The influence of various filter types and extraction conditions on the quantitation of airborne endotoxin with the Limulus amebocyte lysate test was studied by using airborne dusts sampled in a potato processing plant. Samples were collected with an apparatus designed to provide parallel samples. Data from the parallelsampling experiment were statistically evaluated by using analysis of variance. In addition, the influence of storage conditions on the detectable endotoxin concentration was investigated by using commercially available lipopolysaccharides (LPS) and endotoxin-containing house dust extracts. The endotoxin extraction efficiency of 0.05% Tween 20 in pyrogen-free water was seven times higher than that of pyrogen-free water only. Two-times-greater amounts of endotoxin were extracted from glass fiber, Teflon, and polycarbonate filters than from cellulose ester filters. The temperature and shaking intensity during extraction were not related to the extraction efficiency. Repeated freeze (؊20؇C)-and-thaw cycles with commercial LPS reconstituted in pyrogenfree water had a dramatic effect on the detectable endotoxin level. A 25% loss in endotoxin activity per freeze-thaw cycle was observed. Storage of LPS samples for a period of 1 year at 7؇C had no effect on the endotoxin level. House dust extracts showed a decrease of about 20% in the endotoxin level after they had been frozen and thawed for a second time. The use of different container materials (borosilicate glass, ''soft'' glass, and polypropylene) did not result in different endotoxin levels. This study indicates that the assessment of endotoxin exposure may differ considerably between groups when different sampling, extraction, and storage procedures are employed.

A total of 171 swine confinement buildings were studied to determine the concentrations of airborne total and D50 less than or equal to micron 8.5 dust fractions, total and gram-negative bacteria, bacterial endotoxin and NH3. The concentrations of these airborne contaminants then were correlated statistically to a number of environmental factors such as feeding practices, number of animals and ventilation parameters. The results showed that airborne dust, endotoxin, bacteria and NH3 are commonly in high concentrations within the swine confinement buildings and that these are at levels where health effects have been observed in other studies. Correlation of these airborne contaminants to a number of environmental factors showed that while ventilation is an important criteria for airborne contaminants, there are a number of farming practices that significantly contribute to the levels of airborne contaminants currently found. Pearson correlations indicate a number of important criteria that the industrial hygienist should measure when faced with problems in agricultural confinement buildings.

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To study the determinants of CD4% and CD4 counts among HIVnegative Ethiopians, and to identify factors susceptible to explain the low CD4 counts observed among Ethiopian subjects. Cohort studies among factory workers in Akaki and Wonji, Ethiopia. Clinical and laboratory examinations, including determination of HIV serological status and T-cell subsets, were performed during follow-up visits every six months. In addition, micronutrients (retinol, carotenoids, tocopherol, transferrin receptor, and selenium) plasma concentrations were determined in a subset of 38 HIV-positive and 121 HIV-negative participants. HIV-negative participants with at least one CD4 count measurement were 157 females in Akaki, 203 males in Akaki, and 712 males in Wonji. CD4 counts were independently and positively associated with body mass index (through an increase in lymphocyte counts), female gender (through an increase in CD4%), cigarette smoking (through an increase in CD4%), khat chewing (through an increase in both lymphocyte counts and CD4%), and Akaki study site (through a large increase in lymphocyte counts compensating a decrease in CD4%). Intestinal parasitic infections were not associated with CD4% or CD4 counts. Retinol, carotenoids, and α-tocopherol plasma concentrations decreased with HIV infection and advancing immunosuppression, but were not associated with CD4 counts among HIV-negative subjects. Low body mass index among Ethiopians may have contributed to their overall low CD4 counts. Other factors remain to be elucidated.

Data on the vitamin A equivalency of b-carotene in food are inconsistent. We quantified the vitamin A equivalency (mg) of b-carotene in two diets using the dual-isotope dilution technique and the oral-faecal balance technique. A diet-controlled, cross-over intervention study was conducted in twenty-four healthy adults. Each subject followed two diets for 3 weeks each: a diet containing vegetables low in b-carotene with supplemental b-carotene in salad dressing oil ('oil diet') and a diet containing vegetables and fruits high in b-carotene ('mixed diet'). During all 6 weeks, each subject daily consumed a mean of 55 (SD 0·5) mg [