8.3 Endocrine Disruptors

What are endocrine disruptors?

Endocrine disruptors are chemical pollutants that interfere with the hormone (endocrine) system of animals, including humans. They can mimic, block, or alter natural hormones like estrogen, disrupting growth, development, reproduction, and metabolism even at very low concentrations.

Common sources and examples

Sources include pesticides (e.g., atrazine), plastics additives (BPA, phthalates), industrial chemicals like PCBs, and pharmaceuticals (synthetic hormones from birth control) entering waterways via runoff and wastewater. These substances enter aquatic ecosystems and can persist, bioaccumulating in organisms.

Effects on wildlife and humans

Endocrine disruptors cause reproductive abnormalities, feminization of male fish (e.g., intersex fish near wastewater outflows), reduced fertility, developmental defects, and altered behavior. Because they act at low doses and can biomagnify, even trace exposure poses risks to wildlife populations and human health.

Key terms

Endocrine disruptor

A chemical pollutant that mimics, blocks, or alters natural hormones, disrupting growth, reproduction, or development.

BPA

Bisphenol A; a plastics additive that mimics estrogen and disrupts hormone function.

Atrazine

A common herbicide linked to reproductive and developmental abnormalities in amphibians.

Intersex fish

Fish showing both male and female reproductive traits due to exposure to estrogen-mimicking pollutants.

Why low-dose exposure matters

Hormones act at tiny natural concentrations, so even trace amounts of disrupting chemicals can significantly affect body systems.

Try an AP-style question

What do endocrine disruptors do?

1. Break down harmful toxins
2. Improve animal fertility
3. Interfere with hormone systems
4. Filter pollutants from water