Decreasing lead levels in Swedish biota revealed by 36 years (1969–2004) of environmental monitoring

Pronounced declines in heavy metal burdens of Minnesotan mammals over the last century

Humans have drastically altered the ecology of heavy metals, which can have negative effects on animal development and neural functioning. Many species have shown the ability to adapt to anthropogenic increases in metal pollution, but such evolutionary responses will depend on the extent of metal variation over space and time. For terrestrial vertebrates, it is unclear how metal exposure has changed over time: some studies suggest metal content peaked with the enactment of policies controlling lead emissions, while other studies suggest metal levels peaked at least a century earlier. We used 162 specimens of four mammal species (a mouse, shrew, bat, and squirrel) to ask how metal content of the fur and skin has changed over a 90-year time period, and impacts on individual performance (body size and cranial capacity). Using ICP-MS, we show that for lead, cadmium, copper, and chromium, there were significant declines in metal content in mammal tissue over the 90-year time period, with lead levels five times lower now than in the early 1900s. Importantly, metal content began to drop well before the pollution regulation of the 1970s. Effects of time greatly outweighed any effects of an individual living near a human population center. Surprisingly, there were no effects of body metal content on body size, and only manganese was negatively related to relative cranial capacity. Taken together, these results suggest that present day populations of mammals are experiencing levels of heavy metal exposure that are less stressful than they were 100 years ago. In addition, temporal decreases in metal loads likely partly reflect global patterns of pollution decline that affect atmospheric metal deposition rather than local point sources of exposure.

Major lead exposure from hunting ammunition in eagles from Sweden

Exposure to lead (Pb) from ammunition in scavenging and raptorial birds has achieved worldwide recognition based on incidences of lethal poisoning, but exposure implies also sublethal levels with potential harmful effects. Background and elevated Pb levels in liver from 116 golden eagles (GE, Aquila chrysaetos) and 200 white-tailed sea eagles (WTSE, Haliaeetus albicilla) from Sweden 2003-2011 are here examined, with supporting data from a previous WTSE report and eagle owl (EO, Bubu bubo) report. GE and WTSE display seasonal patterns, with no Pb level exceeding a generally accepted threshold for subclinical effects during summer but strongly elevated levels from October. Fledged juveniles show significantly lower levels than all other age classes, but reach levels found in older birds in autumn after the start of hunting seasons. Pb levels in EO (non-scavenger) show no seasonal changes and indicate no influence from ammunition, and are close to levels observed in juvenile eagles before October. In all, 15% WTSE and 7% GE were lethally poisoned. In areas with high-exposure to hunting ammunition, 24% of WTSE showed lethal Pb levels, compared to 7% in both eagle species from low-exposure areas. Lethal poisoning of WTSE remained as frequent after (15%) as before (13%) a partial ban on use of Pb-based shotgun ammunition over shallow waters (2002). Pb levels increased significantly in WTSE 1981-2011, in contrast to other biota from the same period. A significant decrease of Pb in WTSE liver occurred below a threshold at 0.25 μg/g (dry weight), exceeded by 81% of the birds. Trend patterns in Pb isotope ratios lend further support to this estimated cut-off level for environmental background concentrations. Pb from spent ammunition affects a range of scavenging and predatory species. A shift to Pb-free ammunition to save wildlife from unnecessary harm is an important environmental and ethical issue.

High concentrations of lead (Pb) in blood and milk of free-ranging brown bears (Ursus arctos) in Scandinavia

Exposure to lead (Pb) is a global health problem for both humans and wildlife. Despite a dramatic decline in human Pb exposure following restrictions of leaded gasoline and industry and thereby an overall reduction of Pb entering the environment, Pb exposure continues to be a problem for wildlife species. Literature on scavenging terrestrial mammals, including interactions between Pb exposure and life history, is however limited. We quantified Pb concentration in 153 blood samples from 110 free-ranging Scandinavian brown bears (Ursus arctos), 1-25 years old, using inductively coupled plasma sector field mass spectrometry. We used generalized linear models to test effects of age, body mass, reproduction status and spatial distribution on the blood Pb concentrations of 56 female bears. We sampled 28 females together with 56 dependent cubs and paired their blood Pb concentrations. From 20 lactating females, we measured the Pb concentration in milk. The mean blood Pb concentration was 96.6 μg/L (range: 38.7-220.5 μg/L). Both the mean and range are well above established threshold concentrations for developmental neurotoxicity (12 μg/L), increased systolic blood pressure (36 μg/L) and prevalence of kidney disease in humans (15 μg/L). Lactating females had higher Pb blood concentrations compared to younger, non-lactating females. Blood Pb concentrations of dependent cubs were correlated with their mother's blood Pb concentration, which in turn was correlated with the Pb concentration in the milk. Life-long Pb exposure in Scandinavian brown bears may have adverse effects both on individual and population levels. The high blood Pb concentrations found in brown bears contrast the general reduction in environmental Pb contamination over the past decades in Scandinavia and more research is needed to identify the sources and pathways of Pb exposure in the brown bears.

