Biomonitoring of heavy metals (Cd, Hg, and Pb) and metalloid (As) with the Portuguese common buzzard (Buteo buteo)

Factors affecting the concentration of metals and metalloids in the kidneys of a top predator, the Eurasian Buzzard (Buteo buteo) wintering in farmland in Poland

During late autumn and winter, raptors in the western Palearctic face challenges due to food scarcity and dropping temperatures. That time they can be exposed to various elements including toxic ones ingested with food. Kidney samples from 22 females and 19 males of a medium-sized raptor, the Common Buzzard Buteo buteo found dead in farmland of Eastern Poland in winter were analyzed for a concentration of 21 elements. Elemental concentrations were analyzed regarding the age and sex of birds. Results revealed that only 4.9% of individuals had kidney lead levels exceeding 8.0 mg, while 9.8% showed cadmium levels above 8.0 mg/kg, indicating potential poisoning. The study also highlighted the limited entry of arsenic into agricultural ecosystems exploited by Common Buzzards. Sex differences were noted, with females accumulating more lead and vanadium than males which can be associated with foraging niche partitioning between sexes driven by body size dimorphism. Sulfur showed complex interactions with cadmium, mercury, and zinc, with a positive correlation between sulfur and zinc levels in the kidneys, emphasizing dietary needs during food scarcity. A positive correlation was found between zinc and lead concentrations, indicating zinc's role in mitigating lead's impact. The study also revealed positive correlations between selenium and highly toxic elements like mercury (Spearman correlation, rs = 0.41) and cadmium (rs = 0.51), suggesting a mitigating effect of selenium on exposure to heavy metals. This study enhances understanding of year-round environmental contamination exposure for raptors and sheds light on bioaccumulation in a top predator.

Effects of arsenic exposure on blood trace element levels in rats and sex differences

Arsenic (As) is a widespread environmental metalloid and human carcinogen, and its exposure is associated with a wide range of toxic effects, leading to serious health hazards. As poisoning is a complex systemic multi-organ and multi-system damage disease. In this study, a rat model of As poisoning was established to investigate the levels of trace elements in the blood of rats and sex differences in the effect of As on every trace elements in rat blood. Twenty 6-week-old SD (Sprague Dawley) rats were randomly divided into the control group and the As-exposed group. After 3 months, the contents of 19 elements including As in the blood were detected in these two groups by inductively coupled plasma mass spectrometry (ICP-MS). As levels in the blood of As-exposed rats were significantly higher than those in the control group, with increased levels of Rb, Sr, Cs and Ce, and decreased levels of Pd. As showed a significant positive correlation with Rb. There were significant sex differences in blood Se, Pd, Eu, Dy, Ho, and Au levels in the As-exposed group. The results showed that As exposure can lead to an increase of As content in blood and an imbalance of some elements. There were sex differences in the concentration and the correlation between elements of some elements. Elemental imbalances may affect the toxic effects of As and play a synergistic or antagonistic role in As toxicity.

Biological Matrices from Cairina moschata as Non-Destructive Biomonitoring Tools to Study Environmental Quality of Urban and Extra-Urban Areas: A Case Study of Palermo (Sicily, Italy)

Biomonitoring is the qualitative observation and the measurement of biosphere parameters aimed at modelling the environment, evaluating its quality, and studying the effects of alterations on different ecological levels. In this work, trace metal concentrations were assessed using non-destructive biomonitoring tools as blood and feathers of the allochthonous aquatic bird Cairina moschata, collected within two areas of the Palermo metropolitan area, Sicily, differently exposed to air pollution: Parco D'Orleans, in a central urban location, and Monreale, southwest of the city centre. Higher concentrations in both blood and feathers collected in Parco D' Orleans were found for lead, tin and selenium, but the same was not observed for other metals. The concentrations were not above physiological tolerance in any case. The comparison between blood and feathers allowed to realize that the latter are more useful for biomonitoring analyses, as they are indicative of both external contamination and bioaccumulation. Treatment with nitric acid highlighted that the feathers collected in Parco D' Orleans had higher metal bioaccumulation than the ones collected in Monreale; however, the treatment needs standardization. The present study confirms that feathers and blood from C. moschata are a convenient and non-destructive sampling tool for metal contamination analysis.

