Thursday, August 30, 2012

What are Endocrine Disruptors: an introduction.

The next several posts will be devoted to the subject of endocrine disruption with a focus on environmental chemicals that interfere with sex steroids, chiefly estrogens and androgens. Most people are probably familiar with estrogen and testosterone. These are steroids produced by the human body (and the bodies of other species) that play important roles in sexual development and reproduction. They also play many other related roles, influence growth and tissue maintenance, neurological function and behavior.

 An endocrine disruptor is a chemical agent that interferes with very complex, inter-regulating and intertwined endocrine systems. Interference with one steroid hormone can produce chain reactions that impact other hormones that, in turn, influence other systems and other hormones. For example, Bisphenol A, an estrogen mimic will change production of Prolactin (Steinmetz et al. 1997).
A young boy ponders something.

The effects of endocrine disruptors can be strongest during critical periods such as fetal development, infancy, adolescence, conception and pregnancy. These are times of important changes that will have long-term consequences for a child (fry, larvae, pup, chick etc.) and its future children. Thousands of chemicals have been found to be endocrine disruptors. Some of them are very resistant to degradation and remain in the environment and in people's bodies for decades or longer. Many of these are no longer in use even though with can still easily detect them. They were found to be a threat to health and were banned and/or replaced with something less dangerous. There are many other chemicals in use that have not been tested. There are others that are current foci of research and debate. These chemicals were not developed to cause harm to humans (at least not most of them), rather they were found to be harmful after they were already in use. An example that you may be aware of is the plastics additive Bisphenol A.

Bisphenol A is commonly called BPA. After years of debate and conflict among interested parties BPA has been banned from baby bottles in the US. Manufacturers are adapting and produced new products. Consumers can easily find BPA-Free materials and it seems likely that BPA will leave many markets.  While BPA may be in decline the issue of endocrine disruptors is far from resolved. The plastic products used to make some BPA-Free plastics also appear to be endocrine disruptors (Yang et al. 2011.) Some of them appear to be more disruptive than the BPA-laced plastics they are meant to replace.  It would be better to produce Endocrine-Disruptor-free products Instead of  BPA-Free products

It is very difficult to pull something out of the market once it is already there. People's livelihoods have become dependent on continuing use, reputations are at stake, there may be millions of dollars spent on legal fees,  on efforts to fund studies that would show that the product in question was harmless after all, and then more time and more money spent arguing why banning a product would be unfeasible and not worth the cost of replacing it, developing alternative technology, or cleaning up environmental messes. Banning chemicals after they become part of the economy is hugely wasteful, makes people on both sides of the playing field upset and erodes public confidence. We may discuss this in greater detail later, but for now, just be aware that the chemical problem of endocrine disruptors is also an economic and then a political problem as well. This should be resolved eventually, but until then, we may have a very interesting, and for some a painful, ride.

Steinmetz R, Brown NG, Allen DL, Bigsby RM, & Ben-Jonathan N (1997). The environmental estrogen bisphenol A stimulates prolactin release in vitro and in vivo. Endocrinology, 138 (5), 1780-6 PMID: 9112368  

Yang CZ, Yaniger SI, Jordan VC, Klein DJ, & Bittner GD (2011). Most plastic products release estrogenic chemicals: a potential health problem that can be solved. Environmental Health Perspectives, 119 (7), 989-96 PMID: 21367689

No comments:

Post a Comment