Anthropogenic contamination of residential environments from smelter As, Cu and Pb emissions: Implications for human health.

Communities in low-income and middle-income countries (LMIC) are disproportionally affected by industrial pollution compared to more developed nations. This study evaluates the dispersal and associated health risk of contaminant-laden soil and dust at a copper (Cu) smelter in Tsumeb, Namibia. It is Africa's only smelter capable of treating complex Cu ores that contain high arsenic (As) contents (<1%). The analyses focused on the primary trace elements associated with ore processing at the smelter: As, Cu, and lead (Pb). Portable X-Ray fluorescence spectrometry (pXRF) of trace elements in soils (n = 83) and surface dust wipes (n = 80) showed that elemental contamination was spatially associated with proximity to smelter operations. Soil concentrations were below US EPA soil guidelines. Dust wipe values were elevated relative to sites distal from the facility and similar to those at other international smelter locations (As = 1012 µg/m2 (95% CI 687-1337); Cu = 1838 µg/m2 (95% CI 1191-2485); Pb = 1624 µg/m2 (95% CI 862-2385)). Source apportionment for Pb contamination was assessed using Pb isotopic compositions (PbIC) of dust wipes (n = 22). These data revealed that the PbIC of 73% (n = 16/22) of these wipes corresponded to the PbIC of smelter slag and tailings, indicating contribution from industrial emissions to ongoing exposure risk. Modeling of carcinogenic risk showed that dust ingestion was the most important pathway, followed by inhalation, for both adults and children. Dermal contact to trace elements in dust was also determined to pose a carcinogenic risk for children, but not adults. Consequently, contemporary smelter operations remain an ongoing health risk to the surrounding community, in spite of recent efforts to improve emissions from the operations.

Distinguishing between Natural and Industrial Lead in Consumer Products and Other Environmental Matrices.

California's Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) was designed to protect the state's populace from exposures to toxic levels of chemicals in consumer products, including foods, by requiring businesses to warn the public about any of those hazards. There is, however, one qualification in the legislation, which is that warnings are not required if the source of that contamination is natural, as opposed to industrial. That qualification is especially problematic for lead because "natural" and "industrial" lead have a common origin and behave the same in the environment and industrial lead contamination has been pandemic for millennia. As a result of that historic and ongoing contamination, ambient lead levels in the biosphere may be orders of magnitude above natural levels, limiting comparisons of "natural" versus "industrial" lead concentrations in products. Further complicating those comparisons are reports of erroneously high measurements of lead concentrations in the biosphere as a result of sample contamination during collection, storage, and analysis. Some of those problems may be addressed with measurements of lead concentrations using rigorous trace metal clean techniques. These techniques often yield lead concentrations that are below the Act's maximum exposure in foods and non-foods of 0.5 µg/day, eliminating the need for a public alert. Those techniques have also been used to derive natural lead concentrations in a few organisms (marine fish, humans, rats, and dandelions), which range from 2- to 100-fold below ambient levels. However, extrapolating from those few determinations to establish natural lead levels in other organisms is complicated and often inappropriate. Complementary stable lead isotopic composition measurements have also been used to estimate the percent of natural and industrial lead in some consumer products, including foods, wine, and dietary supplements. These measurements, however, require the isotopic compositions of both the "natural" and "industrial" lead end members, which may be poorly defined. In addition, the global market has further complicated identification of the "industrial" lead end member, because lead contamination of foods can occur during production, harvesting, storage, shipping, processing, and packaging, which can happen in different locales within a country, different countries, and even different continents.

Natural Lead Levels in Dandelions ( Taraxacum officinale): A Weed, Folk Medicine, and Biomonitor.