The importance of in-year seasonal fluctuations for biomonitoring of apex predators: A case study of 14 essential and non-essential elements in the liver of the common buzzard (Buteobuteo) in the United Kingdom

Trace elements are chemical contaminants spread in the environment by anthropogenic activities and threaten wildlife and human health. Many studies have investigated this contamination in apex raptors as sentinel birds. However, there is limited data for long-term biomonitoring of multiple trace elements in raptors. In the present study, we measured the concentrations of 14 essential and non-essential trace elements in the livers of the common buzzard (Buteo buteo) collected in the United Kingdom from 2001 to 2019 and investigated whether concentrations have changed during this period. In addition, we estimated the importance of selected variables for modelling element accumulations in tissues. Except for cadmium, hepatic concentrations of harmful elements in most buzzards were lower than the biological significance level of each element. Hepatic concentrations of certain elements, including lead, cadmium, and arsenic, varied markedly seasonally within years. Their peak was in late winter and trough in late summer, except copper which showed an opposite seasonal pattern. In addition, lead in the liver consistently increased over time, whereas strontium showed a decreasing trend. Hepatic concentrations of cadmium, mercury, and chromium increased with age, whereas selenium and chromium were influenced by sex. Hepatic concentrations of arsenic and chromium also differed between different regions. Overall, our samples showed a low risk of harmful effects of most elements compared to the thresholds reported in the literature. Seasonal fluctuation was an important descriptor of exposure, which might be related to the diet of the buzzard, the ecology of their prey, and human activities such as the use of lead shot for hunting. However, elucidating reasons for these observed trends needs further examination, and biomonitoring studies exploring the effects of variables such as age, sex, and seasonality are required.

Sentinel animals for monitoring the environmental lead exposure: combination of traditional review and visualization analysis

In nature, certain animals share a common living environment with humans, thus these animals have become biomonitors of health effects related to various environmental exposures. As one of the most toxic environmental chemicals, lead (Pb) can cause detriment health effects to animals, plants, and even humans through different exposure pathways such as atmosphere, soil, food, water, and dust, etc. Sentinel animals played an "indicative" role in the researches of environmental pollution monitoring and human health. In order to comprehend the usage of sentinel animals in the indication of environmental Pb pollution and human Pb exposure completely, a combination of traditional review and visualization analysis based on CiteSpace literature was used to review earlier researches in this study. In the first instance, present researches on exposure sources and exposure pathways of Pb were summarized briefly, and then the studies using sentinel animals to monitor environmental heavy metal pollution and human health were combed. Finally, visualization software CiteSpace 5.8.R3 was used to explore and analyze the hotspots and frontiers of lead exposure and sentinel animals researches at home and abroad. The results showed that certain mammals were good indicators for human lead exposure. Sentinel animals had been widely used to monitor the ecological environment and human lead exposure. Among them, the blood lead levels of small mammals, particularly for domestic dogs and cats, had a significant correlation with the blood lead levels of human living in the same environment. It indicated that certain biological indicators in animals can be used as surrogates to monitor human body exposure to heavy metals. This study also explored the challenges and perspectives that may be faced in sentinel animal research, in order to provide a certain theoretical basis and train of thought guidance for future research.

Assessment of Toxic Metals (Al, Cd, Pb) and Trace Elements (B, Ba, Co, Cr, Cu, Fe, Mn, Mo, Li, Zn, Ni, Sr, V) in the Common Kestrel (Falco tinnunculus) from the Canary Islands (Spain)

The monitoring of trace elements and toxic metals in apical predators of the trophic chain provides data on the degree of contamination in ecosystems. The common kestrel is one of the most interesting raptors in this respect in the Canary Islands; therefore, the study of the levels of trace elements and toxic metals in this species is of much scientific value. The content of trace elements and toxic metals (B, Ba, Co, Cr, Cu, Fe, Mn, Mo, Li, Zn, Ni, Sr, V, Al, Cd, Pb) was determined in the liver, muscle, and feathers of 200 specimens of common kestrel carcasses (Falco tinnunculus canariensis) from Tenerife. Cr (0.82 ± 2.62 mg/kg), Cu (11.82 ± 7.77 mg/kg), and Zn (198.47 ± 520.80 mg/kg) are the trace elements that stand out in the feather samples; this may be due to their affinity for the pigments that give them their coloring. Li was noteworthy in the liver samples (8.470 ± 5.702 mg/kg). Pb stood out in the feathers (4.353 ± 20.645 mg/kg) > muscle (0.148 ± 0.095 mg/kg) > liver (0.187 ± 0.133 mg/kg). The presence of metals in feathers correlates with recent exposure and reflects environmental contamination. When using raptor feathers as indicators of metal contamination, it is important to know what the levels of each metal signify. The analysis of the different tissues and organs of raptors, such as the common kestrel, provides valuable information on the degree of environmental contamination of the ecosystem in which it lives. Gender was not an influencing factor in this study.

