A new study has found that a type of natural estrogen continues to increase in suburban areas, resulting in the imbalance of frog genders, particularly the decline of the male frog population. Typical frog settlements such as lawns, shrubs and gardens were found to have a dominant female hormone that disrupts the endocrine system of the males.
Researchers from Yale University concentrated on the impact of contaminants caused by humans on the population of wildlife species. The substances that disturb the endocrine system are called Endocrine Disrupting Chemicals (EDC), which work through hormonal networks.
According to the study, EDCs may exhibit significant effects even if levels are low. The most common sources of EDCs are said to be pesticides and exposure to wastewater; however, the researchers delved into other potential contaminant origins and were able to determine a wide range of EDC sources in the suburbs.
The scientists studied ponds with diverse levels of exposure to suburban communities. Some areas examined were situated deep within forested locations, while some were found in the middle of bustling neighborhoods. Some ponds studied by the authors were connected to septic and sewage systems, and others were part of private home backyards.
The findings of the study, published in the Proceedings of the National Academy of Sciences, show that even ordinary lawns contain plants that naturally generate phytoestrogens. With this, the researchers said that the simple act of creating and maintaining a garden or lawn may mean added source of contaminants.
The research was able to demonstrate that suburbs, farms and sewage areas are all similar for frogs, said Max Lambert, study author and doctoral student at the School of Forestry and Environmental Studies at Yale University. The possible association between ornamental plant areas and endocrine disturbance in species came as a surprise to the authors; the study has not, however, delved into the potential causes.
The research results also suggest that the increased levels of estrogen in suburban freshwater areas may be due to trace-element contamination linked to the utilization of lands by humans.
In the end, the researchers say that transforming vegetation lands, such as forests, to suburban lawns and ornamental plantations may hasten the distribution of phytoestrogens in waters, where frogs settle. With this, the authors conclude that endocrine disruption among frogs is rampant in suburban areas and the causes are quite varied.
Photo: Liz West | Flickr