The natural lead concentration of dandelion ( Taraxacum officinale) leaves is estimated to be 0.2 µg/g (dry weight), or 1-3 orders of magnitude below most contemporary measurements of that value for dandelions and other plants. This estimate is based on analyses of lead concentrations of dandelions grown in a trace metal clean laboratory, with environmental lead concentrations approximating natural levels. The protocols used in this study paralleled those in our previous study that estimated the natural blood lead level in humans (0.016 µg/dL), which is also 1-3 orders of magnitude below most contemporary measurements. Analyses of the isotopic ratios (206Pb/207Pb:208Pb/207Pb) of the lead in the plants grown in the laboratory and greenhouse and those collected in the field, as well as the isotopic ratios of the soils the plants were grown in in the laboratory, indicate that anthropogenic lead makes up a substantial amount of labile lead in today's environments. Consequently, this estimate of the natural lead level in dandelion leaves provides both a benchmark for comparison of lead concentrations in contemporary plants and yet another measure of persistent lead contamination in the biosphere.

Historic and Industrial Lead within the Northwest Pacific Ocean Evidenced by Lead Isotopes in Seawater.

We report the continued lead (Pb) contamination of the Northwest Pacific Ocean in 2002 and present the first comprehensive Pb isotope data set for that region. In the upper ocean, a Pb concentration maxima (64-113 pmol kg-1) extended throughout the entire North Pacific Subtropical Gyre (NPSG). We determined most of the Pb in this feature was from industrial emissions by many nations in the 1980s and 1990s, with the largest contributions from leaded gasoline emissions. In contrast, the deep water (>1000 m) Pb concentrations were lower (6-37 pmol kg-1), and constituted a mix of background (natural) Pb and anthropogenic Pb inputs from preceding decades. Deep water below the Western Subarctic Gyre (WSAG) contained more industrial Pb than below the NPSG, which was attributed to a calculated 60-fold greater flux of particulate Pb to abyssal waters near the Asian continent. Assuming Pb isotope compositions in the North Pacific Ocean were homogeneous prior to large-scale 20th century anthropogenic inputs, this evidence suggests a relatively faster change in Pb isotope ratios of North Pacific deep water below the WSAG versus the NPSG.

Increases in Anthropogenic Gadolinium Anomalies and Rare Earth Element Concentrations in San Francisco Bay over a 20 Year Record.

We evaluated both the spatial distribution of gadolinium (Gd) and other rare earth elements (REE) in surface waters collected in a transect of San Francisco Bay (SFB) and their temporal variations within the Bay over two decades. The REE were preconcentrated using the NOBIAS PA-1 resin prior to analysis by high-resolution inductively coupled plasma mass spectrometry. Measurements revealed a temporal increase in the Gd anomaly in SFB from the early 1990s to the present. The highest Gd anomalies were observed in the southern reach of SFB, which is surrounded by several hospitals and research centers that use Gd-based contrast agents for magnetic resonance imaging. Recent increases in that usage presumably contributed to the order of magnitude increase in anthropogenic Gd concentrations in SFB, from 8.27 to 112 pmol kg(-1) over the past two decades, and reach the northeast Pacific coastal waters. These measurements (i) show that "exotic" trace elements used in new high-tech applications, such as Gd, are emerging contaminants in San Francisco Bay and that anthropogenic Gd concentrations increased substantially over a 20 year period; (ii) substantiate proposals that REE may be used as tracers of wastewater discharges and hydrological processes; and (iii) suggest that new public policies and the development of more effective treatment technologies may be necessary to control sources and minimize future contamination by REE that are critical for the development of new technologies, which now overwhelm natural REE anomalies.

Lead Sources to the Amundsen Sea, West Antarctica.

The global prevalence of industrial lead (Pb) contamination was exemplified decades ago by the predominance of anthropogenic Pb in samples of Antarctic surface ice and in Southern Ocean surface waters. Decreases in environmental Pb contamination corresponding with the near-global phase-out of leaded automobile gasoline beginning in the 1970s have since been observed. Measurements of Pb concentration in snow and ice core samples from Antarctica show that recent fluxes of industrial Pb to Antarctica have similarly declined. Here, we present measurements of Pb concentrations and isotopic compositions in seawater and surface sediments from the Amundsen Sea continental shelf including the Amundsen Sea Polynya. Both sets of measurements show that most (∼60-95%) of the Pb at our sites, at the time of sampling, is natural in source: that is, derived from the weathering of Antarctic continental rocks. These fluxes of natural Pb then become entrained into polynya waters either from sediment resuspension or from the transport of sediment-laden glacial melt waters to the polynya.

