Risk assessment of endocrine active chemicals: Identifying chemicals of regulatory concern

The European regulation on plant protection products (1107/2009) (EC, 2009a), the revisions to the biocides Directive (COM[2009]267) (EC, 2009b), and the regulation concerning chemicals (Regulation (EC) No. 1907/2006 ‘REACH’) (EC.2006) only support the marketing and use of chemical products on the basis that they do not induce endocrine disruption in humans or wildlife species. In the absence of agreed guidance on how to identify and evaluate endocrine activity and disruption within these pieces of legislation a European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) task force was formed to provide scientific criteria that may be used within the context of these three legislative documents. The resulting ECETOC technical report (ECETOC, 2009a) and the associated workshop (ECETOC, 2009b) presented a science-based concept on how to identify endocrine activity and disrupting properties of chemicals for both human health and the environment. The synthesis of the technical report and the workshop report was published by the ECETOC task force (Bars et al., 2011a and Bars et al., 2011b). Specific scientific criteria for the determination of endocrine activity and disrupting properties that integrate information from both regulatory (eco)toxicity studies and mechanistic/screening studies were proposed. These criteria combined the nature of the adverse effects detected in studies which give concern for endocrine toxicity with an understanding of the mode of action of toxicity so that adverse effects can be explained scientifically. A key element in the data evaluation is the consideration of all available information in a weight-of-evidence approach. However, to be able to discriminate chemicals with endocrine properties of low concern from those of higher concern (for regulatory purposes), the task force recognised that the concept needed further refinement. Following a discussion of the key factors at a second workshop of invited regulatory, academic and industry scientists (ECETOC, 2011), the task force developed further guidance, which is presented in this paper. For human health assessments these factors include the relevance to humans of the endocrine mechanism of toxicity, the specificity of the endocrine effects with respect to other potential toxic effects, the potency of the chemical to induce endocrine toxicity and consideration of exposure levels. For ecotoxicological assessments the key considerations include specificity and potency, but also extend to the consideration of population relevance and negligible exposure. It is intended that these complement and reinforce the approach originally described and previously published in this journal (Bars et al., 2011a and Bars et al., 2011b).     

Risk assessment of ‘endocrine substances’: Guidance on identifying endocrine disruptors

The European regulation on plant protection products (1107/2009) and other related legislation only support the marketing and use of chemical products on the basis that they do not induce endocrine disruption in humans or wildlife species. This legislation would appear to make the assumption that endocrine active chemicals should be managed differently from other chemicals presumably due to an assumed lack of a threshold for adverse effects. In the absence of agreed scientific criteria and guidance on how to identify and evaluate endocrine activity and disruption within these pieces of legislation, a European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) task force was formed to provide scientific criteria that may be used within the context of these three legislative documents. The first ECETOC technical report and associated workshop, held in 2009, presented a science-based concept on how to identify endocrine activity and disrupting properties of chemicals for both human health and the environment. Specific scientific criteria for the determination of endocrine activity and disrupting properties that integrate information from both regulatory toxicity studies and mechanistic/screening studies were proposed. These criteria combined the nature of the adverse effects detected in studies which give concern for endocrine toxicity with an understanding of the mode of action of toxicity so that adverse effects can be explained scientifically. A key element in the data evaluation is the consideration of all available information in a weight-of-evidence approach.     

Decision trees for evaluating skin and respiratory sensitizing potential of chemicals in accordance with European regulations

Guidance for determining the sensitizing potential of chemicals is available in EC Regulation No. 1272/2008 Classification, Labeling, and Packaging of Substances; REACH guidance from the European Chemicals Agency; and the United Nations Globally Harmonized System (GHS). We created decision trees for evaluating potential skin and respiratory sensitizers. Our approach (1) brings all the regulatory information into one brief document, providing a step-by-step method to evaluate evidence that individual chemicals or mixtures have sensitizing potential; (2) provides an efficient, uniform approach that promotes consistency when evaluations are done by different reviewers; (3) provides a standard way to convey the rationale and information used to classify chemicals. We applied this approach to more than 50 chemicals distributed among 11 evaluators with varying expertise. Evaluators found the decision trees easy to use and recipients (product stewards) of the analyses found that the resulting documentation was consistent across users and met their regulatory needs. Our approach allows for transparency, process management (e.g., documentation, change management, version control), as well as consistency in chemical hazard assessment for REACH, EC Regulation No. 1272/2008 Classification, Labeling, and Packaging of Substances and the GHS.     

