Zur Kristallstruktur der intermetallischen Phasen MoAs und Mo5AS4

Es wird ein Verfahren zur Herstellung kleiner Einkristalle von MoAs und Mo5As4 durch gerichtete Erstarrung von GaAs- (Mo, As) -Eutektika beschrieben. Die Kristallstrukturen von MoAs und Mo5As4 wurden auf röntgenographischem Weg an Hand von Einkristallen und Pulverproben untersucht. MoAs kristallisiert im MnP-Struktur-Typ mit den Gitterkonstanten a = 5,978Å, b=3,360Å, c = 6,415 A. Mo5As4 besitzt eine Ti5Te4-Struktur; die Gitterkonstanten betragen: α = 9,591 A, c = 3,281Å.

Die Struktur von Mo5As4 wird diskutiert.

Personal and indoor PM2.5 exposure from burning solid fuels in vented and unvented stoves in a rural region of China with a high incidence of lung cancer

The combustion of biomass and coal is the dominant source of household air pollution (HAP) in China, and contributes significantly to the total burden of disease in the Chinese population. To characterize HAP exposure related to solid fuel use and ventilation patterns, an exposure assessment study of 163 nonsmoking female heads of households enrolled from 30 villages was conducted in Xuanwei and Fuyuan, two neighboring rural counties with high incidence of lung cancer due to the burning of smoky coal (a bituminous coal, which in health evaluations is usually compared to smokeless coal--an anthracite coal available in some parts of the area). Personal and indoor 24-h PM2.5 samples were collected over two consecutive days in each household, with approximately one-third of measurements retaken in a second season. The overall geometric means (GM) of personal PM2.5 concentrations in Xuanwei and Fuyuan were 166 [Geometric Standard Deviation (GSD):2.0] and 146 (GSD:1.9) μg/m(3), respectively, which were similar to the indoor PM2.5 air concentrations [GM(GSD):162 (2.1) and 136 (2.0) μg/m(3), respectively]. Personal PM2.5 was moderately highly correlated with indoor PM2.5 (Spearman r = 0.70, p < 0.0001). Burning wood or plant materials (tobacco stems, corncobs etc.) resulted in the highest personal PM2.5 concentrations (GM:289 and 225 μg/m(3), respectively), followed by smoky coal, and smokeless coal (GM:148 and 115 μg/m(3), respectively). PM2.5 levels of vented stoves were 34-80% lower than unvented stoves and firepits across fuel types. Mixed effect models indicated that fuel type, ventilation, number of windows, season, and burning time per stove were the main factors related to personal PM2.5 exposure. Lower PM2.5 among vented stoves compared with unvented stoves and firepits is of interest as it parallels the observation of reduced risks of malignant and nonmalignant lung diseases in the region.

Occupational exposure to trichloroethylene and serum concentrations of IL-6, IL-10, and TNF-alpha

To evaluate the immunotoxicity of trichloroethylene (TCE), we conducted a cross-sectional molecular epidemiology study in China of workers exposed to TCE. We measured serum levels of IL-6, IL-10, and TNF-α, which play a critical role in regulating various components of the immune system, in 71 exposed workers and 78 unexposed control workers. Repeated personal exposure measurements were taken in workers before blood collection using 3 M organic vapor monitoring badges. Compared to unexposed workers, the serum concentration of IL-10 in workers exposed to TCE was decreased by 70% (P = 0.001) after adjusting for potential confounders. Further, the magnitude of decline in IL-10 was >60% and statistically significant in workers exposed to <12 ppm as well as in workers with exposures ≥ 12 ppm of TCE, compared to unexposed workers. No significant differences in levels of IL-6 or TNF-α were observed among workers exposed to TCE compared to unexposed controls. Given that IL-10 plays an important role in immunologic processes, including mediating the Th1/Th2 balance, our findings provide additional evidence that TCE is immunotoxic in humans.

