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N.B. Vyas

Publications and source records attributed to N.B. Vyas.

15 recordsLinked to original sources
USGS2009

Acute oral toxicities of wildland fire control chemicals to birds

Wildland fire control chemicals are released into the environment by aerial and ground applications to manage rangeland, grassland, and forest fires. Acute oral 24 h median lethal dosages (LD50) for three fire retardants (Fire-Trol GTS-R?, Phos-Chek D-75F?, and Fire-Trol LCG-R?) and two Class A fire suppressant foams (Silv-Ex? and Phos-Chek WD881?) were estimated for northern bobwhites, Colinus virginianus, American kestrels, Falco sparverius, and red-winged blackbirds, Agelaius phoeniceus. The LD50s of all chemicals for the bobwhites and red-winged blackbirds and for kestrels dosed with Phos-Chek WD881? and Silv-Ex? were above the predetermined 2000 mg chemical/kg body mass regulatory limit criteria for acute oral toxicity. The LD50s were not quantifiable for kestrels dosed with Fire-Trol GTS-R?, Phos-Chek D-75F?, and Fire-Trol LCG-R? because of the number of birds which regurgitated the dosage. These chemicals appear to be of comparatively low order of acute oral toxicity to the avian species tested.

Ecotoxicology and Environmental Safety↗
USGS2007

Effects of Phos-Chek® G75-F and Silv-Ex® on red-winged blackbird ( Agelaius phoeniceus ) embryos

Effects of field application levels of wildfire control chemicals, Phos-Chek ® G75-F (PC) and Silv-Ex ® (SE), were examined on red-winged blackbird ( Agelaius phoeniceus ) embryos. Embryos were more sensitive to PC and SE when eggs were immersed for 10 s at an early developmental stage (days 3–5 of incubation) than at a later stage (days 6–9 of incubation). The LC 50 (concentration causing 50% mortality) for early stage embryos exposed to PC was 213.3 g/L (slope = 1.6; 95% confidence interval [CI] = 129.1–326.1). The no observed effect concentration (NOEC) was below 135 g PC/L, which caused a significant increase in embryonic mortality and represents the lowest field coverage level of 1 gal/100 feet 2 . The LC 50 for early stage embryos exposed to SE was 19.8 g/L (slope = 1.5; 95% CI = 11.7–52.2). Significant mortality was observed at 10 g SE/L and marginal at 7.5 g SE/L with an apparent NOEC around 5 g SE/L. Neither chemical resulted in apparent developmental malformations.

Environmental Pollution↗
USGS2006

Dermal insecticide residues from birds inhabiting an orchard

The US Environmental Protection Agency conducts risk assessments of insecticide applications to wild birds using a model that is limited to the dietary route of exposure. However, free-flying birds are also exposed to insecticides via the inhalation and dermal routes. We measured azinphos-methyl residues on the skin plus feathers and the feet of brown-headed cowbirds ( Molothrus ater ) in order to quantify dermal exposure to songbirds that entered and inhabited an apple ( Malus x domestica ) orchard following an insecticide application. Exposure to azinphos-methyl was measured by sampling birds from an aviary that was built around an apple tree. Birds sampled at 36 h and 7-day post-application were placed in the aviary within 1 h after the application whereas birds exposed for 3 days were released into the aviary 4-day post-application. Residues on vegetation and soil were also measured. Azinphos-methyl residues were detected from the skin plus feathers and the feet from all exposure periods. Our results underscore the importance of incorporating dermal exposure into avian pesticide risk assessments.

