Lead Toxicosis Research Articles

Evaluation and treatment of lead toxicosis in rehabilitated avian species: 95 cases (2014-2023).

To evaluate avian patients presented to a wildlife rehabilitation facility with confirmed lead toxicity for clinical signs associated with blood lead level groups, efficacy of subcutaneous chelation therapy with calcium disodium EDTA, and case outcome based on presenting blood lead levels. A retrospective record review of 95 avian cases representing 19 species treated for lead toxicosis from a wildlife rehabilitation center in Wisconsin between 2014 and 2023 was conducted. Data were evaluated for presenting complaints, clinical signs, radiographic findings, chelation therapy protocol, clinical pathology data, and case outcome. A low lead level of < 20 µg/dL was the most commonly diagnosed level in avian patients. The presence of neurologic disease was found most commonly in birds with higher blood lead levels, whereas poor body condition, trauma, and anemia were most common in birds with low lead levels. Bald eagles (Haliaeetus leucocephalus) and tundra swans (Cygnus columbianus) were the most prevalent species presented. All methods of chelation therapy evaluated resulted in a reduction of blood lead levels. Patients with intake blood lead levels > 60 µg/dL were more likely to die or be euthanized while in care. A bird with a blood lead level > 60 µg/dL is more likely to present with neurologic disease and have a poor case outcome. Diluted calcium disodium EDTA was clinically effective when administered SC. Initial blood lead level, in conjunction with species, clinical signs, and radiographic changes, can help guide clinical decision-making for avian patients with lead toxicosis.

Validation of the Lead Care II System in Cape vultures (Gyps coprotheres) in comparison to ICP-MS using pure standards

Lead toxicosis remains a concern in raptors, especially following feeding on carcasses sourced from hunting. Rapid diagnosis of lead exposure and easy field monitoring is desirable. The LeadCareII analytical system, validated for rapid diagnoses of lead toxicity in humans, has been described as a useful evaluation system in various species. For this study we attempt to validate the LeadCareII system in the Cape Vulture (CV) (Gyps coprotheres). Blood samples from CV housed under captive conditions and low background lead exposure, were pooled and spiked with known concentrations of a lead standard (0–60 µg/dL). Samples were analyzed by the LeadCareII system and by ICP-MS. The final results showed that despite good linearity the LeadCareII system underestimated lead concentrations by up to 50 %. While the results can be corrected by the derived equation, this is not supported due to the large underestimations evident. The reason for the underestimation is presently unknown.

Assessing Lead Exposure in Free-Ranging Gray Wolves (Canis lupus) in Minnesota, USA

The gray wolf (Canis lupus) is both an apex predator and a scavenger in Minnesota, US. Monitoring the health of Minnesota's gray wolf population is an important component of wolf management. Concern regarding whether wolves are being exposed to lead through scavenging viscera of hunter-harvested cervids left on the landscape, led to our study to determine lead-exposure rates. In fall 2012, livers from 147 hunter-harvested wolves (89 females, 58 males) were screened for lead and 20 other elements by inductively coupled plasma-atomic emission spectroscopy. Ten wolves (6.8%) were exposed to lead; only one had high enough exposure (6.14 ppm) to suggest lead toxicosis. Lead exposure varied by time of harvest, with nearly all lead-exposed wolves taken in the late hunting and trapping season (from 24 November 2012 to 31 January 2013), compared with the earlier hunting-only season (3-18 November 2012). Further, eight of 10 lead-exposed wolves were taken from deer-permit areas that harvested >1 deer/km2; only two of 10 were taken where deer harvest was less. This suggests the availability of viscera on the landscape may influence exposure risk of lead to wolves. More research is needed to determine baseline levels for toxic concentrations of lead in gray wolves and to determine clinical signs of lead poisoning in wild canids.

