Fish exposed to the endocrine-disrupting chemicals bisphenol A (BPA) or 17a-ethinylestradiol (EE2) in a laboratory have been found to pass adverse reproductive effects onto their offspring up to three generations later, according to a new study by the U.S. Geological Survey and the University of Missouri.
Aquatic environments are the ultimate reservoirs for many contaminants, including chemicals that mimic the functions of natural hormones. Fish and other aquatic organisms often have the greatest exposures to such chemicals during critical periods in development or even entire life cycles.
Scientists exposed fish to either BPA or EE2 for one week during embryonic development, while subsequent generations were never exposed. Future generations showed a reduced rate of fertilization and increased embryo mortality. The full study, published in the journal Scientific Reports, is available online.
“This study shows that even though endocrine disruptors may not affect the life of the exposed fish, it may negatively affect future generations,” said USGS visiting scientist and University of Missouri Assistant Research Professor, Ramji Bhandari. “This is the first step in understanding how endocrine disruptors affect future generations, and more studies are needed to determine what happens in the natural environment.”
There were no apparent reproductive abnormalities in the first two generations of fish, except for two instances of male to female sex reversal in adults of the EE2 exposed generation. Findings show a 30 percent decrease in the fertilization rate of fish two generations after exposure, and a 20 percent reduction after three generations. If those trends continued, the potential for declines in overall population numbers might be expected in future generations. These adverse outcomes, if shown in natural populations, could have negative impacts on fish inhabiting contaminated aquatic environments.
This study examined concentrations of EE2 and BPA that are not expected to be found in most environmental situations. However, concerns remain about the possibility of passing on adverse reproductive effects to future generations at lower levels. At this time, the ability to evaluate mixtures of estrogenic chemicals working jointly is limited.
The scientists studied BPA and EE2 because they are chemicals of environmental concern and represent different classes of endocrine disrupters. BPA is a chemical used primarily to manufacture polycarbonate plastics and epoxy resins, but is also an additive in other consumer products. Due to extensive use of these products in daily human life, the accumulation of BPA-containing waste in the environment has been a serious concern and a potential threat to public and wildlife health. EE2 is used in oral contraceptives designed for women, and about 16 – 68 percent of each dose is excreted from the body. As a result, EE2 has been found in aquatic environments downstream of wastewater treatment plants.
For more information on endocrine disruptors visit the USGS Columbia Environmental Research Center web page.