An approach to the identification and regulation of endocrine disrupting pesticides

Recent decades have seen an increasing interest in chemicals that interact with the endocrine system and have the potential to alter the normal function of this system in humans and wildlife. Chemicals that produce adverse effects caused by interaction with endocrine systems are termed Endocrine Disrupters (EDs). This interest has led regulatory authorities around the world (including the European Union) to consider whether potential endocrine disrupters should be identified and assessed for effects on human health and wildlife and what harmonised criteria could be used for such an assessment. This paper reviews the results of a study whereby toxicity data relating to human health effects of 98 pesticides were assessed for endocrine disruption potential using a number of criteria including the Specific Target Organ Toxicity for repeat exposure (STOT-RE) guidance values used in the European Classification, Labelling and Packaging (CLP) Regulation. Of the pesticides assessed, 27% required further information in order to make a more definitive assessment, 14% were considered to be endocrine disrupters, more or less likely to pose a risk, and 59% were considered not to be endocrine disrupters.     

ECETOC florence workshop on risk assessment of endocrine substances,including the potency concept

The European regulation on plant protection products (1107/2009) and the Biocidal Products Regulation (EC Regulation 528/2012) only support the marketing and use of chemicals if they do not cause endocrine disruption in humans or wildlife species. Also, substances with endocrine properties are subject to authorization under the European regulation on the registration, evaluation, authorization and restriction of chemicals (REACH; 1907/2006).     

Exposure-driven risk assessment: Applying exposure-based waiving of toxicity tests under REACH

The REACH Regulation 1907/2006/EC aims to improve knowledge of the potential risks to humans and the environment of the large number of chemicals produced and used in the EU. The testing requirements are likely to trigger numerous toxicological studies, potentially involving millions of experimental animals, despite the professed goal of REACH to reduce vertebrate testing. It may be necessary therefore to shift emphasis away from animal studies towards more pragmatic strategies, reserving animal tests for the substances of greatest concern. One approach is to waive certain tests based on levels of exposure to the substance. This review explores application of ‘Exposure-Based Waiving’ (EBW) of toxicity studies, with a particular focus on inhalation where possible, considering the potential qualitative and quantitative supporting arguments that might be made, including the use of thresholds of toxicological concern. Incorporating EBW into intelligent testing strategies for substance registration could advance the goals of REACH and the 3Rs (reduction, replacement and refinement of animals in research) by reducing the usage of animals in toxicity tests, whilst maintaining appropriate protection of human health and the environment. However greater regulatory evaluation, acceptance and guidance are required for EBW to achieve its full impact.     

Health risk assessment procedures for endocrine disrupting compounds within different regulatory frameworks in the European Union

In this study we have investigated how different regulatory frameworks in Europe cope with identification and risk assessment of endocrine disrupting compounds (EDCs). Four regulatory groups were selected for the investigation: existing industrial chemicals, environmental pollutants in food, pharmaceuticals and plant protection products. The legislation and guidelines for each of these groups were scrutinized and compared in detail. In addition, one recent European risk assessment document each for three identified EDCs, i.e. bisphenol A, dioxins and vinclozolin, were reviewed and compared. We found that the requirements for toxicity testing and availability and scope of risk assessment guidelines varied between the four regulatory frameworks. Also, the general principles regarding the human relevance of the mode of action identified in animal tests differed in the different risk assessments. In conclusion, there is little conformity in the risk assessment processes between these groups of chemicals. Because of the complicated nature of endocrine disruption, test methods, principles and criteria for data interpretation traditionally used might not be directly applicable to EDCs and further development of a transparent and reliable risk assessment process for this type of substances is needed.     

