Validation of a semi-quantitative job exposure matrix at a Soderberg aluminum smelter. (17/76)

OBJECTIVES: We tested the validity of a job exposure matrix (JEM) for coal tar pitch volatiles (CTPV) at a Soderberg aluminum smelter. The JEM had been developed by a committee of company hygienists and union representatives for an earlier study of cancer incidence and mortality. Our aim was to test the validity and reliability of the expert-based assignments. METHODS: Personal CTPV exposure measurements (n = 1879) overlapped 11 yr of the JEM. The arithmetic mean was calculated for 35 job/time period combinations (35% of the exposed work history), categorized using the original exposure intervals, and compared with the expert-based assignments. RESULTS: The expert-based and the measurement-based exposure assignments were only moderately correlated (Spearman's rho = 0.42; weighted kappa = 0.39, CI 0.10-0.69). Only 40% of the expert-based medium category assignments were correctly assigned, with better agreement in the low (84%) and high (100%) categories. Pot operation jobs exhibited better agreement (rho = 0.60) than the maintenance and pot shell repair jobs (rho = 0.25). The mid-point value of the medium category was overestimated by 0.3 mg/m(3). CONCLUSIONS: The expert-based exposure assignments may be improved by better characterizing the transitions between exposure categories, by accounting for exposure differences between pot lines and by re-examining the category mid-point values used in calculating the cumulative exposure. Lack of historical exposure measurements often requires reliance on expert knowledge to assess exposure levels. Validating the experts' estimates against available exposure measurements may help to identify weaknesses in the exposure assessment where improvements may be possible, as was shown here.  (+info)

Mortality from obstructive lung diseases and exposure to polycyclic aromatic hydrocarbons among asphalt workers. (18/76)

Work in the asphalt industry has been associated with nonmalignant respiratory morbidity and mortality, but the evidence is not consistent. A historical cohort of asphalt workers included 58,862 men (911,209 person-years) first employed between 1913 and 1999 in companies applying and mixing asphalt in Denmark, Finland, France, Germany, Israel, the Netherlands, and Norway. The relations between mortality from nonmalignant respiratory diseases (including the obstructive lung diseases: chronic bronchitis, emphysema, and asthma) and specific chemical agents and mixtures were evaluated using a study-specific exposure matrix. Mortality from obstructive lung diseases was associated with the estimated cumulative and average exposures to polycyclic aromatic hydrocarbons and coal tar (p values of the test for linear trend = 0.06 and 0.01, respectively). The positive association between bitumen fume exposure and mortality from obstructive lung diseases was weak and not statistically significant; confounding by simultaneous exposure to coal tar could not be excluded. The authors lacked data on smoking and full occupational histories. In conclusion, exposures to polycyclic aromatic hydrocarbons, originating from coal tar and possibly from bitumen fume, may have contributed to mortality from obstructive lung diseases among asphalt workers, but confounding and bias cannot be ruled out as an explanation for the observed associations.  (+info)

Molecular phylogenetic inference from saber-toothed cat fossils of Rancho La Brea. (19/76)

A method for the successful extraction of sequestered cellular DNA from 14,000-year-old fossil bones was developed and applied to asphalt-preserved specimens of the extinct saber-toothed cat, Smilodon fatalis. Two distinct gene segments, the mitochondrial gene for 12S rRNA and nuclear FLA-I (the feline class I major histocompatibility complex gene), from three different individual fossil specimens were cloned and sequenced after PCR amplification. Comparison of fossil-derived DNA sequences to homologous regions in 15 living carnivorous species, including 9 species of Felidae and 6 nonfelids, affirmed the phylogenetic placement of Smilodon within the modern radiation of Felidae distinct from the Miocene paleofelid (Nimravidae) saber-toothed "cat" species. These results raise the prospect of obtaining genetically informative DNA from preserved bones of extinct fossil species, particularly among the 2 million specimens excavated from the asphaltic sediments at Rancho La Brea in metropolitan Los Angeles.  (+info)

Abundance of dioxygenase genes similar to Ralstonia sp. strain U2 nagAc is correlated with naphthalene concentrations in coal tar-contaminated freshwater sediments. (20/76)

We designed a real-time PCR assay able to recognize dioxygenase large-subunit gene sequences with more than 90% similarity to the Ralstonia sp. strain U2 nagAc gene (nagAc-like gene sequences) in order to study the importance of organisms carrying these genes in the biodegradation of naphthalene. Sequencing of PCR products indicated that this real-time PCR assay was specific and able to detect a variety of nagAc-like gene sequences. One to 100 ng of contaminated-sediment total DNA in 25-microl reaction mixtures produced an amplification efficiency of 0.97 without evident PCR inhibition. The assay was applied to surficial freshwater sediment samples obtained in or in close proximity to a coal tar-contaminated Superfund site. Naphthalene concentrations in the analyzed samples varied between 0.18 and 106 mg/kg of dry weight sediment. The assay for nagAc-like sequences indicated the presence of (4.1 +/- 0.7) x 10(3) to (2.9 +/- 0.3) x 10(5) copies of nagAc-like dioxygenase genes per microg of DNA extracted from sediment samples. These values corresponded to (1.2 +/- 0.6) x 10(5) to (5.4 +/- 0.4) x 10(7) copies of this target per g of dry weight sediment when losses of DNA during extraction were taken into account. There was a positive correlation between naphthalene concentrations and nagAc-like gene copies per microgram of DNA (r = 0.89) and per gram of dry weight sediment (r = 0.77). These results provide evidence of the ecological significance of organisms carrying nagAc-like genes in the biodegradation of naphthalene.  (+info)

