| Author |
Stafford, Jennifer M. Lambert, Charles E. Zyskowski, Justin A. Engfehr, Cheryl L. Fletcher, Oscar J. Clark, Shanna L. Tiwary, Asheesh Gulde, Cynthia M. Sample, Bradley E. |
| Description |
Country affiliation: United States Author Affiliation: Stafford JM ( Carolina Research Center, Smithers Viscient, Snow Camp, NC, 27349, USA. jstafford@smithers.com.); Lambert CE ( McDaniel Lambert Inc. (an Intrinsik Company), 1608 Pacific Ave, Suite 201, Venice, CA, 90291, USA. clambert@intrinsik.com.); Zyskowski JA ( Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, 4125 Beaumont Rd, Lansing, MI, 48910, USA. zyskows1@dcpah.msu.edu.); Engfehr CL ( Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University, 4125 Beaumont Rd, Lansing, MI, 48910, USA. Engfehrc@dcpah.msu.edu.); Fletcher OJ ( Department of Population Health & Pathobiology, College of Veterinary Medicine, NC State University, 1060 William Moore Dr., Raleigh, NC, 27607, USA. Oscar_Fletcher@ncsu.edu.); Clark SL ( Chevron Energy Technology Company, 1200 Smith Street, Houston, TX, 77002, USA. shanna.clark@chevron.com.); Tiwary A ( Chevron Energy Technology Company, 1200 Smith Street, Houston, TX, 77002, USA. asheesh.tiwary@chevron.com.); Gulde CM ( Chevron EMC, 116 Inverness Drive East, Suite 207, Englewood, CO, 80112, USA. cgulde@chevron.com.); Sample BE ( Ecological Risk, Inc., 15036 Magno Ct., Rancho Murieta, CA, 95683, USA. bsample@ecorisk.com.) |
| Abstract |
Limited data are available on the effects of molybdenum (Mo) on avian wildlife, which impairs evaluation of ecological exposure and risk. While Mo is an essential trace nutrient in birds, little is known of its toxicity to birds exposed to molybdenum disulfide (MoS2), the predominant form found in molybdenite ore. The chemical form and bioavailability of Mo is important in determining its toxicity. Avian toxicity tests typically involve a soluble form of Mo, such as sodium molybdate dihydrate (SMD, Na2MoO4·2H2O); however MoS2 is generally insoluble, with low bioaccessibility under most environmental conditions. The current study monitored survival and general health (body weight and food consumption) of 9-day old northern bobwhite exposed to soluble Mo (SMD) and ore-related Mo (MoS2) in their diet for 30 days. Toxicity and bioavailability (e.g. tissue distribution) of the two Mo forms were compared. Histopathology evaluations and serum, kidney, liver, and bone tissue sample analyses were conducted. Copper, a nutrient integrally associated with Mo toxicity, was also measured in the diet and tissue. No treatment-related mortality occurred and no treatment-related lesions were recorded for either Mo form. Tissue analyses detected increased Mo concentrations in serum, kidney, liver, and bone tissues following exposure to SMD, with decreasing concentrations following a post-exposure period. For the soluble form, a No-Observed-Adverse-Effect Concentration (NOAEC) of 1200 mg Mo as SMD/kg feed (134 mg SMD/kg body weight/day) was identified based on body weight and food consumption. No adverse effects were observed in birds exposed to MoS2 at the maximum dose of 5000 mg MoS2/kg feed (545 mg MoS2/kg body weight/day). These results show that effects associated with MoS2, the more environmentally prevalent and less bioavailable Mo form, are much less than those observed for SMD. These data should support more realistic representations of exposure and risks to avian receptors from environmental Mo. |