Abstract 112: Transcriptomic changes in the oral mucosal epithelium reflect the physiologic response to indoor burning of solid fuels

RATIONALE: Human exposure to indoor smoke emissions from the domestic burning of solid fuels (e.g. coal, wood, plant materials) is a major cause of morbidity and mortality that affects nearly half of the world's population. While epidemiologic studies on the health impact of indoor air pollution (IAP) have yielded valuable insights from the use of various exposure assessments (e.g. personal and area air sampling, urinary metabolites), there is a need to connect these exposure measures to biomarkers of the host's physiologic response to exposure. We have previously shown that gene-expression (GE) profiles in the upper airway epithelium are affected by tobacco smoke. Thus, we sought to determine whether transcriptomic changes in the oral mucosal epithelium might also capture physiologic responses to IAP from the burning of solid fuels. METHODS: Buccal mucosa epithelial cell scrapings were collected from healthy, non-smoking female subjects in rural Xuanwei, China, where female lung cancer rates are among the highest in the world. Benzo(a)pyrene (BaP) exposure levels from indoor burning of solid fuels (primarily coal) for cooking and heating were measured by personal in-home air monitoring. RNA from 18 samples was extracted and processed onto Affymetrix Gene 1.0 ST arrays. Student's t-test and DAVID were used to identify and characterize genes that vary between relatively high levels of BaP exposure (n=8; BaP 99.0 +/- 45.9) and low (n=10; BaP 16.2 +/- 6.1) exposure. Using GSEA, results were compared to independent airway epithelial GE profiles that distinguish current smokers from never smokers and bronchial GE profiles in subjects with and without lung cancer. RESULTS: We identified 227 genes that were differentially expressed between subjects with high and low BaP exposure (p&lt;0.01). Genes elevated with high BaP exposure were enriched for genes involved in the activation of apoptosis and the Toll-Like Receptor Signaling pathway. Genes that we have previously shown to have altered expression in the bronchial, buccal, and nasal epithelium of current smokers relative to never smokers were enriched among the genes associated with BaP exposure (GSEA; q&lt;0.01). There was also a significant enrichment for bronchial epithelial airway genes that were altered in subjects with and without lung cancer in a previous report (GSEA; q&lt;0.01). CONCLUSION: Buccal epithelial GE is affected by BaP exposure in a population that uses coal and other solid fuels for indoor cooking and heating among healthy women in Xuanwei, China. Solid fuel emissions may elicit some of the same transcriptomic responses as cigarette smoke and lung cancer. This demonstrates the feasibility of using non-invasively collected buccal GE profiling to assess physiologic responses to other inhaled toxins such as coal smoke in population-based studies.

Citation Format: Teresa W. Wang, Qing Lan, Bozena Krystyna, Nathaniel Rothman, Roberta Florido, Wei Hu, Katrina Steiling, Gang Liu, Ji Xiao, Yuriy Alekseyev, Jun Xu, Fusheng Wei, H. Dean Hosgood, Boris Reiss, George Downward, Marc Lenburg, Roel Vermeulen, Avrum Spira. Transcriptomic changes in the oral mucosal epithelium reflect the physiologic response to indoor burning of solid fuels. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 112. doi:10.1158/1538-7445.AM2013-112

Occupational exposure to formaldehyde and alterations in lymphocyte subsets

BACKGROUND

Formaldehyde is used in many occupational settings, most notably in manufacturing, health care, and embalming. Formaldehyde has been classified as a human carcinogen, but its mechanism of action remains uncertain.

METHODS

We carried out a cross-sectional study of 43 formaldehyde-exposed workers and 51 unexposed age and sex-matched controls in Guangdong, China to study formaldehyde's early biologic effects. To follow up our previous report that the total lymphocyte count was decreased in formaldehyde-exposed workers compared with controls, we evaluated each major lymphocyte subset (i.e., CD4(+) T cells, CD8(+) T cells, natural killer [NK] cells, and B cells) and T cell lymphocyte subset (CD4(+) naïve and memory T cells, CD8(+) naïve and memory T cells, and regulatory T cells). Linear regression of each subset was used to test for differences between exposed workers and controls, adjusting for potential confounders.

