Studies in the 1990s indicated that certain chemicals had the potential to cause developmental and reproductive abnormalities in fish, wildlife, and experimental animals. Concern grew over potential adverse effects on the endocrine systems of humans by the hormone-like effects of the same types of chemicals.
In the 2002 World Health Organization (WHO)/International Programme on Chemical Safety (IPCS) report, Global assessment of the state-of-the-science of endocrine disruptors, endocrine-disrupting chemicals are defined as follows:
An endocrine disruptor is an exogenous substance or mixture that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations.
Endocrine disruptors (EDs) can exert their effects through a number of mechanisms, “including receptor binding, altered post-receptor activation, altered steroidogenesis (modulation of hormone synthesis), perturbation of hormone storage, release, clearance, and homeostasis.” The effects of EDs are mediated in part by their binding to a family of nuclear receptors called steroid hormone receptors. ED binding can interfere with transcriptional regulation that is modulated by a hormone-dependent region of the steroid hormone receptors.
Currently, the US EPA is the only regulatory agency to require endocrine testing. Discussions are ongoing in the European Union regarding criteria to identify endocrine active substances. Current EU pesticide (Plant Protection Products) and biocide regulations prohibit the registration of any endocrine active substance. Procedures for consideration of endocrine activity for industrial chemicals through REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) are currently being formulated.
To provide the US Environmental Protection Agency (EPA) with the mandate to address concerns about hormonal effects of certain chemicals, Congress enacted legislation in 1996 that requires the EPA to test pesticides and other chemicals for their potential to act as endocrine disruptors. The EPA’s Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) recommended the two-tiered testing approach, now known as the Endocrine Disruptor Screening Program (EDSP), and proposed including male hormones (androgens), the thyroid system, and effects on fish and wildlife.
The EPA established the Endocrine Disruptor Screening Program in 1998 as a two-tiered testing program based on a series of Tier 1 and Tier 2 screening assays. Tier 1 screening consists of a battery of 11 in vitro and short-term in vivo assays; proposed Tier 2 testing will involve 5 multi-generation in vivo assays. Tier 1 screening is intended to identify chemicals with the potential to interact with the endocrine system; Tier 2 screening is intended to identify chemical and dose-related health effects.
The Organization for Economic Cooperation and Development (OECD) provides Test Guidelines (TGs), Guidance Documents (GDs), and other reports on various animal testing approaches for endocrine active substances.
The OECD Conceptual Framework for Testing and Assessment of Endocrine Disrupters (GD 150, August 2012) is a guide to methods available to evaluate chemicals for endocrine disruption, “but is not intended to be a testing strategy.” This guide outlines 5 levels of available tests, according to the OECD Conceptual Framework for testing and assessment of endocrine disrupters (as updated in 2012), as follows:
Level 1: Existing data and non-test information
Level 2: In vitro assays providing data about selected endocrine mechanism(s)/pathways(s)
Level 3: In vivo assays providing data about selected endocrine mechanism(s)/pathway(s)
Level 4: In vivo assays providing data on adverse effects on endocrine relevant endpoints
Level 5: In vivo assays providing more comprehensive data on adverse effects on endocrine relevant endpoints over more extensive parts of the life cycle of the organism
|BG1Luc ER TA Test Method||Endocrine disruptor screening assay|
OECD TG 457 (2012)
Draft Performance Standards for TG 457 (2012)
|H295R Steroidogenesis Assay||Endocrine disruptor screening assay|
OECD TG 456 (2011)
US EPA OPPTS TG 890.1550 (2009)
|Estrogen Receptor (ER)-alpha Transcriptional Activation Assay (HeLa cell line)||Endocrine disruptor screening assay|
Updated OECD TG 455 (2012)
Draft Performance Standards for TG 455 (2011)
US EPA OPPTS TG 890.1300 (2009)
|Aromatase Inhibition Assay (human recombinant)||Endocrine disruptor screening assay||ICCVAM agency|
US EPA OPPTS TG 890.1200 (2009)
|Androgen receptor binding assay rat prostate cytosol (ex vivo – animal required for test material)||Endocrine disruptor screening assay||ICCVAM agency|
US EPA OPPTS TG 890.1150 (2009)
|Estrogen receptor binding assay rat uterine cytosol (ex vivo – animal required for test material)||Endocrine disruptor screening assay||ICCVAM agency|
US EPA OPPTS TG 890.1250 (2009)
Like other screening assays described on this page, human cell-based estrogen receptor-alpha transcriptional activation assay described by OECD TG 455 “provides mechanistical information, and can be used for screening and prioritization purposes.”
Five in vitro/ex vivo endocrine disruptor screening assays have been accepted as part of the test battery known as the US EPA Tier 1 Screening Battery.
These assays are accepted as test guidelines by the EPA’s Office of Chemical Safety and Pollution Prevention (OCSPP) (Series 890 Test Guidelines), and include the following methods:
The BG1Luc Estrogen Receptor (ER) Transcriptional Activation (TA) assay described in OECD TG 457 can detect both ER agonists and antagonists. The validation status of the BG1Luc ER TA test method was reviewed by an ICCVAM international scientific peer review panel in March 2011. “The panel agreed with ICCVAM draft recommendations that the BG1 test method could be used as an initial screen to identify substances with the potential to enhance [agonist activity] or inhibit [antagonist activity] activation of the estrogen receptor.” The panel also concluded that the “accuracy of this assay is at least equivalent to the current ER TA included in regulatory testing guidance” [OECD TG 455]. ICCVAM transmitted final recommendations on this test method to US agencies in 2011. The BG1Luc ER TA test method has also been adapted to a high throughput screening (HTS) format for incorporated into Tox21 screening.
JaCVAM is in the process of reviewing several of the existing in vitro methods for identifying endocrine active substances (EACs).
Further information on in vitro methods being developed for endocrine active substance testing can be found at:
Sherry L. Ward, PhD, MBA
AltTox Contributing Editor
AltTox Editorial Board reviewer(s):
Catherine E. Willett, PhD
Humane Society of the United States
The information provided here is intended only as an overview, and is neither guidance or a comprehensive review of the laws and regulations on endocrine disruptor testing. Individual countries/ regions and their regulatory authorities usually provide specific guidance on hazard/ toxicity testing requirements.