Endocrine Disruption

The endocrine system is the collection of glands that produce hormones that help regulate many functions of the human body. Some natural and man-made chemicals can and do interact with the endocrine system, or are “endocrine-active.” 

In some cases, interaction between the endocrine system and substances that are endocrine-active is harmless: the substances lack sufficient potency or exposures may be so low that no effects occur at all; in other cases the body naturally adjusts, and the exposure causes no health effect.

However, some substances under certain exposure scenarios go beyond a simple interaction and can result in adverse health effects—these substances are often referred to as “endocrine disruptors.” An endocrine disruptor is a natural or manmade substance, external to the body, that evidence shows directly alters the function of the endocrine system, and consequently causes negative health impacts that are confirmed through thorough scientific study.

Policy Background

Governments around the globe are analyzing how to best study and test for potential effects of chemicals on the endocrine system and determine if certain exposures to specific chemicals are cause for concern.

In the United States, the U.S. Environmental Protection Agency (EPA) Endocrine Disruptor Screening Program is a science-based endocrine screening and testing program focused on protecting public health and the environment. EPA uses high quality, validated screening assays and test methods to determine which substances have the potential to interact with the endocrine system. Substances with such potential may then be further evaluated by EPA to determine whether adverse effects can occur and what exposures might trigger such responses.

Chemicals that are found to cause adverse effects will be subjected by EPA to a comprehensive risk assessment, so researchers can understand the potential for exposure to the chemical and the likelihood of harm under real-life scenarios.

This science-based risk assessment helps scientists determine the difference between the levels of exposure that can produce adverse effects, and the typical exposure levels experienced by humans and wildlife. EPA would then determine if this safety standard is appropriate to protect public health and the environment, including groups that might be particularly sensitive, or if limiting certain uses of the chemical should be considered.

ACC Principles for Identifying Endocrine-Active and Endocrine-Disrupting Chemicals

Through the efforts of governments, academia and industry, considerable progress has been made to develop methods, tests and data that could help answer questions about endocrine active and endocrine disrupting chemicals. As the science is refined and improved, certain principles should be incorporated into testing programs to ensure that results are reliable and relevant to regulators and the public: 

  • Precise and Accurate Characterizations: The distinction between “endocrine active” and “endocrine disrupting” chemicals is frequently overlooked, and chemicals with no proven endocrine-related adverse effects have been mischaracterized and stigmatized.

  • Credible Testing Methods and Data: Like all chemical regulatory testing programs, endocrine screening and testing should adhere to the highest standards of scientific rigor to ensure the integrity of the program and its findings.

  • Thorough Investigation: Mechanistic information alone cannot be used for classification or regulatory purposes—determinations must consider biological factors such as absorption, distribution, metabolism and excretion. 

  • Mutual Acceptance of Data: Governments and regulators should accept data generated by other testing programs if the tests are consistent with the OECD Conceptual Framework and Standardized Test Guidelines for Evaluating Chemicals for Endocrine Disruption.

  • Transparent Decision Making: Testing and assessment programs should incorporate a transparent and consistent decision-making process throughout prioritization, screen and test development, selection of methods, determination of findings, identification of substances and regulatory outcomes. 

  • Effective and Efficient: Testing and assessment programs should be designed to maximize efficiency and reduce delays without compromising the quality of evaluations.

  • Advanced Technology: The latest technology, such as EPA’s ToxCast program™ and EDSP21, should be employed to reduce the need for animal testing and improve effectiveness and timelines.

  • Consideration of Real World Exposures: Exposure and hazard together determine the actual risk that is posed by the substance; assessments and conclusions cannot be based on hazard characteristics alone.

  • Weight of The Evidence Analysis: Conclusions must be made based on a Weight of the Evidence evaluation so all relevant evidence is considered including data from environmental releases, laboratory studies, and field studies and data related to biological and environmental effects.

  • Protective Approach: Assessments should be comprehensive, risk-based and protective in nature, and screens as accurate as possible while erring on the side of indicating false positives for endocrine interaction.

  • Safe Levels of Exposure: Through evidence-based analysis, scientific researchers can and should determine exposure levels at which endocrine-active chemicals do not cause adverse effects.