Mercury offloaded in Northern elephant seal hair affects coastal seawater surrounding rookery.

Methylmercury (MeHg) is a potent neurotoxin that is biomagnified approximately 1-10 million-fold in aquatic carnivores such as the Northern elephant seal (Mirounga angustirostris), whose excreta and molted pelage, in turn, constitute a source of environmental MeHg contamination at the base of marine food chains. The potential for this top-down contamination is greatest in coastal areas with productive marine ecosystems that provide ideal habitats for large marine mammal colonies that can number in the thousands. This recycling of MeHg was evidenced by comparing total mercury (HgT) and MeHg concentrations in seawater, and HgT in molted pelage of M. angustirostris, at the Año Nuevo State Reserve pinniped rookery with concentrations at neighboring coastal sites in Central California. Seawater MeHg concentrations around the rookery (average = 2.5 pM) were markedly higher than those at the comparison coastal sites (average = 0.30 pM), and were as high as 9.5 pM during the M. angustirostris molting season. As a consequence, excreta and molts from this marine mammal colony, and presumably other marine predator populations, constitute a major source of MeHg at the base of the local marine food chain.

Total and monomethyl mercury in terrestrial arthropods from the central California coast.

The aim of this project was to obtain a baseline understanding and investigate the concentration of mercury (Hg) in the tissue of terrestrial arthropods. The 4-month sampling campaign took place around Monterey Bay, California. Total mercury (HgT) concentrations (x ± SD, dry weight) for the captured specimens ranged from 22 to 188 ng g(-1) in the Jerusalem crickets (Orthoptera: Stenopelmatidae); 65-233 ng g(-1) in the camel crickets (Orthoptera: Rhaphidophoridae); 25-227 ng g(-1) in the pill bugs (Isopoda: Armadillidiidae); 19-563 ng g(-1) in the ground beetles (Coleoptera: Carabidae); 140-441 ng g(-1) in the variegated meadowhawk dragonflies (Odonata: Libellulidae); 607-657 ng g(-1) in the pacific spiketail dragonflies (Odonata: Cordulegastridae); and 81-1,249 ng g(-1) in the wolf spiders (Araneae: Lycosidae). A subset of samples analyzed for monomethyl mercury (MMHg) suggest detrital pill bugs have a higher MMHg/HgT ratio than predatory ground beetles.

Trace metal inventories and lead isotopic composition chronicle a forest fire's remobilization of industrial contaminants deposited in the angeles national forest.

The amounts of labile trace metals: [Co] (3 to 11 µg g-1), [Cu] (15 to 69 µg g-1), [Ni] (6 to 15 µg g-1), [Pb] (7 to 42 µg g-1), and [Zn] (65 to 500 µg g-1) in ash collected from the 2012 Williams Fire in Los Angeles, California attest to the role of fires in remobilizing industrial metals deposited in forests. These remobilized trace metals may be dispersed by winds, increasing human exposures, and they may be deposited in water bodies, increasing exposures in aquatic ecosystems. Correlations between the concentrations of these trace metals, normalized to Fe, in ash from the fire suggest that Co, Cu, and Ni in most of those samples were predominantly from natural sources, whereas Pb and Zn were enriched in some ash samples. The predominantly anthropogenic source of excess Pb in the ash was further demonstrated by its isotopic ratios (208Pb/207Pb: 206Pb/207Pb) that fell between those of natural Pb and leaded gasoline sold in California during the previous century. These analyses substantiate current human and environmental health concerns with the pyrogenic remobilization of toxic metals, which are compounded by projections of increases in the intensity and frequency of wildfires associated with climate change.

Lead isotopic compositions of ash sourced from Australian bushfires.

