Application of Stable Isotopic Ratio Analysis to Identify the Cause of Acute Versus Chronic Lead Poisoning of a Tundra Swan (Cygnus columbianus): A Case Study.

We utilized lead (Pb) stable isotopes to identify the source of acute Pb poisoning in a Tundra Swan (Cygnus columbianus) and evaluated overall Pb exposure. Upon necropsy, we obtained samples of blood, liver, kidney, heart, thigh, breast, femur, and metallic objects (i.e., fishing sinker, spring and swivels) from the gizzard for Pb isotopic analysis. Pb isotope ratios of blood and soft tissues were essentially identical to the Pb ratios of the sinker, the likely source of acute poisoning. The spring and swivels had lower Pb content and ratios distinct from tissue, suggesting no significant contribution to poisoning. Femur Pb isotopic composition was the most distinct biological sample and indicative of a combination of sources. These results demonstrate isotopic analysis as a viable method for determining the source of acute Pb poisoning, and that Pb isotope ratios in bone most likely record a lifetime-averaged metric of Pb exposure.

Spatial Variation in Particulate Matter Components over a Large Urban Area.

To characterize exposures to particulate matter (PM) and its components, we performed a large sampling study of small-scale spatial variation in size-resolved particle mass and composition. PM was collected in size ranges of < 0.2, 0.2-to-2.5, and 2.5-to-10 µm on a scale of 100s to 1000s of meters to capture local sources. Within each of eight Southern California communities, up to 29 locations were sampled for rotating, month-long integrated periods at two different times of the year, six months apart, from Nov 2008 through Dec 2009. Additional sampling was conducted at each community's regional monitoring station to provide temporal coverage over the sampling campaign duration. Residential sampling locations were selected based on a novel design stratified by high- and low-predicted traffic emissions and locations over- and under-predicted from previous dispersion model and sampling comparisons. Primary vehicle emissions constituents, such as elemental carbon (EC), showed much stronger patterns of association with traffic than pollutants with significant secondary formation, such as PM2.5 or water soluble organic carbon. Associations were also stronger during cooler times of the year (Oct through Mar). Primary pollutants also showed greater within-community spatial variation compared to pollutants with secondary formation contributions. For example, the average cool-season community mean and standard deviation (SD) for EC were 1.1 and 0.17 µg/m3, respectively, giving a coefficient of variation (CV) of 18%. For PM2.5, average mean and SD were 14 and 1.3 µg/m3, respectively, with a CV of 9%. We conclude that within-community spatial differences are important for accurate exposure assessment of traffic-related pollutants.

Private drinking water quality in rural Wisconsin.

Between July 1, 2007, and December 31, 2010, Wisconsin health departments tested nearly 4,000 rural drinking water supplies for coliform bacteria, nitrate, fluoride, and 13 metals as part of a state-funded program that provides assistance to low-income families. The authors' review of laboratory findings found that 47% of these wells had an exceedance of one or more health-based water quality standards. Test results for iron and coliform bacteria exceeded safe limits in 21% and 18% of these wells, respectively. In addition, 10% of the water samples from these wells were high in nitrate and 11% had an elevated result for aluminum, arsenic, lead, manganese, or strontium. The high percentage of unsafe test results emphasizes the importance of water quality monitoring to the health of nearly one million families including 300,000 Wisconsin children whose drinking water comes from a privately owned well.

Contribution of tailpipe and non-tailpipe traffic sources to quasi-ultrafine, fine and coarse particulate matter in southern California.