Temporal Changes in Concentrations of Lead and Other Trace Metals in Free-Ranging Eurasian Eagle Owls Bubo bubo in Sweden

Patterns of lead and other trace metals were examined in 122 Eurasian eagle owls Bubo bubo found dead in Sweden in the period 1978-2013. Environmental lead (Pb) has decreased over recent decades from reduced anthropogenic emissions but mortality by Pb poisoning is still frequently reported for avian raptors and scavengers exposed to Pb ammunition. One objective here was to determine if Pb concentrations in a nocturnal non-scavenging raptor follow the general decline observed in other biota. Pb concentration in owl liver was significantly correlated with body weight, sex, latitude, longitude and season. Pb showed a significant decreasing trend towards north and west. Starved birds had significantly higher concentrations. Total Pb concentrations in liver averaged 0.179 μg g^-1 dry weight (median 0.103) and decreased by 5.6% per year 1978-2013, or 5.3% after adjustment for confounding factors, similar to trends in other species. Among 14 other trace elements only antimony and arsenic showed decreasing trends. Lead isotope ratios ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb increased from 1.138 and 2.408 in 1978-1985 to 1.170 and 2.435 in 2010-2013, respectively, demonstrating that the decreasing Pb concentration in eagle owl is related to the phase-out of leaded gasoline in Europe, where Pb additives had much lower isotope ratios than natural lead in Swedish soils. Only one incidence of suspected Pb poisoning (40.7 μg g^-1 in liver) was observed indicating that poisoning from ingestion of metallic lead is rare (< 1%) in eagle owl in Sweden, in contrast to what has been reported for eagles.

Comparative Study of Lead Concentration in Feathers of Urban and Rural Passerines in Merida, Mexico

Lead is a commonly monitored heavy metal because of potential health effects on exposed organisms. We quantified lead in secondary feathers of two passerine bird species, clay-colored thrushes (Turdus grayi) and great-tailed grackles (Quiscalus mexicanus), from an urban and a rural site in the municipality of Merida, Yucatan. Urban lead concentration was significantly higher than its rural counterpart for both species (p < 0.05). In the urban site, lead concentration was similar in both species (p = 0.14). However, data from the rural site showed that lead concentration was significantly higher in thrush feathers (p < 0.05). Lead levels herein presented are among the lowest ever reported suggesting that either lead accumulation or absorption is limited. Finally, our data seem to support the hypothesis that species feeding ecology plays a major role in lead accumulation.

A baseline study of metals in herring (Clupea harengus) from the Norwegian Sea, with focus on mercury, cadmium, arsenic and lead

The Norwegian spring spawning (NSS) herring is an ecologically and economically important fish population in the Norwegian Sea. It was the first of several Norwegian fish stocks subject to a baseline study designed to give a comprehensive account of the levels of contaminants in a fish species from most of its area of distribution and during different seasons. During 2006 and 2007, 800 individual herring were sampled in their feeding areas in the Norwegian Sea in spring and autumn and at their spawning grounds off the coast of Norway during late winter. Metals including Hg, Cd, As and Pb were determined in muscle samples of individual herring, and mean concentrations±sd (mg kg(-1) ww) were: Hg: 0.04±0.03, Cd: 0.010±0.006, As: 2.2±0.6 and Pb: <0.01-0.10. Apart from one sample, no individual herring exceeded the EU's maximum level for any of these elements, as has been seen also in previous monitoring. Hg and Cd concentration increased with increasing fish age and As concentration varied seasonally, possibly due to uptake during feeding (summer), elimination during starvation (winter) and up-concentration during spawning (spring).

