Exposure to amorphous silica fibers and other particulate matter during rice farming operations

Robert J. Lawson, Marc B Schenker, Stephen A Mccurdy, Bryan Jenkins, Lee Anne Lischak, Walter John, Don Scales

Research output: Contribution to journalArticle

28 Scopus citations


Occupational exposure to biogenic amorphous silica fibers was found during all phases of rice farming. Exposure during field preparation was the highest, followed by harvest and then rice stubble burning. The highest personal exposure was 1.9 fibers/cc for fibers >5 μm in length in the respirable dust fraction. The highest level seen in area samples was 9.9 fibers/cc for fibers >5 μm in length in the respirable dust fraction. The median fiber length was 2.8 μm, with a range from 0.5 to 20 μm. (Fibers <0.5 μm were not counted.) Ninety percent of fibers were <9 μm in length. The median fiber width was 0.9 μm, with a range from 0.2 to 7 μm. Ninety percent of fibers were <2.5 μm in width. Samples for airborne amorphous silica fibers were collected with personal sampling pumps and polycarbonate filters. Samples were analyzed using X-ray fluorescence to identify composition and electron diffraction to determine the crystalline state of fibers. Fiber counting methodology was adapted from standard asbestos analytical procedures. The biogenic amorphous silica fibers were of complex morphology, often having no parallel sides. Although the fibers did not have needlelike or hairlike shapes, ends of some fibers were sharply pointed.

Original languageEnglish (US)
Pages (from-to)677-684
Number of pages8
JournalApplied Occupational and Environmental Hygiene
Issue number8
StatePublished - Aug 1995


ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health

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