Phosphorus Amendment Reduces Hepatic and Renal Oxidative Stress in Mallards Ingesting Lead-Contaminated Sediments

Abstract

Lead poisoning of waterfowl has been reported for decades in the Coeur d'Alene River Basin (CDARB) in Idaho as a result of the ingestion of lead-contaminated sediments. This study was conducted to determine whether the addition of phosphoric acid to CDARB sediments would reduce the bioavailability and toxicity of lead to the liver and kidney of mallards (Anas platyrhynchos). Mallards received diets containing 12% clean sediment (controls) or 12% sediment from three different CDARB sites containing 4520, 5390, or 6990 μ g/g lead (dry weight) with or without phosphoric acid amendment. Liver and kidney lead concentrations were significantly higher in all CDARB treatment groups and ranged from geometric mean values of 18.2 (liver) and 28.7 (kidney) for the first 2 sites to 22.5 (liver) and 45.6 (kidney) μ g/g (wet weight) for the third site. With amendments all liver lead concentrations were reduced 36 to 55%, and all kidney lead concentrations were lowered 54 to 73%. Unamended CDARB sediment from the third site resulted in the following hepatic effects: over 1.6-fold elevation of liver glutathione (reduced form; GSH) concentration, higher GSH S-transferase and oxidized glutathione (GSSG) reductase activities, and lower protein-bound thiols (PBSH) concentration. Renal effects included higher kidney GSH concentrations for all CDARB sites, with over 2.1-fold higher for the third site. Resulting kidney GSSG to GSH ratios were lower at two sites. At the third site, gamma-glutamyl transferase (GGT) activity was elevated, and lipid peroxidation as thiobarbituric acid-reactive substances (TBARS) was 1.7-fold greater. Amendment restored all hepatic variables as well as the renal variables TBARS and GGT so they did not differ from controls. Although amendments of phosphorus substantially reduced the bioavailability of lead and some of the adverse effects, lead concentrations in the tissues of mallards fed the amended sediments were still above those considered to be harmful to waterfowl under the present conditions.

We thank Anne Dailey for overall support and coordination of this project. The planning and study design were a multiagency effort, including the U.S. EPA (Anne Dailey, Mark Sprenger, and Mary Jane Nearman), Idaho Department of Environmental Quality (Nick Zilka and Kathy Johnson), U.S. Fish and Wildlife Service (Brad Frazier and Julie Campbell), Coeur d'Alene Indian Tribe (Phil Cernera), and many others who provided helpful suggestions. Mark Snyder, Nick Zilka, Julie Campbell, Brad Frazier, Stan Peterson, and Jon Munkers helped in the treatment of sediments in the field and the collection of sediments. Brad Frazier and Stan Peterson provided advice and assistance in adding the amendments in the lab. Carol Erwin, Dan Murray, Michael Hoffman, and Michael Hammond cared for the ducks; Glenn Olsen took blood samples from the ducks; and Shannon Kondrad helped analyze the data. Funding for the study came from the U.S. Environmental Protection Agency.

Notes

We thank Anne Dailey for overall support and coordination of this project. The planning and study design were a multiagency effort, including the U.S. EPA (Anne Dailey, Mark Sprenger, and Mary Jane Nearman), Idaho Department of Environmental Quality (Nick Zilka and Kathy Johnson), U.S. Fish and Wildlife Service (Brad Frazier and Julie Campbell), Coeur d'Alene Indian Tribe (Phil Cernera), and many others who provided helpful suggestions. Mark Snyder, Nick Zilka, Julie Campbell, Brad Frazier, Stan Peterson, and Jon Munkers helped in the treatment of sediments in the field and the collection of sediments. Brad Frazier and Stan Peterson provided advice and assistance in adding the amendments in the lab. Carol Erwin, Dan Murray, Michael Hoffman, and Michael Hammond cared for the ducks; Glenn Olsen took blood samples from the ducks; and Shannon Kondrad helped analyze the data. Funding for the study came from the U.S. Environmental Protection Agency.

^a nmol NADPH oxidized/min/mg of 10,000 g supernatant protein.

^b nmol/min/mg of 10,000 g supernatant protein.

^c Significantly different from the Round Lake group (p ≤ .05).

^d Significantly different from the corresponding unamended group for that site (p ≤ .05).

^a nmol NADPH oxidized/min/mg of 10,000 g supernatant protein.

^b nmol/min/mg of 10,000 g supernatant protein.

^c Significantly different from the Round Lake group (p ≤ .05).

^d Significantly different from the corresponding unamended group for that site (p ≤ .05).

Connor, E. E. 1993. Soil ingestion and lead concentration in wildlife species. MS thesis, Virginia Polytechnic Institute and State University, Blacksburg

U.S. Environmental Protection Agency Region 10. 2001. Consensus plan for soil and sediment lead concentrations in the CDARB. Ecotoxicol 9:207—Studies: Coeur d'Alene River soils and sediments bioavailability studies. Prepared by URS Corp., February, 2001, Seattle