Chemicals that Disrupt Hormones: BPA, DDT, PCBs, and Triclosan

Endocrine Disruptors Examples

The human body’s endocrine system depends on hormones to perform many vital functions. But some chemicals mimic, block or interfere with the production and action of these hormones.

These man-made chemicals can be found in everyday products such as plastic bottles, metal food cans, cosmetics, detergents and flame retardants. They are known as endocrine disruptors and examples include BPA, DDT, PCBs, and Triclosan.


Bisphenol A (BPA) is a chemical that mimics the hormone estrogen, and interferes with the body’s delicate endocrine system. It has been linked to reproductive and developmental problems, and it may also contribute to a variety of health conditions.

It is particularly dangerous for pregnant women, infants, and children, because it can disrupt normal hormone function during critical periods of development. BPA has been linked to a variety of problems, including obesity, infertility, and low birth weight. It has also been linked to behavioral problems, such as hyperactivity and attention deficit disorder.

Several studies have shown that BPA can alter the expression of genes involved in the endocrine system. It can also trigger cellular growth and tumor formation, which could lead to a poor prognosis for cancer patients. It can also inhibit the effectiveness of chemotherapy in some cancer cells. This is because it upregulates the expression of ERRg, a gene that promotes breast and ovarian cancer cell proliferation.


The endocrine system sends messages that regulate everything from growth and reproduction to hunger and body temperature. An endocrine disruptor can interfere with these delicately tuned signals, even at low doses. Many pharmaceutical drugs, including antibiotics like triclosan and diethylstilbestrol, industrial chemicals such as polychlorinated biphenyls and bisphenol A, and pesticides like DDT act as endocrine disruptors.

DDT is a potent insecticide that affects the nervous and reproductive systems of aquatic organisms. Its neurotoxic effects include repetitive discharge of the abdominal nerve cord and convulsions in animals, as well as inhibition of calcium influx into nerve terminals and delayed sodium channel inactivation in neurons.

In humans, DDT and its metabolites (including DDE) have been associated with breast cancer in epidemiological studies. Its toxicity to the fetus and its endocrine disruption effects on birds were highlighted in Rachel Carson’s 1962 book, Silent Spring. DDT and its metabolites also bind weakly to the androgen receptor in the prostate, while binding more strongly to estrogen receptors.


Polychlorinated biphenyls (PCBs), like DDT, PFAS and some flame retardants, are extremely persistent, toxic and bioaccumulative chemicals that are known to have adverse effects on the nervous, immune and reproductive systems at low doses. They can mimic natural hormones, block their action or alter the breakdown or synthesis of hormones in the body. These chemicals are found in food, air and personal products and they can persist in the environment for decades, accumulating in fatty fish, breast milk and house dust.

PCBs are known to affect the hypothalamus-pituitary-gonadal axis and have been linked with decreased sperm motility, lower fecundity and earlier menarche in females. They are also known to interfere with thyroid hormone function and to cause cognitive-behavioral disorders. A new study shows that prenatal and early postnatal exposure to a commercial mixture of PCBs, Aroclor 1254, delays radial neuronal migration in the developing cortex in rats and leads to altered cognitive functions. The findings were presented Thursday at ENDO 2023, the Endocrine Society’s annual meeting in Chicago.


Triclosan is an antimicrobial chemical that is added to many household and industrial products to prevent bacterial contamination. It is highly effective in reducing the growth of bacteria and fungi, but it also has been shown to have adverse effects on human health. These effects include increased risk of allergies, decreased fertility, and disruptions in thyroid function.

The chemical can be absorbed through the skin and enters the bloodstream. It is also found in urine and breast milk. It is particularly concerning for women and people assigned female at birth because it can cross the placenta and enter a woman’s body, where it can interfere with hormones.

In a study conducted in mice, triclosan caused a decrease in serum thyroid hormone levels and a delay in the onset of puberty. The same effect was observed in a study of prenatal triclosan exposure and anatomical measurements in Danish infants. The authors suggest that the results may indicate that triclosan has endocrine disrupting properties.

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