Exposure to traffic-related air pollution (TRAP) in the near-roadway environment is associated with multiple adverse health effects. To characterize the relative contribution of tailpipe and non-tailpipe TRAP sources to particulate matter (PM) in the quasi-ultrafine (PM0.2), fine (PM2.5) and coarse (PM2.5-10) size fractions and identify their spatial determinants in southern California (CA). Month-long integrated PM0.2, PM2.5 and PM2.5-10 samples (n = 461, 265 and 298, respectively) were collected across cool and warm seasons in 8 southern CA communities (2008-9). Concentrations of PM mass, elements, carbons and major ions were obtained. Enrichment ratios (ER) in PM0.2 and PM10 relative to PM2.5 were calculated for each element. The Positive Matrix Factorization model was used to resolve and estimate the relative contribution of TRAP sources to PM in three size fractions. Generalized additive models (GAMs) with bivariate loess smooths were used to understand the geographic variation of TRAP sources and identify their spatial determinants. EC, OC, and B had the highest median ER in PM0.2 relative to PM2.5. Six, seven and five sources (with characteristic species) were resolved in PM0.2, PM2.5 and PM2.5-10, respectively. Combined tailpipe and non-tailpipe traffic sources contributed 66%, 32% and 18% of PM0.2, PM2.5 and PM2.5-10 mass, respectively. Tailpipe traffic emissions (EC, OC, B) were the largest contributor to PM0.2 mass (58%). Distinct gasoline and diesel tailpipe traffic sources were resolved in PM2.5. Others included fuel oil, biomass burning, secondary inorganic aerosol, sea salt, and crustal/soil. CALINE4 dispersion model nitrogen oxides, trucks and intersections were most correlated with TRAP sources. The influence of smaller roadways and intersections became more apparent once Long Beach was excluded. Non-tailpipe emissions constituted ~8%, 11% and 18% of PM0.2, PM2.5 and PM2.5-10, respectively, with important exposure and health implications. Future efforts should consider non-linear relationships amongst predictors when modeling exposures. Implications: Vehicle emissions result in a complex mix of air pollutants with both tailpipe and non-tailpipe components. As mobile source regulations lead to decreased tailpipe emissions, the relative contribution of non-tailpipe traffic emissions to near-roadway exposures is increasing. This study documents the presence of non-tailpipe abrasive vehicular emissions (AVE) from brake and tire wear, catalyst degradation and resuspended road dust in the quasi-ultrafine (PM0.2), fine and coarse particulate matter size fractions, with contributions reaching up to 30% in PM0.2 in some southern California communities. These findings have important exposure and policy implications given the high metal content of AVE and the efficiency of PM0.2 at reaching the alveolar region of the lungs and other organ systems once inhaled. This work also highlights important considerations for building models that can accurately predict tailpipe and non-tailpipe exposures for population health studies.

Cd isotope fractionation during tobacco combustion produces isotopic variation outside the range measured in dietary sources.

Cadmium production has risen 1000-fold in the past 100 years, from under 20 to over 20,000 tons per year, causing anthropogenically-mobilized Cd to overwhelm natural sources in global cycling. Cadmium has no known biological function in humans, yet has biochemical behaviors similar to zinc and manganese, making exposure detrimental to human health. Identifying and quantifying the sources of Cd for human sub-populations is key to reducing exposures. Cadmium stable isotopes may provide a method for tracing Cd sources throughout the environment and the human body, but at present the limited database for high precision Cd isotopic compositions is inadequate to support such an analysis. Here, we provide new Cd isotope data on dietary sources, cigarette smoking components, and environmentally relevant standard reference materials. Results indicated that minor but significant variations are observed in food products (e.g., peanuts, sunflower seeds, spinach, kale, lettuce, cocoa powder; ~0.9‰ at 4 amu) that may be useful for tracing contamination in agricultural soils. In contrast, Cd isotope fractionation during smoking is larger (~6‰ at 4 amu) and has implications for tracing cadmium sources from tobacco combustion in the environment and throughout the human body. The primary inhaled component of cigarette smoke contains highest delta values (δ116/112Cd or δ114/110Cd ~5.2‰), while the second-hand smoke and cigarette ash have the lowest delta values (δ116/112Cd or δ114/110Cd ~-0.9‰). Used cigarette butts have δ114/110Cd ~2.4‰, in between the values measured in ash/s hand smoke and the inhaled smoke components. The high delta values of the inhaled smoke indicate that Cd isotopes may be used to determine the extent of Cd exposure due to smoking in human biological samples. This study provides new data for previously uncharacterized isotopic reservoirs that can be included in future studies of Cd source-exposure tracing.

High-Precision (MC-ICPMS) Isotope Ratio Analysis Reveals Contrasting Sources of Elevated Blood Lead Levels of an Adult with Retained Bullet Fragments, and of His Child, in Milwaukee, Wisconsin.

