236 (± 216) 113 (± 67) 239 (± 30)

426 (± 78) 349 (± 339) 203 (± 176) 543 (± 269)

Raman et al. (2001) Williams (2002)

BDL = below detection limit.

BDL = below detection limit.

The concentration of steroid hormones in dairy waste and sludge is dependant on the level of waste effluent treatment and storage and this is reflected in the concentration ranges shown in Table 2. Furthermore, analysis of total estrogens within a pile of dairy cow manure demonstrated estrogen levels as high as 1000 ^g/kg at the surface of the heap, but only about 3% of that within the heap (Mostl et al. 1997).

The variability in concentrations of steroid hormones measured in dairy waste effluents suggests the composition of the waste entering treatment systems varies considerably over time. The relatively high concentrations of steroid hormones measured in diary waste effluents and lagoons can be several orders of magnitude higher than that typically encountered in municipal wastewater treatment plants. Furthermore, the measured levels are significantly higher than the nanograms per litre (ppt) levels at which feminisation of fish has been observed to occur (Jobling et al. 1998).

Steroid Hormones Associated with Animal Waste in New Zealand

New Zealand is a small country with numerous lakes, rivers and streams, a rapidly expanding dairy industry, and established beef, sheep, pig and poultry production. Pasture grass and farm animals dominate more than half the country's land surface, and affect nearly all catchments. For many years, wastes from New Zealand dairy farms were largely treated in oxidation ponds before discharge to nearby waterways. However, in recent years, application of animal wastes to the land has become a permitted activity allowing farmers to apply effluent directly to the land without resource consent as long as they follow prescribed conditions set out by their respective regional councils (Sarmah and Northcott 2004).

It has been reported that the New Zealand livestock population excretes about 40 times more waste than the human population (Sarmah 2003; Sarmah et al. 2008). Within the Waikato region, animal waste is now applied to pasture by 70% of dairy farms and this proportion is steadily growing (Ministry for the Environment 1997). This proportion is higher in some other regions of New Zealand where land application of dairy effluents predominates as a means of disposal, for instance in Canterbury. In addition to the application of the effluent onto land by irrigation, a significant quantity of waste is excreted directly onto land by grazing animals. The potential therefore exists for contamination of surface and groundwater by EDCs sourced from diary operations due to run-off and/or leaching processes within receiving soils.

Steroid hormone levels measured in 5 dairy farms randomly selected within the Waikato region showed that significant amounts of steroid hormones were present in the dairy effluent samples collected from the point of discharge from oxidation ponds. The combined load for these natural excreted estrogens varied from 60 ng/l to > 4000 ng/l in the analysed effluents, and estriol was not detected in any of the collected samples (Table 4). The a epimer of estradiol was more prevalent in dairy effluent compared with the P epimer.

Table 4. Concentration of estrogens (^g/l) in dairy effluent across selected dairy farms within the Waikato region, NZ
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