William A. Groves

Effectiveness of roll-over protective structures in reducing farm tractor fatalities

OBJECTIVE The purpose of this systematic review was to evaluate the effectiveness of roll-over protection structures (ROPS) as an engineering control for prevention of fatalities from farm tractor roll-overs. METHODS Using a systematic approach to literature searching, relevant studies from peer-reviewed journals, technical and government reports, and unpublished reports were retrieved. Studies meeting initial criteria for possible inclusion were screened to determine whether they addressed the review topic (ROPS), included comparison data and included outcomes data such as injury or fatality. Articles that evaluated the use and impact of ROPS on operators of agricultural tractors were reviewed. Outcomes included two primary categories: implementation of ROPS and fatalities. MAIN RESULTS Of a total 207 citations reviewed, 53 met initial screening criteria and 21 studies were included in this review. Farm tractor roll-overs result in approximately 200 fatalities per year in the United States. ROPS or crush-proof cabs, which are designed to protect the farmer during a roll-over incident, are currently used on only about 50% of the estimated 4.8 million tractors in the United States. A significant proportion of tractors built after 1985 (when manufacturers began implementing a voluntary ROPS standard) have had ROPS removed. Evidence from Sweden and other Northern European countries clearly demonstrates that ROPS can essentially eliminate roll-over fatalities. In the United States, the only fatalities associated with roll-overs of ROPS-equipped tractors occurred when farmers did not use a seatbelt to hold them within the protective envelope of the ROPS. Estimates of costs of programs to retrofit older tractors with ROPS range from approximately

Analysis of solvent vapors in breath and ambient air with a surface acoustic wave sensor array.

500,000 to

Prototype Instrument Employing a Microsensor Array for the Analysis of Organic Vapors in Exhaled Breath

900,000 per life saved, which is comparable to other accepted life-saving interventions. CONCLUSIONS Future research efforts should include the development of collapsible and telescoping ROPS that can be used in low clearance areas such as dairy barns and fruit orchards. ROPS retrofits also need to be developed for many older tractor models. Effective educational and incentive programs need to be developed to increase the acceptance and use of ROPS among U.S. farmers. A national policy should be implemented to ensure that all tractors operated in the United States are equipped with ROPS or crush-proof cabs.

Risk assessment for loader- and dozer-related fatal incidents in U.S. mining

This article describes the development and evaluation of a small prototype instrument employing an array of four polymer-coated surface acoustic wave (SAW) sensors for rapid analysis of organic solvent vapors in exhaled breath and ambient air. A thermally desorbed adsorbent preconcentrator within the instrument is used to increase sensitivity and compensate for background water vapor. Calibrations were performed for breath and dry nitrogen samples in Tedlar bags spiked with 16 individual solvents and selected binary mixtures. Responses were linear over the 50- to 400-fold concentration ranges examined and mixture responses were additive. The resulting library of vapor calibration response patterns was used with extended disjoint principal components regression and a probabilistic artificial neural network to develop vapor-recognition algorithms. In a subsequent analysis of an independent data set all individual vapors and most binary mixture components were correctly identified and were quantified to within 25% of their actual concentrations. Limits of detection for a 0.25 l. sample collected over a 2.5-min period were <0.3xTLV for 14 of the 16 vapors based on the criterion that all four sensors show a detectable response. Results demonstrate the feasibility of this technology for workplace analysis of breath and ambient air.

Surface acoustic wave (SAW) microsensor array for measuring VOCs in drinking water

A prototype portable instrument capable of selectively measuring organic vapors in breath at low- and sub-ppm concentrations was tested. The instrument employs an array of four polymer-coated surface-acoustic-wave (SAW) resonators and microprocessor-controlled pumps, valves, and heating elements for preconcentration and thermal desorption of breath samples. Response data are passed to an external personal computer for processing. Sensor responses are based on the reversible changes in the mass and viscoelasticity of the polymeric coatings accompanying vapor sorption. Calibrations were performed for perchloroethylene, trichloroethylene, and methoxyflurane at 100% relative humidity using 15 mg of TenaxTA as the preconcentrator adsorbent. Analyses were then conducted of 250-mL breath samples prepared in Tedlar bags spiked with one of the three solvents within the range of 2 to 18 ppm. Differences between concentrations measured using the prototype instrument and those measured by gas chromatography ranged from -6 to 17% for perchloroethylene. Similar results were obtained for trichloroethylene and methoxyflurane with larger differences occurring at lower concentrations. Estimated limits of detection of 0.7, 0.6, and 4 ppm were achieved for perchloroethylene, trichloroethylene, and methoxyflurane, respectively. These preliminary results demonstrate the feasibility of using SAW sensor technology for field breath analysis.