Exposure to the neurotoxic element lead (Pb) continues to be a major human health concern, particularly for children in US urban settings, and the need for robust tools for assessment of exposure sources has never been greater. The latest generation of multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) instrumentation offers the capability of using Pb isotopic signatures as a tool for environmental source tracking in public health. We present a case where MC-ICPMS was applied to isotopically resolve Pb sources in human clinical samples. An adult male and his child residing in Milwaukee, Wisconsin, presented to care in August 2015 with elevated blood lead levels (BLLs) (>200 µg/dL for the adult and 10 µg/dL for the child). The adult subject is a gunshot victim who had multiple bullet fragments embedded in soft tissue of his thigh for approximately 10 years. This study compared the high-precision isotopic fingerprints (<1 ‰ 2σ external precision) of Pb in the adult's and child's whole blood (WB) to the following possible Pb sources: a surgically extracted bullet fragment, household paint samples and tap water, and a Pb water-distribution pipe removed from servicing a house in the same neighborhood. Pb in the bullet and adult WB were nearly isotopically indistinguishable (matching within 0.05-0.56 ‰), indicating that bullet fragments embedded in soft tissue could be the cause of both acute and chronic elevated blood Pb levels. Among other sources investigated, no single source dominated the child's exposure profile as reflected in the elevated BLL.

Speciation of aqueous methylmercury influences uptake by a freshwater alga (Selenastrum capricornutum).

Uptake of methylmercury (MeHg) by the alga Selenastrum capricornutum was measured in freshwater batch culture bioassays. The concentration of MeHg in the alga increased rapidly (within 15 min), reached a maximum by 6 h, and then declined because of growth dilution. The alga's rapid growth rate (doubling time, approximately 10 h) contributed to the importance of growth dilution. Conditional first-order rate constants were calculated for uptake (k1 = 6.95 x 10(-9) L/cell/h) and growth (kG = 0.07/h). A competitive synthetic ligand, disodium ethylenediaminetetra-acetate, formed strong complexes with MeHg and reduced MeHg uptake, consistent with the biotic ligand model. A conditional equilibrium formation constant (K) for the MeHg-algae complex was estimated to be approximately 10(16) and was used to model the influence of natural ligands on MeHg bioavailability. Model results suggested MeHg would be most bioavailable at concentrations of dissolved organic matter (DOM) less than 10 mg/L and increasingly unavailable at higher DOM concentrations for the specific humic acid modeled. Similarly, at molar concentrations of sulfide (and, possibly, metal-sulfide clusters) equal to approximately half the MeHg concentration, MeHg was predicted to be unavailable to algae because of the formation of strong 2:1 MeHg-sulfide complexes.

Factors affecting enhanced mercury bioaccumulation in inland lakes of Isle Royale National Park, USA.

We investigated factors causing mercury (Hg) concentrations in northern pike to exceed the consumption advisory level (>500 ng/g) in some inland lakes of Isle Royale National Park. Using Hg-clean techniques, we collected water, zooplankton, macro invertebrates, and fishes in 1998 and 1999 from one advisory lake, Sargent Lake, for analysis of total mercury (Hg(T)) and methylmercury (MeHg). For comparison, samples were also collected from a non-advisory lake, Lake Richie. Concentrations of Hg(T) in northern pike were significantly higher in Sargent Lake (P<0.01). Counter to expectations, mean concentrations of both Hg(T) and MeHg in open water samples were slightly higher in Lake Richie. However, zooplankton in Sargent Lake contained higher average concentrations of Hg(T) and MeHg than in Lake Richie. Mercury concentrations in macro invertebrates were similar between lakes, but different between taxa. The two lakes exhibited similar Hg(T) concentrations in age-1 yellow perch and adult perch but concentrations in large adult perch (>160 mm) in Sargent Lake were twice the concentrations in Lake Richie. Analysis of stable isotopes (delta(13)C and delta(15)N) in biota showed that pike from the two lakes are positioned at the same trophic level (4.2 and 4.3), but that the food web is more pelagic-based in Sargent and benthic-based in Richie. Factors causing concentrations in large pike to be higher in Sargent Lake may include higher bioavailability of methylmercury and a food web that enhances bioaccumulation.

