Potentially toxic metals in aquatic production systems receiving urban wastewater in Vietnam and Cambodia Helle Marcussen 1&2,, Karin Joergensen 1 Peter E. Holm 1 and Anders Dalsgaard 2 Departments of 1 Natural Sciences and 2 Veterinary Pathobiology and, The Royal Veterinary and Agricultural University (KVL), Denmark

Objectives Determine potentially toxic metal concentrations and assess food safety of water spinach produced with wastewater use Investigate influence of seasonality on metal concentrations in water spinach Determine potentially toxic metal concentrations and assess food safety of fish grown in wastewater Determine potentially toxic metal concentrations in sediment and investigate the distribution of metals through out production systems

Location and samples in Hanoi Study sites:Hoang Liet (HL), Than Phu (TP), Yen So (YS) in Thanh Tri district, Hanoi Control site:Duc Tu (DT) in Dong Anh district, Hanoi Sample typeSampling periodNo. samples (No. replicates) Water spinachDec 2003 May 2004 Sept – Nov 2004 TP: 4 TP: 6(3) TP: 2(4), YS: 1(4), HL: 4(4), DT: 2(4) FishApril 2005Silver carp - YS: 10, HL: 10 Tilapia - YS: 10, HL: 10 Comm. carp - YS: 10, HL: 10 SedimentSept – Nov 2004 April 2005 TP: 2(4), YS: 1(4), HL: 4(4), DT: 2(4) HL: 3(4), YS: 3(4)

Location and samples in Phnom Penh Study site:Boeng Cheung Ek lake Control site:Small pond with water spinach in Cheung Ek village Sample typeSampling periodNo. samples (No. replicates) Water spinachMay 2004 Nov 2004 Jan (4) + 1 control (4) FishMarch – April 2005Walking catfish: 5 Spineless ell: 6 Snakehead: 6 SedimentJan (4) + control (4)

Materials and methods Water spinach samples: Composite samples with 20 plants in each were collected The hole edible part or the different parts of the plant were analysed Wash in distilled water, dried at 45º and pounded to powder Sediment samples: The upper 10 cm sediment were collected as composite samples Dried at 45º, sieved through a 2 mm pounded to powder Fish samples: Fish were dissected into liver, skin and muscle Stored at -18º C until time of digestion All samples were digested in acids and analyzed by GFAAS or ICP-MS

Results Preliminary screening of 40 different elements showed generally low metal concentrations. Therefore, focus was on Pb, Cd and As which are toxic at low concentrations Ni, As and Pb concentration were highest in plant roots. For all other plant parts no significant difference could be observed

Results from Hanoi PbCdAs Water spinach Range (mg/kg w.w) < Limit value (mg/kg w.w.) Max. intake mg/(day*60 kg b.w.) Max. intake of water spinach (kg/day) Sediment Range (mg/kg d.w.) < Limit value (VN) (mg/kg d.w.)70212

Pb, Cd and As in fish, Hanoi Pb (mg/kg w.w) Cd (mg/kg w.w)As (mg/kg w.w) C. carp muscle< < <0.15 C. carp liver< < <0.15 C. carp skin< < <0.15 Silver carp muscle <0.032< <0.15 Silver carp liver<0.032< <0.15 Silver carp skin<0.032<0.0033<0.15 Tilapia muscle< < <0.15 Tilapia liver <0.15 Tilapia skin< < <0.15 Limit value

As and Pb in water spinach from Phnom Penh

Cd concentrations in water spinach from Phnom Penh

Metals in sediment from Phnom Penh Threshold limits for agricultural soils:Pb 70 mg/kg As 12 mg/kg Cd 2 mg/kg Detection limit for Cd:0.4 mg/kg

Pb, Cd and As in fish, Phnom Penh Pb (mg/kg w.w)Cd (mg/kg w.w)As (mg/kg w.w) catfish muscle<0.032<0.0033<0.15 catfish liver< < <0.15 catfish skin Spineless eel muscle <0.032<0.0033<0.15 Spineless eel liver<0.032<0.0033<0.15 Spineless eel skin<0.032<0.0033<0.15 Snakehead muscle<0.032<0.0033<0.15 Snakehead liver<0.032<0.0033<0.15 Snakehead skin<0.032<0.0033<0.15 Limit value

Conclusions Consumption of water spinach produced with use of wastewater does not seem to constitute a food safety problem with regards to toxic metals in Hanoi and Phnom Penh Consumption of fish from Boeng Cheung Ek does not seem to constitute a food safety problem, except for skin of walking catfish Consumption of tilapia and common carp grown in ponds in Hanoi can constitute a food safety problem. Especially the liver should not be consumed Pollution with Pb and Cd is taking place, but the metals seem mainly deposited in wastewater canals and less so in ponds and fields. However, there is still a need to follow the metal build up in productions systems in the future