Lead Exposure is Unrelated to Wind Turbine Mortality in Golden Eagles

ABSTRACTLead toxicosis is well established as an important contributor to mortalities in bald and golden eagles (Haliaeetus leucocephalus and Aquila chrysaetos, respectively), California condors (Gymnogyps californianus), and a variety of waterfowl. The effects of lead toxicosis may predispose birds to traumatic encounters, such as collision with power lines. Rotating wind turbine blades have caused the death of many bird species, including bald and golden eagles, when flight paths intersect wind farms. We conducted an analysis of the relationship between liver lead concentrations and mortality from collisions with wind‐turbine blades (WT) in golden eagles submitted to the National Fish and Wildlife Forensic Laboratory (NFWFL) from 2011 to 2016 from across the United States. During that time, 116 golden eagles were determined to have died of wind turbine blade collision and 52 were tested for lead exposure. Liver lead concentrations in our sample were compared to those from 25 golden eagles that died of other causes including electrocution, gunshot, and other trauma. Eagles that died from wind turbine blade collision had lower (P &lt; 0.01) lead concentrations (geometric mean 0.25 ppm wet weight [ww]; median 0 ppm ww) than those with other mortality factors (geometric mean 0.65 ppm ww; median 0.42 ppm ww). Across both control (non‐WT mortality) and WT groups, liver lead concentrations did not differ significantly between males and females (P = 0.95), or between adults and sub‐adults (P = 0.45). The ratios of life stages and sexes in the WT group were similar to that of the broader population of golden eagles submitted to NFWFL during the same time period. Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

Mortality among free-ranging California condors (Gymnogyps californianus) during 2010–2014 with determination of last meal and toxicant exposure

Over the past 30 years, the California condor (Gymnogyps californianus) population has rebounded from 22 individuals to over 200 birds living in the wild. Historical impacts to the population have been largely anthropogenic. In this study, we explore mortality and cause of death data from condors that died during the years 2010-2014 and compare these to mortality data described by Rideout et al. in 2012, covering the years 1992-2009. In addition, morphologic and genetic analysis of the contents of the upper gastrointestinal (GI) tract was performed on the 2010-2014 condor mortalities to determine animal origins of the last meal eaten. The maximum population at risk within this time frame was 329 birds. During this time, 88 condors died and underwent post-mortem examination, and 41 birds were lost to tracking efforts and presumed dead (crude mortality rate of 39%; 129/329). A cause of death was determined for 66 of the 88 necropsied birds. Lead toxicosis remained a significant negative factor in condor population recovery, being related to the deaths of 37 adult and juvenile condors (proportional mortality rate 56%). Compared to condors succumbing to other causes of death, cattle were less often part of the last meal of lead-intoxicated condors. Based on these data, continued efforts to mitigate the impact of lead on California condors should be pursued.

The urban lead burden in humans, animals and plants

Urban residence is a risk factor for children’s elevated lead exposures. Evidence from domesticated and wild animals shows that the phenomenon crosses species lines. Plants also suffer under lead’s phytotoxicity. The Industrial Revolution lured and drove more than half of the US populations from the countryside into cities. Leaded paint, lead in public water systems and later, leaded gasoline, were the principal contributors to lead contamination of US cities. Lead’s incredible utility has resulted in thousands of commercial applications in electronics, hardware, paints and pigments, many types of glass, ceramic glazes and coatings, cable sheaths, machinery and manufacturing, light industry, radiation protection, post and telecommunications, metallurgy, chemical production, transportation (rail, automobile and aviation), construction, weapons, aerospace, oil, plastics and petrochemicals, plumbing, pesticides, hair products, etc. Historically, commercial and industrial activities occurred coterminously to habitation, so the beginnings of all these uses occurred within urban areas. Consequently, urban areas have high lead pollution levels. Lead toxicosis in urban areas is evident across animal species, including pets (Zook et al 1998, Langlois et al 2017), feral pigeons (Cai and Calisi 2016), wild raccoons (Hamir et al 1995) and foxes (Dip et al 2000) and gazing animals (Ward and Savage 1994), Indeed, in 1970, pigeons were considered a sentinel for urban lead pollution (Tansy and Roth); society has continued to use children. Plants in urban areas are also significantly affected by high lead levels (EPA 1984). We used an integrated One Health approach to assess lead’s urban burden in humans, animals and plants. In the future, we will develop conceptual and pragmatic guidance for urban planners and decision makers to address the urban lead burden in humans, animals and plants.

Postmortem Evaluation of Reintroduced Migratory Whooping Cranes (Grus americana) in Eastern North America.

