Crystalline silica exposure, radiological silicosis, and lung cancer mortality in diatomaceous earth industry workers.
(17/1985)
BACKGROUND: The role of silicosis as either a necessary or incidental condition in silica associated lung cancer remains unresolved. To address this issue a cohort analysis of dose-response relations for crystalline silica and lung cancer mortality was conducted among diatomaceous earth workers classified according to the presence or absence of radiological silicosis. METHODS: Radiological silicosis was determined by median 1980 International Labour Organisation system readings of a panel of three "B" readers for 1809 of 2342 white male workers in a diatomaceous earth facility in California. Standardised mortality ratios (SMR) for lung cancer, based on United States rates for 1942-94, were calculated separately for workers with and without radiological silicosis according to cumulative exposures to respirable crystalline silica (milligrams per cubic meter x years; mg/m3-years) lagged 15 years. RESULTS: Eighty one cases of silicosis were identified, including 77 with small opacities of > or = 1/0 and four with large opacities. A slightly larger excess of lung cancer was found among the subjects with silicosis (SMR 1.57, 95% confidence interval (CI) 0.43 to 4.03) than in workers without silicosis (SMR 1.19, 95% CI 0.87 to 1.57). An association between silica exposure and lung cancer risk was detected among those without silicosis; a statistically significant (p = 0.02) increasing trend of lung cancer risk was seen with cumulative exposure, with SMR reaching 2.40 (95% CI 1.24 to 4.20) at the highest exposure level (> or = 5.0 mg/m3-years). A similar statistically significant (p = 0.02) dose-response gradient was observed among non-silicotic subjects when follow up was truncated at 15 years after the final negative radiograph (SMR 2.96, 95% CI 1.19 to 6.08 at > or = 5.0 mg/m3-years), indicating that the association among non-silicotic subjects was unlikely to be accounted for by undetected radiological silicosis. CONCLUSIONS: The dose-response relation observed between cumulative exposure to respirable crystalline silica and lung cancer mortality among workers without radiological silicosis suggests that silicosis is not a necessary co-condition for silica related lung carcinogenesis. However, the relatively small number of silicosis cases in the cohort and the absence of radiographic data after employment limit interpretations. (+info)
Etiology and pathogenesis of airway disease in children and adults from rural communities.
(18/1985)
Asthma is the most common chronic disease of childhood and affects nearly 5 million children. The prevalence and severity of childhood asthma have continued to increase over the past decade despite major advances in the recognition and treatment of this condition. A comparison of urban and rural children suggests that the etiology of airway disease is multifactorial and that unique exposures and genetic factors contribute to the development of asthma in both settings. The most important environmental exposure that distinguishes the rural environment and is known to cause asthma is the organic dusts. However, animal-derived proteins, common allergens, and low concentrations of irritants also contribute to the development of airway disease in children and adults living in rural communities. A fundamental unanswered question regarding asthma is why only a minority of children who wheeze at an early age develop persistent airway disease that continues throughout their life. Although genetic factors are important in the development of asthma, recurrent airway inflammation, presumably mediated by environmental exposures, may result in persistent airway hyperresponsiveness and the development of chronic airway disease. Increasing evidence indicates that control of the acute inflammatory response substantially improves airflow and reduces chronic airway remodeling. Reducing exposure to agricultural dusts and treatment with anti-inflammatory medication is indicated in most cases of childhood asthma. In addition, children with asthma from rural (in comparison to urban) America face multiple barriers that adversely affect their health e.g., more poverty, geographic barriers to health care, less health insurance, and poorer access to health care providers. These unique problems must be considered in developing interventions that effectively reduce the morbidity and mortality of asthma in children from rural communities. (+info)
Nasal patency and lavage biomarkers in relation to settled dust and cleaning routines in schools.
(19/1985)
OBJECTIVES: This study determined the relations between settled dust and cleaning routines in classrooms on one hand, and nasal symptoms, nasal cavity dimensions, and the concentration of selected biomarkers of inflammation in nasal lavage on the other. METHODS: Measurements of settled dust via standardized vacuum cleaning and an investigation of the cleaning routines were performed in 12 randomly selected primary schools in the municipality of Uppsala. Clinical examinations including acoustic rhinometry and nasal lavage were performed in the school environment among 279 school personnel working in the main buildings of the schools. Eosinophil cationic protein (ECP), myeloperoxidase (MPO), lysozyme, and albumin were analyzed in the lavage fluid. The relationships between the medical and hygienic data were analyzed both bivariately and with a multiple regression model controlling for age, gender, smoking, atopy, room temperature, and urban vicinity of the school. RESULTS: The amount of settled dust was positively related to subjective nasal obstruction and smaller nasal cavity dimensions measured with acoustic rhinometry. The noses were less patent, and the levels of ECP or lysozyme in the lavage were increased for the subjects in schools with a lower frequency of floor mopping, a lower frequency of desk cleaning, and where wet mopping was used. CONCLUSIONS: Our results indicate that the actual dust levels in Swedish classrooms can affect the occurrence of nasal obstruction among school personnel. A beneficial effect on the clinical signs of the nasal mucosa was observed for a higher frequency of both floor mopping and desk cleaning, whereas the use of wet mopping seemed disadvantageous in comparison with dry mopping. These findings illustrate the need for adequate cleaning procedures to minimize the environmental effects on the airway mucosa. (+info)
A 15-week experimental exposure of pigs to airborne dust with added endotoxin in a continuous flow exposure chamber.
