Student Focus

Links related to this story

Environmental Estrogen

Emily Notch spent four years involved in salmon habitat restoration in the Pacific Northwest before she decided to turn her attention to research addressing the larger issues concerning the biological effects of toxicants on freshwater fish.

Now, three years into her doctoral research at the University of Maine, Notch has found evidence that waterborne synthetic hormones, like those in oral contraceptives and hormone replacement therapies, do more than impair fish reproduction. Synthetic estrogens and similar hormones have the potential to disrupt an aquatic organism's natural ability to perform DNA repair, which could lead to mutations and tumors.

Her work has implications not only for fish, including endangered wild Atlantic salmon, but also humans.

"There's so much that we don't understand about what we're putting into the environment and how it affects aquatic organisms," says Notch, a native of Scotia, N.Y., who was recently named one of 66 graduate students nationwide to receive a U.S. Environmental Protection Agency (EPA) Science to Achieve Results (STAR) Fellowship.

"Now the research is spinning into a cancer realm, which is how (the focus) comes back around to (humans). What makes this research so interesting to me is how it all ties together."

Synthetic hormones like estrogen, excreted by millions of women taking oral contraceptives or hormone replacement therapies, enter the natural aquatic environment via wastewater treatment plants. Estrogens are known carcinogens, but current science lacks a complete understanding of estrogen-induced cancer.

In her research as a Ph.D. candidate in the laboratory of Greg Mayer, an assistant professor of molecular and environment toxicology, Notch has studied the effects of one synthetic estrogen, ethinylestradiol (EE2), in zebrafish and found it has the potential to suppress nucleotide excision repair (NER) in organisms.

NER is the molecular pathway in organisms — from fish to humans — capable of recognizing and repairing DNA damage caused by environmental carcinogens.

Notch's research findings on EE2's ability to decrease the expression of multiple liver repair genes in zebrafish, a model organism for human health, were published this past summer in the journal Aquatic Toxicology.

Now with three years of funding with the EPA STAR Fellowship, awarded to graduate students in environmental fields, Notch will further study whether environmental estrogens alter DNA repair, leading to increased mutations and, ultimately, cancer.

Notch is UMaine's third EPA STAR Fellow in the past three years. In 2004, Ph.D. student Karen Merritt in civil and environmental engineering, and Nicolas Blouin, a master's student in marine sciences, were named fellows.

"For humans who take birth control, the question ultimately is what is the effect on them long term," says Notch. "For fish, what is the effect of swimming in estrogen, hydrocarbons, metals and other pollutants? The subtle interactions — how they impact fish and have implications for human health — are fascinating. A big puzzle to me."