Use of wood stoves and risk of cancers of the upper aero-digestive tract: a case-control study.
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BACKGROUND: Incidence rates for cancers of the upper aero-digestive tract in Southern Brazil are among the highest in the world. A case-control study was designed to identify the main risk factors for carcinomas of mouth, pharynx, and larynx in the region. We tested the hypothesis of whether use of wood stoves is associated with these cancers. METHODS: Information on known and potential risk factors was obtained from interviews with 784 cases and 1568 non-cancer controls. We estimated the effect of use of wood stove by conditional logistic regression, with adjustment for smoking, alcohol consumption and for other sociodemographic and dietary variables chosen as empirical confounders based on a change-in-estimate criterion. RESULTS: After extensive adjustment for all the empirical confounders the odds ratio (OR) for all upper aero-digestive tract cancers was 2.68 (95% confidence interval [CI] : 2.2-3.3). Increased risks were also seen in site-specific analyses for mouth (OR = 2.73; 95% CI: 1.8-4.2), pharyngeal (OR = 3.82; 95% CI: 2.0-7.4), and laryngeal carcinomas (OR = 2.34; 95% CI: 1.2-4.7). Significant risk elevations remained for each of the three anatomic sites and for all sites combined even after we purposefully biased the analyses towards the null hypothesis by adjusting the effect of wood stove use only for positive empirical confounders. CONCLUSIONS: The association of use of wood stoves with cancers of the upper aero-digestive tract is genuine and unlikely to result from insufficient control of confounding. Due to its high prevalence, use of wood stoves may be linked to as many as 30% of all cancers occurring in the region. (+info)
Effects of 2 low-fat stanol ester-containing margarines on serum cholesterol concentrations as part of a low-fat diet in hypercholesterolemic subjects.
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BACKGROUND: Full-fat sitostanol ester-containing margarine reduces serum total and LDL cholesterol, but the effect of plant stanol ester-containing margarine as part of a low-fat, low-cholesterol diet has not been studied. OBJECTIVE: We investigated the cholesterol-lowering effects of 2 novel, low-fat stanol ester-containing margarines as part of a low-fat diet recommended for hypercholesterolemic subjects. DESIGN: In a parallel, double-blind study, 55 hypercholesterolemic subjects were randomly assigned after a 4-wk high-fat diet (baseline) to 3 low-fat margarine groups: wood stanol ester-containing margarine (WSEM), vegetable oil stanol ester-containing margarine (VOSEM), and control margarine (no stanol esters). The groups consumed the margarines for 8 wk as part of a diet resembling that of the National Cholesterol Education Program's Step II diet. The daily mean total stanol intake was 2.31 and 2.16 g in the WSEM and VOSEM groups, respectively. RESULTS: During the experimental period, the reduction in serum total cholesterol was 10.6% (P < 0.001) and 8.1% (P < 0.05) greater and in LDL cholesterol was 13.7% (P < 0.01) and 8.6% (P = 0.072) greater in the WSEM and VOSEM groups, respectively, than in the control group. Serum campesterol concentrations decreased 34.5% and 41.3% (P < 0.001) in the WSEM and VOSEM groups, respectively. Serum HDL cholesterol, sitostanol, campestanol, beta-carotene, and fat-soluble vitamin concentrations did not change significantly from baseline. CONCLUSIONS: We conclude that the low-fat, plant stanol ester-containing margarines are effective cholesterol-lowering products in hypercholesterolemic subjects when used as part of a low-fat, low-cholesterol diet. They offer an additional, clinically significant reduction in serum cholesterol concentrations to that obtained with a low-fat diet alone. (+info)
Toxicity of combustion products from burning polymers: development and evaluation of methods.
