A. Bartekova, P. Raynor, J. Adgate, University of Minnesota, Minneapolis, MN.
The long-term goal of this project is to develop small, wearable liquid crystal monitors for the measurement of personal exposure to organophosphate pesticides. This study was conducted to optimize methods for quantification of organophosphate pesticide using the new monitors and to compare the response of the monitors to a conventional sampling method under laboratory conditions. We devised a system to test organophosphate monitors against a NIOSH standard method; developed a protocol for reading the monitors with a flatbed scanner; and built a stainless steel chamber in which we can expose up to six monitors at a time to various concentrations of an organophosphate pesticide at a broad range of temperatures and relative humidities. All experiments were performed using either pure diazinon or a commercial formulation diazinon AG 500, either in the vapor phase or as mixed vapor and aerosol over time scales of 8 to 72 hr. Practical minimum and maximum concentrations were established by comparing short-term, high-concentration performance to long-term, low-concentration performance. A range of 0.2-2 mm response in the monitors was observed over a range of diazinon concentration of 3-55 ppb. The three pesticide concentration levels (low, medium, and high), three temperature levels (10°, 21°, and 32°), and three humidity levels (15%, 50%, and 85%) were tested to represent the approximate range of conditions in the field. The stability of the response signal was evaluated as a function of time, temperature, and humidity. The exposure at higher temperature had a significant impact on both diazinon concentration and the response of the monitors. Humidity had a smaller effect on the response. Plots of the monitor response against the product of diazinon concentration and time were similar for different concentration levels. Our data showed an acceptable batch-to-batch reproducibility for the monitors.
Y. Hsu, C. Wu, D. Lundgren, University of Florida, Gainesville, FL; B. Birky, Florida Institute of Phosphate Research, Bartow, FL.
Strong inorganic acid mists containing sulfuric acid are human laryngeal and lung carcinogens. Aerosols with various aerodynamic diameters deposit in different regions in the human respiratory tract, and cascade impactors can be used to obtain aerosol size distribution information. NIOSH Method 7903, which uses one glass fiber filter and two sections of silica gel, is used to determine the total concentrations of acid mists in workplace air. Both the cascade impactor and NIOSH Method 7903 were employed to collect acid mists at phosphoric acid and concentrated phosphate fertilizer production plants in Florida. These plants produce phosphoric acid by acidulation of phosphate rock with sulfuric acid. The product phosphoric acid is filtered to remove calcium sulfate. An ion chromatography (IC) system was used to determine ionic speciation of samples taken at specific production locations within the processing plants. Sampling results indicated that sulfuric acid pump tank areas had the highest sulfuric acid mist concentration and rotating table/belt filter floors had the highest phosphoric acid mist concentration. Both mists existed mainly in the coarse mode that deposit in the upper respiratory system. Sulfuric acid mist concentrations from the NIOSH method were higher than those from the cascade impactor. The ratio ranged from 1.5 to 229. One possible explanation is interference of sulfur dioxide adsorbed by the glass fiber filter and silica gel. The adsorbed sulfur dioxide can be oxidized to form sulfate during analysis, which employs IC eluant solution, sodium carbonate as the extraction solution, and a water bath at 373 K for 10 min to aid the desorption. Sulfite oxidation was investigated at three conditions of the NIOSH method. The sulfite conversion percentage reached 100% in 5 min, and the oxidation rate was 0.0156 ± 0.0083 (1/s) when 9 millimoles sodium carbonate solution and water bath at 373 K were applied.
W. Menrath, S. Clark, P. Succop, University of Cincinnati, Cincinnati, OH; S. Greenberg, Environmental Health Watch, Cleveland, OH.
The U.S. Housing and Urban Development (HUD) guidelines for the evaluation and control of lead-based paint hazards in housing specify the use of a wipe method for measuring dust lead levels in interior and exterior work areas, following lead hazard control activities to determine if the lead levels are safe. A vacuum method was developed by the University of Cincinnati (UC) for use on numerous environmental health studies. This method utilizing a portable 12-V vacuum was also used on a HUD study to determine the influence of exterior dust and soil lead on interior dust lead levels. An additional vacuum method has been developed by an Environmental Protection Agency (EPA) contractor for use in collecting interior end exterior dust samples adjacent to an active lead smelter. This method, which uses a 120-V vacuum equipped with a high-efficiency particulate air (HEPA) filter, is being used by EPA and others to collect anthrax spores. A comparison study of these three methods was recently completed in three phases. In the first phase, colocated exterior area samples were collected in an ongoing study in Cleveland, Ohio, from housing that had undergone exterior and interior lead hazard control activities three to five years earlier. In the second phase, the two vacuum methods were compared in a Cincinnati neighborhood. The third phase of the study attempted to measure the recovery efficiencies of the three methods from two different exterior surface types with different levels of deterioration. In the first phase, the geometric mean dust lead loading from samples collected with the HEPA vacuum method was 50% higher than for samples with the UC vacuum method. The value for the wipe samples was about 16% percent lower than with the UC method. The relative amounts of lead collected by the three methods varied considerably.
