Identifying the origin of lead poisoning in white-backed vulture (Gyps africanus) chicks at an important South African breeding colony: a stable lead isotope approach

Elevated lead levels in scavenging raptors can originate from a variety of environmental and anthropogenic sources, including soil, water, mining activities and legacy lead from leaded fuel, but has mostly been attributed to fragments of lead-based ammunition embedded in the tissues of carcasses. To identify the origins of lead in the tissues of white-backed vulture (Gyps africanus) chicks at Dronfield Nature Reserve, South Africa, we used MC-ICP-MS to compare the isotopic composition of lead in blood samples to those of soil in the chicks' immediate environment, different mining activities in South Africa and lead ammunition commonly used in hunting and game management practices. The isotopic ratios in vulture blood samples ranged widely (207Pb/206Pb: 0.827-0.911), but fell within those measured for ammunition (0.761-0.938). Dronfield water can be excluded as a significant source, as the lead concentration for water was below detection limits. Uranium, coal, atmospheric Pb, legacy Pb from fuel and Pb mining can also be excluded as significant sources, based on the limited overlap with Pb isotopic ratios measured in vulture blood. Whereas 55% of chicks we sampled displayed isotopic ratios consistent with Dronfield soil, the low local Pb concentration and the low extractable Pb levels in South African soil in general, imply that soil Pb is unlikely the major source of Pb in WBV chicks, especially in birds with elevated blood Pb levels, i.e. > 20 µg/dL. Our results, when considered in the context of vulture feeding ecology and low Pb levels in non-scavenging birds in South Africa, imply the major source of elevated Pb levels in WBV chicks to be fragments of lead-based ammunition embedded in the carrion fed to them by their parents.

A systematic review and risk matrix of plastic litter impacts on aquatic wildlife: A case study of the Mekong and Ganges River Basins

Plastic litter is a pollutant of aquatic environments worldwide, with some of the world's highest litter densities occurring in freshwater ecosystems. Little information about the risk that plastic litter poses to aquatic wildlife is available across the world's most polluted waterways. To help assess the risk to aquatic species where empirical data is lacking, our review presents i) a risk assessment methodology for predicting plastic litter impacts on aquatic wildlife in data poor environments, ii) a case study demonstrating this risk assessment methodology for wildlife across two heavily polluted river basins in Asia, the Mekong and Ganges River Basins; and iii) a broad review summarising common trends in litter interactions and risk to freshwater fish, aquatic birds, cetaceans and raptors. This risk analysis unites a systematic review approach with risk matrices following International Standards Organization's risk assessment criteria, evaluating the risk of plastic entanglement and ingestion and the potential for harm to the animal. In the Mekong and Ganges River Basins, we found that the risk of litter entanglement is higher than litter ingestion. Four species were forecast to be at high risk of entanglement: Ganges River dolphin, Gharial, Mekong giant catfish and Irrawaddy dolphin. The eastern imperial eagle and greater spotted eagle were noted to be at moderate risk of entanglement. Both the Ganges River dolphin and Irrawaddy dolphin were predicted to have a moderate risk of plastic ingestion. Interestingly, cranes, waterfowl and wading birds were deemed at low or negligible risk from plastic litter. This risk matrix methodology can be applied to other waterways and taxa to assess the risk posed by plastic. It can also be readily updated as more information becomes available. This review enables decision makers to bridge a data gap by providing a tool for conservation and management before comprehensive empirical data is available.

