Saturday, 15 July 2006

Transport and Concentration of Allergens and Light Organics in Dust.

Richard E. Zartman and William F. Jaynes. Texas Tech Univ, Plant and Soil Science Dept, P. O. Box 42122, Lubbock, TX 79409-2122

Many plants and microorganisms produce allergens, pollen, spores, and toxins. These biological organics have a much lower density than soil particles and often occur as small particles. For example, peanuts contain the globular protein, Peanut Seed Lectin (PSL), which is an extremely allergenic protein. The dispersal of powdered PSL could potentially affect large populations due to dust transport. Dispersal of this material would be similar to organic toxins or other materials that might pose a long-term health threat due to transport in dust. Mixed with soil particles, an allergen/toxin might not be detected until many people were exposed. Wind action might effectively concentrate the allergen/toxin as breathable dust particles dispersed in the air. The objective of this study was to examine the transport of PSL in dust. For this purpose, dust fractions from soil samples containing powdered peanut lectin were collected. Dust fraction analysis was used to examine transport of peanut lectin. The effect of soil texture and other parameters on dust generation were examined. Dust transport of peanut lectin should have a wider relevance to the transport of other biological or chemical toxins in dust. Southern High Plains of Texas soil samples were collected and passed through a 1-mm sieve. Brownfield loamy fine sand (Loamy, mixed, superactive, thermic Arenic Paleustalfs) and a Pullman clay (Fine, mixed, superactive, thermic Torrertic Paleustolls) soil samples were used. A mortar and pestle was used to mix soil samples with 5% dried peanut extract powder. A miniature dust generator/collection system was constructed based on a much larger USDA-ARS dust generator/collection system. The dust generator consisted of two glass cylinders perpendicularly attached to a 4-rpm electric motor. Ball valves were fitted into the glass cylinders that alternately open and close to admit air into the system. The glass cylinders were attached to a series of four Erlenmeyer flasks that served as dust traps and were connected together with glass tubing. The last dust trap was connected to a vacuum pump. When a soil sample was placed in the dust generator and the motor and vacuum pump were started, air was drawn into dust generator and soil particles moved into the dust traps. Dust trap3 and 4 contained water to trap the finest dust particles. The dust fractions were collected, weighed, and an enzyme-linked immunoassay technique (ELISA) was used to measure PSL concentrations in standards and in dust fractions. Coarser sand fractions remained in the dust generator after operation of the dust-generator/collection system, whereas, progressively finer particles were collected in trap1, trap2, trap3, and trap4. The coarse-textured Brownfield soil contained >84% sand which explains why 93% of the sample was retained in the first trap. The very coarse residual soil material that remained in the dust generator was PSL-depleted and contained only 0.03% of added PSL, whereas, very fine dust collected in the last (aqueous) trap contained more than 7% of added PSL and consisted of almost pure peanut extract. Most (55 to 98%) of the PSL moved as a fine dust and was collected in trap3 and trap4. Because of the finer texture, the Pullman soil (49%) generated more fine dust than the Brownfield soil (16%). The dust PSL concentration was 6 to 8 times greater than in the original soil sample. The coarse residual material left in the dust generator from the Pullman clay was also greatly depleted in PSL. However, because of the greater abundance of fine soil particles in clay, PSL was not as effectively concentrated in finer dust fractions of the Pullman clay as for the Brownfield loamy fine sand. Peanut seed lectin was effectively transported along with soil particles in a miniature dust-generating device. Most of the PSL was collected with the finest soil particles in the last traps and was greatly depleted in the coarse residual material left in the dust generator. The PSL was more concentrated in the finer dust fractions with concentrations up to 9.5 times greater (48%) in the finest dust fractions than in the original (5%) sample. The lower density of PSL relative to soil particles contributed to greater transport compared to soil particles and concentration of PSL in the finer fractions. Due to the coarser texture, PSL was more effectively concentrated in the Brownfield loamy fine sand dust fractions than in the Pullman clay dust fractions. Dust transport of other organic powders would likely be similar. Inhalation of dust generated from soils contaminated with toxic materials could pose a serious health hazard.

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