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Pulmonary deposition modeling with airborne fiber exposure data: a study of workers manufacturing refractory ceramic fibers.

Authors
Lentz-TJ; Rice-CH; Succop-PA; Lockey-JE; Dement-JM; LeMasters-GK
Source
Appl Occup Environ Hyg 2003 Apr; 18(4):278-288
NIOSHTIC No.
20023245
Abstract
Increasing production of refractory ceramic fiber (RCF), a synthetic vitreous material with industrial applications (e.g., kiln insulation), has created interest in potential respiratory effects of exposure to airborne fibers during manufacturing. An ongoing study of RCF manufacturing workers in the United States has indicated an association between cumulative fiber exposure and pleural plaques. Fiber sizing data, obtained from electron microscopy analyses of 118 air samples collected in three independent studies over a 20-year period (1976-1995), were used with a computer deposition model to estimate pulmonary dose of fibers of specified dimensions for 652 former and current RCF production workers. Separate dose correction factors reflecting differences in fiber dimensions in six uniform job title groups were used with data on airborne fiber concentration and employment duration to calculate cumulative dose estimates for each worker. From review of the literature, critical dimensions (diameter <0.4 microm, length <10 microm) were defined for fibers that may translocate to the parietal pleura. Each of three continuous exposure/dose metrics analyzed in separate logistic regression models was significantly related to plaques, even after adjusting for possible past asbestos exposure: cumulative fiber exposure, chi(2) = 15.2 (p < 0.01); cumulative pulmonary dose (all fibers), chi(2) = 14.6 (p < 0.01); cumulative pulmonary dose (critical dimension fibers), chi(2) = 12.4 (p < 0.01). Odds ratios (ORs) were calculated for levels of each metric. Increasing ORs were statistically significant for the two highest dose levels of critical dimension fibers (level three, OR = 11, 95%CI = [1.4, 98]; level four, OR = 25, 95%CI = [3.2, 190]). Similar associations existed for all metrics after adjustment for possible asbestos exposure. It was concluded that development of pleural plaques follows exposure- and dose-response patterns, and that airborne fibers in RCF manufacturing facilities include those with critical dimensions associated with pleural plaque formation. Analysis of additional air samples may improve estimates of the dose-response relationship.
Keywords
Pulmonary-system-disorders; Lung-cancer; Mesothelial-cells; Refractories; Ceramic-materials; Airborne-fibers; Dose-response; Exposure-levels; Exposure-limits; Industrial-exposures; Vitreous-enameling; Synthetic-fibers; Synthetic-fibers-industry; Respiratory-system-disorders; Mathematical-models; Statistical-analysis; Analytical-methods
CODEN
AOEHE9
Publication Date
20030401
Document Type
Journal Article
Funding Amount
1070124
Funding Type
Grant
Fiscal Year
2003
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-T42-CCT-510420
Issue of Publication
4
ISSN
1047-322X
NIOSH Division
EID
Source Name
Applied Occupational and Environmental Hygiene
State
NC; OH
Performing Organization
Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio
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