Health risks of metal(loid)s in maize (Zea mays L.) in an artisanal zinc smelting zone and source fingerprinting by lead isotope

Metal(loid) contamination caused by industrial activities in agricultural soils has become a universal environmental and food safety concern. This study revealed the contamination, pathway, and source contribution of metal(loid)s such as lead (Pb), zinc (Zn) and cadmium (Cd) in maize and soils in different residential areas impacted by long-term historical artisanal zinc smelting activities from Southwest China. Results revealed that the soils were contaminated heavily by metals like Pb, Zn and Cd, with contents of 40-14,280, 150-47,020 and 1.28-61.7 mg/kg, respectively. Hazard quotients of food uptake for Pb, Cd and Cr in maize grains were extremely high for residents, in particular for the children. To trace the sources of metal health risk, lead isotope fingerprinting and binary mixing modeling were applied. It indicated that the anthropogenic activities contributed over 80% to the Pb contamination in maize grains. The findings highlighted warning levels of health risks to the residents in consuming maize grains in the historical artisanal PbZn smelting area. Therefore, an effective strategy including pollution source control and remediation measures must be taken to improve the soil quality and guarantee food safety around the historical smelting areas likewise.

Lead isotopic signatures in blood from incubating common eiders (Somateria mollissima) in the central Baltic Sea

The Christiansø colony of common eiders (Somateria mollissima) in the central Baltic Sea were exposed to high levels of Pb during the 2018 breeding season that were not present in 2017. Due to these high Pb blood levels, the present study investigated possible Pb sources and Pb dynamics within this vulnerable colony. We analyzed body mass and lead isotopic ratios (Pb-IRs) in blood taken from the same incubating eiders at the early (day 4) and late (day 24) stages of incubation during the 2018 breeding season (n = 23). Pb-IRs 208/207, 208/206, 206/207, and 207/206 were analyzed using high resolution inductively coupled mass spectrometry. We found largely similar Pb-IRs from the different stages of incubation indicating a predominantly constant endogenous source of Pb exposure. We suggest the increasing Pb levels come from pre-nesting and nesting foraging and from medullary bone release. The similar Pb-IRs also indicate continued metabolization of the medullary bone to meet the nutritional and energy demands of incubation. Comparisons to Pb-IR reports from the Baltic Sea showed multiple sources of pollution distinguished by a difference between Pb-IRs in individuals with Pb blood concentrations >500 μg/kg ww and <500 μg/kg ww. The most highly contaminated individuals in the present study had Pb-IRs similar to those of Pb ammunition indicating shot pellet uptake. This study further emphasizes the need for continued biomonitoring of the Christiansø colony, including fecal sampling and environmental field sampling to identify the origin and extent of dietary Pb exposure on Christiansø. As a representative unit of the Baltic Flyway population; the Christiansø colony provides an important opportunity for continued investigation into Pb contamination, population dynamics, and declines.

Completing a worldwide picture: preliminary evidence of lead exposure in a scavenging bird from mainland Australia

Lead toxicity from ammunition has been shown to be a threat to scavenging birds across the globe. Despite decades of research in Europe, North and South America, Asia and Africa, there have been no studies to investigate this phenomenon in Australia despite that continent having many species of scavenging birds and widespread shooting practices. We present preliminary evidence of lead exposure in Australia's largest bird of prey, the wedge-tailed eagles (Aquila audax) through analysis of bone and eggshell samples from south-western Australia. From 11 bone samples, three birds (27%) had lead levels exceeding literature thresholds for elevated levels (>6.75 ppm). From 36 eggshell samples, no samples had lead levels >0.5 ppm, suggesting some limitations for this matrix as an indicator of lead exposure. Isotope ratios suggested ammunition as a likely source of the lead found in bone samples with elevated lead levels but other potential sources of lead require further investigation. Our preliminary results demonstrate that lead exposure is occurring in scavenging birds in Australia, and like the rest of the world, is likely to be derived from ammunition. This study supports an urgent call for further research into this worldwide phenomenon in Australia.

