Monday, July 23, 2012

Endocrine Disruption and What’s in the Potomac River Watershed

Recently in the Susquehanna River in Pennsylvania, smallmouth bass have been found with benign skin tumors. Two skin samples of lesions from fish removed from the river were sent to Dr. Vicki Blazer a mairine biologistand researcher at the U.S. Geological Survey, USGS. Dr. Blazer who received the American Fisheries Society 2010 Publications Award for her article investigating the mortality of fish in the Potomac River basin and is a fish biologist at the West Virginia Science Center studying the impact of contaminants of emerging concern in rivers and streams of the lifecycle and health of fish,  found that one of the samples  tested positive for a type of benign skin tumor. These samples were sent to the USGS because an ongoing collaborative effort between the USGS, the U.S. Fish and Wildlife Service, state agencies in West Virginia, Maryland, and Virginia, and the Potomac Riverkeeper has been studying the impacts of trace contaminants on fish health. Areas of study have been endocrine disruption, immune system impact, cancer/neoplasia promotion, secondary sex characteristics, oxidative damage and behavior. I follow Dr. Blazer’s talks at conferences.

Endocrine disruptors are chemicals that may interfere with the body’s endocrine system and produce adverse developmental, reproductive, neurological, and immune effects in both humans and wildlife. Research evidence suggests that these chemicals, can mimic hormones or interfere with the function of the body’s own hormones. Endocrine disruptors are found in many of the everyday products we use, including some plastic bottles and containers, food can liners, detergents, flame retardants, toys, cosmetics, and pesticides. These hormones and hormone like substances are typically highly soluble in water and are easily transported in the blood. These compounds are of particular concern because they can alter the critical hormonal balances required for proper health and development. The glands that make up the endocrine system are: pituitary gland, thyroid glands, adrenal glands pancreas, ovaries, testies, pineal gland and the thymus.

The marine life work in this area began with the studies of fish kills more than 15 years ago. Preliminary analysis at that time did not find any chemicals or pesticides in concentrations that were sufficient to stress fish and be a cause of the fish kills. Yet there were fish kills. As Dr.Blazer pointed out in a recent conference almost all of our knowledge about concentrations likely to cause a health impact are based on acute toxicity or gross impact such as size. In most cases there are no criteria for sub-lethal effects such as immune modulation or endocrine disruption. Dr. Blazer and others believe that methodology used to detect these chemicals in recent studies may not have been sensitive enough, and may indeed be above the concentration thought to impact these fish. Two examples given by Dr. Blazer at a recent conference were that based on research studies in more than 25 fish species, scientists have suggested that 1 ng/L (parts per trillion) may be the “no effects level” for natural estrogen concentrations on fish. Unfortunately, all the river studies performed in the Potomac River and Shenandoah River passive sampler studies use 1.3 ng/L as the lower detection limit. The detection limit for Potomac and Shenandoah Rivers studies for ethynylesradiol is almost twice the level recently set as the aquatic “no effects” level. Studies along the Potomac and Shenandoah Rivers have only studied smallmouth bass that were found to be intersexed and have measurable amounts of vitellogenin (a protein that is a precursor to egg yoke) in their blood. Vitellogenin is normally only found in the blood of sexually matures egg-laying females, though males typically carry an inactive gene that is “turned on” by the presence of estrogen. Further research is necessary to not only determine if the problem is more widespread geographically and among species, but to identify the mode and mechanism of impact.

Fish health turns out to be a way to track ecosystem health. The smallmouth bass population has been presenting a variety of skin lesions, bacterial, viral and fungil infections, high parasite loads and intersex in normally gonochorist fish ( where embryonic gonad subsequently divides into ovaries or testes). The findings are not at all consistent, but show wide spread biological impact. Scientists like Dr. Blazer are looking to determine if these impacts to fish are being caused by something being put in or released from wastewater treatment plants, farms, or storm water runoff. Until the cause is identified, nothing can be done to stop them and prevent impact to animal and human populations.
Slide taken from Dr. Viki Blazer of USGS presentation

The Potomac fish kills studied by Dr. Blazer and others suggest that there are stressed populations of fish that at some point are overwhelmed by environmental stressors such as increased water temperatures, low dissolved oxygen, excess nutrients, high pH, or chemicals that cause immuno-supression leading to a wide variety of opportunistic infections and the large fish kills. There is increasing evidence that estrogenic chemicals and other endocrine disrupting substance modulate the immune response and disease resistance. In a study of female bass from the Shenandoah River south fork scientists found the BDE (a flame retardant), triclosan (an antibacterial and antifungal agent used in a wide variety of consumer products including toothpaste, mouthwash, deodorant and cleaning supplies) and pesticides had accumulated selectively within the endocrine system with lower concentrations in the brain, skin, kidneys. In talking about the bass, it is reported by Marcia Moore of the Daily Item that Dr. Blazer said, “The good news, for people anyway, is the muscle has the lowest concentration,” indicating that the fish could be eaten. “It’s not such good news for the fish because we’re finding it in the brain, ovaries, kidneys and skin.” The location of the increased concentrations seen in Dr. Blazer’s slide and potential sources of contaminants raises questions about potential human exposure.  

All water on earth is part of the hydraulic cycle and is reused over the course of time. These traces of chemicals have managed to slip through the earth’s natural filtration and some of them through treatment systems to be released into rivers and consumed by humans. Finished and source water (as well as food and beverages) have been found to have low levels of these emerging chemicals, but whether this low level of exposure is bio-accumulating in humans and can cause any health or developments effects is yet unknown. Endocrine disruptors can sometimes affect reproduction, development, and behavior, certainly these impacts on fish is being studied. These potentially endocrine disrupting chemicals come from a variety of sources and have diverse molecular structures. If these chemicals are introduced into water systems from human waste and food, then it is possible that human tissues might also contain detectable levels of contaminants. We might be experiencing subtle population impacts from chemical exposure during fetal and newborn development. Potential human effects from chemical contaminants in tissues of the endocrine system are cancer (particularly breast cancer and testicular cancer), infertility, disorders of sex development, asthma and other immune related syndromes, autism, ADHD, learning and behavioral disorders, diabetes, thyroid disorders, and testicular dysgenesis syndrome (poor semen quality, testis cancer, undescended testis and hypospadias).

The endocrine system of fish bears some similarity to the human endocrine system, but we do not live our lives in the waters of the Potomac. Two million people rely on the Washington Aqueduct for their drinking water and millions of people in other parts of the country drink source water with similar observed occurrences of endocrine disruption. The impact on human life and the ecosystem of these emerging contaminants is not known, but now is the time to find out the impact from the substance we’ve been allowing to enter the waters of the earth. We need to determine the impact and fate of these micro pollutants before we implement the watershed cleanup plans to make sure we are implementing the right strategies for the health of the entire ecosystem which may include eliminating the use of certain chemicals.  

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