Laboratory and field evaluation of a SAW microsensor array for measuring perchloroethylene in breath.

The paper presents the results of research aimed at developing a risk assessment process that can be used to more thoroughly characterise risks associated with loader- and dozer-related fatal incidents in US mining. The assessment is based on historical data obtained from the US Mine Safety and Health Administration investigation reports, which includes 77 fatal incidents that occurred from 1995 to 2006. The Preliminary Hazard Assessment method is used in identifying and quantifying risks. Risk levels are then developed using a pre-established risk matrix that ranks them according to probability and severity. The resulting assigned risk value can then be used to prioritise risk control strategies. A total of 10 hazards were identified for loaders. The hazards ‘failure to follow adequate maintenance procedure’ and ‘failure of mechanical/electrical/hydraulic components’ were the most severe and frequent hazards and they fell into the category of ‘high’ risk. The same number of hazards was identified for dozers. The hazard ‘failure to identify adverse site/geological conditions’ was the most severe and frequent hazard and it fell into the category of ‘high’ risk.

Prototype sampling system for measuring workplace protection factors for gases and vapors

Exposure to volatile organic chemicals (VOCs) in drinking water has been linked to a number of adverse health effects including cancer, liver, and kidney damage. However, the large number of potential contaminants and the cost and complexity of existing analytical methods limits the extent to which water quality is routinely characterized. This project focused on the laboratory development and evaluation of an instrument for field analysis of VOCs in drinking water. The instrument is based on an array of six polymer-coated surface-acoustic-wave microsensors. A test-set consisting of dichloromethane, chloroform, 1,1,1-trichloroethane, perchloroethylene, and m-xylene was used in a series of experiments designed to optimize the purge-trap preconcentration system, calibrate the instrument over the concentration range of 0.2-2 times the USEPA maximum contaminant levels (MCLs), and compare results to those of a reference laboratory. The primary goal was to develop a cost-effective alternative for on-site evaluation of VOCs in water. Calibration and evaluation test results for spiked water samples demonstrate adequate sensitivity for 19 of the 21 regulated VOCs considered using a ten minute sampling and analysis cycle. Monte Carlo simulations characterized the performance of trained artificial neural networks (ANNs) which had correct classification rates of 99%, 90%, and 80% for the five individual test-set vapors and their binary and ternary mixtures, respectively. These results demonstrate the excellent potential of this technology for addressing the need for improved VOC field-screening methods for water supplies.

Effects of covered solid sorbent tube sample holders on organic vapor measurements.

This article describes the laboratory and field performance evaluation of a small prototype instrument employing an array of six polymer-coated surface acoustic wave (SAW) sensors and a thermal desorption preconcentration unit for rapid analysis of perchloroethylene in breath. Laboratory calibrations were performed using breath samples spiked with perchloroethylene to prepare calibration standards spanning a concentration range of 0.1–10 ppm. A sample volume of 250 mL was preconcentrated on 40 mg of Tenax® GR at a flow rate of 100 mL/min, followed by a dry air purge and thermal desorption at a temperature of 200°C. The resulting pulse of vapor was passed over the sensor array at a flow rate of 20 mL/min and sensor responses were recorded and displayed using a laptop computer. The total time per analysis was 4.5 min. SAW sensor responses were linear, and the instruments limit of detection was estimated to be 50 ppb based on the criterion that four of the six sensors show a detectable response. Field performance was evaluated at a commercial dry-cleaning operation by comparing prototype instrument results for breath samples with those of a portable gas chromatograph (NIOSH 3704). Four breath samples were collected from a single subject over the course of the workday and analyzed using the portable gas chromatograph (GC) and SAW instruments. An additional seven spiked breath samples were prepared and analyzed so that a broader range of perchloroethylene concentrations could be examined. Linear regression analysis showed excellent agreement between prototype instrument and portable GC breath sample results with a correlation coefficient of 0.99 and a slope of 1.04. The average error for the prototype instrument over a perchloroethylene breath concentration range of 0.9–7.2 ppm was 2.6% relative to the portable GC. These results demonstrate the field capabilities of SAW microsensor arrays for rapid analysis of organic vapors in breath.