Environmental Monitoring and Assessment↗
USGS2006

Field evaluation of an avian risk assessment model

We conducted two laboratory subacute dietary toxicity tests and one outdoor subacute dietary toxicity test to determine the effectiveness of the U.S. Environmental Protection Agency's deterministic risk assessment model for evaluating the potential of adverse effects to birds in the field. We tested technical-grade diazinon and its D Z N- 50W (50% diazinon active ingredient wettable powder) formulation on Canada goose (Branta canadensis) goslings. Brain acetylcholinesterase activity was measured, and the feathers and skin, feet. and gastrointestinal contents were analyzed for diazinon residues. The dose-response curves showed that diazinon was significantly more toxic to goslings in the outdoor test than in the laboratory tests. The deterministic risk assessment method identified the potential for risk to birds in general, but the factors associated with extrapolating from the laboratory to the field, and from the laboratory test species to other species, resulted in the underestimation of risk to the goslings. The present study indicates that laboratory-based risk quotients should be interpreted with caution.

Environmental Toxicology and Chemistry↗
USGS2004

Decomposed gosling feet provide evidence of insecticide exposure

Canada goose goslings were exposed to turf sprayed with D · Z · N® diazinon 50W application (2.24 kg a.i./ha). The control plot was subjected to a water application. One foot from each bird was placed outdoors for 7 d to decompose and the other foot was kept frozen. Diazinon residues were analyzed on both feet. Results showed that diazinon was detected from undecomposed and decomposed feet of the birds. Diazinon residues were below the level of detection (<0.01 ppm, a.i.) on the feet from the control goslings. Decomposed feet may be used for determining insecticide exposure when the traditional matrices are not available.

Environmental Monitoring and Assessment↗
USGS2003

Insecticide residues on weathered passerine carcass feet

Nine brown-headed cowbirds ( Molothrus ater ) were exposed to turf sprayed with either EarthCare® (25% diazinon; 4.77 L a.i./ha) or Ortho-Klor® (12.6% chlorpyrifos; 5.21 L a.i./ha). Birds were euthanized and one foot from each bird was weathered outdoors for up to 28 days and the other foot was kept frozen until residue analysis. When compared to the unweathered feet, feet weathered for 28 days retained 43% and 37% of the diazinon and chlorpyrifos, respectively. Insecticide residues were below the level of detection (1.0 ppm) on control feet. Weathered feet may be used for determining organophosphorus insecticide exposure to birds.

Environmental Forensics↗
USGS2003

Pesticide-laced predator baits: considerations for prosecution and sentencing

The illegal use of pesticide-laced baits for predator control is a wildlife crime that is underreported, inadequately documented, and insufficiently punished. The crime occurs when some ranchers, farmers, and hunting groups illegally lace baits with pesticides to control avian and mammalian predators. The activity has poisoned birds protected by the Endangered Species Act, Migratory Bird Treaty Act, and the Bald and Golden Eagle Protection Act. However, because of difficulties in discovering, reporting, and confirming the baitings and the wildlife kills, the crimes often appear inconsequential. The limited knowledge of these crimes in the public, regulatory, and judicial arenas distorts their importance .for some prosecutors and judges. The United States pesticide regulatory system has positioned federal and state prosecutors and judges in a critical role for protecting wildlife from the illegal practice of lacing baits with pesticides. In this article, the authors provide an overview of the crime and describe the ways in which the crime is investigated. They then present investigative and experimental evidence on the extent of the illegal practice and the magnitude of the kills in order to elucidate their importance with respect to prosecution and sentencing. The authors conclude by recommending that sufficient resources be made available, public awareness and education increased, and persistent prosecution occur in order to improve the effectiveness of all federal wildlife enforcement.

Environmental Lawyer↗
USGS2002

Effects of Phos-Chek G75-F and Silv-Ex on developing Northern Bobwhite Quail (Colinus virginianus)