A nationwide survey of trace metals and Zn isotopic signatures in mussels (Mytilus edulis) and oysters (Crassostrea gigas) from the coast of South Korea

Thirteen trace metals and Zn isotopic signatures were investigated in mussels and oysters collected from the coast of South Korea to evaluate their bioavailability in bivalve mollusks. The average Cu, Zn, and Cd concentrations were 2.6-17.7 times higher in oysters than mussels, and high biota sediment accumulation factors (>30) were observed for these metals in oysters. Except for Pb in mussels, most metals had no correlation with total sediment concentrations. In oysters, Fe, V, Cu, Zn, Sn, and Pb concentrations were significantly correlated with sediments. The average values of δ⁶⁶Zn_IRMM3702 in mussels, oyster, and sediments were +0.09‰, +0.12‰, and -0.06‰, respectively. Soft tissues of mussels and oysters with high Zn concentrations tended to contain lighter Zn isotopes. The results indicate that oysters are a better biomonitoring organism for metal contamination than mussels and can be used in the monitoring and management of coastal environments and ecosystems.

High Frequency of Lead Exposure in the Population of an Endangered Australian Top Predator, the Tasmanian Wedge-Tailed Eagle (Aquila audax fleayi)

Lead poisoning, mainly through incidental ingestion of lead ammunition in carcasses, is a threat to scavenging and predatory bird species worldwide. In Australia, shooting for animal control is widespread, and a range of native scavenging species are susceptible to lead exposure. However, the prevalence of lead exposure in Australia's scavenging and predatory birds is largely unknown. We evaluated the degree to which the Tasmanian wedge-tailed eagle (Aquila audax fleayi), an endangered Australian raptor and facultative scavenger, showed evidence of lead exposure. We detected lead in 100% of femur and liver tissues of 109 eagle carcasses opportunistically collected throughout Tasmania between 1996 and 2018. Concentrations were elevated in 10% of 106 liver (>6 mg/kg dry wt) and 4% of 108 femur (>10 mg/kg dry wt) samples. We also detected lead in 96% of blood samples taken from 24 live nestlings, with 8% at elevated concentrations (>10 μg/dL). Of the liver samples with elevated lead, 73% had lead^207/206 isotope ratios within the published range of lead-based bullets available in Tasmania. These first comprehensive data on lead exposure of an Australian raptor are comparable to those for raptor studies elsewhere that identify lead-based ammunition exposure as a conservation threat. Our findings highlight the importance of further research and efforts to address lead contamination throughout the Tasmanian ecosystem and in other Australian regions. Environ Toxicol Chem 2021;40:219-230. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Lead contamination in raptors in Europe: A systematic review and meta-analysis

Lead contamination is a widely recognised conservation problem for raptors worldwide. There are a number of studies in individual raptor species but those data have not been systematically evaluated to understand raptor-wide lead exposure and effects at a pan-European scale. To critically assess the extent of this problem, we performed a systematic review compiling all published data on lead in raptors (1983-2019) and, through a meta-analysis, determined if there was evidence for differences in exposure across feeding traits, geographical regions, between hunting and non-hunting periods, and changes over time. We also reviewed the impact of lead on raptors and the likely main source of exposure. We examined 114 studies that were unevenly distributed in terms of time of publication and the countries in which studies were performed. Peer-reviewed articles reported data for 39 raptor species but very few species were widely monitored across Europe. Obligate (vultures) and facultative scavengers (golden eagle, common buzzard and white-tailed sea eagle) accumulated the highest lead concentrations in tissues and generally were the species most at risk of lead poisoning. We found no evidence of a spatial or decadal trend in lead residues, but we demonstrated that high lead blood levels relate to hunting season. Exposure at levels associated with both subclinical and lethal effects is common and lead from rifle bullets and shot is often the likely source of exposure. Overall, our review illustrates the high incidence and ubiquity of lead contamination in raptors in Europe. However, we did not find studies that related exposure to quantitative impacts on European raptor populations nor detailed studies on the impact of mitigation measures. Such information is urgently needed and requires a more harmonised approach to quantifying lead contamination and effects in raptors across Europe.

