Washington, Feb 17 : A new study has shed more light on the dangers of flushing toxic chemicals into the ecosystem through municipal sewer systems, by finding that the miniscule amounts of estrogen present in municipal wastewater discharges can decimate the sex lives of wild fish populations living downstream.
The seven-year research, led by Dr. Karen Kidd, an NSERC-funded biology professor at the University of New Brunswick (Saint John) and the Canadian Rivers Institute, confirms that synthetic estrogen used in birth control pills can wreak havoc on the sex lives of fish.
Women excrete small amounts of estrogen naturally whether or not they are taking birth control pills.
Male fish exposed to estrogen become feminised, producing egg protein normally synthesized by females. In female fish, estrogen often retards normal sexual maturation, including egg production.
"We've known for some time that estrogen can adversely affect the reproductive health of fish, but ours was the first study to show the long-term impact on the sustainability of wild fish populations," said Kidd.
"What we demonstrated is that estrogen can wipe out entire populations of small fish - a key food source for larger fish whose survival could in turn be threatened over the longer term," added Kidd.
In the study, the researchers reviewed the Experimental Lakes Area in northwestern Ontario.
Over three summers, they added tiny amounts, low parts per trillion, of the synthetic estrogen used in birth control pills to the lake to recreate concentrations measured in municipal wastewater.
During that period, they observed that chronic exposure to estrogen led to the near extinction of the lake's fathead minnow population as well significant declines in larger fish, such as pearl dace and lake trout.
"Generally, the smaller the fish, the more vulnerable they are to estrogen," said Kidd.
The researchers used synthetic estrogen because it tends to persist longer in the environment than natural estrogens. Yet the problem with estrogen is not its environmental persistence but rather its persistent discharge in municipal wastewater into surface waters.
It is now understood, Kidd said, that removing estrogen through wastewater treatment can reverse the adverse impact of this substance/hormone on wild fish.
The study is published in the Proceedings of the National Academy of Sciences of the United States of America.