Assessment of three approaches for regulatory decision making on pesticides with endocrine disrupting properties

Recent EU legislation has introduced endocrine disrupting properties as a hazard-based “cut-off” criterion for the approval of active substances as pesticides and biocides. Currently, no specific science-based approach for the assessment of substances with endocrine disrupting properties has been agreed upon, although this new legislation provides interim criteria based on classification and labelling.Different proposals for decision making on potential endocrine disrupting properties in human health risk assessment have been developed by the German Federal Institute for Risk Assessment (BfR) and other regulatory bodies. All these frameworks, although differing with regard to hazard characterisation, include a toxicological assessment of adversity of the effects, the evaluation of underlying modes/mechanisms of action in animals and considerations concerning the relevance of effects to humans.Three options for regulatory decision making were tested upon 39 pesticides for their applicability and to analyze their potential impact on the regulatory status of active substances that are currently approved for use in Europe: Option 1, based purely on hazard identification (adversity, mode of action, and the plausibility that both are related); Option 2, based on hazard identification and additional elements of hazard characterisation (severity and potency); Option 3, based on the interim criteria laid down in the recent EU pesticides legislation. Additionally, the data analysed in this study were used to address the questions, which parts of the endocrine system were affected, which studies were the most sensitive and whether no observed adverse effect levels were observed for substance with ED properties.The results of this exercise represent preliminary categorisations and must not be used as a basis for definitive regulatory decisions. They demonstrate that a combination of criteria for hazard identification with additional criteria of hazard characterisation allows prioritising and differentiating between substances with regard to their regulatory concern. It is proposed to integrate these elements into a decision matrix to be used within a weight of evidence approach for the toxicological categorisation of relevant endocrine disruptors and to consider all parts of the endocrine system for regulatory decision making on endocrine disruption.     

Assessment strategies and decision criteria for pesticides with endocrine disrupting properties relevant to humans

There is growing concern that environmental substances with a potential to modulate the hormonal system may have harmful effects on human health. Consequently, a new EU regulation names endocrine disrupting properties as one of the cut-off criteria for the approval of plant protection products, although it currently fails to provide specific science-based measures for the assessment of substances with such properties. Since specific measures are to be presented by the European Commission in 2013 the development of assessment and decision criteria is a key challenge concerning the implementation of this new EU regulation. Proposals of such decision criteria for substances with potential endocrine disrupting properties in human health risk assessment were developed by the German Federal Institute for Risk Assessment (BfR) and discussed at an expert workshop in November 2009. Under consideration of the requirements laid down within the new plant protection product legislation and the scientific discussions during the workshop, a conceptual framework on evaluation of substances for endocrine disrupting properties in a regulatory context is presented in this paper. Central aspects of the framework include assessment of adversity of effects, establishment of a mode/mechanism of action in animals, considerations concerning the relevance of effects to humans and two options for a regulatory decision.     

Incorporation of endocrine disruption into chemical hazard scoring for pollution prevention and current list of endocrine disrupting chemicals

Research continues to support the theory of endocrine disruption. Endocrine disruption is defined as the ability of a chemical contaminating the workplace or the environment to interfere with homeostasis, development, reproduction, and/or behavior in a living organism or it's offspring. Certain classes of environmentally persistent chemicals such as polychlorinated biphenyls (PCBs), dioxins, furans, and some pesticides can adversely effect the endocrine systems of aquatic life and terrestrial wildlife. The University of Tennessee, Knoxville (UTN), developed a method for hazard scoring chemicals for the aquatic ecosystem. The Indiana Clean Manufacturing Technology and Safe Materials Institute at Purdue University (CMTI) later expanded the scoring system to include terms for worker hazard as well as terms for contamination of soil and air quality, and for stratospheric ozone depletion. We call the CMTI chemical hazard score the Purdue score. At West Virginia University, two improvements of the Purdue chemical hazard score are developed, a normalizing of the term for soil contamination, and addition of hazard score terms for ecosystem endocrine disruption. The results of incorporating endocrine disruption terms into the hazard scoring equations resulted in increased hazard rankings, often substantially increased, for 26 endocrine disrupting chemicals (EDCs) among 200 Superfund chemicals. Because data suggesting human endocrine disruption from such chemicals is still controversial, no endocrine disruptor term has been added to the human toxicity portions of the chemical hazard scoring system at this time. The third product of this work is assembly of a current consolidated list of (1) established or probable, mostly synthetic, industrial chemical and medication EDCs and (2) suspect (less certain) synthetic and natural (phytoestrogen) possible endocrine disrupting chemicals, with the goal of contributing to future development of quantitative structure activity relationship software for predicting whether an untested chemical is likely to be an endocrine disruptor. We conclude that enough endocrine disrupting chemicals are now identified to make an attempt at developing structure activity estimates of disrupting potential worthwhile. Further, we conclude that within a group of 200 chemicals of concern to the US EPA, the addition of endocrine disrupting terms to the Purdue score substantially increases its representativeness in reflecting ecological exposure hazard. We have developed this enhanced Purdue score risk management tool to be of assistance to industry.     

