Metalworking fluid exposures in small machine shops: an overview.

Sampling was conducted in 79 small machine shops to assess airborne exposures to metalworking fluids (MWFs). Measured exposures were compared with data from the literature and exposure criteria currently recommended by the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration MWF Standards Advisory Committee. Sixty-two percent of 942 personal samples collected were less than the recommended exposure limit (REL) of 0.50 mg/m3 for total particulate. However, at least 1 sample exceeded the REL in 61 of the 79 facilities studied; 100% of the samples collected in 10 shops were greater than the REL. Similar trends were found for thoracic particulate exposures where 75% of 238 samples were below the thoracic particulate REL of 0.40 mg/m3. The ratio between thoracic and total particulate for 238 paired samples was 0.55 (r2=0.73). Workers exposed to straight fluids had the highest exposures (GM=0.67 mg/m3) when compared with workers exposed to other classes of MWFs. The highest exposures were measured for grinding and hobbing (GM=0.67 and 0.60 mg/m3, respectively). Measurements using personal impactors indicated that particle size distributions of MWF aerosols had an average mass median aerodynamic diameter of 5.3 microm. Straight oils and soluble fluids tended to be associated with larger particles than were other fluid types; grinding and turning produced the largest particles, whereas hobbing resulted in the smallest. In general, exposures were similar in magnitude and particle size to those previously reported in large automotive plants. Therefore, workers in these small shops may have risks of adverse health effects similar to those demonstrated in the automotive industry.

Molar and latent models of cognitive slowing: Implications for aging, dementia, depression, development, and intelligence.

The time that it takes a group of participants to respond in simple cognitive tasks varies systematically with the identity of the group. For example, on most tasks, older adults take longer to respond than younger adults. Similarly, on most tasks, younger children take longer to respond than mature children. More generally, response time has been found to vary reliably with a number of other factors that differentiate groups of participants, including the levels of dementia, depression, and intelligence. For each factor, investigators have sought to determine whether the various mental processes are slowed identically as the level of impairment increases. They have based this determination largely on the relation between the overall response times of the relevant groups. Here it is shown how one can base this determination on the relation between the speeds of the individual latent or mental processes governing the performance of the target groups. Such a shift in emphasis has three important advantages: it reduces the possibility of falsely accepting or rejecting the hypothesis that all processes are slowed identically; it pinpoints the actual processes that are lengthened disproportionately when processes are not slowed identically; and it makes possible the rigorous testing of the effects of changes in speed on other dependent variables (e.g., accuracy).

Comparison of three sampling and analytical methods for measuring m-xylene in expired air of exposed humans.

Three breath sampling and analytical methods were tested following exposure of 12 subjects for 4 hr to 75 ppm m-xylene in a controlled environmental chamber. Mixed-expired breath was sampled for m-xylene from all 12 subjects with a new stainless steel device that permits continuous mainstream or sidestream sampling of the solvents present. The m-xylene was sampled from the mainstream using charcoal cloth and from the sidestream using Tenax TA. Alveolar breath also was sampled for m-xylene from 6 of these subjects using bags. The carbon dioxide concentrations of the mixed and alveolar samples, obtained from these 6 subjects, were also determined and used to assess the accuracy of the mixed-expired sampling and analytical procedures. Breath sampling was conducted over the immediate 240-min postexposure period. All m-xylene samples were analyzed using gas chromatography with flame ionization detection. Carbon dioxide concentrations were determined with an infrared analyzer. Nonlinear regression analysis was used to model the desaturation of m-xylene via the breath. Overall, the desaturation of m-xylene from all subjects by all methods was best described using three-compartment pharmacokinetic models. The precision of each sampling and analytical method, estimated from the residual variabilities of the desaturation curves were 0.13 for alveolar sampling, 0.14 for mainstream-mixed sampling (12 subjects), and 0.23 for sidestream-mixed sampling (12 subjects). For all 12 subjects, the breath m-xylene concentrations determined by sidestream-mixed sampling averaged 83% of those determined by mainstream-mixed sampling; this bias was significant. For the 6 subjects from whom both mixed-expired and alveolar breath samples were obtained, the average m-xylene desaturation rates determined by both mainstream-mixed and alveolar sampling were comparable but substantially different from those determined by sidestream-mixed sampling. For these subjects, comparison of the average and individual mixed to alveolar ratios of m-xylene and carbon dioxide showed that mainstream-mixed sampling was accurate and that sidestream-mixed sampling was not.

Investigation of charcoal cloth as a sorbent for integrated sampling of solvent vapors in mixed-expired breath using a new stainless steel sampler.

A stainless steel device for integrated sampling of solvents present in mixed-expired breath is described. During sampling, the subject inhales breathing air through commercial charcoal inhalation canisters. Exhaled breath is sampled from the mainstream using 45-mm wafers of charcoal cloth or from the sidestream on other sorbents. The device concentrates trace contaminants present in large volumes of breath. The charcoal cloth sorbent was evaluated for sampling and analysis of m-xylene and 1,1,1-trichloroethane under simulated physiological conditions. These samples were collected from atmospheres of either analyte generated at 35 degrees-40 degrees C and 80%-90% relative humidity to simulate an exhaled breath sample matrix. Concentrations sampled ranged from 2.2 to 190 mg/m3 for 1,1,1-trichloroethane and from 0.44 to 35.6 mg/m3 for m-xylene. Volumes sampled ranged from 10 to 50 L. The m-xylene samples were collected using a 3-wafer front and a 2-wafer backup bed of charcoal cloth; 1,1,1-trichloroethane samples were collected using a 10-wafer front and a 1-wafer backup bed. All samples were desorbed in carbon disulfide and analyzed via gas chromatography using a flame ionization detector. The volume of desorption solvent ranged from 1.7 to 2.5 mL per wafer of cloth. The quantitation limit is estimated to be 2.0 micrograms/L for 1,1,1-trichloroethane and 0.4 micrograms/L m-xylene for a 50-L sample. At least 80% recovery was obtained for m-xylene or 1,1,1-trichloroethane samples stored from 1 to 14 days after collection, if the samples were refrigerated at 0 degrees C after an initial 7-day storage period at room temperature. The recovery of hexane, 1-hexene, ethyl acetate, isopropanol, methylene chloride, and methyl isobutyl ketone from the charcoal cloth also has been investigated and is reported. With the exception of isopropanol, all analytes were recovered quantitatively from the charcoal cloth by desorption with carbon disulfide following storage for 1 to 17 days at ambient temperatures.

Sampling and analytical methods for the determination of monochloroacetic acid in air.

A personal sampling and analytical method has been developed for the determination of monochloroacetic acid (MCA) vapor in air. The sampling procedure is the collection of MCA with a solid sorbent sampling tube packed with silica gel. The MCA is leached from the exposed sorbent into distilled, deionized water and quantitated by ion chromatographic analysis. The method has been validated in the concentration range of 0.35 to 29 mg/m3 in 3-L air samples. The capacity of the silica gel is in the range of 3 to 4 mg of MCA per 100 mg of sorbent, which allows for up to 8 hr of sampling at concentrations greater than 40 mg/m3. There are no significant interferences from glycolic acid, acetic acid, dichloroacetic acid, trichloroacetic acid, fluoride and chloride compounds, or water vapor. The effects on the analytical data due to variations in the temperature and humidity of the test atmosphere, sample storage time and chromatographic parameters have been found to be minimal.