We reviewed necropsy records of 124 Whooping Cranes (Grus americana) recovered following reintroduction of 268 individuals from 2001 to 2016 in the eastern US. Causes of death were determined in 62% (77/124) of cases facilitated by active monitoring that limited decomposition and scavenging artifact. The greatest proportions of mortality were caused by predation (0.468; 95% confidence interval 0.356-0.580; 36/77), collision with power lines or vehicles (0.260; 0.162-0.358; 20/77), and gunshot (0.169; 0.085-0.253; 13/77). Six deaths were attributed to infection (0.078; 0.018-0.138; 6/77), including bacterial and fungal etiologies. Lead analysis of 50 liver samples yielded two results with elevated concentrations (3.65 and 10.97 ppm wet weight), and 10 bone samples from partial carcasses lacking suitable liver tissue resulted in one elevated result (48.82 ppm dry weight). These data indicate that underlying subclinical or clinical lead toxicosis may be a factor in up to 5% of deaths attributed to predation or impact trauma. Brain cholinesterase activity testing indicated no exposure to organophosphate or carbamate pesticides (mean±SD=17.32±2.90 µmol/min/g, 31/71). The causes of death and potential underlying factors summarized in this study constitute the first definitive mortality survey of migratory Whooping Cranes based on a high carcass recovery rate. Causes of death by infectious etiologies remained comparatively rare in this study, and occurred as single cases with no evidence of sustained transmission among reintroduced Whooping Cranes.

BLOOD LEAD AND ZINC LEVELS AND THEIR IMPACT ON HEALTH OF FREE-LIVING SMALL CARNIVORES IN TAIWAN, REPUBLIC OF CHINA

Lead and zinc are recognized as the most widespread trace metals in nature and can, at high levels, compromise the health of wildlife and their habitat. Because of their position in a higher trophic level, wild carnivores can be valuable biological indicator species of trace-metal contamination in the environment. We assessed blood lead and zinc concentrations of four small carnivore species native to Taiwan, the small Indian civet (Viverricula indica), the masked palm civet (Paguma larvata), the ferret badger (Melogale moschata), and the crab-eating mongoose (Herpestes urva), from urban and rural areas (Yangmingshan National Park, Xiuguluan River bank, and Da-an River bank). Blood samples were acquired from the anterior vena cava under general anesthesia, and lead and zinc concentrations, hematology, and serum biochemistry results were then obtained. Blood lead levels were significantly higher in ferret badgers in the Yangmingshan area. Although lead concentrations were comparable with those in humans and cats with lead toxicosis, there was no hematological or biochemical evidence that animal health was compromised. Blood zinc levels were within an acceptable range in all four species tested. Overall, we found significant differences in blood lead and zinc levels among four species of carnivores living in areas with different levels of land development in Taiwan. Anthropogenic pollution, mining history, and volcanic activities in Yangmingshan National Park may contribute to significantly high blood lead levels in ferret badgers in this area. Our results provided information about the potential impact of land development on wildlife and may be beneficial to wildlife conservation, public health, and environmental health in Taiwan.

Lead toxicosis in cats and dogs

Lead has no biological role but is ubiquitous in the environment. The incidence of lead poisoning in both humans and animals has declined in the past few decades; however, there are still potential sources in and around the home, including lead paint and lead-containing materials such as curtain weights and lead flashing. Signs of lead poisoning mainly involve the gastrointestinal and neurological systems, and a typical presentation is several days’ history of gastrointestinal signs (anorexia, vomiting) followed by neurological signs such as seizures. Behavioural changes may also be reported. Diagnosis of lead poisoning can be difficult, since a blood lead concentration is not immediately available and does not correlate well with severity of poisoning. Diagnosis is therefore usually based on clinical signs, laboratory findings and client history. Treatment is aimed at identifying the source of poisoning, reducing/eliminating exposure, management of signs, and potential use of a lead chelating agent. Prognosis is good with treatment, but more guarded in animals with severe neurological signs.

ANALYSIS OF HISTORICAL MEDICAL RECORDS OF CALIFORNIA CONDORS ( GYMNOGYPS CALIFORNIANUS) ADMITTED FOR LEAD EXPOSURE TO THE LOS ANGELES ZOO AND BOTANICAL GARDENS BETWEEN 1997 AND 2012: A CASE SERIES STUDY.