INCORPORATION OF ENDOCRINE DISRUPTION INTO CHEMICAL HAZARD SCORING FOR POLLUTION PREVENTION AND CURRENT LIST OF ENDOCRINE DISRUPTING CHEMICALS

Research continues to support the theory of endocrine disruption. Endocrine disruption is defined as the ability of a chemical contaminating the workplace or the environment to interfere with homeostasis, development, reproduction, and/or behavior in a living organism or it's offspring. Certain classes of environmentally persistent chemicals such as polychlorinated biphenyls (PCBs), dioxins, furans, and some pesticides can adversely effect the endocrine systems of aquatic life and terrestrial wildlife. The University of Tennessee, Knoxville (UTN), developed a method for hazard scoring chemicals for the aquatic ecosystem. The Indiana Clean Manufacturing Technology and Safe Materials Institute at Purdue University (CMTI) later expanded the scoring system to include terms for worker hazard as well as terms for contamination of soil and air quality, and for stratospheric ozone depletion. We call the CMTI chemical hazard score the Purdue score. At West Virginia University, two improvements of the Purdue chemical hazard score are developed, a normalizing of the term for soil contamination, and addition of hazard score terms for ecosystem endocrine disruption. The results of incorporating endocrine disruption terms into the hazard scoring equations resulted in increased hazard rankings, often substantially increased, for 26 endocrine disrupting chemicals (EDCs) among 200 Superfund chemicals. Because data suggesting human endocrine disruption from such chemicals is still controversial, no endocrine disruptor term has been added to the human toxicity portions of the chemical hazard scoring system at this time. The third product of this work is assembly of a current consolidated list of (1) established or probable, mostly synthetic, industrial chemical and medication EDCs and (2) suspect (less certain) synthetic and natural (phytoestrogen) possible endocrine disrupting chemicals, with the goal of contributing to future development of quantitative structure activity relationship software for predicting whether an untested chemical is likely to be an endocrine disruptor. We conclude that enough endocrine disrupting chemicals are now identified to make an attempt at developing structure activity estimates of disrupting potential worthwhile. Further, we conclude that within a group of 200 chemicals of concern to the US EPA, the addition of endocrine disrupting terms to the Purdue score substantially increases its representativeness in reflecting ecological exposure hazard. We have developed this enhanced Purdue score risk management tool to be of assistance to industry.     

Exposure based waiving: The application of the toxicological threshold of concern (TTC) to inhalation exposure for aerosol ingredients in consumer products

The inhalation toxicology studies available in the public domain have been reviewed to establish a database for inhalation toxicology and derive thresholds of toxicological concern (TTC) for effects in the respiratory tract and systemically for Cramer class 1 and 3 chemicals. These TTCs can be used as the basis for developing an exposure based waiving (EBW) approach to evaluating the potential for adverse effects from exposure to ingredients in aerosol products, used by consumers. The measurement of consumer exposure in simulated product use is key to the application of an exposure based waiving approach to evaluating potential consumer risk. The detailed exposure evaluation for aerosol ingredients with defined use scenarios, in conjunction with an evaluation of the potential structure activity relationship for toxicity and the TTCs for inhalation exposure could be used to waive undertaking inhalation toxicology studies under REACH. Not all classes of chemicals are suitable for such an approach, but for chemicals with a predictable low potential toxicity, and very low levels of exposure, this approach, could reduce the amount of inhalation toxicology studies required for the implementation of the European REACH legislation. Such an approach is consistent with the concept of developing ‘intelligent testing strategies’ for REACH.     

