Our fresh water fish are not only interesting for those who value them for food or sport, but they are also studied by naturalists, wildlife biologists, ecologists, public health professionals and even biochemists.

We have a lot in common with fish. We intimately share the same water. They swim and breathe in it and we drink and bathe in it. Because of the constant contact with shared water, fish in our lakes and streams become our aqueous mine-canaries signaling problems in the water that will adversely affect our own health.

Many municipalities get their water supply directly from rivers or reservoirs, or from wells supplied from surface waters. City water waste, or sewage, is treated to control disease by removing bacteria, but treatment plants are not designed to take out all the pollutants, especially toxic chemicals.

Downstream the water from treatment plants is often used again by another town or city for domestic water. There it accumulates additional chemical contaminants, is treated and dumped back into the stream. In addition, surface run off water from city streets and industrial areas add chemical contaminants to the stream.

So let us examine some recent observations about the quality of our waters and the health of the fish that swim in it. Having been an investigative biochemist I focus on the contamination of water supply with estrogenic chemicals. These are synthetic, organic chemicals that affect the health of animals in ways similar to that of natural estrogen, a human hormone responsible for development of female traits in animals. Thus, they are called estrogenic chemicals.

Estrogenic chemicals polluting our water come from birth control pills containing synthetic estrogen, insecticides, our plastic containers, plastic water pipes, and industrial and household products. A prominent contaminant is bisphenol-A or BPA, a compound used to harden plastic. BPA leaches out of virtually all plastic, including polycarbonate food and drink containers.

So what are the fish telling us about these chemical additions to our shared water environment? Wildlife biologists report that the ability for salmon and trout to reproduce is adversely affected by the increase in estrogenic chemical pollutants. In the Columbia River system there appears to be a hormone-induced sex reversal of salmon males to females with subsequent generations becoming genetically abnormal males.

In rivers near Boulder Colorado, similar sex-reversal was found in white suckers downstream of waste treatment plants. In tributaries of the Potomac River in West Virginia, researchers found sites where nearly all male smallmouth bass had testes with rudimentary female egg cells. A survey of fish in rivers and streams in the United States shows that a majority of male bass have acquired feminine characteristics.

Closer to home, levels of estrogenic chemicals have been measured to be increasing in Puget Sound and its tributary rivers and streams. Levels are high enough to not only change the reproductive ability of trout, but are cited as being able to affect frogs, river otters and other fish.

Some adverse effects of estrogenic compounds in humans are increased incidences of breast cancer and interference with natural sexual development. BPA is medically linked to these problems and is found to be retained in humans a long time after ingestion, in females more than males.

Water treatment experts tell us that sewage treatment removes a large percentage of the estrogenic compounds as solid waste. However, the solid waste sludge is often returned to the soil as fertilizer for crops which again introduces toxic chemicals into our food and water supplies. Studies show that estrogenic chemicals in solid waste do infiltrate into the ground polluting underground aquifers.

The new Brightwater treatment plant, being built in Snohomish County to process King County sewage, is designed to remove more of the estrogenic compounds than do current plants. So the danger of pollution by BPA is being recognized by our local governments. There is also a strong local movement, promoted by the Sno-King Watershed Council, to limit and isolate ground water run off from areas that feed our domestic water supply.

These are steps in the right direction to reduce the harmful chemical contaminants affecting the fish who are giving us an "early warning." But we all need to help by limiting the use of products responsible for contamination by BPA. We need to curtail use of plastic food containers that contain BPA, and reduce contact of our municipal water with plastic pipes and storage tank linings.

Hearing the increasingly soprano song of our fish, I advise my friends, family, and especially my grandchildren to buy and keep their food and drink in glass containers ... especially for baby bottles.