RESULTS

Total NK cell and T cell counts were about 24% (P = 0.037) and 16% (P = 0.0042) lower, respectively, among exposed workers. Among certain T cell subsets, decreased counts among exposed workers were observed for CD8(+) T cells (P = 0.026), CD8(+) effector memory T cells (P = 0.018), and regulatory T cells (CD4(+) FoxP3(+) : P = 0.04; CD25(+) FoxP3(+) : P = 0.008).

CONCLUSIONS

Formaldehyde-exposed workers experienced decreased counts of NK cells, regulatory T cells, and CD8(+) effector memory T cells; however, due to the small sample size; these findings need to be confirmed in larger studies.

Alterations in serum immunoglobulin levels in workers occupationally exposed to trichloroethylene

Trichloroethylene (TCE) has been associated with a variety of immunotoxic effects and may be associated with an increased risk of non-Hodgkin lymphoma (NHL). Altered serum immunoglobulin (Ig) levels have been reported in NHL patients and in animals exposed to TCE. Recently, we reported that occupational exposure to TCE is associated with immunosuppressive effects and immune dysfunction, including suppression of B-cell counts and activation, even at relatively low levels. We hypothesized that TCE exposure would also affect Ig levels in humans. We measured serum levels of IgG, IgM and IgE, by enzyme-linked immunosorbent assay, in TCE-exposed workers (n = 80) and unexposed controls (n = 45), matched by age and gender, in a cross-sectional, molecular epidemiology study of occupational exposure to TCE in Guangdong, China. Exposed workers had about a 17.5% decline in serum levels of IgG compared with unexposed controls (P = 0.0002). Similarly, serum levels of IgM were reduced by about 38% in workers exposed to TCE compared with unexposed controls (P < 0.0001). Serum levels of both IgG and IgM were significantly decreased in workers exposed to TCE levels below 12 p.p.m., the median exposure level. Adjustment for B-cell counts had minimal impact on our findings. IgE levels were not significantly different between exposed and control subjects. These results provide further evidence that TCE is immunotoxic at relatively low exposure levels and provide additional biologic plausibility for the reported association of TCE with NHL.

Elevated urinary levels of kidney injury molecule-1 among Chinese factory workers exposed to trichloroethylene

Epidemiological studies suggest that trichloroethylene (TCE) exposure may be associated with renal cancer. The biological mechanisms involved are not exactly known although nephrotoxicity is believed to play a role. Studies on TCE nephrotoxicity among humans, however, have been largely inconsistent. We studied kidney toxicity in Chinese factory workers exposed to TCE using novel sensitive nephrotoxicity markers. Eighty healthy workers exposed to TCE and 45 comparable unexposed controls were included in the present analyses. Personal TCE exposure measurements were taken over a 2-week period before urine collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration permissible exposure limit (100 ppm 8h TWA), with a mean (SD) of 22.2 (35.9) ppm. Kidney injury molecule-1 (KIM-1) and Pi-glutathione S transferase (GST) alpha were elevated among the exposed subjects as compared with the unexposed controls with a strong exposure-response association between individual estimates of TCE exposure and KIM-1 (P < 0.0001). This is the first report to use a set of sensitive nephrotoxicity markers to study the possible effects of TCE on the kidneys. The findings suggest that at relatively low occupational exposure levels a toxic effect on the kidneys can be observed. This finding supports the biological plausibility of linking TCE exposure and renal cancer.

Decreased Numbers of CD4(+) Naive and Effector Memory T Cells, and CD8(+) Naïve T Cells, are Associated with Trichloroethylene Exposure