Lead toxicosis remains the primary cause of death in wild populations of California condors ( Gymnogyps californianus). Many condors require medical intervention with lead chelation therapy, among other conservation measures, to survive in the wild. An analysis of historical medical records of California condors admitted for lead exposure to the Los Angeles Zoo and Botanical Gardens (LA Zoo) between 1997 and 2012 was performed to investigate clinical presentation, radiographic findings, and treatment along with the potential impact of these factors on recovery and successful release back into the wild. Of 100 individual condors presented to the LA Zoo for suspected lead toxicosis during this period, 84 condors had records for initial laboratory blood lead levels. For these 84 condors (40 [47.6%] females and 44 [52.4%] males), 277 initial laboratory blood lead levels in total were recorded because of repeated admissions. Thirty-two (38%) condors were admitted once to the zoo and 62% were admitted two or more times. Clinical signs were not observed in 87.5% of the condors admitted with median blood lead concentrations of 26 μg/dl. Of the radiographs taken on initial presentation, 65% did not show evidence of gastrointestinal metallic foreign bodies. Various treatments protocols with edetatum calcium disodium, dimercaptosuccinic acid, and lactated Ringer's solution were documented in the medical records. Of the 277 admissions, 154 admissions had a recorded outcome posttreatment of which 140 (91%) admissions were released back to the wild. This study contributes to a better understanding of how intervention and therapeutic approaches have been essential for the recovery, release, and sustainability of these birds as a wild population. Consistency in data collection of California condors admitted for diagnosis and treatment of lead toxicosis is needed to better assess the impacts of medical interventions.

Lead Levels in the Eggs of a Chicken With Lead Toxicosis

A 1.5-year-old Polish hen was presented with a history of watery droppings and poor vent tone. Results of diagnostic tests revealed blood lead at levels considered to be toxic. Chelation therapy was started with calcium ethylenediaminetetraacetate. The hen was laying eggs before, during, and after chelation therapy. Eggs were tested for the presence of lead by combining yolk and albumen together. Before chelation therapy, the level of lead in the egg tested was 14 μg. Two days after the end of chelation therapy, results of a second blood lead test revealed a drop to nontoxic levels. No lead was detected in the combined yolks and albumen of eggs collected 7-11 days after the end of chelation therapy. Four weeks after the end of chelation therapy, no lead was identified in the shells of tested eggs.

Subclinical Lead Exposure Among Backyard Chicken Flocks in Massachusetts.

Ownership of backyard chickens (BYCs) is increasing in urban areas, and BYCs often have access to soil around the home. Exposure to lead-contaminated soil is a known health risk for people; however, the degree to which BYCs are exposed is unknown. We employed a cross-sectional convenience sample to assess blood lead levels (BLLs) in 57 BYCs from 30 flocks in a region with established environmental lead contamination. Over two-thirds (70.2%) had detectable levels of lead in their blood, which averaged 12.5 μg/dL (range: <3.3 μg/dL to ≥65.0 μg/dL). No chickens demonstrated clinical evidence of lead toxicosis. Almost all owners (96.2%) reported that their chickens had free access to soil, and almost three-quarters (69.2%) of the participants reported giving their chickens unrestricted access to the property. Our findings demonstrate that subclinical but elevated BLLs are common in BYCs that live in an environment where lead contamination may be present. Our data support the inclusion of blood lead testing in the routine veterinary care of BYCs, especially in areas where historic use of leaded paint and environmental lead contamination are reported.

Population‐level effects of lead fishing tackle on common loons

ABSTRACTPoisoning from lead fishing tackle has been identified as the leading cause of mortality in adult common loons (Gavia immer). As a K‐selected species, adult survival is a critical component in the population demography of loons, but the population‐level effects of mortality from ingested lead tackle on loons have not been quantified. We used a long‐term dataset (1989–2012) on common loon mortality in New Hampshire, USA, to describe the types of lead tackle ingested by loons, investigate methods of ingestion of lead tackle, document the number and rate of adult mortalities resulting from lead tackle, and test for a population‐level effect of lead tackle on the loon population in New Hampshire. Nearly half (48.6%) of collected adult mortalities resulted from lead toxicosis from ingested lead fishing tackle, representing an adjusted annual mortality rate of 1.7 ± 0.6% (SD) of the statewide population. Jigs accounted for 52.6% and sinkers for 38.8% of the archived lead tackle objects removed from loons, a higher proportion of jigs than has been reported in previous studies. The timing of lead tackle mortalities and a high incidence of accompanying non‐lead associated fishing gear (hooks, fishing line, leaders, swivels, wire), which peaked in July and August, suggest that loons obtain the majority of lead tackle from current fishing activity rather than from a reservoir of lead tackle on lake bottoms. To project the statewide loon population in the absence of lead fishing tackle as a stressor, we constructed a retrospective population model, which re‐inserted loons that died from lead tackle into the population, and used linear regression to test for a population‐level effect. We defined a population‐level effect as a difference in the population growth rate (λ). We estimated that lead tackle mortality reduced the population growth rate (λ) by 1.4% and the statewide population by 43% during the years of the study. This study suggests that replacing lead fishing sinkers and jigs weighing ≤28.4 g with non‐toxic alternatives would result in an immediate benefit to the loon population in New Hampshire. © 2017 The Wildlife Society.