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Laboratory and room-scale experiments were conducted with natural and synthetic polymers: cotton, paper, wood, wool, acetate, acrylic, nylon, and urethane. Smoke and off-gases from single materials were generated in a dual-compartment 110-liter exposure chamber. Multicomponent, composite fuel loads were burned within a 100 m(3) facility subdivided into rooms. In chamber experiments, mortality depended on the amount of material burned, i.e., fuel consumption (FC). Conventional dose (FC)/mortality curves were obtained, and the amount of fuel required to produce 50% mortality (FC(50)) was calculated. With simple flame ignition, cotton was the only material that produced smoke concentrations lethal to rats; FC(50) values for cotton ranged from 2 g to 9 g, depending on the configuration of the cotton sample burned. When supplemental conductive heat was added to flame ignition, the following FC(50) values were obtained; nylon, 7 g; acrylic, 8 g; newsprint, 9 g; cotton, 10 g; and wood, 11 g. Mortality resulting from any given material depended upon the specific conditions employed for its thermal decomposition. Toxicity of off-gasses from pyrolysis of phosphorus-containing trimethylol propane-polyurethane foams was markedly decreased by addition of a flame ignition source. Further studies are needed to determine the possible relevance of single-material laboratory scale smoke toxicity experiments. Room-scale burns were conducted to assess the relative contributions of single materials to toxicity of smoke produced by a multicomponent self-perpetuating fire. Preliminary results suggest that this approach permits a realistic evaluation of the contribution of single materials to the toxicity of smoke from residential fires. (+info)
Determinants of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment.
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In a lumber mill in the northern inland region of British Columbia, Canada, we measured inhalable particulate, resin acid, and monoterpene exposures, and estimated wood dust exposures. Potential determinants of exposure were documented concurrently, including weather conditions, tree species, wood conditions, jobs, tasks, equipment used, and certain control measures. Over 220 personal samples were taken for each contaminant. Geometric mean concentrations were 0.98 mg/m3 for inhalable particulate, 0.49 mg/m3 for estimated wood dust, 8.04 micrograms/m3 for total resin acids, and 1.11 mg/m3 for total monoterpenes. Multiple regression models for all contaminants indicated that spruce and pine produced higher exposures than alpine fir or mixed tree species, cleaning up sawdust increased exposures, and personnel enclosure was an effective means of reducing exposures. Sawing wood in the primary breakdown areas of the mill was the main contributor to monoterpene exposures, so exposures were highest for the barker operator, the head rig operator, the canter operator, the board edgers, and a roving utility worker in the sawmill, and lowest in the planer mills (after kiln drying of the lumber) and yard. Cleaning up sawdust, planing kiln-dried lumber, and driving mobile equipment in the yard substantially increased exposures to both inhalable particulate and estimated wood dust. Jobs at the front end of the sawmill where primary breakdown of the logs takes place had lower exposures. Resin acid exposures followed a similar pattern, except that yard driving jobs did not increase exposures. (+info)
Biomass cooking fuels and prevalence of tuberculosis in India.
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OBJECTIVES: To examine the relation between use of biomass cooking fuels (wood or dung) and prevalence of active tuberculosis in India. METHODS: The analysis is based on 260,162 persons age 20 and over in India's 1992-93 National Family Health Survey. Logistic regression is used to estimate the effects of biomass fuel use on prevalence of active tuberculosis, as reported by household heads, after controlling for a number of potentially confounding variables. RESULTS: Persons living in households that primarily use biomass for cooking fuel have substantially higher prevalence of active tuberculosis than persons living in households that use cleaner fuels (odds ratio [OR] = 3.56; 95% confidence interval [CI] = 2.82-4. 50). This effect is reduced somewhat when availability of a separate kitchen, house type, indoor crowding, age, gender, urban or rural residence, education, religion, caste or tribe, and geographic region are statistically controlled (OR = 2.58; 95% CI = 1.98-3.37). Fuel type also has a large effect when the analysis is done separately for men (OR = 2.46; 95% CI = 1.79-3.39) and women (OR = 2. 74; 95% CI = 1.86-4.05) and separately for urban areas (OR = 2.29; 95% CI = 1.61-3.23) and rural areas (OR = 2.65; 95% CI = 1.74-4.03). The analysis also indicates that, among persons age 20 years and over, 51% of the prevalence of active tuberculosis is attributable to cooking smoke. CONCLUSIONS: Results strongly suggest that use of biomass fuels for cooking substantially increases the risk of tuberculosis in India. (+info)
A field comparison of inhalable and thoracic size selective sampling techniques.
