Evaluation of four sampling methods for determining exposure of children to lead-contaminated household dust.

Childhood exposure to lead has been demonstrated to result in health effects and lead-contaminated household dust is a primary exposure source. There is a need to establish reliable methods for sampling surfaces to determine levels of lead contamination. Three vacuums (HVS3, GS80, and MVM) and one wipe method were evaluated for the collection of household floor dust under field sampling conditions within a Superfund site and demographically similar control area. Side-by-side floor samples were taken from three locations within 41 randomly selected households between August and September 1995: a child's bedroom, primary play area, and primary entrance. Analysis was performed to assess the relative collection performance of each sampler, spatial distribution of lead within a household, and correlation of lead loading with observed blood lead level, and to determine if discrete or composites samples were more predictive of blood lead levels. Approximately 90% of the floor surfaces were carpeted. The rank order of sampling methods from greatest to lowest collection efficiency was HVS3 > GS80 > wipe > MVM. The HVS3 had the highest level of precision (CV=0.05), with the GS80 and wipe precisions 0.48 and 0.053, respectively. Lead loadings for samples collected in bedrooms and living areas and composite samples using the HVS3 and wipe methods were significantly correlated with blood lead levels. Correlations between blood lead levels and composite samples were stronger for the HVS3 (R(2)=0.33, P=0.003) and wipe (R(2)=0.25, P=0.002) methods than the respective discrete samples. Regression analysis indicated that a blood lead level of 10 microgram/dl corresponds to a carpet wipe sample geometric mean of 68 microgram/ft(2). For ongoing public health purposes, such as screening and clearance testing, use of the wipe sampling method is the most appropriate. This investigation supports findings by others that the present HUD risk levels for lead in floor wipe samples may not be adequate for reducing children's blood lead levels below 10 microgram/dl.

Investigation of bites and itching in a word processing department.

This study investigated arthropod and nonarthropod sources of reported bites and itching in a word processing division of a St. Louis, Mo., municipal department. Bird and rodent mites were suspected as causes of the bites because of the large population of pigeons around window ledges on some floors and the sighting of mice in the office. No mites or other arthropods were found to be responsible for the problem. Air samples were negative for fiber glass. Surface-vacuum samples collected around desks contained small quantities or traces of fiber glass or mineral wool. Humidity in the occupied space was considered low, about 35% relative humidity, with carbon dioxide measurements exceeding 1000 ppm. A single cause of the bites was not identified; however, a combination of surface-borne dust on desk tops and floors, the presence of minute quantities of mineral wool and fiber glass, relatively dry conditions, little or no outdoor air supplied to the work space, evidence of seasonally associated high work load, labor/management strife, and the presence of over 17 computers being used on a 24-hour basis (possibly leading to high levels of static electricity) were suspected as multiple causes of most of the "bites." After removal of loose mineral wool and dirt from an air handling unit and implementation of an aggressive cleaning routine, no more bites or itching were reported after a 6-month, 1- and 2-year follow-up period. Further research is needed to determine the relative importance of surface-borne dust and fibers, work stress, psychosocial support, and static electric fields, to produce bite-like sensations.

The dexamethasone-induced inhibitor of plasminogen activator in hepatoma cells is antigenically-related to an inhibitor produced by bovine aortic endothelial cells.

Glucocorticoids decrease plasminogen activator (PA) activity in HTC rat hepatoma cells by inducing a specific inhibitor of PA activity (PAI). This inhibitor is similar in several biochemical properties to the PAI purified from bovine aortic endothelial cells (BAEs). We have used reverse fibrin autography and antiserum against BAE PAI to establish more fully the biochemical and immunological relationship of these inhibitors. Both inhibitors migrated with an apparent Mr of approximately 50,000, and the activity of both PAIs was stimulated by treatment with SDS suggesting that each of these molecules exists in both an active and a latent form. Antiserum to the BAE PAI immunoprecipitated all of the HTC PAI demonstrable by reverse fibrin autography. Finally, using this antiserum in a functional immunoassay, we have demonstrated that dexamethasone increases both active and latent PAI made by HTC cells. These results indicate that HTC PAI and BAE PAI are antigenically as well as biochemically related molecules.