2006: Ord River (WA) Crocodile Meat: DDT, DDE

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Results of this survey compared with other recent studies in the ORIA.

A recent study of organochlorines in freshwater and saltwater crocodiles in the Ord River (Yoshikane et al. 2006) also found very high levels of DDT congeners (mainly p,p-DDE). Visceral fat and liver samples from specimens collected in the Upper Ord, the ORIA and the lower Ord were analysed for a wide range of organochlorines. The highest concentrations of DDE were found in the visceral fat of freshwater crocodiles collected from the lower Ord and drains of the ORIA. Very high concentrations were also found in the livers.

The study also detected trace levels of camphechlor and heptachlor but concentrations of these OCs were orders of magnitude lower than p,p-DDE levels.

Concentrations of p,p-DDE in visceral fat and livers of freshwater crocodiles collected from ORIA drains and the Ord River downstream of the ORIA.

Lower Ord: DDE in visceral ng/g fresh weight – ~28 000 (mean), ~66 000 (max)

Lower Ord: DDE in liver ng/g fresh weight – ~500 (mean), ~3200 (max)

ORIA: DDE in visceral ng/g fresh weight – ~14 000 (mean), ~33 000 (max)

ORIA: DDE in liver ng/g fresh weight – ~3000 (mean), ~8000 (max)

Source Yoshikane et al 2006

Concentrations have been converted from ng/g lipid to fresh weight using lipid concentrations reported by authors.

Significantly higher levels of DDT have also been found in freshwater crocodiles collected in the ORIA (Yoshikane et al. 2006, see Table 9). Levels of DDT in saltwater crocodiles were lower than in freshwater crocodiles, and high levels of DDT are not expected to be found in freshwater crocodiles from locations away from the ORIA.

Median concentration of DDT in freshwater crocodile in the ORIA drains and downstream of the ORIA and the maximum allowable daily consumption (kg) for adults

Lower Ord

Crocodile visceral fat: 28 200 (mean concentration of DDT in crocodile sample ng/g fresh weight). Tolerable daily intake of foodstuff for adults weighing 60 and 80 kg: 0.02 (60kg), 0.03 (80 kg)

Crocodile liver: 507 (mean concentration of DDT in crocodile sample ng/g fresh weight). Tolerable daily intake of foodstuff for adults weighing 60 and 80 kg: 1.2 (60kg), 1.6 (80 kg)

Ord drains

Crocodile visceral fat: 13 548 (mean concentration of DDT in crocodile sample ng/g fresh weight). Tolerable daily intake of foodstuff for adults weighing 60 and 80 kg: 0.04 (60kg), 0.06 (80 kg)

Crocodile liver: 3023 (mean concentration of DDT in crocodile sample ng/g fresh weight). Tolerable daily intake of foodstuff for adults weighing 60 and 80 kg: 0.2 (60kg), 0.27 (80 kg)

Pesticide concentrations in fish today are an order of magnitude lower than levels measured by GCL in 1979. The median concentration of DDT in fish muscle sampled in the lower Ord River near the ORIA in the 1970s was 420 ng/g, with a maximum level of 8800 ng/g recorded in a bony bream. The median concentration of DDT in fish flesh sampled from the ORIA in this survey was 6.7ng/g (fresh weight) which represents two orders of magnitude reduction in DDT levels over a period of 30 years.

P 15/17 Assessment of pesticides in aquatic organisms – Ord River WA Water resource technical series Report no. 40 October 2008 Government of Western Australia Department of Water/Australian Government