Dietary toxicity of soluble and insoluble molybdenum to northern bobwhite quail (Colinus virginianus)

Ecotoxicology, Dec 2015

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.

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Dietary toxicity of soluble and insoluble molybdenum to northern bobwhite quail (Colinus virginianus)

Ecotoxicology Dietary toxicity of soluble and insoluble molybdenum to northern bobwhite quail (Colinus virginianus) Cheryl L. Engfehr 0 1 2 3 4 5 6 7 8 9 10 11 12 Oscar J. Fletcher 0 1 2 3 4 5 6 7 8 9 10 11 12 Jennifer M. Stafford 0 1 2 3 4 5 6 7 8 9 10 11 12 Charles E. Lambert 0 1 2 3 4 5 6 7 8 9 10 11 12 Justin A. Zyskowski 0 1 2 3 4 5 6 7 8 9 10 11 12 Cheryl L. Engfehr 0 1 2 3 4 5 6 7 8 9 10 11 12 Oscar J. Fletcher 0 1 2 3 4 5 6 7 8 9 10 11 12 Shanna L. Clark 0 1 2 3 4 5 6 7 8 9 10 11 12 Asheesh Tiwary 0 1 2 3 4 5 6 7 8 9 10 11 12 Cynthia M. Gulde 0 1 2 3 4 5 6 7 8 9 10 11 12 Bradley E. Sample 0 1 2 3 4 5 6 7 8 9 10 11 12 0 Chevron EMC , 116 Inverness Drive East, Suite 207, Englewood, CO 80112 , USA 1 Charles E. Lambert 2 Chevron Energy Technology Company , 1200 Smith Street, Houston, TX 77002 , USA 3 Jennifer M. Stafford 4 & Bradley E. Sample 5 Ecological Risk, Inc. , 15036 Magno Ct., Rancho Murieta, CA 95683 , USA 6 Department of Population Health & Pathobiology, College of Veterinary Medicine, NC State University , 1060 William Moore Dr., Raleigh, NC 27607 , USA 7 Diagnostic Center for Population and Animal Health, College of Veterinary Medicine, Michigan State University , 4125 Beaumont Rd, Lansing, MI 48910 , USA 8 McDaniel Lambert Inc. (an Intrinsik Company) , 1608 Pacific Ave, Suite 201, Venice, CA 90291 , USA 9 Carolina Research Center , Smithers Viscient, Snow Camp, NC 27349 , USA 10 Asheesh Tiwary 11 Shanna L. Clark 12 Justin A. Zyskowski 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 orerelated 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 Keywords NOAEC Introduction 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. Molybdenum (Mo) is widely distributed in the environment, with concentrations varying with geology (Adriano 1986; Chappell and Petersen 1976) . Typical, natural concentrations of Mo in soils average 1–2 mg/kg and may range from trace concentrations to 40 mg/kg or greater (Adriano 1986; Kubota 1977; USGS 2015) . Mo residues tend to be elevated in plants and soils near Mo mining and reclamation sites and fossil-fuel power plants. However, Mo concentrations are usually lower in fish and wildlife than in terrestrial plants (Eisler 1989). Concentrations in soils in the vicinity of a Mo mine in Mongolia ranged from 2 to 19 times greater than that in background soils, with concentrations at the tailings impoundment being 60–456 times greater than background (Battogtokh et al. 2014) . At the Benda Mine in British Columbia, Canada, Taylor and McKee (2003) report mean Mo concentrations ranging from 61 to 275 mg/kg for vegetation growing in mine tailings with Mo concentrations of 50–140 mg/kg. At another mine in British Columbia, Mo concentrations in soil ranged from 1.2 to 139 mg/kg, with concentrations in grass and legumes ranging from 2 to 341 mg/kg and 2 to 1030 mg/kg, respectively (Jones 1994) . Limited data are available on the effects of Mo on avian species. Since Mo is an essential trace mineral in birds, the majority of Mo avian studies identified in the literature are dietary studies of soluble forms of Mo [e.g. sodium molybdate (...truncated)


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Jennifer M. Stafford, Charles E. Lambert, Justin A. Zyskowski, Cheryl L. Engfehr, Oscar J. Fletcher, Shanna L. Clark, Asheesh Tiwary, Cynthia M. Gulde, Bradley E. Sample. Dietary toxicity of soluble and insoluble molybdenum to northern bobwhite quail (Colinus virginianus), Ecotoxicology, 2015, pp. 291-301, Volume 25, Issue 2, DOI: 10.1007/s10646-015-1587-5