Application of benzo(a)pyrene and coal tar tumor dose-response data to a modified benchmark dose method of guideline development. (21/76)

Assessment of cancer risk from exposure to polycyclic aromatic hydrocarbons (PAHs) has been traditionally conducted by applying the conservative linearized multistage (LMS) model to animal tumor data for benzo(a)pyrene (BaP), considered the most potent carcinogen in PAH mixtures. Because it has been argued that LMS use of 95% lower confidence limits on dose is unnecessarily conservative, that assumptions of low-dose linearity to zero in the dose response imply clear mechanistic understanding, and that "acceptable" cancer risk rests on a policy decision, an alternative cancer risk assessment approach has been developed. Based in part on the emerging benchmark dose (BMD) method, the modified BMD method we used involves applying a suite of conventional mathematical models to tumor dose-response data. This permits derivation of the average dose corresponding to 5% extra tumor incidence (BMD0.05) to which a number of modifying factors are applied to achieve a guideline dose, that is, a daily dose considered safe for human lifetime exposure. Application of the modified BMD method to recent forestomach tumor data from BaP ingestion studies in mice suggests a guideline dose of 0.08 microg/kg/day. Based on this and an understanding of dietary BaP, and considering that BaP is a common contaminant in soil and therefore poses human health risk via soil ingestion, we propose a BaP soil guideline value of 5 ppm (milligrams per kilogram). Mouse tumor data from ingestion of coal tar mixtures containing PAHs and BaP show that lung and not forestomach tumors are most prevalent and that BaP content cannot explain the lung tumors. This calls into question the common use of toxicity equivalence factors based on BaP for assessing risk from complex PAH mixtures. Emerging data point to another PAH compound--H-benzo(c)fluorene--as the possible lung tumorigen.  (+info)

Squamous cell carcinoma of the skin and coal tar creosote exposure in a railroad worker. (22/76)

A 50-year-old male railroad worker presented to his primary care physician with an erythematous, tender skin lesion on the right knee; a biopsy of this lesion revealed squamous cell carcinoma in situ. The site of the lesion was sun-protected but had been associated with 30 years of creosote-soaked clothing. In this article, we review dermal and other malignancies associated with creosote, along with creosote occupational exposures and exposure limits. This is a unique case, given the lack of other, potentially confounding, polyaromatic hydrocarbons and the sun-protected location of the lesion.  (+info)

Cytogenetic and immunological changes after dermal exposure to polycyclic aromatic hydrocarbons and UV radiation. (23/76)

Goeckerman's therapy (GT), which combines exposure to coal tar (polycyclic aromatic hydrocarbons - PAHs) and UV radiation (UV) is often used as the first option for treatment of psoriasis. However, PAHs and UV represent mutagenic, carcinogenic and immunotoxic agents. Therefore GT can represent a health risk for the patients. The group under observation consisted of thirty patients undergoing GT. Before and after the treatment, blood samples were collected and chromosomal aberrations and selected immunological markers were determined. The relationships between chromosomal aberrations and immunological markers and the extent (duration) of exposure to GT were evaluated. The Psoriasis Area and Severity Index (PASI) score confirmed the high efficacy of GT. However, significantly elevated levels of chromosomal aberrations of peripheral lymphocytes were also found after the therapy (p<0.001). The levels of chromosomal abnormalities correlated to the extent and the total duration of exposure to PAHs (r = 0.682, p<0.01 and r = 0.605, p<0.05). After the therapy, significantly decreased levels of IgE, IgM isotypes of immunoglobulin, alpha(2)-macroglobulin and transferrin together with beta(2)-microglobulin were found. From the immunological markers listed above only the decreased level of alpha(2)-macroglobulin correlated to the extent of exposure to PAHs (r = -0.568, p<0.05). No correlation was found between chromosomal aberrations, significantly changed immunological markers and the duration of UV exposure. Our study revealed that GT has a significant impact on both genetic and immunological parameters of psoriatic patients. The results indicate that GT could increase genotoxic risk and modulates immunity of treated patients.  (+info)

Selected immunological changes in patients with Goeckerman's therapy TNF-alpha, sE-selectin, sP-selectin, sICAM-1 and IL-8. (24/76)

Psoriasis is one of the most frequent inflammatory skin diseases in which abnormal individual immune reactivity plays an important role. The aim of the present study was to describe selected immunological changes, concerning pro-inflammatory cytokines (TNF-alpha, IL-8) and adhesion molecules (sE-selectin, sP-selectin, sICAM-1), in 56 patients cured by Goeckerman's therapy (GT). GT includes dermal application of crude coal tar (containing polycyclic aromatic hydrocarbons) and exposure to UV radiation. When compared with the control group (healthy blood donors), the patients before GT had significantly increased serum levels of sE-selectin (p<0.001), sP-selectin (p<0.001), sICAM-1 (p<0.001) and IL-8 (p<0.001). Significantly decreased serum levels of sE-selectin (p<0.05) and significantly increased serum levels of IL-8 (p<0.05) were found after GT therapy. Serum levels of sICAM significantly correlated with the disease activity and with serum levels of sE-selectin. The level of PASI score (Psoriasis Area and Severity Index) significantly decreased after GT (p<0.001) and confirms the high efficiency GT. These findings confirmed that pro-inflammatory chemokine (IL-8) and adhesion molecules (sE-selectin, sP-selectin, sICAM-1) play an important role in the development and regulation of inflammation in psoriasis. Determination of sE-selectin and sICAM seems to be a promising marker of psoriasis's activity. Chemokine pathway (IL-8) and TNF-alpha activity seem to be modulated by Goeckerman's therapy (polycyclic aromatic hydrocarbons).  (+info)