Trichloroethylene (TCE) is a volatile chlorinated organic compound that is commonly used as a solvent for lipophilic compounds. Although recognized as an animal carcinogen, TCE's carcinogenic potential in humans is still uncertain. We have carried out a cross-sectional study of 80 workers exposed to TCE and 96 unexposed controls matched on age and sex in Guangdong, China to study TCE's early biologic effects. We previously reported that the total lymphocyte count and each of the major lymphocyte subsets (i.e., CD4(+) T cells, CD8(+) T cells, natural killer cells, and B cells) were decreased in TCE-exposed workers compared to controls, suggesting a selective effect on lymphoid progenitors, and/or lymphocyte survival. To explore which T lymphocyte subsets are affected in the same study population, we investigated the effect of TCE exposure on the numbers of CD4(+) naïve and memory T cells, CD8(+) naïve and memory T cells, and regulatory T cells by FACS analysis. Linear regression of each subset was used to test for differences between exposed workers and controls adjusting for potential confounders. We observed that CD4(+) and CD8(+) naïve T cell counts were about 8% (p = 0.056) and 17% (p = 0.0002) lower, respectively, among exposed workers. CD4(+) effector memory T cell counts were decreased by about 20% among TCE-exposed workers compared to controls (p = 0.001). The selective targeting of TCE on CD8(+) naive and possibly CD4(+) naive T cells, and CD4(+) effector memory T cells, provide further insights into the immunosuppression-related response of human immune cells upon TCE exposure.

Combustion-derived nanoparticle exposure and household solid fuel use in Xuanwei and Fuyuan, China

Combustion-derived nanoparticles (CDNPs) have not been readably measurable until recently. We conducted a pilot study to determine CDNP levels during solid fuel burning. The aggregate surface area of CDNP (μm(2)/cm(3)) was monitored continuously in 15 Chinese homes using varying fuel types (i.e. bituminous coal, anthracite coal, wood) and stove types (i.e. portable stoves, stoves with chimneys, firepits). Information on fuel burning activities was collected and PM(2.5) levels were measured. Substantial exposure differences were observed during solid fuel burning (mean: 228.1 μm(2)/cm(3)) compared to times without combustion (mean: 14.0 μm(2)/cm(3)). The observed levels during burning were reduced by about four-fold in homes with a chimney (mean: 92.1 μm(2)/cm(3); n = 9), and effects were present for all fuel types. Each home's CDNP measurement was only moderately correlated with the respective PM(2.5) measurements (r (2) = 0.43; p = 0.11). Our results indicate that household coal and wood burning contributes to indoor nanoparticle levels, which are not fully reflected in PM(2.5) measurements.

Abstract 1876: Assessment of exposure to potential lung carcinogens in Xuanwei and Fuyuan, China: Particulate exposure from cooking and heating stoves

Residents in Xuanwei, China have the highest lung cancer incidence rates in China for both men and women, despite the fact that almost all women are non-smokers. Several lines of research have provided strong support that the excess lung cancer rate in this region is caused primarily by emissions from smoky coal exposure. We have carried out a hospital-based case-control study of non-smoking female lung cancer in Xuanwei and its neighboring county, Fuyuan, to identify which constituents of coal combustion emissions and other indoor environmental exposures are causing the high lung cancer rates in this region. In order to develop individual estimates of exposure to known or suspected lung carcinogens, we designed a comprehensive exposure assessment study of 163 households in this region to evaluate exposure to PAHs, PM2.5, silica, and other exposures from coal and wood burning. Homes that used three main fuel types (i.e., smoky coal, smokeless coal and wood), and eight stove types [e.g., firepit, fixed or portable stove, with or without ventilation] were identified and households were sampled on two consecutive days. Up to 30 households were selected for each combination of fuel and stove type. A subgroup of 53 households was measured at two time-points during the study year (e.g. summer and winter). The female head of each household was asked to wear a 24-hour personal PM2.5 air sampler at the same time that 24-hour area air sampling was employed in the main living area. Personal and area particulate matter samples (PM2.5) were collected in each home. These samples were also used to quantify particle bound PAHs including BaP (by GC/MS), elemental components (by XRF and ICP/MS), and silica (by XRD). XAD2 samples were collected for the quantification of gaseous PAHs. Other samples, including radon and organic vapor, fuel and ash were also obtained. We also collected information on potential factors that could influence exposure, such as house characteristics, stove type, fuel type and use, amount of fuel used, amount of time spent in each room. Initial analyses show that people using wood burned in firepits were exposed to the highest levels of PM2.5 measured in area (536.3±370.5 µg/m3) and personal samples(419.8±283.3 µg/m3). Burning smokeless coal in a high stove with a chimney was associated with the lowest exposure to PM2.5 (62.2±34.1 µg/m3, 62.5±29.9 µg/m3 for area and personal samples, respectively). These data show that there is a wide range of exposure to PM2.5 in this population. These data and other exposure information from this study will be used in the future to model environmental exposures and risk of lung cancer in this special, high risk population.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1876. doi:10.1158/1538-7445.AM2011-1876