Eggs of nesting birds situated in peripheral areas serving as fire breaks are at risk of being sprayed with fire control chemicals. Acute toxicity tests were conducted by immersing northern bobwhite quail eggs for 10 s in different water-based concentrations of Silv-Ex® (SE), a foam-suppressant chemical, and Phos-Chek® G75-F (PC), a fire retardant chemical, on day 4 or day 11 of incubation. An attempt was made to relate the treatment concentrations to the actual field application levels. Mortality appeared higher in most groups exposed on day 11 than on day 4, suggesting that on day 11 the extensive chorioallantoic vascular network permitted greater uptake of chemical. Only 24–60% of the embryos survived to hatch at exposure concentrations of 202, 269, and 454 g/L PC when treated on incubation day 11. At higher concentrations including 681, 956, and 1,211 g/L PC, the compound did not completely dissolve in water and clumped on eggshells, resulting in greater hatching success. Exposures to SE at 100 g/L on incubation day 11 did not significantly affect hatching success of embryos but did significantly reduce the percent hematocrit in blood compared with controls. Incubation day 11 exposure to 202 and 1,211 g/L PC led to a significant increase in plasma aspartate aminotransferase, and day 4 exposure to 1,211 g/L PC resulted in a significant increase in alanine aminotransferase. In addition to elevated liver enzymes, these treatments resulted in a decrease in the number of hepatocyte profiles (1,211 g/L PC at day 4 and day 11) and an increase in hepatocyte size (202 and 1,211 g/L PC at day 11) in hatchlings. A combination of SE and PC was synergistic (202 g/L PC and 50 g/L SE) at day 11 of incubation with respect to decreased hatching success and reduced bone lengths. However, lower concentrations of SE (10 g/L or 30 g/L) combined with 202 g/L of PC appeared antagonistic. This may be due to SE, as a surfactant, altering the ability of PC to penetrate the egg. Our results show fewer adverse effects following exposure to SE than to PC; therefore application of SE may be less harmful to breeding bird populations.

Archives of Environmental Contamination and Toxico↗
USGS2001

Lead shot toxicity to passerines

This study evaluated the toxicity of a single size 7.5 lead shot to passerines. No mortalities or signs of plumbism were observed in dosed cowbirds (Molothrus ater) fed a commercial diet, but when given a more natural diet, three of 10 dosed birds died within 1 day. For all survivors from which shot were recovered, all but one excreted the shot within 24 h of dosing, whereas, the dead birds retained their shot. Shot erosion was significantly greater (P < 0.05) when weathered shot were ingested compared to new shot, and the greatest erosion was observed in those birds that died (2.2-9.7%). Blood lead concentrations of birds dosed with new shot were not significantly different (P=0.14) from those of birds exposed to weathered shot. Liver lead concentrations of birds that died ranged from 71 to 137 ppm, dry weight. Despite the short amount of time the shot was retained, songbirds may absorb sufficient lead to compromise their survival.

Environmental Pollution↗
USGS2000

Lead poisoning of passerines at a trap and skeet range

Our objective was to determine if ground foraging passerines in a woodland surrounding a trap and skeet range were subject to lead poisoning. Lead availability to birds was determined by shot counts and soil and earthworm analysis. Avian exposure to lead was identified by measuring free-erythrocyte protoporphyrin levels in blood and lead in tissues of three passerine species. Results showed that most shot were found in the top 3 cm of soil. Lead measurements ranged from 110 to 27,000 ppm (dry wt) in soil and were 660 and 840 ppm in earthworms. Sparrows held in an aviary at the range (p = 0.02) and free-flying juncos (p = 0.0005) mistnetted at the range displayed significantly higher protoporphyrin levels than those at an uncontaminated site. Sparrow and cowbird carcasses from the aviary carried 37 and 39 ppm lead (dry wt), respectively, whereas a junco liver contained 9.3 ppm lead.

Environmental Pollution↗
USGS1999

Factors influencing estimation of pesticide-related wildlife mortality

Free-ranging wildlife is regularly exposed to pesticides and can serve as a sentinel for human and environmental health. Therefore a comprehensive pesticide hazard assessment must incorporate the effects of actual applications on free-ranging wildlife. Mortality is the most readily reported wildlife effect, and the significance of these data can be realized only when placed in context with the factors that affect the gathering of this type of information. This paper reviews the variables that affect the collection of wildlife mortality data. Data show that most effects on wildlife are not observed, and much of observed mortality is not reported. Delays in reporting or in the response to a report and exposure to multiple stressors distort the exposure-effect relationship and can result in uncertainty in determining the cause of death. The synthesis of information strongly indicates that the actual number of affected animals exceeds the number recovered.