Proximal tubular nephropathy in two dogs diagnosed with lead toxicity

Lead toxicity was diagnosed in two dogs presenting with vague clinical symptoms. Complete blood count, biochemical testing and imaging changes showed a metarubricytosis in dog 1, but were largely normal in dog 2. Both dogs had glucosuria and proteinuria on urinalysis consistent with damage to the proximal renal tubules. Both animals returned elevated blood lead levels. A history of ingestion of lead was reported by the owner in one dog and elucidated from the second owner once the animal had recorded elevated blood lead levels. Lead toxicity is rarely reported in the human literature as a cause of proximal tubular dysfunction. To the author's knowledge this is the first case report specifically examining this in the dog. The clinical awareness that lead is a potential cause of proximal renal tubular dysfunction offers another tool to assist the clinician in the diagnostic process. This is particularly important given that the clinical signs and minimum database findings in animals with lead toxicosis are highly variable. Evidence of proximal tubular dysfunction should trigger the clinician to closely examine the history for a potential source of lead exposure and consider submitting samples to test blood lead levels.

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa.

Generally crocodilians have received little attention with regard to the effects of lead toxicity despite their trophic status as apex, generalist predators that utilize both aquatic and terrestrial habitats, thereby exposing them to a potentially wide range of environmental contaminants. During July-October 2010 we collected whole blood from 34 sub-adult and adult free-ranging Nile crocodiles (Crocodylus niloticus) from three separate populations in northeastern South Africa in order to analyze their blood lead concentrations (BPb). Concentrations ranged from below detectability (<3μg/dL, n=8) to 960μg/dL for an adult male at the Lake St Lucia Estuary. Blood lead concentrations averaged 8.15μg/dL (SD=7.47) for females and 98.10μg/dL (SD=217.42) for males. Eighteen individuals (53%) had elevated BPbs (≥10μg/dL). We assessed 12 general linear models using Akaike's Information Criterion (AIC) and found no significant statistical effects among the parameters of sex, crocodile size and population sampled. On average, crocodiles had higher BPbs at Lake St Lucia than at Ndumo Game Reserve or Kosi Bay, which we attribute to lead sinker ingestion during normal gastrolith acquisition. No clinical effects of lead toxicosis were observed in these crocodiles, even though the highest concentration (960μg/dL) we report represents the most elevated BPb recorded to date for a free-ranging vertebrate. Although we suggest adult Nile crocodiles are likely tolerant of elevated Pb body burdens, experimental studies on other crocodilian species suggest the BPb levels reported here may have harmful or fatal effects to egg development and hatchling health. In light of recent Nile crocodile nesting declines in South Africa we urge further BPb monitoring and ecotoxicology research on reproductive females and embryos.

P.1.h.021 Lead toxicosis and pain sensation in the mouse – an experimental study

P.1.h.021 Lead toxicosis and pain sensation in the mouse – an experimental study

A Rapid Postmortem Screening Test for Lead Toxicosis in Common Loons (Gavia immer) and Bald Eagles (Haliaeetus leucocephalus)

In live animals, lead poisoning can be diagnosed by analyzing blood samples. For postmortem testing, blood samples are not available and analysis of liver or kidney is often used for diagnosis. Liver and kidney analysis is relatively expensive and results might not be quickly available. We examined an inexpensive, rapid method to screen animals for lead toxicosis postmortem by testing the mixture of body fluids (termed "tissue fluids") that pool in the body cavity at necropsy for lead. At necropsy we collected body fluid and liver samples from Common Loon (Gavia immer) and Bald Eagle (Haliaeetus leucocephalus) carcasses and determined concentrations of lead in tissue fluid using a desk-top blood lead analyzer. Concentrations of lead in liver were determined by inductively coupled plasma mass spectroscopy. There was strong correlation between tissue fluid and liver tissue lead concentrations, and receiver-operating characteristic analysis gave an area under the curve of 0.91, indicating that postmortem measurements of lead in tissue fluids can be utilized as a screening method for lead toxicosis.