Blood concentrations of 50 elements in Eagle owl (Bubo bubo) at different contamination scenarios and related effects on plasma vitamin levels

Some metals and metalloids (e.g. Pb, Hg, Cd and As) are well-known for their bioaccumulation capacity and their toxic effects on birds, but concerns on other minor elements and rare earth elements (ME and REE) are growing due to their intensive use in modern technology and potential toxicity. Vitamins and carotenoids play essential roles in nestling growth and proper development, and are known to be affected by the metals classically considered as toxic. However, we are unaware of any attempts to evaluate the exposure to 50 elements and related effects in plasma vitamins and carotenoids in raptor species. The main goals of this study are: (i) to assess the exposure to 50 elements (i.e. classic toxic elements, trace elements, REE and ME) in nestling Eagle owls (Bubo bubo) inhabiting three differently polluted environments (mining, industrial and control areas) in southeastern Spain, and (ii) to evaluate how element exposure affects plasma vitamin and carotenoid levels, hematocrit and body measurements (mass and wing length) of the individuals. Our results show that local contamination in the mining area contributes to increased blood concentrations of Pb, As and Tl in nestlings, while diet differences between control and mining/industrial areas may account for the different levels of Mn, Zn, and Sr in blood, and lutein in plasma. Plasma tocopherol levels were increased in the mining-impacted environment, which may be a mechanism of protection to prevent toxic element-related oxidative stress. Plasma α-tocopherol was enhanced by 20% at blood Pb concentrations ≥8 ng/ml, and nestlings exhibited up to 56% increase in α-tocopherol levels when blood Pb concentrations reached 170 ng/ml. Tocopherol seems to be a sensitive biomarker under an exposure to certain toxic elements (e.g. Pb, As, Tl).

Effects of lead from ammunition on birds and other wildlife: A review and update

Poisoning of wild birds following ingestion of lead from ammunition has long been recognised and considerable recent research has focused on terrestrial birds, including raptors and scavengers. This paper builds upon previous reviews and finds that both the number of taxa affected and geographical spread of cases has increased. Some lead may also be absorbed from embedded ammunition fragments in injured birds which risk sub-lethal and welfare effects. Some papers suggest inter-specific differences in sensitivity to lead, although it is difficult to disentangle these from other factors that influence effect severity. Sub-lethal effects have been found at lower blood lead concentrations than previously reported, suggesting that previous effect-level 'thresholds' should be abandoned or revised. Lead poisoning is estimated to kill a million wildfowl a year in Europe and cause sub-lethal poisoning in another ≥ 3 million. Modelling and correlative studies have supported the potential for population-level effects of lead poisoning in wildfowl, terrestrial birds, raptors and scavengers.

Assessment of the exposure to heavy metals and arsenic in captive and free-living black kites (Milvus migrans) nesting in Portugal

Due to their high trophic level, raptor species may serve as important indicators of environmental contamination by heavy metals. This study was conducted to determine if the habitat of the black kite (Milvus migrans) is contaminated by heavy metals and arsenic and to assess the degree and type of exposure that may be present. For this purpose, this study was conducted on a group of captive birds (n = 12) and on a group of free-living birds admitted to two wildlife rehabilitation centers (n = 31). Blood samples were taken for analysis of arsenic (As), mercury (Hg) and lead (Pb) concentrations by inductively coupled plasma mass spectrometry (ICP-MS). Captive birds had the lowest blood concentrations for all toxic elements examined, but significant differences from the concentrations found in free-living birds were only observed for Hg and Pb (p < 0.01). Arsenic concentrations were almost three times higher in free-living birds (4.521 ± 5.695 µg/dl) then in captive birds (1.566 ± 0.753 µg/dl). In all the samples of captive birds' mercury was not detected, while in free-living birds we observed a concentration of 7.493 ± 8.464 µg/dl (p < 0.01). Regarding lead, we observed a concentration almost four-fold higher in free-living birds (19.430 ± 29.294 µg/dl) then in captive birds (4.449 ± 1.987 µg/dl) (p < 0.01). Therefore, available sources of Pb and Hg seem to be present in the habitat of the black kite.

