This study documented the formaldehyde exposures of a group of veterinary medicine students. It also investigated the feasibility of biologically monitoring the exposures. The biological monitoring was based on the fact that the formaldehyde is metabolized in the body to formic acid, and may then be excreted in the urine. Therefore, exposures to formaldehyde could theoretically create a shift in the formic acid levels in the urine. Normal baseline levels of urinary formic acid were first established for each subject. The baselines of most students were quite variable. Very few exhibited a "tight variability" in their baseline. Next, three sets of pre- and post-exposure urine samples were taken. A series of paired t-tests were run on these "pre" and "post" sets. The results indicated that no significant formic acid shift was seen. A subset of the samples was "corrected" for specific gravity. However, this adjustment did not have an effect upon the relative formic acid levels. In addition, no significant formic acid shift was seen in the adjusted group. Exposure levels of the students were less than 0.5 ppm of formaldehyde. Therefore, the main conclusion of the study was that biological monitoring of formaldehyde exposures (via formic acid shifts) at these low levels was not a feasible technique.
Accepted practice by most professional industrial hygienists in government and industry is to use "closed-face" filter cassette techniques as standard sampling procedures for the majority of aerosols. A two-phase, field study was conducted to determine whether a gravimetric bias exists between "open" and "closed-face" sampling methods. Phase I involved an in-depth analysis of the potential gravimetric viability as it applies to an industrial paint spray mist, and Phase II was a series of pilot studies, of small sample base, to determine if this phenomena exists over a range of aerosol types. Dusts of wood, grain, cellulose, Portland cement and perlite, welding fumes, and chromic acid mist were sampled in Phase II. Paired breathing zone samples, "open" and "closed-face", 37 mm, 3-piece filter cassettes were utilized in both phases of the study. In both phases of the study, "open-face" concentrations were consistently higher than "closed-face" concentrations, with the exception of cellulose dust. Based on the concentration for both sampling techniques, the data suggests that "closed-face" sampling techniques (4.0 mm inlet diameter) might be size selective against large particles. This could lead to an underestimation of a worker's total aerosol exposure.
A study was conducted to characterize the aerosol found in turkey rearing confinements, to study biological response to inhalation of the aerosol, and to evaluate a water spray, dust suppression system in one confinement as compared to a control barn. A significant reduction in aerosol concentration in the "sprayed" barn was inferred by many environmental and biological sampling parameters. Similarity of physical and biological factors in both study populations, with the exception of the dust suppression system, implied that a mortality rate increase of 1.74 of control versus "sprayed" barn was directly related to aerosol concentration.
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