Lead toxicosis of captive vultures: case description and responses to chelation therapy

BackgroundLead, a serious threat for raptors, can hamper the success of their conservation. This study reports on experience with accidental lead intoxication and responses to chelation therapy in captive Cinereous (Aegypius monachus) and Egyptian (Neophron percnopterus) Vultures.ResultsSoil contamination by lead-based paint sanded off the steel aviary resulted in poisoning of eight Cinereous and two Egyptian Vultures. A male Egyptian Vulture developed signs of apathy, polydipsia, polyuria, regurgitation, and stupor, and died on the next day. Liver, kidney and blood lead concentrations were 12.2, 8.16 and 2.66 μg/g, respectively. Laboratory analyses confirmed severe liver and kidney damage and anaemia. Blood Pb levels of Pb-exposed Cinereous Vultures were 1.571 ± 0.510 μg/g shortly after intoxication, decreased to 0.530 ± 0.165 μg/g without any therapy in a month and to 0.254 ± 0.097 μg/g one month after CaNa2EDTA administration. Eight months later, blood lead levels decreased to close to the background of the control group. Blood parameters of healthy Pb-non-exposed Cinereous Vultures were compared with those of the exposed group prior to and after chelation therapy. Iron levels in the lead-exposed pre-treatment birds significantly decreased after chelation. Haematocrit levels in Pb-exposed birds were significantly lower than those of the controls and improved one month after chelation. Creatine kinase was higher in pre-treatment birds than in the controls but normalised after therapy. Alkaline phosphatase increased after chelation. A marked increase in the level of lipid peroxidation measured as thiobarbituric acid reactive species was demonstrated in birds both prior to and after chelation. The ferric reducing antioxidant power was significantly lower in pre-treatment vultures and returned to normal following chelation therapy. Blood metallothionein levels in lead-exposed birds were higher than in controls. Reduced glutathione dropped after CaNa2EDTA therapy, while oxidised glutathione was significantly lower in both pre- and post-treatment birds. A chick in an egg produced by a Cinereous Vulture female two months after lead toxicosis died on day 40 of artificial incubation. Lead concentrations in foetal tissues were consistent with levels causing avian mortality.ConclusionsThe reported blood parameters and reproduction impairment in captive birds may have implications for professionals dealing with lead exposure in wild birds.

Ingluviotomy Tube Placement for Lead-induced Crop Stasis in the California Condor (Gymnogyps californianus)

Six free-flying California condors (Gymnogyps californianus) were diagnosed with acute lead toxicosis that caused crop distension and stasis. Between January 2006 and January 2007, the birds were referred to the Phoenix Zoo in Arizona for emergency treatment. In 5 birds, an ingluviotomy was performed to place a feeding tube from the crop to the proventriculus, which allowed a temporary bypass of the dysfunctional esophagus until normal function and motility were regained. A crop-support pressure bandage was placed in 4 birds to improve crop emptying into the proventriculus and to prevent crop distension. Although chelation therapy is the gold standard treatment for lead toxicosis, severe cases of lead-induced crop stasis are not acutely reversible with pharmaceuticals. In these condors, placement of a feeding tube was deemed prudent to ensure a viable enteric route of nutritional support during the standard treatment and recovery period in acute lead toxicosis with crop stasis.

PATTERNS OF MORTALITY IN FREE-RANGING CALIFORNIA CONDORS (GYMNOGYPS CALIFORNIANUS)

We document causes of death in free-ranging California Condors (Gymnogyps californianus) from the inception of the reintroduction program in 1992 through December 2009 to identify current and historic mortality factors that might interfere with establishment of self-sustaining populations in the wild. A total of 135 deaths occurred from October 1992 (the first post-release death) through December 2009, from a maximum population-at-risk of 352 birds, for a cumulative crude mortality rate of 38%. A definitive cause of death was determined for 76 of the 98 submitted cases, 70% (53/76) of which were attributed to anthropogenic causes. Trash ingestion was the most important mortality factor in nestlings (proportional mortality rate [PMR] 73%; 8/11), while lead toxicosis was the most important factor in juveniles (PMR 26%; 13/50) and adults (PMR 67%; 10/15). These results demonstrate that the leading causes of death at all California Condor release sites are anthropogenic. The mortality factors thought to be important in the decline of the historic California Condor population, particularly lead poisoning, remain the most important documented mortality factors today. Without effective mitigation, these factors can be expected to have the same effects on the sustainability of the wild populations as they have in the past.