This study identifies natural and industrial lead remobilized in ash deposits from three bushfires in relatively pristine areas of Australia in 2011 using lead isotopic compositions ((208)Pb/(207)Pb; (206)Pb/(207)Pb). Lead concentrations in the ash ranged from 1 to 36 mg/kg, bracketing the range of lead (4-23 mg/kg) in surface soils (0-2 cm), subsurface (40-50 cm) soils and rocks. The lead isotopic compositions of ash and surface soil samples were compared to subsurface soils and local bedrock samples. The data show that many of the ash and surface soil lead isotopic compositions were a mixture of natural lead and legacy industrial lead depositions (such as leaded petrol combustion). However, some of the ash samples at each of the sites had lead isotopic compositions that did not fit a simple two end-member mixing model, indicating other, unidentified sources.

A new method for stable lead isotope extraction from seawater.

A new technique for stable lead (Pb) isotope extraction from seawater is established using Toyopearl AF-Chelate 650M(®) resin (Tosoh Bioscience LLC). This new method is advantageous because it is semi-automated and relatively fast; in addition it introduces a relatively low blank by minimizing the volume of chemicals used in the extraction. Subsequent analyses by HR ICP-MS have a good relative external precision (2σ) of 3.5‰ for (206)Pb/(207)Pb, while analyses by MC-ICP-MS have a better relative external precision of 0.6‰. However, Pb sample concentrations limit MC-ICP-MS analyses to (206)Pb, (207)Pb, and (208)Pb. The method was validated by processing the common Pb isotope reference material NIST SRM-981 and several GEOTRACES intercalibration samples, followed by analyses by HR ICP-MS, all of which showed good agreement with previously reported values.

New assessment of organic mercury formation in highly polluted sediments in the Lenga estuary, Chile.

Anomalously high levels of mercury in sediment in the Lenga estuary, Chile are comparable to the most contaminated sites previously reported elsewhere. Total mercury (Hgtotal) concentrations range from 0.5 to 129 mg kg(-1) and organic mercury (Hgorg) from 11 to 53 µg kg(-1). The highest levels are in areas near the previous wastewater outfall of a chlo-alkali plant. The results show that the proportion of Hgorg/Hgtotal in the sediment varies by more than two orders of magnitude (0.02-5.7%) according to the concentration of Hgtotal. No correlation between the concentration of Hgorg and Hgtotal was found. The lack of correlation does contrast with the findings of other authors in culture media. Our results indicate that even at very high concentrations of Hgtotal and organic matter do not influence organic mercury formation in estuary sediments. The disparity in Hgtotal and Hgorg concentrations also attests to environmental differences in the formation.

Asian industrial lead inputs to the North Pacific evidenced by lead concentrations and isotopic compositions in surface waters and aerosols.

Recent trends of atmospheric lead deposition to the North Pacific were investigated with analyses of lead in aerosols and surface waters collected on the fourth Intergovernmental Oceanographic Commission Contaminant Baseline Survey from May to June, 2002. Lead concentrations of the aerosols varied by 2 orders of magnitude (0.1-26.4 pmol/m(3)) due in part to variations in dust deposition during the cruise. The ranges in lead aerosol enrichment factors relative to iron (1-119) and aluminum (3-168) were similar, evidencing the transport of Asian industrial lead aerosols across the North Pacific. The oceanic deposition of some of those aerosols was substantiated by the gradient of lead concentrations of North Pacific waters, which varied 3-fold (32.7-103.5 pmol/kg), were highest along with the Asian margin of the basin, and decreased eastward. The hypothesized predominance of Asian industrial lead inputs to the North Pacific was further corroborated by the lead isotopic composition of ocean surface waters ((206)Pb/(207)Pb = 1.157-1.169; (208)Pb/(206)Pb = 2.093-2.118), which fell within the range of isotopic ratios reported in Asian aerosols that are primarily attributed to Chinese industrial lead emissions.

Pyrogenic remobilization of historic industrial lead depositions.