Fatal gunshot injuries in the common buzzard Buteo buteo L. 1758 - imaging and ballistic findings

The conservation of the common buzzard is assured by the European Union law. In Poland, this wild bird is under strict species protection and it is used as a bioindicator for heavy metals in the environment. A case of the fatal shooting of a buzzard with a firearm by an unidentified shooter is described here. Macroscopic evaluation, X-ray imaging, post-mortem computed tomography, ballistic examination of the isolated bullets and finally a simulation of the assumed position of the bird at the time of the shot were performed. Numerous pellets were found inside the body, together with multiple bone fractures and central nervous system trauma. The buzzard died most probably as a result of spinal cord injury from a single shot that was fired from a smoothbore hunting gun. Collected evidence was insufficient to identify the shooter, which sadly confirms that identification of the perpetrator in wildlife forensics remains low.

Concentrations of lead and other elements in the liver of the white-tailed eagle (Haliaeetus albicilla), a European flagship species, wintering in Eastern Poland

As a top predator, the white-tailed eagle (Haliaeetus albicilla) may serve as a good indicator species, providing information about the bioavailability of contaminants and their transfer within the food chain. In this study, we aimed to determine the common sources of origin of 17 metals and other elements in the liver of white-tailed eagles, and to compare the variations in their hepatic concentrations by age (adults vs immatures) and sex (males vs females) in groups of white-tailed eagles wintering in Eastern Poland. The element concentrations followed the pattern of S > K > Na > Fe > Mg > Ca > Zn > Cu > Mn > Se > Pb > Hg > Cd > Cr > Sr > V > Sc. We found significant age-related differences in the hepatic concentrations of some of the elements. Adults showed higher concentrations of Pb, Cd, Ca, Fe, and Zn and lower concentrations of Cu and Se than immatures. These differences may be explained by age-related differences in wintering strategy (adults are sedentary, and immatures are migratory) and hunting skills (adults are more successful when hunting for agile prey). Our study indicates that ingested Pb ammunition poses a serious threat to the health and lives of white-tailed eagles in Poland (32% of the studied individuals had acute lead poisoning). Our study also indicates a serious need for banning the use of lead hunting ammunition in the parts of Europe (including Poland) where it is still allowed.

Concentration of 12 Metals and Metalloids in the Blood of White Stork (Ciconia ciconia): Basal Values and Influence of Age and Gender

The white stork (Ciconia ciconia) is being increasingly used in biomonitoring programmes of environmental contaminants due to its growing population in Europe; however, studies on inorganic elements are scarce. The blood of 70 white storks was collected and analysed by inductively coupled plasma mass spectroscopy (ICP-MS) to determine the presence of the following elements: lead (Pb), mercury (Hg), arsenic (As), nickel (Ni), iron (Fe), zinc (Zn), copper (Cu), selenium (Se), manganese (Mn), chromium (Cr), cobalt (Co), and cadmium (Cd). Our main goals were to determine the mean concentrations of these elements in the blood and to study its association with age and gender. Mean concentrations were highest for Fe, followed by Zn, and lowest for Co and Cd. The metal levels were similar to the values referred in the literature for the same species from different locations. No statistically significant differences were found between males and females. Regarding age, statistically significant differences were observed for Ni, Cu, Se, Hg, and Pb between young and adult animals (except for Pb, values in adults were higher than in fledglings). Many element concentrations were correlated, with the strongest correlations between the pairs Hg-Se, Hg-As, and Fe-Zn, mainly in adults. This study provides the baseline data for a monitoring program based on white stork blood as a nondestructive sample.

