Scientists now tell us there is something in our waters that we least expected.

That “something” is a class of chemicals called endocrine disruptors, and Dr. Vicki Blazer, a fisheries biologist at the United States Geological Survey, thinks the chemicals are responsible for the high concentrations of intersex fish found in the Potomac, and other rivers in the mid-Atlantic.

The chemicals also prove a threat to human health, but a bit of explanation, first.

Our body’s endocrine system is a complex network of glands and hormones that regulate growth, development, and the operation of various organs. The endocrine glands (for example the thyroid, adrenal, pancreas, testes, ovaries and pituitary glands) release hormones that act as chemical messengers and regulate many life functions.

Endocrine disrupters are chemicals that interfere with this system, by either acting like a hormone, or blocking a hormone’s function. They can be natural, but many are man-made such as PCBs, dioxin, DDT and other pesticides, pharmaceuticals and plasticizers. They are found in many products, including plastic bottles, metal food cans, detergents, flame retardants, food, toys, cosmetics and pesticides. They enter the environment and are now commonly found in our streams, rivers, bays and oceans, where scientists are observing problems.

For example, Blazer has found male smallmouth bass with both male and female sex organs attempting to lay eggs. Coincidentally, estrogen levels from disposed drugs such as birth control pills and urine from hormone-treated livestock have increased in waters.

In 2003, these disturbing findings were reported in the upper reaches of the Potomac River. Since then, endocrine disruptors and their effects on fish have been reported throughout the mid-Atlantic.

Environmental scientist Eugene P. Macri reports that the Susquehanna is a “toxic soup” with chemicals and endocrine disruptors. Environmental agencies in Pennsylvania have failed to see the cumulative effects of endocrine disruptors in the Susquehanna watershed, Macri argues.

“Contrary to the myth (about the river’s good health). … the Susquehanna is a dying ecosystem.”

These chemicals are rooted in our lifestyle choices,” Blazer said. For example, virtually all personal care products contain phthalates, which cause sex problems in frogs and may damage the workings of the human endocrine system.

Scientists are quick to point out that with new pollutants entering our water systems every day, and we really don’t know what safe levels are.

“This is the dilemma when we look at toxins in the water at parts per billion,” said Dr. Robert Lawrence of the Johns Hopkins University School of Public Health. “We are beginning to see a disturbing amount of genital abnormalities in male babies and impaired fertility influenced by endocrine disruptors.”

Right now, “the burden of proof is on those who say that levels of endocrine disruptors in the water are too low to be harmful. We need to take into account that humans are long-lived species and endocrine disruptors have a capacity to have synergy with other toxins and become harmful over time. Parents should be very careful in terms of what kind of drinking water they give to their young children.”

Lawrence added that we need strict law enforcement procedures for water treatment, not mere monitoring.

“Ten new chemicals per day are being manufactured globally that end up in our water systems. Testing can’t keep up. It’s scary, very scary.”

The situation won’t improve unless there is a major public outcry against our rivers becoming toxic chemical waterways. Unless we firmly control our drinkable, fishable and swimmable waters, we may face frightening consequences as a species. The effects of endocrine disruptors, so evident in fish, can be extrapolated to the human body. Thus in the future impaired waters may in turn lead to impaired people.

John R. Wennersten is the author of numerous books on the Chesapeake Bay and regional environments in the Mid-Atlantic. This column is distributed by Bay Journal News Service.