Relatively high levels (4.3 to 51 µg/g) of labile lead (Pb) in ash from the 2009 Jesusita Fire in Santa Barbara County, California attest to the pyrogenic remobilization of historic industrial lead depositions in this relatively pristine area in Southern California, USA. The primarily industrial origin of that lead was evidenced by its poor correlations (simple linear regressions) with lithogenic aluminum (r = 0.18, p = 0.354, n = 30) and iron (r = 0.21, p = 0.270, n = 30) concentrations and by its associated enrichment factors (EFs): EF using aluminum as conservative element (f-Al) vs lead concentration [Pb] (r = 0.79, p < 0.001, n = 30), and EF using iron as conservative element (f-Fe) vs [Pb] (r = 0.83, p < 0.001, n = 30). The industrial origins of much of that lead were corroborated by its isotopic compositions ((206)Pb/(207)Pb and (208)Pb/(207)Pb), which fell between those of natural lead in the Santa Barbara Basin and previous leaded gasoline emissions in Southern California. This apparent pyrogenic remobilization of legacy lead pollution indicates that it-and other persistent pollutants-will increase with the projected increase in the frequency and intensity of forest fires in the Southwest U.S. and elsewhere as a consequence of climate change.

Lead isotopes reveal different sources of lead in balsamic and other vinegars.

Fifty-eight brands of balsamic vinegars were analyzed for lead concentrations and isotopic compositions ((204)Pb, (206)Pb, (207)Pb, and (208)Pb) to test the findings of a previous study indicating relatively high levels of lead contamination in some of those vinegars--more than two thirds (70%) of them exceeded California's State Maximum Level (34 µg/L) based on consumption rates ≥0.5 µg Pb per day. The lead isotopic fingerprints of all those vinegars with high lead concentrations were then found to be primarily anthropogenic. This isotopic analysis unquestionably reveals multiple contamination sources including atmospheric pollutant Pb and an unidentified contamination source, likely occurring after grape harvest. Organically grown grape vinegars display the same Pb content and isotopic signatures as other vinegars. This implies that pesticides might not be a significant source of pollutant Pb in vinegars. A significant post-harvest contamination would be inherited from chemicals added during production and/or material used during transport, processing or storage of these vinegars. This is consistent with the highest Pb levels being found in aged vinegars (112±112 µg/L) in contrast to other vinegars (41.6±28.9 µg/L) suggesting contamination during storage. It is, therefore, projected that lead levels in most vinegars, especially aged balsamic and wine vinegars, will decrease with improvements in their manufacture and storage processes consequential to recent concerns of elevated levels of lead in some vinegars.

Modeled trace element concentrations and partitioning in the San Francisco estuary, based on suspended solids concentration.

Although trace element (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) and methylmercury (MeHg) concentrations have been systematically sampled 1-3 times per year throughout the San Francisco Bay estuary for more than two decades, those collections do not capture episodic events that may govern the biogeochemical cycles of these elements in the Bay and adjacent Pacific coastal waters. Analyses of the partitioning of in situ elemental concentrations between particulate and total dissolved (<0.45 microm) phases coupled with optically based measurements of suspended solids concentration (SSC) showed highly significant (p<0.001) associations between all elemental concentrations and SSC in the Bay. Predictive models were developed to estimate the distribution ratio (D), or partition coefficient (Kd), and total concentration of each element in the water column based solely on SSC measurements. Modeled predictions of total element concentrations and distribution ratios were then coupled with measured SSC to predict the concentrations of dissolved trace elements in the water column. These predicted total and dissolved concentrations of trace elements can provide both better diagnostics of biogeochemical cycling within the estuary and better estimates of fluxes to adjacent coastal waters, overcoming the limitations of the long-running but limited direct measurements of trace elements from existing sampling programs.

Declining-but persistent-atmospheric contamination in central California from the resuspension of historic leaded gasoline emissions as recorded in the lace lichen (Ramalina menziesii Taylor) from 1892 to 2006.

