One study found that several lagoons and monitoring wells from two facilities (a nursery and a farrowing sow operation) contained high levels of all three types of estrogen. For the nursery, lagoon effluent concentrations ranged from 390 to 620 ng/L for estrone, 180 to 220 ng/L for estriol, and 40 to 50 ng/L for estradiol. For the farrowing sow operation, digester and primary lagoon effluent concentrations ranged from 9,600 to 24,900 ng/L for estrone, 5,000 to 10,400 ng/L for estriol, and 2,200 to 3,000 ng/L for estradiol. Ethinylestradiol was not detected in any of the lagoon or ground water samples. Natural estrogen concentrations in ground water samples were generally less than 0.4 ng/L, although, a few wells at the nursery operation showed quantifiable but low levels."