Abstract 4646: Occupational exposure to trichloroethylene and plasma concentrations of IL6, IL10, and TNF alpha

Trichloroethylene (TCE) is a chlorinated solvent primarily used as a vapor degreaser in many industries. TCE is currently classified by IARC as probably carcinogenic to humans (Group 2A), and has been associated with non-Hodgkin lymphoma (NHL) in some epidemiological studies, although the findings have been inconsistent. To explore the biologic plausibility that TCE may be a lymphomagen, we conducted a cross-sectional study of workers exposed to TCE in Guangzhou, China and tested if plasma levels of the cytokines IL6, IL10, and TNF-alpha, which play a critical role in regulating various components of the immune system, were altered in exposed workers. We enrolled 80 workers from factories where TCE was used as well as 96 unexposed controls matched by sex and age from food and clothes manufacturing factories. Personal exposure measurements were taken over a three-week period, two to three per subject, in the exposed subjects for a full work shift using a 3M badge, as well as for a subgroup of the control workers. Blood samples were collected from each subject, and plasma concentrations of IL6, IL10, and TNF-alpha were measured by ELISA. Linear regression using the natural logarithm of each endpoint and adjusting for potential confounders was used to test for differences in marker concentrations between controls and exposed workers. The mean TCE exposure level in exposed subjects was 23.9 ppm (95% C.I. 14.2-33.6 ppm). Compared to unexposed workers, the plasma concentration of IL10 in workers exposed to TCE was decreased by more than 50% compared to controls (p=0.003), while there was no difference in levels of IL6 or TNF-alpha in TCE exposed workers and controls. IL10 plays a critical role in mediating the Th1/Th2 balance, apoptosis, and regulation of inflammation. Genotypes associated with altered IL10 expression have also been associated with the development and progression of NHL. Given that immunologic alterations are suspected to play a role in lymphomagenesis, and IL10 plays an important role in immunologic processes, our findings provide some support for the biologic plausibility that TCE is associated with lymphoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4646. doi:10.1158/1538-7445.AM2011-4646

CSA: the online portal for determining the clinical standing of ceramic restorations in practice

For the individual dentist, the Ceramic Success Analysis (CSA) is atried and tested internet-based platform for monitoring the clinical success of all-ceramic restorations. After compiling an insertion protocol and recording the findings from regular clinical follow-up examinations, an analysis follows which culminates in the re-evaluation of the indication and the treatment approach. The evaluations of the 12-year results confirm a high success rate for all-ceramic restorations. Factors which influence the long-term success are: tooth vitality, an indicated crown, the use of a two-bottle dentin adhesive, and the placement of rubber-dam in the adhesive cementation technique.

Occupational exposure to trichloroethylene is associated with a decline in lymphocyte subsets and soluble CD27 and CD30 markers

