A global report released February 19 by UNEP and WHO shows that humans and wildlife are being exposed to diverse chemicals and there is growing evidence and concern about their health impacts. These chemicals – called endocrine disruptors – interfere with the system that controls metabolism, development and reproduction in us, birds, mammals, amphibians, reptiles, and invertebrates.
A UNB Saint John professor, Karen Kidd, was one of the editors of this review which covers the scientific advances in our understanding of endocrine system diseases and disorders in wildlife and humans. It has several sobering messages.
Humans and wildlife are exposed to many diverse chemicals every day. Dozens of chemicals are in the blood, fats and breast milk of humans and we find very similar chemicals in fish, whales, and polar bears. These chemicals include plasticizers, additives in personal care products and cleaners, flame retardants, pesticides and many banned substances like PCBs.
“While we understand how some of these individual chemicals are interfering with the endocrine system in wildlife, the effects of these mixtures on wildlife and humans is a big knowledge gap and a big concern.”, Kidd says.
“I hope that this report raises awareness of this issue globally, especially with policy makers. It is critical to reduce the risk that some chemicals pose to human and wildlife health. We are especially concerned about the developing fetus and newborns because chemical exposure at these early stages in life can reprogram tissues and lead to diseases and disorders later in life”, she says.
Some chemicals are present in wildlife and humans globally, even in remote polar environments, because of their transport long distances through wind and water currents and global trade. Many persist and are stored in the body while others are rapidly excreted, lasting only a few hours.
When production and use of a chemical increases, levels in humans and wildlife go up. When chemicals are taken off the market, levels in humans and wildlife go down.
There is also more understanding that chemicals are affecting wildlife in similar ways to humans. This is because there are some similarities between humans and wildlife in how endocrine systems work and the hormones that both use to control development, growth and reproduction. For example, exposures to PCBs are linked to lower thyroid hormones in marine mammals, fish, birds and humans. The synthetic estrogen in the birth control pill is effective at preventing pregnancy in humans and reproduction in fish because, once released in municipal wastewaters, it feminizes male fish and reduces their ability to spawn.
There are global declines of wildlife species. Though some of this is due to loss of their habitat, climate change and overexploitation, we now have more evidence that exposure to chemicals contributes to the decline of wildlife populations. When chemicals have been banned (such as antifouling compounds, pesticides like DDT, and PCBs), environmental levels of these chemicals have declined and numbers of birds, marine mammals and molluscs have increased.
We also know that diseases and disorders of the endocrine system are on the rise. Globally there are increases in several endocrine cancers (e.g. breast, testes, thyroid), other diseases (e.g. Type 2 diabetes) and disorders (e.g. obesity, testicular non-descent) in humans. Incidences of these diseases and disorders are increasing faster than can be explained by genetics alone and are likely linked to environmental factors like chemical exposure.
Contact Dr. Karen Kidd for more information.