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Technically Speaking
Environmental Fate of Hormones Not Well Understood
By Terry Mader
Concerns about the concentration of hormones in animal waste produced from concentrated animal-feeding operations (CAFOs) have recently attracted the attention of the European Union Regulatory Agencies, Environmental Protection Agency and livestock industry groups. Reproductive hormones such as testosterone, estrogen and progesterone are receiving the most interest, although synthetic compounds with similar biological activity are also of interest. Estrogens in particular under high enough concentrations have been shown to alter reproductive traits in some fish and other aquatic species. However, new and more stringent guidelines for CAFO waste-management systems are likely to result in feedlot runoff being less of a concern than in the past, although runoff from land areas in which animal waste has been applied poses the potential to contaminate streams or other bodies of water.
Reproductive hormones are abundant in nature and are found in molds, plants and seeds as well as in animals, including fish. They are essential to the function and propagation of almost all organisms. In addition, significant quantities of both natural and synthetic hormones are used for birth control and in menopause therapies for humans. In general, the use of synthetic hormones in animals constitutes a very small part of the total use of pharmaceutical hormones worldwide.
Estrogens have been found in the effluent of wastewater treatment plants. Also, concentrated lagoon waste from poultry and swine units have been found to have relatively high levels of estrogens, while dairy and beef lagoon waste may have lower levels of estrogen. Thus, the occurrence and potential effects of these compounds in municipal waste and livestock waste from confined animal facilities is a current area of interest for consumers, environmentalists, government regulators, scientists and the domestic livestock industry.
The environmental fate of hormones is not well understood. These compounds decompose naturally, but the rates vary with compound and environmental conditions. Estrogens are excreted as either free estrogens or bound to other compounds called conjugates. The conjugated forms are less biologically active but can be converted to the free estrogen form in the environment. The extent the bound estrogen becomes active after excretion is yet to be fully determined. In addition, these compounds are not always excreted in the original form they were made. Thus there are several different metabolites of these compounds in human- and animal-waste products that may or may not be potentially problematic.
Because of the interests in these substances, numerous studies are being conducted, including at UNL, to determine the amounts of naturally produced and synthetic hormones that occur in animal waste and the different forms in which these compounds may be found.
Preliminary data is expected in July 2008 and publishable data next fall. We may have some analysis of manure samples later this winter. UNL researchers shipped cattle in late September and planned to stockpile and compost manure with the intent to apply the compost material to field plots next spring.
The effect of stockpiling manure versus composting on rates of decomposition plus the potential runoff from land application of these materials is being assessed. These studies are designed to provide objective answers to questions concerning the fate of synthetic as well as naturally produced hormones derived from CAFOs. Techniques have been developed to detect levels approaching parts per trillion (about one ounce in 31 million tons). Because these substances are so common in nature, the question is not whether they will be found, but rather what concentrations and in what form (biologically active or inactive) will they be found? How do levels of naturally occurring hormones compare to levels of synthetic compounds, plus what type of variation (range) do we see in hormone levels in waste? Are these compounds more inclined to leach through the soil or will they be more prevalent in runoff from the soil fertilized or conditioned with waste?
Survey and laboratory data, in addition to data from simulated studies, in which entire bodies of water were spiked with estrogens have shown that aquatic environments contaminated with even low levels of these compounds could potentially result in permanent changes in aquatic organisms, especially in lower-tropic level organisms such as tadpoles and some species of minnows. However, no data has shown any significant long-term and/or permanent changes in the aquatic species or environment due to naturally produced or manmade hormonal compounds. With good management practices and the current stringent animal waste controls in place today, the likelihood of waste from livestock facilities contributing to ecological changes in aquatic environments is less likely today or in the future than it would have been 10 or 20 years ago.
Finally, the use of growth promoting compounds has been an issue that has restricted some U.S. beef from entering foreign markets even though significant levels of the synthetic hormones cannot be found in the edible tissues. Hormones (synthetic) in animal waste may be another reason foreign countries justify banning these products for there own domestic beef production, thus limiting foreign beef from entering the country. It is highly unlikely that these attitudes will change even if very low levels of these compounds are found in studies characterizing the fate of hormones in animal waste. Y By Terry Mader, a professor of animal science and an Extension beef specialistat the Haskell Agricultural Laboratory in Concord. |