Effects of Endocrine Disruptors (College Board AP® Environmental Science): Study Guide

What are endocrine disruptors?

• Endocrine disruptors (EDCs) are chemicals that interfere with the body's hormones

• The endocrine system releases hormones from ductless glands in the body and includes:

  • ovaries and testes produce estrogen and testosterone

  • thyroid and parathyroid produces hormones that affect every cell in your body, from growth to metabolism

  • adrenals produce epinephrine (adrenaline) and norepinephrine (no adrenaline)

  • pituitary

  • pineal

  • pancreas

  • hormone-releasing cells in the gastrointestinal tract, the kidneys, heart, and placenta

• EDCs can be found in many household and industrial products and include:

  • Triclosan, used in antibacterial and personal care products, such as liquid body wash

  • Atrazine, a herbicide used to control weeds

  • Dioxins are released when garbage is burnt and during wildfires

  • Bisphenol A (BPA), used in water bottles, food packaging, toys, and other applications

  • Perchlorate, a colorless salt used in fireworks, explosives, and rockets

  • Phthalates, used as liquid plasticizers in cosmetics, food packaging, and more

  • Polybrominated diphenyl ethers (PBDE), used to make flame retardants

  • Polychlorinated biphenyls (PCBs), used to make electrical equipment

• Sources of EDCs include:

  • Air, diet, skin, and water

  • Sewage effluents

  • Water storage materials such as plastics

  • Domestic wastewater containing pharmaceutical compounds, metals, pesticides, and personal care product additives

Impacts of endocrine disruptors

• Animal growth and reproduction can be altered by EDCs

• Humans are vulnerable to a number of illnesses and problems with reproduction

• EDCs can cause birth defects, gender imbalances, and developmental challenges

• BPA in plastic products pollutes the oceans and harms wildlife by releasing EDCs

• Some endocrine disruptors take a long time to break down, causing further damage as more species come in contact with them

• Exposure to multiple EDCs makes it challenging to identify the particular origins of these disorders and their impacts

Effects on wildlife

• As a result of increased exposure, wildlife displays greater signs of endocrine disruption

• Human medications excreted into sewage are a common source of wildlife EDCs

• EDCs can cause bird egg thinning, imposex mollusks, feminization in freshwater fish exposed to treated sewage outflow, and changes in alligator and turtle reproduction

  • atrazine (a herbicide) binds to receptors of cells that should convert estrogen into testosterone in male frogs, leading to: high estrogen in males, low sperm count, and feminization

• Less well-known effects are issues with

  • reproduction in whales, seals, and polar bears

  • compromised immune system function in seals

  • abnormal skeletal characteristics in frogs

Effects on humans

• Normally, the endocrine system makes small adjustments to hormone levels

• These changes have significant biological and developmental effects

• However, EDCs have altered human health over decades

• Examples of these changes include:

  • Reduced sperm production

  • Hormone-related cancers

  • Increased male genetic defects

• Sexuality and brain development may also be impacted by EDCs; however, this is disputed among scientists

• This shows how dangerous even small doses of endocrine-disrupting substances can be long-term