Mercury content and speciation in the plankton and benthos of Lake Superior.

As part of a study is to assess the importance of watersheds in controlling sources, transport, fate, and bioavailability of monomethyl mercury (MeHg) in Lake Superior, biotic samples were collected and analyzed to determine total mercury (HgT) and MeHg content, and to examine size, species, trophic and geographic trends. Plankton was collected in two ways: vertical tows of non-metallic, 153 microm mesh net (bulk zooplankton), and by passively filtering near-surface water through stacked Nitex sieves, generating size-fractionated seston (<35, 35-63, 63-112, and >112 microm). Benthos was sampled using a Ponar grab to collect sediment, and a non-metallic sieve to separate biota from substrate. Samples were processed to quantify dry weights, HgT and MeHg. Results for bulk zooplankton sampled offshore showed a range of approximately from 35 to 50 ng MeHg/gram dry weight (gdw) and from 80 to 130 ng HgT/gdw during April, and from 15 to 25 ng MeHg/gdw and from 20 to 70 ng HgT/gdw during August. Results from sieved, near-surface water from offshore sites in April showed a dominance by the <35 microm size fraction both in total mass and mass of MeHg compared to other size fractions. On a dry weight basis, however, we found little difference between the size fractions in April (MeHg ranges from 2 to 10 ng/gdw). During the summer cruise, we found similar concentrations in the <35 microm fraction, but higher in the 112-243 microm size fraction (MeHg 14-16 ng/gdw). The MeHg concentration in Mysis relicta ranged from 33 to 54 ng/gdw throughout the lake. Chironomid larvae were 8 ng MeHg/gdw and amphipods were 32 ng MeHg/gdw.

Characterization of the elemental composition of newborn blood spots using sector-field inductively coupled plasma-mass spectrometry.

We developed extraction and analysis protocols for element detection in neonatal blood spots (NBSs) using sector-field inductively coupled plasma-mass spectrometry (SF-ICP-MS). A 5% (v/v) nitric acid element extraction protocol was optimized and used to simultaneously measure 28 elements in NBS card filter paper and 150 NBSs. NBS element concentrations were corrected for filter paper background contributions estimated from measurements in samples obtained from either unspotted or spotted NBS cards. A lower 95% uncertainty limit (UL) that accounted for ICP-MS method, filter paper element concentration, and element recovery uncertainties was calculated by standard methods for each individual's NBS element concentration. Filter paper median element levels were highly variable within and between lots for most elements. After accounting for measurement uncertainties, 11 elements (Ca, Cs, Cu, Fe, K, Mg, Na, P, Rb, S, and Zn) had lower 95% ULs>0 ng/spot with estimated concentrations ranging from 0.05 to >50,000 ng/spot in ≥50% of NBS samples in both correction methods. In a NBS sample minority, Li, Cd, Cs, Cr, Ni, Mo, and Pb had estimated concentrations ≥20-fold higher than the respective median level. Taking measurement uncertainties into account, this assay could be used for semiquantitative newborn blood element measurement and for the detection of individuals exposed to supraphysiologic levels of some trace elements. Adequate control of filter paper element contributions remains the primary obstacle to fully quantitative element measurement in newborn blood using NBSs.

Deposition and cycling of sulfur controls mercury accumulation in Isle Royale fish.

Mercury contamination of fish is a global problem. Consumption of contaminated fish is the primary route of methylmercury exposure in humans and is detrimental to health. Newly mandated reductions in anthropogenic mercury emissions aim to reduce atmospheric mercury deposition and thus mercury concentrations in fish. However, factors other than mercury deposition are important for mercury bioaccumulation in fish. In the lakes of Isle Royale, U.S.A., reduced rates of sulfate deposition since the Clean Air Act of 1970 have caused mercury concentrations in fish to decline to levels that are safe for human consumption, even without a discernible decrease in mercury deposition. Therefore, reductions in anthropogenic sulfur emissions may provide a synergistic solution to the mercury problem in sulfate-limited freshwaters.