Evaluation of trace-element contamination from serum collection tubes used by the California Biobank Program.

BACKGROUND: Serum samples archived by the California Biobank Program (CBP) can be a valuable resource to researchers with multiple benefits: affordability, relatively large sample sizes, and racial and geographical representativeness. However, there has been little attention given to the reliability of CBP samples for trace-element analysis. The objectives of this study are to estimate the contamination levels from the serum separation tubes (SST, BD 367983) utilized by the CBP for 13 trace elements (Cr, Mn, Co, As, Se, Sr, Mo, Cd, Sb, Hg, Tl, Pb and U) and to evaluate the feasibility of the use of CBP serum samples for biomonitoring trace elements in human body. METHODS: Serum separation tubes were tested using deionized (DI) water and whole blood and compared with two alternative sampling devices, plasma separation tubes (PST, BD 365047) and acid-cleaned blood tubes (ABT, BD 367856). RESULTS AND CONCLUSIONS: The leaching tests for SSTs with DI water demonstrated that detectable levels of Cr, Mn, Co, Sr, Sb, Pb and U were measured, while Sb was elevated. Tests of PSTs also revealed contamination of Mn, Co, Sr and Sb, with Co and Sr being much higher than those found from SSTs. As a more direct approach to estimate trace element contamination, a 45-day time series was conducted using human blood. The differences in elemental concentrations leached into serum/plasma was not considerable between the three types of sampling tubes for Cr, As, Se, Mo, Cd, Hg and Tl. However, SSTs had far greater concentrations than the ABTs for Mn, Co, Sr, Sb and U. For Co and Sr, the PSTs had higher concentrations throughout the experiment than both ABTs and SSTs. Pb showed lower concentrations from the PSTs than the other tubes; we speculate this may be due to re-suspension of settled cellular materials that are elevated in Pb, or re-dissolution of Pb from these materials. Trace-element measurements from 200 samples archived by the CBP using SSTs suggest that SST contamination was negligible for Se and Mo. For Mn, As, Sr, Cd and Hg, based on our leaching results, only a fraction of these samples had considerably high concentrations (e.g., > 10×) compared to the contamination from the SST. For Cr, Co, Sb, Tl, Pb and U, analyte levels were too low in most samples compared to the contamination from the SSTs. Our study also demonstrated that the PSTs could be a "cleaner" alternative to SSTs for analytes such as Cr, As, Cd, Hg, Tl, Pb and U.

Heavy Metals in California Women Living in a Gold Mining-Impacted Community.

Gold mining activities occurred throughout the foothills of the Sierra Nevada Mountains in California, leaving behind persistent toxic contaminants in the soil, dust, and water that include arsenic and cadmium. Despite a high level of concern among local residents about potential exposure and high breast cancer rates, no biomonitoring data has been collected to evaluate the levels of heavy metals. We conducted a study to characterize the urinary levels of heavy metals among women in this region by working with the community in Nevada County. Sixty women provided urine samples and completed a questionnaire. We examined levels of arsenic, cadmium, and other metals in relation to the length of residency in the area, age, dietary factors, recreational activities, and smoking. We compared urinary metal levels in participants to levels in the United States National Health and Nutrition Examination Survey (NHANES). Overall, study participants had higher urinary levels of arsenic than women in the national sample. Cadmium levels were similar to the national average, although they were elevated in women ≥35 years who had lived in the region for 10 years or more. Arsenic levels were higher among women who smoked, ate fish, ate home-grown produce, and who reported frequent hiking or trail running, although these differences were not statistically significant. This study established a successful community-research partnership, which facilitated community dialogue about possible human health consequences of living in a mining-impacted area.

Biogeochemical factors affecting mercury methylation in sediments of the Venice Lagoon, Italy.