Occupational cohort and case-control studies suggest that trichloroethylene (TCE) exposure may be associated with non-Hodgkin lymphoma (NHL) but findings are not consistent. There is a need for mechanistic studies to evaluate the biologic plausibility of this association. We carried out a cross-sectional molecular epidemiology study of 80 healthy workers that used TCE and 96 comparable unexposed controls in Guangdong, China. Personal exposure measurements were taken over a three-week period before blood collection. Ninety-six percent of workers were exposed to TCE below the current US Occupational Safety and Health Administration Permissible Exposure Limit (100 p.p.m. 8 h time-weighted average), with a mean (SD) of 22.2 (36.0) p.p.m. The total lymphocyte count and each of the major lymphocyte subsets including CD4+ T cells, CD8+ T cells, natural killer (NK) cells and B cells were significantly decreased among the TCE-exposed workers compared with controls (P < 0.05), with evidence of a dose-dependent decline. Further, there was a striking 61% decline in sCD27 plasma level and a 34% decline in sCD30 plasma level among TCE-exposed workers compared with controls. This is the first report that TCE exposure under the current Occupational Safety and Health Administration workplace standard is associated with a decline in all major lymphocyte subsets and sCD27 and sCD30, which play an important role in regulating cellular activity in subsets of T, B and NK cells and are associated with lymphocyte activation. Given that altered immunity is an established risk factor for NHL, these results add to the biologic plausibility that TCE is a possible lymphomagen.

Occupational exposure to formaldehyde, hematotoxicity, and leukemia-specific chromosome changes in cultured myeloid progenitor cells

There are concerns about the health effects of formaldehyde exposure, including carcinogenicity, in light of elevated indoor air levels in new homes and occupational exposures experienced by workers in health care, embalming, manufacturing, and other industries. Epidemiologic studies suggest that formaldehyde exposure is associated with an increased risk of leukemia. However, the biological plausibility of these findings has been questioned because limited information is available on the ability of formaldehyde to disrupt hematopoietic function. Our objective was to determine if formaldehyde exposure disrupts hematopoietic function and produces leukemia-related chromosome changes in exposed humans. We examined the ability of formaldehyde to disrupt hematopoiesis in a study of 94 workers in China (43 exposed to formaldehyde and 51 frequency-matched controls) by measuring complete blood counts and peripheral stem/progenitor cell colony formation. Further, myeloid progenitor cells, the target for leukemogenesis, were cultured from the workers to quantify the level of leukemia-specific chromosome changes, including monosomy 7 and trisomy 8, in metaphase spreads of these cells. Among exposed workers, peripheral blood cell counts were significantly lowered in a manner consistent with toxic effects on the bone marrow and leukemia-specific chromosome changes were significantly elevated in myeloid blood progenitor cells. These findings suggest that formaldehyde exposure can have an adverse effect on the hematopoietic system and that leukemia induction by formaldehyde is biologically plausible, which heightens concerns about its leukemogenic potential from occupational and environmental exposures.

Powdering or spraying

Application--especially in combination with the new camera--is so easy and advantageous that it has advanced to become the standard procedure in our practice. Potential for improvement still exists in the stiffness of the cannula, in a release mechanism located separately from the cannula and in the impudent demand to completely do away with powder and spray. Despite announcements to the contrary by alternative systems, the fulfilment of this desire appears to be a long way off.

Challenges of exposure assessment for health studies in the aftermath of chemical incidents and disasters

Exposure assessment during and after acute chemical incidents and disasters is essential for health studies that may follow. During chemical incidents, the focus usually lies on risk assessment and afterward attention shifts toward possible (long-term) health effects. This may lead to insufficient available data on exposure to study the association between exposure and health outcome, and collection of additional exposure data is often required. Literature on health studies conducted after several chemical incidents was reviewed to obtain better insight on the needs of health studies. Four different types of scenarios were distinguished based on when exposure data were collected and the exposure data used for health studies. These four scenarios gave insight on exposure data needed for conclusive health studies and when different methods of exposure data collection should be used. Literature indicated that adequate and rapid exposure assessment during chemical incidents is vital for health studies, because data that are not collected during or directly after an incident may be irretrievably lost. Poor exposure assessment is not always the only problem in health studies. Problems in health studies including poor exposure assessment may be prevented when the general design and needs of health studies are taken into account when designing contingency plans. Together with measures that will help facilitate funding, design, and coordination of health studies, disaster management programs should, among others, prepare for methods that lead to a swift identification of released substances, determination of concentrations and dispersion of released substances, designing basic questionnaire outlines, and rapid evaluation of the usefulness and necessity of employing biological sampling.