Analyses of lead concentration and isotopic composition of recent and archived samples of the lace lichen (Ramalina menziesii) chronicle more than a century of atmospheric lead contamination in central California. The contamination extends back to our oldest sample from 1892, when lead levels in lichen from the northern reach of the San Francisco Bay estuary were 9-12 microg/g and their isotopic composition corresponded to those of high lead emissions from the Selby smelter (e.g., (206)Pb/(207)Pb = 1.165) that were killing horses in adjacent fields at that time. By the mid-1950s lead isotopic compositions of lichens shifted to the more radiogenic leaded gasoline emissions (e.g., (206)Pb/(207)Pb = 1.18-1.22). Lead concentrations in the lichen peaked at 880 microg/g in 1976, corresponding with the maximum of leaded gasoline emissions in California in the 1970s. After that, lead concentrations in lichen declined to current levels, ranging from 0.2 to 4.7 microg/g. However, isotopic compositions of contemporary samples still correspond to those of previous leaded gasoline emissions in California. This correspondence is consistent with other observations that attest to the persistence of environmental lead contamination from historic industrial emissions in central California.

Aeolian contamination of Se and Ag in the North Pacific from Asian fossil fuel combustion.

Energy production from fossil fuels, and in particular the burning of coal in China, creates atmospheric contamination that is transported across the remote North Pacific with prevailing westerly winds. In recent years this pollution from within Asia has increased dramatically, as a consequence of vigorous economic growth and corresponding energy consumption. During the fourth Intergovernmental Oceanographic Commission baseline contaminant survey in the western Pacific Ocean from May to June, 2002, surface waters and aerosol samples were measured to investigate whether atmospheric deposition of trace elements to the surface North Pacific was altering trace element biogeochemical cycling. Results show a presumably anthropogenic enrichment of Ag and of Se, which is a known tracer of coal combustion, in the North Pacific atmosphere and surface waters. Additionally, a strong correlation was seen between dissolved Ag and Se concentrations in surface waters. This suggests that Ag should now also be considered a geochemical tracer for coal combustion, and provides further evidence that Ag exhibits a disturbed biogeochemical cycle as the result of atmospheric deposition to the North Pacific.

Submarine groundwater discharge of total mercury and monomethylmercury to central California coastal waters.

Fluxes of total mercury (Hg(T)) and monomethylmercury (MMHg) associated with submarine groundwater discharge (SGD) at two sites onthe central California coast were estimated by combining measurements of Hg(T) and MMHg in groundwater with the use of short-lived, naturally occurring radium isotopes as tracers of groundwater inputs. Concentrations of Hg(T) were relatively low, ranging from 1.2 to 28.3 pM in filtered groundwater, 0.8 to 11.6 pM in filtered surface waters, and 2.5 to 12.9 pM in unfiltered surface waters. Concentrations of MMHg ranged from < 0.04 to 3.1 pM in filtered groundwater, < 0.04 to 0.53 pM in filtered surface waters, and 0.07 to 1.2 pM in unfiltered surface waters. Multiple linear regression analysis identified significant (p < 0.05) positive correlations between dissolved groundwater concentrations of Hg(T) and those of NH4+ and SiO2, and between dissolved groundwater concentrations of MMHg and those of Hg(T) and NH4+. However, such relationships did not account for the majority of the variability in concentration data for either mercury species in groundwater. Fluxes of Hg(T) via SGD were estimated to be 250 +/- 160 nmol day m(-1) of shoreline at Stinson Beach and 3.0 +/- 2.0 nmol m(-2) day(-1) at Elkhorn Slough. These Hg(T) fluxes are substantially greater than net atmospheric inputs of Hg(T) reported for waters in nearby San Francisco Bay. Calculated fluxes of MMHg to coastal waters via SGD were 10 +/- 12 nmol day(-1) m(-1) of shoreline at Stinson Beach and 0.24 +/- 0.21 nmol m(-2) day at Elkhorn Slough. These MMHg fluxes are similar to benthic fluxes of MMHg out of surface sediments commonly reported for estuarine and coastal environments. Consequently, this work demonstrates that SGD is an important source of both Hg(T) and MMHg to coastal waters along the central California coast.