Saturday, October 8, 2011

Our Poisoned Waterways: Endocrine Disruptors, Intersex, Fish, and Humans

Alex Prud’homme provides a comprehensive overview of the issues associated with our water supplies in his book: The Ripple Effect. Of particular concern is the buildup of chemicals, both medical and industrial, in our water systems. Prud’homme points out that essentially every chemical used ends up in our water supplies. Every time we take a shower or flush a toilet we are adding to a chemical stew that is accumulating. Every storm washes fertilizers, pesticides, manure, and industrial chemicals from our streets and fields into our water sources. We know very little about how most of these chemicals affect our health, and almost nothing about how they might work in combinations. He provides this context.
"....consider that over sixty thousand different types of chemicals are used in America each year, yet the EPA has assessed the toxicity of only a few of them. By 2000 the EPA’s list of regulated chemicals had steadily climbed to ninety-one, but then the list suddenly stopped growing. Since then, roughly seven hundred new chemicals have been introduced to the marketplace every year, but the agency has not added a single new substance to its restricted list."

It is becoming clear that these chemicals are attaining concentrations where effects can be observed. Prud’homme tells of a condition known as intersex that is becoming increasingly common in fish.
"Intersex, in humans and other animals, is the presence of intermediate or atypical combinations of physical features that usually distinguish female from male."

Prud’homme tells of investigators trying to understand fish kills in the Potomac River.

"When they sliced open the testes of the bass....discovered clusters of immature eggs nestled where only sperm should be. This known as intersex."

Intersex can occur in both humans and animals. In this case they found that nearly all the male smallmouth bass in the Potomac and its tributaries suffered from the condition. Something in the water had to be causing it. In 2009 the USGS studied 16 types of fish in 111 locations across the country. The only place where they did not encounter fish suffering from intersex was in the Yukon basin in Alaska where there are few people and little of their waste materials.

What could cause such transformations? The evidence points towards endocrine disruptors, chemicals that can cause a great deal of damage.

"Endocrine disruptors are chemicals that interfere with endocrine (or hormone system) in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders. Specifically, they are known to cause learning disabilities, severe attention deficit disorder, cognitive and brain development problems, deformations of the body (including limbs); sexual development problems, feminizing of males or masculine effects on females, etc. Any system in the body controlled by hormones, can be derailed by hormone disruptors. The critical period of development for most organisms is between the transition from a fertilized egg, into a fully formed infant. As the cells begin to grow and differentiate, there are critical balances of hormones and protein changes that must occur. Therefore, a dose of disrupting chemicals can do substantial damage to a developing fetus (baby). Whereas, the same dose may not significantly affect adult mothers."

Prud’homme suggests many possible sources for the chemicals affecting fish.

"....a prime suspect is high levels of estrogen in the water....Synthetic estrogens come from pharmaceuticals such as birth control pills, or agricultural runoff loaded with pesticides, or industrial runoff laced with plastics. Also, a group of compounds are known as estrogen mimics, the chemical structure of which allows them to act like estrogen. These range from herbicides to personal-care products such as antibacterial soap, and even perfume. Indeed, so many chemicals show varying degrees of estrogenic activity that methods to identify them are still being developed."

The evidence is persuasive, but still circumstantial. It prompted a Karen Kidd and her collaborators to perform an experiment in a lake in Canada set aside for these kinds of studies. They doped the lake with a component common in birth control pills. The concentration was tuned to reproduce the levels of such compounds found in waterways. The results:

"We conducted a 7-year, whole-lake experiment at the Experimental Lakes Area (ELA) in northwestern Ontario, Canada, and showed that chronic exposure of fathead minnow....led to feminization of males through the production of vitellogenin mRNA and protein, impacts on gonadal development as evidenced by intersex in males and altered oogenesis in females, and, ultimately, a near extinction of this species from the lake. Our observations demonstrate that the concentrations of estrogens and their mimics observed in freshwaters can impact the sustainability of wild fish populations."

Prud’homme is moved to ask this question.

"....if these chemicals are affecting the endocrine systems of fish, which are basically the same as the endocrine systems of humans, then couldn’t we face some of the same negative health effects as fish?"

A good question indeed! We are seeing a number of conditions beginning to grow more common in our children: Autism, other psychological disorders, asthma, obesity, food allergies.... If exposure to chemicals at the observed levels can cause harm to fish, couldn’t they also cause harm to a tiny fetus in the process of constructing a new human?

It is time to begin worrying more about these issues. Instead of threatening the EPA for taking actions, we should be demanding that it become more proactive. Our children are at risk.

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