Potential effects of certain persistent organic pollutants and endocrine disrupting chemicals on the health of children

Persistent organic pollutants are lipophilic, man-made chemicals that are highly resistant to degradation. Due to their persistence, they have become distributed in small quantities throughout the world. They bioaccumulate in thefood chain and are stored in fatty tissues. Biomagnifications up the food chain result in potential widespread human exposure to these chemicals. Exposure to persistent organic pollutants has been associated with many adverse human health effects, including impaired neurodevelopment, immune and reproductive function. Many persistent organic pollutants also possess the ability to disrupt the normal functioning of the endocrine system. There is an increasing concern that low-level exposure to these endocrine disrupting chemicals may have adverse health impacts, particularly during fetal, neonatal, and childhood development. Both the nature and severity of health outcomes may depend on the developmental time-period during which chemical exposure occurs. This report summarizes scientific evidence on health effects of low-level exposure to persistent organic pollutants and endocrine disrupting chemicals.     

Refinement of the ECETOC approach to identify endocrine disrupting properties of chemicals in ecotoxicology

To use and implement an assessment scheme for the evaluation of endocrine disrupting properties of chemicals in ecotoxicology, the types of effect need to be agreed. Effects that merit further consideration in this context should fulfil the following three criteria: caused by an endocrine mode of action, be adverse, and be relevant at the population level to reflect the protection goal of ecotoxicological assessments. Thereafter, a comparison of effect values, regardless of the causative mechanisms, should be made, firstly to determine if endocrine toxicity generates the lowest endpoint within a taxon, and secondly if it is the lowest endpoint compared to that of other taxa living in the same compartment. These comparisons inform on two levels of specificity and determine if endocrine-mediated side-effects determine the ecotoxicological profile of a chemical. Various quantitative measures for the assessment of potency are also presented, which could assist in determining how to handle substances in the risk assessment when a regulatory concern is identified. Finally, derogation criteria should be defined for compounds that were designed as endocrine disruptors for non-vertebrates and those for which there is ‘negligible exposure’. This paper discusses and provides proposals on how to apply these concepts for assessment of substances.     

Endocrine disruption: Fact or urban legend?

Endocrine disruptors (EDs) are substances that cause adverse health effects via endocrine-mediated mechanisms in an intact organism or its progeny or (sub) populations. Purported EDCs in personal care products include 4-MBC (UV filter) or parabens that showed oestrogenic activity in screening tests, although regulatory toxicity studies showed no adverse effects on reproductive endpoints. Hormonal potency is the key issue of the safety of EDCs. Oestrogen-based drugs, e.g. the contraceptive pill or the synthetic oestrogen DES, possess potencies up to 7 orders of magnitude higher than those of PCP ingredients; yet, in utero exposure to these drugs did not adversely affect fertility or sexual organ development of offspring unless exposed to extreme doses. Additive effects of EDs are unlikely due to the multitude of mechanisms how substances may produce a hormone-like activity; even after uptake of different substances with a similar mode of action, the possibility of additive effects is reduced by different absorption, metabolism and kinetics. This is supported by a number of studies on mixtures of chemical EDCs. Overall, despite of 20 years of research a human health risk from exposure to low concentrations of exogenous chemical substances with weak hormone-like activities remains an unproven and unlikely hypothesis.     