Feeding Ecology Drives Lead Exposure of Facultative and Obligate Avian Scavengers in the Eastern United States

Lead poisoning of scavenging birds is a global issue. However, the drivers of lead exposure of avian scavengers have been understood from the perspective of individual species, not cross-taxa assemblages. We analyzed blood (n = 285) and liver (n = 226) lead concentrations of 5 facultative (American crows [Corvus brachyrhynchos], bald eagles [Haliaeetus leucocephalus], golden eagles [Aquila chrysaetos], red-shouldered hawks [Buteo lineatus], and red-tailed hawks [Buteo jamaicensis]) and 2 obligate (black vultures [Coragyps atratus] and turkey vultures [Cathartes aura] avian scavenger species to identify lead exposure patterns. Species and age were significant (α < 0.05) predictors of blood lead exposure of facultative scavengers; species, but not age, was a significant predictor of their liver lead exposure. We detected temporal variations in lead concentrations of facultative scavengers (blood: median = 4.41 µg/dL in spring and summer vs 13.08 µg/dL in autumn and winter; p = <0.001; liver: 0.32 ppm in spring and summer vs median = 4.25 ppm in autumn and winter; p = <0.001). At the species level, we detected between-period differences in blood lead concentrations of bald eagles (p = 0.01) and red-shouldered hawks during the winter (p = 0.001). During summer, obligate scavengers had higher liver lead concentrations than did facultative scavengers (median = 1.76 ppm vs 0.22 ppm; p = <0.001). These data suggest that the feeding ecology of avian scavengers is a determinant of the degree to which they are lead exposed, and they highlight the importance of dietary and behavioral variation in determining lead exposure. Environ Toxicol Chem 2020;39:882-892. © 2020 SETAC.

Thallium contamination, health risk assessment and source apportionment in common vegetables

As an element with well-known toxicity, excessive thallium (Tl) in farmland soils, may threaten food security and induce extreme risks to human health. Identification of key contamination sources is prerequisite for remediation technologies. This study aims to examine the contamination level, health risks and source apportionment of Tl in common vegetables from typical farmlands distributed over a densely populated residential area in a pyrite mine city, which has been exploiting Tl-bearing pyrite minerals over 50 years. Results showed excessive Tl levels were exhibited in most of the vegetables (0.16-20.33 mg/kg) and alarming health risks may induce from the vegetables via the food chain. Source apportionment of Tl contamination in vegetables was then evaluated by using Pb isotope fingerprinting technique. Both vegetables and soils were characterized with overall low ²⁰⁶Pb/²⁰⁷Pb. This indicated that a significant contribution may be ascribed to the anthropogenic activities involving pyrite deposit exploitation, whose raw material and salgs were featured with lower ²⁰⁶Pb/²⁰⁷Pb. Further calculation by binary mixing model suggested that pyrite mining and smelting activities contributed 54-88% to the thallium contamination in vegetables. The results highlighted that Pb isotope tracing is a suitable technique for source apportionment of Tl contamination in vegetables and prime contamination from pyrite mining/smelting activities urges authorities to initiate proper practices of remediation.

Lead in piscivorous raptors during breeding season in the Chesapeake Bay region of Maryland and Virginia, USA

Sources of lead exposure of many bird species are poorly understood. We analyzed blood lead concentrations from osprey (n = 244; Pandion haliaetus) and bald eagles (n = 68; Haliaeetus leucocephalus) and documented potential sources of lead they may encounter. Adult bald eagles had higher blood lead concentrations than did adult osprey. However, blood lead concentrations of nestlings were similar for both species. Although 62% of osprey had detectable lead concentrations ( x¯  = 1.99 ± 4.02 μg/dL, mean ± standard deviation [SD]), there was no difference in the detection frequency or lead concentrations between osprey adults and nestlings. Likewise, we found no differences in the detection frequency or lead concentrations in osprey adults and nestlings from high- and low-salinity areas. Of the bald eagle samples tested, 55% had detectable lead levels ( x¯  = 6.23 ± 10.74 μg/dL). Adult bald eagles had more detectable and higher lead concentrations than did nestlings or pre-adults. Among environmental samples, paint had the highest lead concentrations, followed by sediment, blue catfish (Ictalurus furcatus), and gizzard shad (Dorosoma cepedianum). There was no correlation between blood lead concentrations of osprey adults and their offspring. Our results indicate that, in the Chesapeake Bay region of Maryland and Virginia (USA), there are multiple sources by which piscivorous raptors may be exposed to lead. Environ Toxicol Chem 2019;38:862-871. © Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.