Comparison of three enzyme immunoassays for measuring 17beta-estradiol in flushed dairy manure wastewater.

Natural steroidal estrogens are an environmental concern because low nanogram per liter concentrations in water can adversely affect aquatic vertebrate species by disrupting the normal function of their endocrine systems. There is a critical need to accurately measure estrogens in dairy wastes, a potential source of estrogens such as 17beta-estradiol, to assess the risk of estrogen contamination of agricultural drainage waters resulting from land application. Commercially available enzyme immunoassay (EIA) kits have been used for measuring 17beta-estradiol in livestock manure, but it is not known if different EIAs provide similar results. We compared three EIAs by measuring 17beta-estradiol in two samples of flushed dairy manure wastewater (FDMW). The measured concentrations of 17beta-estradiol in FDMW differed according to the immunoassay used. The differences were attributed to a matrix interference associated with coextracted humic substances. Future research should develop methods that enable routine measurement of 17beta-estradiol in livestock wastes by more conclusive analytical techniques such as gas chromatography-mass spectrometry.