Mercury methylation and sulfate reduction rates, total Hg, and monomethyl Hg in the sediments of the Venice Lagoon (Italy) were measured in June 2005 in order to identify the factors affecting the methylation of inorganic Hg. While the rates of Hg methylation and sulfate reduction were generally higher in the surface layers (0-2.5 cm), the correlation between Hg methylation and sulfate reduction rates was not significant when considering all depths and sites. This discrepancy is discussed considering two factors: the activity of sulfate-reducing bacteria and Hg solubility. The former factor is important in determining the Hg methylation rate in comparable geochemical conditions as evidenced by similar vertical profiles of Hg methylation and sulfate reduction rates in each sediment core. The latter factor was assessed by comparing the Hg methylation rate with the particle-water partition coefficient of Hg. The Hg methylation rates normalized to sulfate reduction rates showed a negative linear correlation with the logarithm of the particle-water partition coefficient of Hg, suggesting that the availability of dissolved Hg is a critical factor affecting Hg methylation. Solid FeS seems to play an important role in controlling the solubility of Hg in Venice Lagoon sediments, where sulfate and iron reductions are the dominant electron-accepting processes. Overall, the production of monomethyl Hg in the Venice Lagoon is controlled by a fine balance between microbial and geochemical processes with key factors being the microbial sulfate reduction rate and the availability of dissolved Hg.

Evaluation of gene expression changes in human primary uroepithelial cells following 24-hr exposures to inorganic arsenic and its methylated metabolites.

Gene expression changes in primary human uroepithelial cells exposed to arsenite and its methylated metabolites were evaluated to identify cell signaling pathway perturbations potentially associated with bladder carcinogenicity. Cells were treated with mixtures of inorganic arsenic and its pentavalent or trivalent metabolites for 24 hr at total arsenic concentrations ranging from 0.06 µM to 18 µM. One series (five samples) was conducted with arsenite and pentavalent metabolites and a second (10 samples) with arsenite and trivalent metabolites. Similar gene expression responses were obtained for pentavalent or trivalent metabolites. A suite of eight gene changes was consistently identified across individuals that reflect effects on key signaling pathways: oxidative stress, protein folding, growth regulation, metallothionine regulation, DNA damage sensing, thioredoxin regulation, and immune response. No statistical significance of trend (NOSTASOT) analysis of these common genes identified lowest observed effect levels (LOELs) from 0.6 to 6.0 µM total arsenic and no observed effect levels (NOELs) from 0.18 to 1.8 µM total arsenic. For the trivalent arsenical mixture, benchmark doses (BMDs) ranged from 0.13 to 0.92 µM total arsenic; benchmark dose lower 95% confidence limits (BMDLs) ranged from 0.09 to 0.58 µM total arsenic. BMDs ranged from 0.53 to 2.7 µM and BMDLs from 0.35 to 1.7 µM for the pentavalent arsenical mixture. Both endpoints varied by a factor of 3 across individuals. Thisstudy is the first to examine gene expression response in primary uroepithelial cells from multiple individuals and to identify no effect levels for arsenical-induced cell signaling perturbations in normal human cells exposed to a biologically plausible concentration range.

Spatial and habitat-based variations in total and methyl mercury concentrations in surficial sediments in the San Francisco Bay-Delta.

Recent studies indicate significant amounts of mercury (Hg) are annually transported into the San Francisco Bay-Delta (Bay-Delta) as a result of historic gold and Hg mining activities. We examined temporal and spatial variation in concentrations of total Hg (Hg(T)) and monomethylmercury (MMHg) in surficial sediments of various ecosystem types in the Bay-Delta. We sampled surficial sediments across the Bay-Delta system and found Hg(T) sediment concentrations in the central Delta were generally 100-200 ng g(-1) and increased westward through Suisun Bay to 250-350 ng g(-1). MMHg concentrations in the central Delta were between 1 and 3 ng g(-1), while those in sediments in the perimeter waterways and adjacent bays were less than 1 ng g(-1). Six sites were monitored monthly for over a year to identify seasonal changes in Hg sediment concentrations. Hgtau sediment concentrations ranged from 48 to 382 ng g(-1) and varied as a function of location not season. However, MMHg concentrations varied seasonally, increasing from 1 ng g(-1) during winter months to 6 ng g(-1) during spring and summer. Transects conducted at three marshes in the central Delta revealed MMHg sediment concentrations of 4-8 ng g(-1) at the interior and 2 ng g(-1) at the exterior of the marshes. Habitat type was a major factor controlling MMHg concentration and the MMHg to Hg(T) ratio in sediments of the Bay-Delta. MMHg was significantly correlated to Hgt (r2 = 0.49) in marsh sediments.