Trace elements in the livers of cod (Gadus morhua L.) from the Baltic Sea: levels and temporal trends

This paper presents and discusses the levels and temporal trends of concentrations of Cd, Pb, Hg, Cu, Zn, and As in livers and Hg in the muscle tissues of cod (Gadus morhua L) from the Baltic Sea during the period 1994-2010. Concentrations of Pb, Hg, and Cd exhibited significant downward trends. Cu and Zn concentrations exhibited upward trends in the period 1994 to 2010. No trends were detected for concentrations of As. The temporal trends identified in heavy metal concentrations in cod livers corresponded to the directions of changes in concentrations of these elements introduced into the Baltic Sea via river runoff and atmospheric emission, and those in surface and deep waters of the Baltic. Downward trends in the concentrations of toxic metals in cod livers suggest that advantageous changes are occurring in concentrations of heavy metals in the environment of the southern Baltic Sea.

Ingestion of lead from ammunition and lead concentrations in white-tailed sea eagles (Haliaeetus albicilla) in Sweden

In this study we show for the first time that lead poisoning from ammunition is a significant mortality factor for white-tailed sea eagle (WSE) (Haliaeetus albicilla) in Sweden. We analyzed 118 WSEs collected between 1981 and 2004 from which both liver and kidney samples could be taken. A total of 22% of all eagles examined had elevated (>6 microg/gd.w.) lead concentrations, indicating exposure to leaded ammunition, and 14% of the individuals had either liver or kidney lead concentrations diagnostic of lethal lead poisoning (>20 microg/gd.w.). Lead concentrations in liver and kidney were significantly correlated. In individuals with lead levels <6 microg/g, concentrations were significantly higher in kidney than in liver; in individuals with lead levels >20 microg/g, concentrations were significantly higher in liver. The lead isotope ratios indicate that the source of lead in individuals with lethal concentrations is different from that of individuals exhibiting background concentrations of lead (<6 microg/gd.w.) There were no significant sex or age differences in lead concentrations. A study from the Baltic reported in principle no biomagnification of lead, but background lead concentrations in WSE liver in this study were still four to >10 times higher than concentrations reported for Baltic fish from the same time period. In contrast to other biota there was no decrease in lead concentrations in WSE over the study period. The proportion of lead poisoned WSE remained unchanged over the study period, including two years after a partial ban of lead shot was enforced in 2002 for shallow wetlands. The use of lead in ammunition poses a threat to all raptors potentially feeding on shot game or offal. The removal of offal from shot game and alternatives to leaded ammunition needs to be implemented in order to prevent mortality from lead in raptors and scavengers.

Yearly measurements of blood lead in Swedish children since 1978: the declining trend continues in the petrol-lead-free period 1995-2007

BACKGROUND

We have measured blood lead concentrations (B-Pb) in Swedish children, yearly since 1978. As reported previously, a substantial decrease of B-Pb was found for the period 1978-1994 (2440 children measured), as an effect of gradual reduction of lead in petrol. In another report focusing on the petrol-lead-free period 1995-2001, we noted that B-Pb seemed to stabilize at an average level close to 20 microg/L.

OBJECTIVE

We here analyze data from the extended petrol-lead-free period 1995-2007.

METHODS

B-Pb was measured in 1268 children, aged 7-11 years, from the municipalities of Landskrona and Trelleborg in southern Sweden, yielding 1407 measurements on B-Pb (since 139 children were measured in two different calendar years).

RESULTS

We observed statistically significant decreases of the average concentrations during the recent years. The average B-Pb reduction rate was close to 5%/yr in the petrol-lead-free period 1995-2007; a similar reduction rate was estimated for the period with gradual reduction of lead in petrol, 1978-1994. The most recent geometric mean of B-Pb was 13.1 (range, 6.9-29.1)microg/L in Trelleborg (sample year 2005) and 13.2 (5.7-58.5)microg/L in Landskrona (2007). A declining B-Pb time trend was observed during the recent years among children who lived in near smelter, urban, and rural residential areas, respectively. B-Pb was influenced by the variables sex (boys had higher B-Pb), parents' smoking habits (children with one or both parents smoking had higher B-Pb), and potentially lead-exposing hobbies (for example, shooting air guns).

CONCLUSION

Children's B-Pb levels can continue to decline markedly more than a decade after lead in petrol has been phased out in a country.