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We measured inhalable, thoracic, and so-called "total" wood dust exposure in British Columbia lumber mill workers. Particle-size selective sampling was conducted using the GSP and Seven hole inhalable samplers, the PEM thoracic sampler and the 37-mm closed-face cassette "total" sampler. All measurements were full-shift personal samples, obtained from randomly selected workers. We obtained intersampler comparison data for the following pairs of instruments: GSP and 37-mm sampler; GSP and seven-hole sampler (SHS); and PEM and 37-mm sampler. The intersampler measurement ratios were estimated as: GSP/37-mm sampler = 4.2; GSP/SHS = 1.7; and PEM/37-mm sampler = 1.6. The GSP/37-mm sampler ratio is consistent with previously reported findings, while PEM/37-mm sampler and GSP/SHS ratios were both larger than expected. We found that in all comparisons, the measurement ratio had significant variability that was greatest at low ambient dust concentrations. Although it was not possible to attribute the source of the variability to specific sampler types, we concluded that the GSP sampler might be susceptible to "projectile" particles not normally aspirated, and may be vulnerable to direct aspiration of dust from accidentally contacted surfaces. The PEM was designed for environmental monitoring, and it is possible that it is unsuited to the higher particulate concentrations found in some occupational settings. Disparities among inhalable sampling techniques such as that between GSP and SHS should be investigated further in light of the proposed adoption of the inhalable method as an industrial standard. (+info)
Spectroscopic properties of oxidation species generated in the lignin of wood fibers by a laccase catalyzed treatment: electronic hole state migration and stabilization in the lignin matrix.
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A laccase catalyzed oxidative treatment of wood pulp fibers has been found to induce unusual modifications of these fibers that are qualitatively different from those encountered when more severely degraded fibers are subjected to similar enzymatically catalyzed oxidative treatments. These results suggest that the physical/conformational state of the lignin of wood fibers determines which oxidation pathways dominate in a given oxidative treatment, leading to different lignin modifications depending on both the chemical and the physical structure of the lignin polymer. Spectroscopic measurements (ESR, IR, UV-Vis and fluorescence) show that the laccase treatment results in the formation of two different species in the dried fibers: one is interpreted as chemically transformed (via oxygen) lignin products, and the other as initial oxidation radicals which have gained stabilization against transformation into the first mentioned products via a migration mechanism. It is argued that these initial radicals may likely be cation radical (or hole state) parts in lignin. The migration mechanism is identified with site-to-site transfer or 'hopping' via electron transfer and it is postulated that this mechanism 'carries' cation radical parts of the lignin, produced at the surface of the fiber, into parts of the lignin where chemical transformation pathways are suppressed due to the lignin conformational state. The possible existence of such a migration mechanism, the relative dominance of which should depend sensitively on the polymer conformational state, may have implications for the biogeneration and biodegradation of lignin as well as for oxidative treatments of non-natural conjugated polymers. (+info)
Neuroimaging of a wooden foreign body retained for 5 months in the temporalis muscle following penetrating trauma with a chopstick--case report.
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A 48-year-old female was stabbed by her husband with a chopstick made of wood in the left temporal region during a quarrel. She suffered laceration of the left temporal scalp. At initial examination, she concealed the assault with a chopstick. Radiography showed no abnormality, so the wound was sutured. One month after the injury, a painless subcutaneous mass appeared in the left temporal region which grew rapidly for 3 months. She was then admitted to our department. Computed tomography (CT) on admission showed a hyperdense area at the center of the mass. This area was hypointense on both T1- and T2-weighted magnetic resonance (MR) images. Temporalis muscle tumor with accompanying central necrosis, old hematoma, and inflammatory granuloma was considered. The mass was totally resected for cosmetic purposes and was found to be wooden foreign body granuloma. High density on CT and hypointensity on both T1- and T2-weighted MR images are characteristic of a chronically retained wooden foreign body in the living body and are useful for detecting wooden foreign bodies in the chronic granulomatous phase. (+info)