V. Daliessio, S. Van Etten, EMSL Analytical, Westmont, NJ.
Sampling of mercury in air is most effectively performed in the field using NIOSH Method 6009, Mercury by Cold Vapor Atomic Absorption. Under the Method, the maximum volume indicated is 100 liters. At a practical instrument quantitation limit of 0.05ug, the lowest air concentration that can be reported at this volume is 0.5ug/m3. A quantitation and validation study are needed to determine whether NIOSH 6009 can be extended to meet lower concentrations, such as the EPA Reference Concentration (Rfc) of 0.3 ug/m3, the ATSDR Minimal Risk Level (MRL) of 0.2 ug/m3, or even 0.1 ug/m3.
Mercury-spiked tubes were evaluated after sampling at breakthrough volumes exceeding NIOSH 6009 that would allow detection limits below the recommended concentrations of the agencies. Procedures for doing this will be discussed. Data will be presented showing recoveries at various volumes.
C. Pugh, T. Palmer, P. Carr, American Electric Power, Columbus, OH.
The recent reduction in OSHA standard for hexavalent chromium requires increased employee exposure determinations to be performed. The standard applies to CrVI in both soluble and insoluble forms. In some cases, the solubility of the test samples is unknown. Therefore, this study focused on the following significant variables: concurrent analysis of both soluble and insoluble CrVI, and removal of turbidity responses either from filters or other sources. To test turbidity, blank polyvinyl chloride (PVC) filters were placed in centrifuge tubes and extracted according to NIOSH Method 7600. Analysis of replicates yielded a standard deviation of 1.39. After the aliquots were filtered using a Buchner funnel there was significant reduction of the response. Finally, the filtrates were centrifuged for 2 min and yielded the least response. In determining an MDL the same phenomena was observed for spiked filters when filtered and centrifuged. The centrifuged aliquots had the lowest detection limit. Again, use of the centrifuge to eliminate turbidity was significant. An alkaline extraction on soluble CrVI was performed to test concurrent analysis of soluble and insoluble Cr(VI). A filter was spiked with 0.50 ug of CrVI, allowed to dry and then extracted with the alkaline solution. Replicates had a 109.4% recovery. Centrifuging spikes was useful in eliminating the CO2 interference for the alkaline extraction. In summary, the use of a centrifuge resulted in significant turbidity reduction and therefore a lower method detection limit. Also, the use of an alkaline extraction did not negatively impact the soluble CrVI. Therefore, the incorporation of this extraction for all samples will result in the inclusion of both soluble and insoluble CrVI and a more accurate assessment of exposure.
F. Boelter, C. Simmons, Boelter Associates, Inc., Park Ridge, IL; L. Berman, U.S. Environmental Protection Agency, Chicago, IL; P. Scheff, University of Illinois, Chicago, IL.
There are greater than 80 types of welding processes, with electric arc welding being the most common. Shielded metal arc welding (SMAW), or stick welding, is the main process used. Exposure is determined in field assessments, but most all data regarding fume generation rates is laboratory data. Our field study attempted to determine actual fume generation rates. Welding fume samples were collected under field conditions inside a boiler room and in an outdoors breezeway and assessed for total particulate (TP), Fe and Mn. The long-term personal sample TWAs in the boiler room results were TP, 5.35 to 5.75 mg/m3; Fe, 0.62 to 0.85 mg/m3; and Mn, 0.16 mg/m3. The average 15-min personal sample results were TP, 5.00 to 5.90 mg/m3; Fe, 0.48 to 0.67 mg/m3; and Mn, 0.10 mg/m3. Area TWA samples results were TP, 1.37 mg/m3; Fe, 0.25 mg/m3; and Mn, 0.040 mg/m3. A two-zone mass balance model was applied to estimate exposures. The field-based generation rate for TP ranged from 39 to 44 mg/min, Fe was 6.2 to 8.3 mg/min, and Mn was 1.2 mg/min. Laboratory-derived generation (emission) rates published in the literature range from 280 to 650 mg/min for TP. Laboratory-derived emission rates are unrealistic for prediction of field-based welding activities and when used in modeling likely highly overestimate actual exposures.