In 1980, a waste pond at the Tower Chemical Company overflowed into Lake Apopka in central Florida releasing large volumes of the pesticides DDT and DICOFOL. Five years later, Dr. Louis Guillette, Zoology professor at University of Florida, discovered juvenile alligators from the lake with wild hormone levels, tiny penises and malformed ovaries. Decades of research followed in the field and laboratory, and a definite link between certain environmental contaminants and a disruption of endocrine systems was found.
The endocrine system controls internal communication. Glands in the body send chemical messengers, or hormones, through the circulatory system to faraway organs where they deliver a message that causes a change in behavior. Hormones instruct cells to do certain things at certain times in certain ways. In order to relay a message, hormones must fit precisely into another cell’s receptor, like a hand fits a glove. Dr. Guillette and others found that some environmental contaminants mimic hormones, fit into receptors and activate responses. Others block receptors so hormones can’t bind to them. Either way these compounds garble the conversation between cells so messages don’t go through and the necessary action isn’t taken. During that crucial stage of development in the alligators of Lake Apopka, the instructions needed for developing the necessary male and female genitalia were garbled.
Deleterious effects of endocrine disrupting chemicals aren’t confined to alligators. Pelicans were almost wiped out when DDT, banned in 1972, caused the birds to lay thin, brittle eggs which were crushed during incubation. Numerous studies on fish, birds, turtles, gastropods and mammals, show long term, irreversible abnormalities such as decreases in reproductive success, impaired immune system and thyroid dysfunction. Humans are not immune to endocrine disruption either. Many women at risk of miscarriage before 1971 were prescribed DES or Diethylstilbestrol, a synthetic estrogen or female hormone, during pregnancy. Daughters born to these mothers suffer a reduction in fertility and an increase in immune system disorders, depression and reproductive tract cancer.
Toxicologists typically look for contaminants that cause cancer and death then try to determine threshold exposure levels or safe doses. The higher the dose, the larger the risk. Endocrine disrupters are more complicated; there may be no safe dose. Hormones, or contaminants that mimic hormones can trigger responses at extremely low levels. Timing though is crucial. The critical window of development, when animals are most vulnerable to endocrine disrupters, is in the prenatal and early postnatal stage.
Many pesticides, flame retardants, birth control pills, dioxin, PCBs and heavy metals are known to be endocrine disrupters. The list also includes two compounds used widely in plastics: Bisphenol A (BPA) and phthalate (DEHP). These are plasticizers, added to increase flexibility, durability and transparency in plastics and other products. BPA is one of the most common industrial chemicals in the world. By the late 1970s, almost every plastic food and water container was made with BPA. It was taken out of baby bottles and pacifiers in 2011 and removed from water bottles in 2012 due to health concerns. BPA is still widely used in other products including the sealant in cans of food, bottle caps and water supply pipes. Phthalates are found in hundreds of products including food packaging, medical devices, enteric coatings on pills, eye shadow, detergents, scented items and more. We are exposed to BPA and phthalates everywhere, everyday, yet evidence for the link between endocrine disrupters and compromised endocrine systems continues to build.
To reduce our exposure to BPA and phthalates found in plastics, experts advise against microwaving food in plastic, eating from #3, #6 and #7 plastics, and eating food from cans with plastic liners. Cutting down on the plastic we use to package food can reduce our exposure to endocrine disrupting chemicals and has the added benefit of reducing the plastic waste that is piling up in our environment. To help keep plastic waste off our shores and out of the ocean, grab a bag from a BlueTube on your shore, pick up trash and throw it away. Add your clean, used plastic bags to BlueTubes and make it easy for others to keep plastic waste out of the environment too.