Environmental Health - Toxic Substances Hydrology Program
An international group of scientists from the U.S. Geological Survey (USGS) and Agroscope Reckenholz-Tänikon, Research Station ART (Switzerland) have documented the common occurrence of six phytoestrogens and two mycotoxins in streams across Iowa. Phytoestrogens (derived from plants) and mycotoxins (derived from fungi) are naturally occurring compounds. Scientists have known that phytoestrogens and select mycotoxins have some of the same characteristics and function as the hormone estrogen; however, very little is known about their occurrence in aquatic environments or their potential adverse ecological effects, such as the disruption of hormone systems (endocrine disruption). The data collected in this study during the 2008 growing season (March through October) provides the first baseline assessment of the occurrence of phytoestrogen and mycotoxin compounds in streams draining agricultural land in the United States.
The compounds most frequently detected include:
Atrazine, a herbicide commonly applied on corn, also was measured and was detected in all the water samples with a maximum concentration of 7,300 ng/L. The streams sampled drained about 90 percent of Iowa, including many areas with significant agriculture. However, the relative amount of these natural compounds that was contributed from native and non-native plants as well as from municipal wastewater treatment plants, and a wide range of agricultural activities (row crops, such as corn and soybeans; cover crops; livestock production; and application of livestock manure to fields) is yet to be determined.
The sampling network consisted of 13 interior stream basins and two sites on the large border rivers of Iowa (the Missouri and Mississippi Rivers). All sites were sampled five times in 2008: March (pregrowing season), June (early growing season), July/August (mid-growing season), September (late growing season), and October (harvest). The greatest phytoestrogen and mycotoxin concentrations were observed during spring snowmelt conditions during March. While phytoestrogens and mycotoxins were commonly detected during this study, concentrations were typically less than 50 ng/L. The estrogenic properties of these compounds are several orders of magnitude less than the potent natural estrogen 17ß-estradiol. Therefore, significantly higher concentrations of these compounds than 17ß-estradiol would be required to achieve a comparable estrogenic potency. The ecotoxicological implications of these chemicals, which come from both natural and man-made sources in the environment, are poorly understood.
Kolpin, D.W., Hoerger, C.C., Meyer, M.T., Wettstein, F.E., Hubbard, L.E., and Bucheli, T.D., 2010, Phytoestrogens and mycotoxins in Iowa streams--An examination of underinvestigated compounds in agricultural basins: Journal of Environmental Quality, v. 39, no. 6, p. 2089-2099, doi:10.2134/jeq2010.0121.