American Industrial Hygiene Association journal最新文献

This study was performed to establish which factors related to the hot application of bitumen products are relevant to worker exposure to benzene-soluble matter (as part of the total fume emission) and to the polycyclic aromatic compound (PAH) content of bitumen fume. Because personal exposure measurements in field surveys can be influenced by many uncontrollable variables, a simple laboratory rig was developed in which bitumen fumes can be generated reproducibly under well-controlled conditions. Laboratory results were related to personal exposure measurements during asphalt paving and roofing. A quantitative relationship for predicting the laboratory fume emission was derived, with bitumen volatility and temperature the only variables. The variable part of the equation is termed the fuming index (FI). The FI correlates well with measured personal exposures in asphalt paving and in roofing and can be used to predict average personal exposures during these activities if bitumen volatility, application temperature, and for paving, the asphalt type, are known. The laboratory fumes, generated at a standard temperature of 160 degrees C, are representative for fumes emitted in the temperature range relevant for asphalt paving, those generated at 250 degrees C for roofing. The PAH profiles of the fumes collected as personal samples during asphalt paving and roofing operations were similar to those of the fumes generated in the laboratory from the same bitumen and at the same temperature. Because it produces conditions representative of actual bitumen operations, this laboratory set-up is an excellent tool for assessing bitumens in terms of fuming tendency and PAH emissions/exposures.

Part of an investigation of data collection methods in epidemiologic studies of farmers evaluated exposures received by farmers from the application of insecticides to animals. Twenty farmers were monitored during a normal application using a fluorescent dye surrogate for the active ingredient (AI). Two exposure measures were estimated, AI concentration and the time-weighted average for the application period (TWAa). Four application methods were used: high- (n = 5) and low-pressure (n = 3) spraying, backpack (n = 2) and pour-on (n = 10). The two farmers using a backpack sprayer had nondetectable levels of dye. Only two of the farmers using the pour-on method had detectable dye levels, but these levels were high. All of the low- and high-pressure sprayers had detectable amounts of dye. Multiple layers of clothing, gloves, and boots (n = 10) were associated with a low mean AI concentration for the exposed farmers (18 micrograms) and more than two-thirds of the farmers wearing this amount of clothing had nondetectable exposures. In contrast, clothing providing little or no protection was associated with a significantly higher (p < 0.01) average AI concentration (4420 micrograms), and less than a third of the farmers with this degree of protection had nondetectable exposures. Poor work practices (leaking equipment, contact with wet animals or fences, and back splash) were associated with statistically higher exposure levels (p < 0.01) than the absence of such practices. There was a moderate statistically significant association between AI concentration and TWAa with total volume of the AI/dye/water mixture using the Spearman coefficient. Time was significantly inversely proportional to the two exposure measures. The association between the two exposure measures and AI volume was not significant.

In response to concerns about lead-based paint (LBP) in an 85-year old high school, an evaluation was conducted to determine whether a lead exposure hazard existed for adult school staff. Deteriorating LBP was present on walls and ceilings throughout the school. At the time of the evaluation, abatement of LBP had been completed in approximately one-third of the school. One-hundred eighteen wipe samples for lead dust were collected from floors, teachers' desks, and interior window sills. Areas selected for sampling were based on the work location of the 45 participants providing blood for lead analysis. Wipe samples from hands were collected from all participants. The geometric means (GMs) for lead dust loadings on sills in unabated rooms (n = 23) and abated rooms (n = 16) were 342 and 102 micrograms/ft2, respectively. Nine sills in unabated rooms and one sill in an abated room exceeded the Housing and Urban Development (HUD) guidelines (500 micrograms/ft2 lead) for residential housing following abatement activity. GMs for lead loadings on floors in unabated rooms (n = 26) and abated rooms (n = 14) were 136 and 70 micrograms/ft2 lead, respectively. Seventeen floor samples from unabated rooms and 3 samples from abated rooms exceeded HUD guidelines (100 micrograms/ft2 lead). The GM blood lead level (BLL) was 2.2 micrograms/dL (range: 0.6-5.6 micrograms/dL), similar to that of the general U.S. population. Despite peeling LBP and significant lead dust loadings, a hazard from LBP was not found for staff at the school. There were no relationships between surface lead and hand lead, BLL and abatement status of assigned work area, or BLL and hand lead.

An approach to sampling and analysis for total isocyanates (monomer plus any associated oligomers of a given isocyanate) in workplace air has been developed and evaluated. Based on a method developed by the Occupational Health Laboratory, Ontario Ministry of Labour, Ontario, Canada, isocyanates present in air are derivatized with a fluorescent reagent, tryptamine, in an impinger and subsequently analyzed via high-performance liquid chromatography (HPLC) with fluorescence detection. Excitation and emission wavelengths are set at 275 and 320 nm, respectively. A modification to the Ontario method was made in the replacement of the recommended impinger solvents (acetonitrile and 2,2,4-trimethylpentane) with dimethyl sulfoxide (DMSO). DMSO has the advantages of being compatible with reversedphase HPLC and not evaporating during sampling, as do the more volatile solvents used in the Ontario method. DMSO also may dissolve aerosol particles more efficiently during sampling than relatively nonpolar solvents. Several formulations containing diisocyanate prepolymers have been tested with this method in the laboratory. This method has been issued as National Institute for Occupational Safety and Health (NIOSH) Method 5522 in the first supplement to the fourth edition of the NIOSH Manual of Analytical Methods. This method is recommended for area sampling only due to possible hazards from contact with DMSO solutions containing isocyanate derivatives. The limits of detection are 0.1 microgram/sample for 2,4-toluene diisocyanate, 0.2 microgram/sample for 2,6-toluene diisocyanate, 0.3 microgram/sample for methylene bisphenyl diisocyanate, and 0.2 microgram/sample for 1,6-hexamethylene diisocyanate.

