Seals and Endocrine Disrupting Chemicals

Endocrine disrupting chemicals (EDCs) can have an impact on marine organisms that inhibit the planet. These chemicals mimic hormones or they can block them which will have a negative affect on the organism(1). When these hormone levels are altered, the messenger system can effect processes like reproduction, development or immune function(1).


Grey Seals, Horsey” by Jeremy Halls licensed by CC by 2.0

EDCs Found in Seals and Marine Habitats

Seals come in contact with EDCs via food and water. Below are some of the most common that seals come in contact with.

PCBs: or polychlorinated biphenyls were used widely in electrical equipment like capacitors and transformers. Although they have been banned or highly restricted these are still effecting our environment. They are soluble in fat so that is why this pollutant can stay in the the fat of mammals–like seals.  The route of exposure for PCBs in the general population is the consumption of contaminated foods, particularly meat, fish, poultry, even drinking water (2).

Phthalates: are found in a lot things that you and I may use daily. Items that may contain phthalates are shampoos, laundry detergent, food packaging, children toys,  hairspray, after shave and lotions.  These chemicals usually make it into run off water via landfill sites. Phthalates are also lipophilic (3).

Pesticides: DDT and other pesticides also have an impact on the seal population. They enter the ocean by run off via agriculture fields. Even though DDT was banned from the U.S. it is a lipopilic molecule that can stay around in fats for a while (4).

So What?

Persistent organochlorides like PCBs and DDT, are passed down to generations. If a pregnant seal passes this down to her fetus is can affect the development of the unborn pup.  After birth, these chemicals are then passed to the seal pup again via the milk from the mother.  In adult seals, when they eat contaminated prey, they are accumulating more EDcs in their body (5). There has been a strong correlation found between high PCB levels in the seal blubber and low reproductive rates. This would cause a reduction in the seal population in itself (5). Another study, conducted by B.M Backlin also found this to be true(6).


Seal Mom and Pup” by mafzail licensed by CC by 2.0

Stockholm University is doing research on the effects EDCs in humans and wildlife. This university has a few different projects going on that involve this research. One project is called the EDC-MixRisk. If you want to learn more about the research taken place at this university, please click here.


Want to learn more about Baltic seals? Please click here!!

If you want to learn about the seal population and EDCs, please click here!


1. “Endocrine Disruptors.” National Institutes of Health. U.S. Department of Health and Human Services, 05 Jan. 2017. Web. 02 May 2017. <;.

2. “Learn about Polychlorinated Biphenyls (PCBs).” EPA. Environmental Protection Agency, 13 Feb. 2017. Web. 02 May 2017. <;.

3. Center for Food Safety and Applied Nutrition. “Ingredients – Phthalates.” U S Food and Drug Administration Home Page. Center for Food Safety and Applied Nutrition, n.d. Web. 02 May 2017.

4. “DDT – A Brief History and Status.” EPA. Environmental Protection Agency, 22 Nov. 2016. Web. 02 May 2017. <;.

5. Lutter, Stephan. “Seals & Endocrine Disruptors.” (n.d.): n. pag. WWF. Web. 2 May 2017. <;.

6. Backlin, B.M, L. Eriksson, and M. OloVsson. “Histology of Uterine Leiomyoma and Occurrence in Relation to Reproductive Activity in the Baltic Gray Seal (Halichoerus Grypus).” Veterinary Pathology. N.p., 01 Mar. 2003. Web. 02 May 2017. <;.