(20/1985)
The purpose of this study was to evaluate the effect of longterm exposure to airborne dust and endotoxin on the respiratory system of pigs. A continuous flow exposure chamber was built for the purpose of exposing pigs to selected airborne contaminants. Pigs (n = 6) were exposed to a combination of a very fine corn/soybean meal (40.6 mg/m3) with added lipopolysaccharide (LPS; 12.4 microg/m3) for 8 h/d over 5 d for 15 wk (75 d of exposure). Control pigs (n = 6) were housed in a room with minimal contamination of these airborne contaminants. Surprisingly, dust in the exposure chamber and the control room was highly contaminated with peptidoglycan. Changes in the lung were monitored by collecting bronchoalveolar lavage (BAL) fluid for cytology at 5 different time points throughout the exposure period. Blood samples were collected at the same time for hematology. A non-specific respiratory inflammatory response was found in exposed and control pigs, as suggested by the increased neutrophils in BAL fluid and the small inflammatory areas in the lung tissue. No macroscopic lung lesions were observed in control or exposed pigs. The findings in the control pigs imply that even low dust concentrations and possibly peptidoglycan contamination can induce cellular changes in the BAL fluid and that a true control pig does not exist. In addition, the exposed pigs developed a mild eosinophilia, indicating an allergic response to the airborne contaminants. (+info)
A healthy home environment?
(21/1985)
Over the past seven years, the U.S. Environmental Protection Agency has consistently ranked indoor air pollution among the top five risks to public health. One of the most dangerous indoor air pollutants is carbon monoxide (CO). CO can be lethal, but perhaps more important, many people suffer ill health from chronic, often undetected exposure to low levels of this gas, resulting in fatigue, headache, dizziness, nausea, and vomiting. Another dangerous pollutant is volatile organic compounds (VOCs), which come from sources including building products, cleaning agents, and paints. One VOC, formaldehyde, can act as an irritant to the conjunctiva and upper and lower respiratory tract. Formaldehyde is also known to cause nasal cancer in test animals. (+info)
Cloning and expression of Der f 6, a serine protease allergen from the house dust mite, Dermatophagoides farinae.
(22/1985)
House dust mite allergen is thought to be a major cause of asthma. Characterization of these allergen molecules is therefore an important step for the development of effective diagnostic and therapeutic agents against mite-associated allergic disorders. Here we report molecular cloning and expression of the group 6 (chymotrypsin-like) allergen from the house dust mite, Dermatophagoides farinae. Sequencing analysis indicates that cloned cDNA, designated Der f 6, encodes a 279 amino acid polypeptide which conserves a primary structure characteristic for chymotrypsin-like serine proteases found in mammals. Recombinant Der f 6 expressed in Escherichia coli bound IgE in a pool made of 20 sera, and induced histamine release from patients' peripheral blood cells. (+info)
Use of a field portable X-Ray fluorescence analyzer to determine the concentration of lead and other metals in soil samples.
(23/1985)
Field portable methods are often needed in risk characterization, assessment and management to rapidly determine metal concentrations in environmental samples. Examples are for determining: "hot spots" of soil contamination, whether dust wipe lead levels meet housing occupancy standards, and worker respiratory protection levels. For over 30 years portable X-Ray Fluorescence (XRF) analyzers have been available for the in situ, non-destructive, measurement of lead in paint. Recent advances made possible their use for analysis of airborne dust filter samples, soil, and dust wipes. Research at the University of Cincinnati with the NITON 700 Series XRF instrument (40 millicurie Cadmium 109 source, L X-Rays) demonstrated its proficiency on air sample filters (NIOSH Method No. 7702, "Lead by Field Portable XRF; limit of detection 6 microg per sample; working range 17-1,500 microg/m3 air). Research with lead dust wipe samples from housing has also shown promising results. This XRF instrument was used in 1997 in Poland on copper smelter area soil samples with the cooperation of the Wroclaw Medical Academy and the Foundation for the Children from the Copper Basin (Legnica). Geometric mean soil lead concentrations were 200 ppm with the portable XRF, 201 ppm with laboratory-based XRF (Kevex) and 190 ppm using atomic absorption (AA). Correlations of field portable XRF and AA results were excellent for samples sieved to less than 125 micrometers with R-squared values of 0.997, 0.957, and 0.976 for lead, copper and zinc respectively. Similarly, correlations were excellent for soil sieved to less than 250 micrometers, where R-squared values were 0. 924, 0.973, and 0.937 for lead, copper and zinc, respectively. The field portable XRF instrument appears to be useful for the determination of soil pollution by these metals in industrial regions. (+info)
Role of allergy in nasal polyps of Thai patients.
(24/1985)
As distinct from many countries, allergy in Thailand is of the perennial type which may play a role in the formation of nasal polyps. Forty consecutive patients with nasal polyps and 30 normal subjects as control were studied at the Allergy Clinic, Department of Otolaryngology, Pramongkutklao Hospital. A positive clinical history and skin allergy testing are diagnostic criteria for allergy. In the nasal polyps group, these were 28 males and 12 females, aged between 12-65 years, with an average age of 38.5 years. In the control group, there were 18 males and 12 females, aged between 15-53 yeas, with an average age of 34 years. All had received prick skin testing with 6 common aeroallergens. The prick skin test was considered positive when the wheal was > or = 3 mm with surrounding erythema. Twenty-four of 40 patients (60%) with nasal polyps had a positive prick skin test, while 6 in the 30 control cases (20%) had a positive prick skin test. This difference was statistically significant (P = 0.0019), Odd's ratio = 6.0 which means allergic persons were 6 times more prone to have polyps form than normal persons. (+info)