Experimental Designs to Assess Endocrine Disrupting Effects in Invertebrates A Review

In order to gain basic understanding of the ecological effects of vertebrate Endocrine Disrupting Chemicals (EDCs), many research groups are currently testing these chemicals using aquatic invertebrates. Small crustaceans, such as cladocerans and copepods, are of particular interest since they are ecologically important and their short life cycles allow obtaining information on demographic parameters. Despite the existence of diverse literature on the development, growth and reproductive effects of EDCs on these crustaceans, only a few studies have unambiguously assessed a truly endocrine disrupting effect. This review discusses new experimental designs to differentiate between endocrine disruption and other causes of reproductive and developmental impairment. Our findings clearly illustrate that many studies may have falsely concluded that chemicals have endocrine disrupting modes of action when in fact a much simpler explanation was not previously ruled out (e.g., egg mortality, feeding inhibition). This means that there is an urgent need for integration of toxic effects on energy intake to toxicity assessments. Such an approach would permit different ectotoxicological models of action, including endocrine disrupting effects, to be distinguished and their relative roles in the overall toxic response to be clarified.     

Critical comments on the WHO-UNEP State of the Science of Endocrine Disrupting Chemicals – 2012

Early in 2013, the World Health Organization (WHO) released a 2012 update to the 2002 State of the Science of Endocrine Disrupting Chemicals. Several significant concerns have been identified that raise questions about conclusions reached in this report regarding endocrine disruption. First, the report is not a state-of-the-science review and does not follow the 2002 WHO recommended weight-of-evidence approach. Second, endocrine disruption is often presumed to occur based on exposure or a potential mechanism despite a lack of evidence to show that chemicals are causally established as endocrine disruptors. Additionally, causation is often inferred by the presentation of a series of unrelated facts, which collectively do not demonstrate causation. Third, trends in disease incidence or prevalence are discussed without regard to known causes or risk factors; endocrine disruption is implicated as the reason for such trends in the absence of evidence. Fourth, dose and potency are ignored for most chemicals discussed. Finally, controversial topics (i.e., low dose effects, non-monotonic dose response) are presented in a one-sided manner and these topics are important to understanding endocrine disruption. Overall, the 2012 report does not provide a balanced perspective, nor does it accurately reflect the state of the science on endocrine disruption.     

Endocrine effects of chemicals: Aspects of hazard identification and human health risk assessment

Hazard and risk assessment of chemicals with endocrine activity is hotly debated due to claimed non-monotonous dose–response curves in the low-dose region. In hazard identification a clear definition of “endocrine disruptors” (EDs) is required; this should be based on the WHO/IPCS definition of EDs and on adverse effects demonstrated in intact animals or humans. Therefore, endocrine effects are a mode of action potentially resulting in adverse effects; any classification should not be based on a mode of action, but on adverse effects. In addition, when relying on adverse effects, most effects reported in the low-dose region will not qualify for hazard identification since most have little relation to an adverse effect. Non-monotonous dose–response curves that had been postulated from limited, exploratory studies could also not be reproduced in targeted studies with elaborate quality assurance. Therefore, regulatory agencies or advisory bodies continue to apply the safety-factor method or the concept of “margin-of-exposure” based on no observed adverse effect levels (NOAELs) in the risk assessment of chemicals with weak hormonal activity. Consistent with this approach, tolerable levels regarding human exposure have been defined for such chemicals. To conclusively support non-monotonous dose–response curves, targeted experiments with a sufficient number of animals, determination of adverse endpoints, adequate statistics and quality control would be required.     

Insights into possibilities for grouping and read-across for nanomaterials in EU chemicals legislation

This paper presents a comprehensive review of European Union (EU) legislation addressing the safety of chemical substances, and possibilities within each piece of legislation for applying grouping and read-across approaches for the assessment of nanomaterials (NMs). Hence, this review considers both the overarching regulation of chemical substances under REACH (Regulation (EC) No 1907/2006 on registration, evaluation, authorization, and restriction of chemicals) and CLP (Regulation (EC) No 1272/2008 on classification, labeling and packaging of substances and mixtures) and the sector-specific pieces of legislation for cosmetic, plant protection and biocidal products, and legislation addressing food, novel food, and food contact materials. The relevant supporting documents (e.g. guidance documents) regarding each piece of legislation were identified and reviewed, considering the relevant technical and scientific literature. Prospective regulatory needs for implementing grouping in the assessment of NMs were identified, and the question whether each particular piece of legislation permits the use of grouping and read-across to address information gaps was answered.