Levels of blood lead in Griffon vultures from a Wildlife Rehabilitation Center in Spain

Lead is considered a highly toxic contaminant with important impacts to bird wildlife. Griffon vultures (Gyps fulvus) are a sensitive indicator of the level of environmental contamination due to their position at the top of the food chain and their dependence on human activities. The aim of this study was to assess susceptibility to lead intoxication in Griffon vultures admitted to Wildlife Rehabilitation Centers (WRC), measuring blood lead levels and determining if blood lead concentrations are related to clinical signs, hematological, biochemical or radiographic findings. Also, the influence of age, gender, body condition, season and primary cause of admission were evaluated. This study was realized in all Griffon vultures admitted during a period of one year in the Rehabilitation Center GREFA. Blood lead levels are measured by using anodic stripping voltammetry. In Griffon vultures, we observed that 26% of the analyzed birds presented lead levels above 20µg/dL with 74% below 20µg/dL ([Pb]_<20 =9.34±5.60µg/dL). In our study, statistically significant differences were found for lead according to sex, season of admission to the center and body condition. A negative correlation was found between levels of metal and hematocrit. No association was found between clinical signs and blood lead levels in Griffon vultures, except for digestive signs as stasis and weight loss. On numerous occasions, the intoxication in this specie is related to ingestion of lead ammunition; however, we have not detected radiographic lead in our vultures. Compared with other studies, we generally found low levels of lead in blood of Griffon vultures but the blood of all birds admitted to WRC presented detectable lead concentrations. This species apparently presents a higher sensibility to the toxic effects of this metal than that described by other authors. It have been observed that there is some evidence that suggests that subclinical levels of lead could be related with a predisposition to injury or diseases, even though these birds might be admitted for other causes. The detection of levels of blood lead in animals that are admitted to a recovery center will give valuable information which could be used to monitor spatial and temporal variations and provide a clearer picture of temporal levels of this contaminant in this emblematic avian specie.

Trace element concentrations in livers of Common Buzzards Buteo buteo from eastern Poland

In this study, our aim was to determine the common sources of origin of 18 elements in the livers of Common Buzzards collected during the breeding season in an extensive agricultural landscape in south-east Poland with respect to age (adults and immatures) and sex (males and females). In all 34 specimens collected, the element concentrations followed the pattern of S > Na > Fe > Mg > Zn > Si > Cu > Mn > Ba > Se > B > Pb > Hg > Cd > Cr > Ni > Sr > V. Among the heavy metals examined, only the concentration of Pb was relatively high. Given the prevalence of farmland in the studied area (and the wide use of fertilizers), common use of lead-hunting ammunition and moderate concentration of Pb in fertilizers, the indirect influence of hunting ammunition ingested with food or as gastroliths was apparently responsible for the elevated levels of Pb in the livers of Common Buzzards. In our study, no significant sex-related differences were detected in the hepatic concentrations of any element. However, a significant age effect was observed for three elements, which had elevated levels in adults (Hg) and immature birds (B, Pb), and a significant age x sex interaction was found for S and Fe. These results might be explained by the importance of these elements in bone growth in immature birds (B), variable strategies of foraging between adults and immature birds (Pb), and possible intersex differences in the immature cohort in response to the presence of lead (S, Fe).

The role of density-dependence regulation in the misleading effect of the Aznalcollar mining spill on the booted eagle fecundity

The aim of this study was to assess the exposure and potential effects of the toxic elements released by the Aznalcollar spillage on the fecundity of the booted eagle (Hieraetus pennatus) population of Doñana National Park. We measured As, Cd, Cu, Pb, Zn, Sb and Tl levels in the blood of 24 individuals after the accident and also used data of reproductive performance of the species from 1976 to 2000. While As, Sb and Tl were below their detection limits and only 3 samples were above detection limit for Cd (0.02-0.04μg/dl), mean levels of Cu, Zn and Pb (μg/dl) were found to be 38.736, 532.937 and 0.719, respectively, in fledglings; and 66.112, 652.571 and 1.825, respectively, in adults. These levels were higher in adults, but they did not differ significantly between age classes and were at safe levels. In addition, a positive relationship between relative fecundity and the combination of Cu, Zn and Pb was observed. Following the mining spill, the mean population fecundity was lower (0.536 fledglings per pair in the population) than before (1.093). However, the decrease in fecundity over time was also related to the increase of breeding pairs, suggesting a density-dependent regulation and nullifying the mining spillage effect. Thus, although raptors have proved to be highly valuable biomonitors of environmental pollution, we must be especially cautious and go beyond the apparent effects that sometimes we quickly believe to detect, leading us to reach mistaken conclusions that could affect our management plans.