Ecosystems & Environment: Animal Feeding Operations
There are an estimated 376,000 animal agricultural feed operations in the United States, producing approximately 128 billion pounds of waste each year. The largest such operations, called concentrated animal feeding operations (CAFOs), house at least a thousand animals and the waste from these animals is generally stored in lagoons. The waste contains nutrients such as nitrogen and phosphorus, but also endocrine disrupting compounds (EDCs) - mainly estrogens, testosterone and other hormones released directly from the animals. The ability of lagoons to contain waste and prevent it from leaking into surrounding surface water and groundwater is variable due to factors such as the quality of the material used to line the lagoon. CAFO waste is generally spread on surrounding agricultural land, and most CAFOs are required by the EPA to have Nutrient Management Plans to control land application. These plans are designed to protect groundwater from nutrient contamination, and it is possible that if they work for nutrients they will also protect groundwater from hormones. Very little is known about how CAFOs affect nearby surface waterways and groundwater with respect to EDCs.
Because EDCs can exert environmental effects at very low levels, EPA researchers have been developing or modifying analytical methods to accurately measure these compounds in CAFO lagoons, surface water, and groundwater. Using these tools, EPA researchers are assessing CAFOs to determine their contribution to EDCs that can be found in nearby groundwater and waterways.
Research on surface waters suggests that hormones released by CAFOs may affect fish communities by reducing diversity and skewing the sex ratio towards the production of males. Other tools are being deployed to detect other EDCs such as 17a- and 17b-trenbolone. These are compounds derived from a synthetic testosterone-like hormone (androgen) widely used in the United States to promote growth of beef cattle. 17a- and 17b-trenbolone act as potent male hormones in fish and mammals and have been detected in discharges from cattle feeding lots. One tool that can measure the activity of such compounds are genetically-modified (recombinant) human cell lines. The cells contain a gene that only turns on in response to a compound that acts like testosterone, literally lighting up the cell with luciferase, a glowing dye derived from jellyfish, beetles, and fireflies. EPA researchers have also been studying the effect of CAFOs on groundwater. One study examined groundwater near seven CAFOs, housing pigs, beef cattle, dairy cows, or poultry. The researchers detected estrogens in groundwater associated with lagoons or piping that leaked directly into aquifers and were known to be discharging nutrients such as nitrogen into groundwater. For instance, groundwater at one site contained 1000 ng/liter estrone, a form of estrogen that can be converted to estradiol, which can affect proper reproductive development of fish at levels as low as 10 ng/liter.
Preliminary findings suggest that land application of CAFO waste may not contribute substantially to estrogen in groundwater because certain soil conditions may foster the biochemical breakdown of these hormones. EPA scientists have also examined the effects of tilling on reducing CAFO runoff after land application. Estrogens in the runoff were present at about 3-fold higher levels in untilled fields, although the timing and intensity of rainfall affected the data.
EPA research can help the development of management strategies for protecting groundwater from endocrine disruptors in CAFO waste. Preliminary data suggest the possibility that proper management of nitrate contamination may also reduce concentrations of other environmental stressors such as estrogen hormones to acceptable risk levels. Additional field studies are needed to test this hypothesis. While EPA researchers have shown the potential for CAFOs to contaminate surface and groundwater with endocrine disrupting chemicals, they have not established the prevalence of such contamination. For instance, nothing is known about how many CAFOs in the United States have significant leakage in barns and lagoons. EPA researchers will continue assessing these issues by comparing hormones released from CAFOs housing, researching different types of animals and looking more closely at a range of different hormones. Such studies will help provide more information regarding CAFOs as a source of endocrine disrupting chemicals in the environment.