA) have relied on industry-funded studies conducted under good laboratory practice protocols (GLP) requiring guideline end points and detailed record keeping, while also claiming to examine (but rejecting) thousands of published findings by academic scientists. Guideline protocols initially formalized in the mid-twentieth century are still used by many regulatory agencies. EFSA used a 21st century approach in its reassessment of BPA and conducted a transparent, but time-limited, systematic review that included both guideline and academic research. The German Federal Institute for Risk Assessment (BfR) opposed EFSA's revision of the TDI for BPA.

OBJECTIVES

We identify the flaws in the assumptions that the German BfR, as well as the FDA, have used to justify maintaining the TDI for BPA at levels above what a vast amount of academic research shows to cause harm. We argue that regulatory agencies need to incorporate 21st century science into chemical hazard identifications using the CLARITY-BPA (Consortium Linking Academic and Regulatory Insights on BPA Toxicity) nonguideline academic studies in a collaborative government-academic program model.

DISCUSSION

We strongly endorse EFSA's revised TDI for BPA and support the European Commission's (EC) apparent acceptance of this updated BPA risk assessment. We discuss challenges to current chemical risk assessment assumptions about EDCs that need to be addressed by regulatory agencies to, in our opinion, become truly protective of public health. Addressing these challenges will hopefully result in BPA, and eventually other structurally similar bisphenols (called regrettable substitutions) for which there are known adverse effects, being eliminated from all food-related and many other uses in the EU and elsewhere. https://doi.org/10.1289/EHP13812.

The bisphenol S contamination level observed in human follicular fluid affects the development of porcine oocytes

Bisphenol S (BPS), the main replacement for bisphenol A (BPA), is thought to be toxic, but limited information is available on the effects of Bisphenol S on ovarian follicles. In our study, we demonstrated the presence of Bisphenol S in the follicular fluid of women at a concentration of 22.4 nM. The effect of such concentrations of Bisphenol S on oocyte maturation and subsequent embryo development is still unknown. Therefore, we focused on the effect of Bisphenol S on in vitro oocyte maturation, fertilization, and embryo development. As a model, we used porcine oocytes, which show many physiological similarities to human oocytes. Oocytes were exposed to Bisphenol S concentrations similar to those detected in female patients in the ART clinic. We found a decreased ability of oocytes to successfully complete meiotic maturation. Mature oocytes showed an increased frequency of meiotic spindle abnormalities and chromosome misalignment. Alarming associations of oocyte Bisphenol S exposure with the occurrence of aneuploidy and changes in the distribution of mitochondria and mitochondrial proteins were demonstrated for the first time. However, the number and quality of blastocysts derived from oocytes that successfully completed meiotic maturation under the influence of Bisphenol S was not affected.

Addressing systemic problems with exposure assessments to protect the public's health

BACKGROUND

Understanding, characterizing, and quantifying human exposures to environmental chemicals is critical to protect public health. Exposure assessments are key to determining risks to the general population and for specific subpopulations given that exposures differ between groups. Exposure data are also important for understanding where interventions, including public policies, should be targeted and the extent to which interventions have been successful. In this review, we aim to show how inadequacies in exposure assessments conducted by polluting industries or regulatory agencies have led to downplaying or disregarding exposure concerns raised by communities; that underestimates of exposure can lead regulatory agencies to conclude that unacceptable risks are, instead, acceptable, allowing pollutants to go unregulated; and that researchers, risk assessors, and policy makers need to better understand the issues that have affected exposure assessments and how appropriate use of exposure data can contribute to health-protective decisions.

METHODS

We describe current approaches used by regulatory agencies to estimate human exposures to environmental chemicals, including approaches to address limitations in exposure data. We then illustrate how some exposure assessments have been used to reach flawed conclusions about environmental chemicals and make recommendations for improvements.

RESULTS

Exposure data are important for communities, public health advocates, scientists, policy makers, and other groups to understand the extent of environmental exposures in diverse populations. We identify four areas where exposure assessments need to be improved due to systemic sources of error or uncertainty in exposure assessments and illustrate these areas with examples. These include: (1) an inability of regulatory agencies to keep pace with the increasing number of chemicals registered for use or assess their exposures, as well as complications added by use of 'confidential business information' which reduce available exposure data; (2) the failure to keep assessments up-to-date; (3) how inadequate assumptions about human behaviors and co-exposures contribute to underestimates of exposure; and (4) that insufficient models of toxicokinetics similarly affect exposure estimates.

CONCLUSION

We identified key issues that impact capacity to conduct scientifically robust exposure assessments. These issues must be addressed with scientific or policy approaches to improve estimates of exposure and protect public health.

Best practices to quantify the impact of reproductive toxicants on development, function, and diseases of the rodent mammary gland

Work from numerous fields of study suggests that exposures to hormonally active chemicals during sensitive windows of development can alter mammary gland development, function, and disease risk. Stronger links between many environmental pollutants and disruptions to breast health continue to be documented in human populations, and there remain concerns that the methods utilized to identify, characterize, and prioritize these chemicals for risk assessment and risk management purposes are insufficient. There are also concerns that effects on the mammary gland have been largely ignored by regulatory agencies. Here, we provide technical guidance that is intended to enhance collection and evaluation of the mammary gland in mice and rats. We review several features of studies that should be controlled to properly evaluate the mammary gland, and then describe methods to appropriately collect the mammary gland from rodents. Furthermore, we discuss methods for preparing whole mounted mammary glands and numerous approaches that are available for the analysis of these samples. Finally, we conclude with several examples where analysis of the mammary gland revealed effects of environmental toxicants at low doses. Our work argues that the rodent mammary gland should be considered in chemical safety, hazard and risk assessments. It also suggests that improved measures of mammary gland outcomes, such as those we present in this review, should be included in the standardized methods evaluated by regulatory agencies such as the test guidelines used for identifying reproductive and developmental toxicants.

Signaling Proteins That Regulate Spermatogenesis Are the Emerging Target of Toxicant-Induced Male Reproductive Dysfunction

There is emerging evidence that environmental toxicants, in particular endocrine disrupting chemicals (EDCs) such as cadmium and perfluorooctanesulfonate (PFOS), induce Sertoli cell and testis injury, thereby perturbing spermatogenesis in humans, rodents and also widelife. Recent studies have shown that cadmium (e.g., cadmium chloride, CdCl₂) and PFOS exert their disruptive effects through putative signaling proteins and signaling cascade similar to other pharmaceuticals, such as the non-hormonal male contraceptive drug adjudin. More important, these signaling proteins were also shown to be involved in modulating testis function based on studies in rodents. Collectively, these findings suggest that toxicants are using similar mechanisms that used to support spermatogenesis under physiological conditions to perturb Sertoli and testis function. These observations are physiologically significant, since a manipulation on the expression of these signaling proteins can possibly be used to manage the toxicant-induced male reproductive dysfunction. In this review, we highlight some of these findings and critically evaluate the possibility of using this approach to manage toxicant-induced defects in spermatrogenesis based on recent studies in animal models.