An intensive program of benzene monitoring using new techniques was undertaken in Western Europe in the late 1960s and early 1970s. Significant exposure was found in the transport of benzene and gasoline, particularly during the loading of barges, and during the loading and operation of sea-going vessels. The ceiling threshold limit value of 25 ppm recommended at that time generated problems in assessing exposure, so alternative criteria were proposed. During that period some shore-based exposures were reported, and their significance was discussed in several articles. The information gained at that time is reexamined by physiologically based pharmacokinetic (PBPK) modeling and is used to help validate an improved PBPK model, which is described and tested on results from experimental exposure in a companion article. The old field data, comprising five specific studies, confirm the relevance of modeling to assessment of occupational exposure, and demonstrate its value for interpretation of field data, which is seldom as complete, systematic, or accurate as that obtained in experimental work. The model suggests that metabolism of benzene in humans may not be restricted to the liver. Sites and processes of metabolism merit further investigation.

The combined effects of respirator wear and low-intensity work on decision making and mood were assessed in eight subjects during 60 min of low-intensity treadmill walking with and without a respirator to determine whether the stresses of respirator wear negatively impact decision making. Subjects completed walks during no mask wear, wear of a respirator with high inspiratory resistance, and wear of a respirator with low resistance. Cognitive tasks included choice reaction (CHO), serial addition/subtraction (ADD), logical reasoning (LOG), and serial reaction (SER). Mood was measured using a questionnaire with 36 adjectives representing the factors of activity, anger, depression, fear, happiness, and fatigue. Data were obtained preexercise, after 20 and 40 min of walking, and postexercise. Combined respirator wear and low-intensity exercise did not affect accuracy, speed, or throughout in any of the cognitive tasks. Likewise, no significant effects of condition on the six mood factor scores were observed. These results show that the combination of respirator wear and low-level activity does not adversely alter cognitive performance or mood.

A seven-compartment physiologically based pharmacokinetic (PBPK) model was developed to predict biological levels of tetrahydrofuran under various exposure scenarios. Affinities for the tissue were estimated from measurements of liquid-gas partition coefficients for water, olive oil, and blood. Metabolism was assumed to follow a rapid first order reaction. urinary excretion was simulated considering passive reabsorption of tetrahydrofuran in the tubules. The validity of the model was tested by comparison with available experimental and field data. Agreement was satisfactory with all studies available except one, which showed much higher results than expected. The source of this difference could not be identified, but cannot be explained by different exposure conditions, such as duration, concentration, or physical work load. However, it is recommended that this particular study not be used in the establishment of a biological exposure index. Simulation of repeated occupational exposure with the PBPK model allowed the prediction of biological levels that would be reached after repeated exposure at the American Conference of Governmental Industrial Hygienists' threshold limit value, time-weighted average of 200 ppm. For samples taken at the end of the shift, the PBPK model predicts 5.1 ppm for breath, 57 mumol/L (4.1 mg/L) for venous blood, and 100 mumol/L (7.2 mg/L) for urine.

A pharmacokinetic model for benzene has been developed and validated for the inhalation aspects of its operation. The validation shows reasonable agreement between the model outputs and human biological data for phenol in urine, benzene in alveolar air, and benzene in mixed exhaled air.

This article (the second of a two-part series) provides a discussion of currently accepted methodology and possible future happenings regarding measurement of benzene in workplaces. The gap between occupational and environmental monitoring is becoming narrow. Environmental levels will always be lower than the occupational, but as the push for lower threshold limit values continues, the focus should be on the environmental aspect as the ultimate limiting factor with respect to measurement. The charcoal tube/carbon disulfide desorption procedure is slowly being stretched to its limit with respect to benzene. It may be time for serious consideration in North America regarding adoption of the proven European procedure of thermal desorption using a porous polymer tube for analysis of benzene.

The Heat Stress Index was an early model for the assessment of heat stress. The International Organization for Standardization (ISO) standard for required sweat rate is the current generation of heat balance methods for occupational heat stress. The method assumes cotton clothing and works adequately for cotton/polyester blends. To extend the usefulness of the model, the thermal characteristics of a variety of commercially available and prototype protective clothing ensembles have been determined for application in the ISO method. The fundamental principle for assessing thermal characteristics of work clothing is establishing the critical environmental conditions in which test subjects were just able to maintain thermal equilibrium. Critical conditions were found for warm, humid conditions; hot, dry conditions; intermediate conditions of temperature and humidity; and/or moderate conditions in which metabolic rate was increased to a limiting thermal load. Typically, five subjects at each condition for each ensemble were used. Metabolic rate, average skin temperature, and the environmental conditions (air temperature and vapor pressure) were noted at the critical conditions, and the total insulation was estimated for each ensemble. From these values, the total evaporative resistance, the clothing factor for dry heat exchange (CFcl), and the clothing factor for evaporative cooling (CFpcl) were determined. When compared with reports of others on thermal characteristics the results agreed when pumping factors and clothing wetness were considered. The result was higher than expected values for CFcl and lower values for CFpcl.