Evaluation of a fluorometric method for measuring low concentrations of ammonia in ambient air

A prototype sampling system for measuring respirator workplace protection factors (WPFs) was developed. Methods for measuring the concentration of contaminants inside respirators have previously been described; however, these studies have typically involved continuous sampling of aerosols. Our work focuses on developing an intermittent sampling system designed to measure the concentration of gases and vapors during inspiration. This approach addresses two potential problems associated with continuous sampling: biased results due to lower contaminant concentrations and high humidity in exhaled air. The system consists of a pressure transducer circuit designed to activate a pair of personal sampling pumps during inspiration based on differential pressure inside the respirator. One pump draws air from inside the respirator while the second samples the ambient air. Solid granular adsorbent tubes are used to trap the contaminants, making the approach applicable to a large number of gases and vapors. Laboratory testing was performed using a respirator mounted on a headform connected to a breathing machine producing a sinusoidal flow pattern with an average flow rate of 20 L/min and a period of 3 seconds. The sampling system was adjusted to activate the pumps when the pressure inside the respirator was less than -0.1 inch H(2)O. Quantitative fit-tests using human subjects were conducted to evaluate the effect of the sampling system on respirator performance. A total of 299 fit-tests were completed for two different types of respirators (half- and full-facepiece) from two different manufacturers (MSA and North). Statistical tests showed no significant differences between mean fit factors for respirators equipped with the sampling system versus unmodified respirators. Field testing of the prototype sampling system was performed in livestock production facilities and estimates of WPFs for ammonia were obtained. Results demonstrate the feasibility of this approach and will be used in developing improved instrumentation for measuring WPFs.

Analyzing organic vapors in exhaled breath using a surface acoustic wave sensor array with preconcentration : Selection and characterization of the preconcentrator adsorbent

A study was conducted to examine whether there are significant differences between organic vapor concentrations measured using charcoal tubes with three different configurations: uncovered sample holder (open tube), SKC, and Buck brand covered sample holders. A fractional factorial experimental design was used with the following factors and levels: vapor (n-hexane vs. m-xylene), pump type (pulsating vs. continuous), exposure profile (variable vs. constant), flow rate (30 mL/min vs. 200 mL/min), duration (30 min vs. 80 min), and sample placement (mannequin vs. free hanging). Two of each sampler configuration (six total) were placed in an exposure chamber, and a dynamic test-atmosphere generation system was used to prepare atmospheres containing approximately 12–15 ppm n-hexane or m-xylene with exposure profiles and sampling conducted according to a run sheet generated for the experimental design. A total of 24 runs were completed with six samplers per run, yielding 144 samples that were analyzed by gas chromatography/flame ionization detector. Concentration results for each pair of SKC and Buck covered sample holders were averaged and normalized by dividing by the average result for the open tube sampler from the same run to eliminate the effect of daily variation in chamber concentrations. The resulting ratio of covered sample tube holder and open tube concentrations was used as the response variable. Results of analysis of variance using the general linear model (MINITAB 16) identified statistically significant main effects and/or interactions for pump type, exposure profile, flow rate, and sample holder. However, the magnitude of the effects was generally less than 10%, and overall mean concentration ratios were 0.989 and 1.02 for the Buck and SKC sample holders, respectively. These results show good agreement between covered sample holder results and open tube measurements and demonstrate that exposure assessment errors resulting from the use of covered sorbent tube sample holders for organic vapor monitoring are relatively small (<10%) and not likely to be of practical importance.