Toxicology and Industrial Health↗
USGS1998

Possible mechanisms for sensitivity to organophosphorus and carbamate insecticides in eastern screech-owls and American kestrels

Effects of a single dietary exposure to fenthion and carbofuran on the survival, feeding behavior and brain ChE activity of eastern screech-owls, Otus asio and American kestrels, Falco sparverius , were evaluated. Birds were exposed to fenthion (23.6–189.0 ppm) or carbofuran (31.7–253.6 ppm) via meatballs. Carbofuran-exposed owls ate either ≤10% or ≥80% of the meatball whereas all kestrels ate ≤10% of the meatball before exhibiting acute signs of toxicity. Fenthion-exposed owls and kestrels displayed a wide spectrum of meatball consumption (<10–100%). Significant brain ChE inhibition was observed in dead and surviving kestrels exposed to fenthion and carbofuran and dead owls exposed to fenthion ( P <0.0001). Brain ChE activity of owls exposed to carbofuran that survived was not different from that of controls ( P =0.25). Data suggest: (1) slow feeding on a carbamate-contaminated item may provide limited protection from the toxicity of the chemical at certain rates of exposure; (2) the degree of ChE inhibition at neuromuscular junctions may be critical in determining the sensitivity of a species to a carbamate insecticide; (3) sensitivity may be a function of the ChE affinity for the carbamate inhibitor; and (4) the importance of neuromuscular junction ChE depression in determining the sensitivity of an animal may be species-specific.

Comparative Biochemistry and Physiology, Part C: P↗
USGS1996

Regional cholinesterase activity in white-throated sparrow brain is differentially affected by acephate (Orthene®)

Effects of a 14-day dietary exposure to an organophosphorus pesticide, acephate (acetylphosphoramidothioic acid O,S-dimethyl ester), were determined on cholinesterase activity in three regions (basal ganglia, hippocampus, and hypothalamus) of the white-throated sparrow, Zonotrichia albicollis , brain. All three regions experienced depressed cholinesterase activity between 0.5–2 ppm acephate. The regions exhibited cholinesterase recovery at 2–16 ppm acephate; however, cholinesterase activity dropped and showed no recovery at higher dietary levels (>16 ppm acephate). Evidence indicates that the recovery is initiated by the magnitude of depression, not the duration. In general, as acephate concentration increased, differences in ChE activity among brain regions decreased. Three terms are introduced to describe ChE response to acephate exposure: 1) ChE resistance threshold, 2) ChE compensation threshold, and 3) ChE depression threshold. It is hypothesized that adverse effects to birds in the field may occur at pesticide exposure levels customarily considered negligible.

Comparative Biochemistry and Physiology, Part C: P↗
USGS1995

Acephate affects migratory orientation of the white-throated sparrow (Zonotrichia albicollis)

Migratory white-throated sparrows ( Zonotrichia albicollis ) were exposed to acephate (acetylphosphoramidothioic acid O, S -dimethyl ester), an organophosphorus pesticide, to determine its effects on migratory orientation and behavior. Birds were also exposed to polarizer sheets to determine the mechanism by which acephate may affect migratory orientation. Adult birds exposed to 256 ppm acephate a.i. were not able to establish a preferred migratory orientation and exhibited random activity. All juvenile treatment groups displayed a seasonally correct southward migratory orientation. We hypothesize that acephate may have produced aberrant migratory behavior by affecting the memory of the migratory route and wintering ground. This experiment reveals that an environmentally relevant concentration of a common organophosphorus pesticide can alter migratory orientation, but its effect is markedly different between adult and juvenile sparrows. Results suggest that the survival of free-flying adult passerine migrants may be compromised following organophosphorus pesticide exposure.

Environmental Toxicology and Chemistry↗