Thomas J. Slavin

Relationships Among Particle Number, Surface Area, and Respirable Mass Concentrations in Automotive Engine Manufacturing

This study investigated the relationships between particle number, surface area, and respirable mass concentration measured simultaneously in a foundry and an automotive engine machining and assembly center. Aerosol concentrations were measured throughout each plant with a condensation particle counter for number concentration, a diffusion charger for active surface area concentration, and an optical particle counter for respirable mass concentration. At selected locations, particle size distributions were characterized with the optical particle counter and an electrical low pressure impactor. Statistical analyses showed that active surface area concentration was correlated with ultrafine particle number concentration and weakly correlated with respirable mass concentration. Correlation between number and active surface area concentration was stronger during winter (R 2 = 0.6 for both plants) than in the summer (R 2 = 0.38 and 0.36 for the foundry and engine plant respectively). The stronger correlation in winter was attributed to use of direct-fire gas fired heaters that produced substantial numbers of ultrafine particles with a modal diameter between 0.007 and 0.023 μ m. These correlations support findings obtained through theoretical analysis. Such analysis predicts that active surface area increasingly underestimates geometric surface area with increasing particle size, particularly for particles larger than 100 nm. Thus, a stronger correlation between particle number concentration and active surface area concentration is expected in the presence of high concentrations of ultrafine particles. In general, active surface area concentration may be a concentration metric that is distinct from particle number concentration and respirable mass concentration. For future health effects or toxicological studies involving nano-materials or ultrafine aerosols, this finding needs to be considered, as exposure metrics may influence data interpretation.

A Critical Assessment of Studies on the Carcinogenic Potential of Diesel Exhaust

After decades of research involving numerous epidemiologic studies and extensive investigations in laboratory animals, a causal relationship between diesel exhaust (DE) exposure and lung cancer has not been conclusively demonstrated. Epidemiologic studies of the transportation industry (trucking, busing, and railroad) show a small elevation in lung cancer incidence (relative risks [RRs] generally below 1.5), but a dose response for DE is lacking. The studies are also limited by a lack of quantitative concurrent exposure data and inadequate or lack of controls for potential confounders, particularly tobacco smoking. Furthermore, prior to dieselization, similar elevations in lung cancer incidence have been reported for truck drivers, and in-cab diesel particulate matter (DPM) exposures of truck drivers were comparable to ambient highway exposures. Taken together, these findings suggest that an unidentified occupational agent or lifestyle factor might be responsible for the low elevations in lung cancer reported in the transportation studies. In contrast, underground miners, many of whom experience the highest occupational DPM exposures, generally do not show elevations in lung cancer. Laboratory studies must be interpreted with caution with respect to predicting the carcinogenic potential of DE in humans. Tumors observed in rats following lifetime chronic inhalation of very high levels of DPM may be attributed to species-specific overload mechanisms that lack relevance to humans. Increased tumor incidence was not observed in other species (hamsters or mice) exposed to DPM at very high levels or in rats exposed at lower levels (≤2000 μg/m3). Although DPM contains mutagens, mutagenicity studies in which cells were exposed to concentrated extracts of DPM also have limited application to human risk assessment, because such extracts can be obtained from DPM only by using strong organic solvents, agitation, and heat. Most studies have shown that whole DPM itself is not mutagenic because the adsorbed organic compounds are minimally bioavailable in aqueous-based fluids. In the past two decades, dramatic changes in diesel engine technology (e.g., low-sulfur fuel and exhaust after-treatment) have resulted in >99% reduction in DPM and other quantitative and qualitative changes in the chemical and physical characteristics of diesel exhaust. Thus, the current database, which is focused almost entirely on the potential health effects of traditional diesel exhaust (TDE), has only limited utility in assessing the potential health risks of new-technology diesel exhaust (NTDE). To overcome some of the limitations of the historical epidemiologic database on TDE and to gain further insights into the potential health effects of NTDE, new studies are underway and more studies are planned.

Health, safety, and productivity in a manufacturing environment

The Health and Productivity Management model at International Truck and Engine Corporation includes the measurement, analysis, and management of the individual component programs affecting employee safety, health, and productivity. The key to the success of the program was the iterative approach used to identify the opportunities, develop interventions, and achieve targets through continuous measurement and management. In addition, the integration of multiple disciplines and the overall emphasis on employee productivity and its cost are key foci of the International Model. The program was instituted after economic and clinical services’ analyses of data on International employees showed significant excess costs and a high potential for health care cost reductions based on several modifiable health risk factors. The company also faced significant challenges in the safety, workers’ compensation, and disability areas. The program includes safety, workers’ compensation, short-term disability, long-term disability, health care, and absenteeism. Monthly reports/analyses are sent to senior management, and annual goals are set with the board of directors. Economic impact has been documented in the categories after intervention. For example, a comprehensive corporate wellness effort has had a significant impact in terms of reducing both direct health care cost and improving productivity, measured as absenteeism. Workers’ compensation and disability program interventions have had an impact on current costs, resulting in a significant reduction of financial liability. In the final phase of the program, all direct and indirect productivity costs will be quantified. The impact of the coordinated program on costs associated with employee health will be analyzed initially and compared with a “silo” approach.

The burden of allergies--and the capacity of medications to reduce this burden-in a heavy manufacturing environment.

This article addresses the observational findings of the first systematic study undertaken by a manufacturer to address the impact of allergies and use of allergy medications on health, safety, and productivity. It provides background for 3 other papers from the same project, including an evaluation of an intervention to promote appropriate medication use among affected employees, which appear in this issue. The observational data are developed on 10,714 employees from: 1) 2 employee surveys; 2) administrative databases monitoring employee absenteeism, workers compensation, short-term disability, and group health. The results show that health, productivity, absenteeism, workplace injury, and workers compensation measures register consistent declines as allergy severity levels increase. This pattern is present but less pronounced for the short-term disability and group health measures. In addition, among the 16 measures registering a significant allergy burden, 6 posted significant advantages for the use of nonsedating antihistamines relative to other medication regimens that included sedative antihistamines. These results document the burden of allergies and the capacity of medications to reduce this burden. Effective intervention programs that target this condition can achieve improved health, productivity, and related outcomes.

Characterization and Mapping of Very Fine Particles in an Engine Machining and Assembly Facility

Very fine particle number and mass concentrations were mapped in an engine machining and assembly facility in the winter and summer. A condensation particle counter (CPC) was used to measure particle number concentrations in the 0.01 μ m to 1 μ m range, and an optical particle counter (OPC) was used to measure particle number concentrations in 15 channels between 0.3 μ m and 20 μ m. The OPC measurements were used to estimate the respirable mass concentration. Very fine particle number concentrations were estimated by subtracting the OPC particle number concentrations from 0.3 μ m to 1 μ m from the CPC number concentrations. At specific locations during the summer visit, an electrical low pressure impactor was used to measure particle size distribution from 0.07 μ m to 10 μ m in 12 channels. The geometric mean ratio of respirable mass concentration estimated from the OPC to the gravimetrically measured mass concentration was 0.66 with a geometric standard deviation of 1.5. Very fine particle number concentrations in winter were substantially greater where direct-fire natural gas heaters were operated (7.5 × 105 particles/cm3) than where steam was used for heat (3 × 105 particles/cm3). During summer when heaters were off, the very fine particle number concentrations were below 105 particles/cm3, regardless of location. Elevated very fine particle number concentrations were associated with machining operations with poor enclosures. Whereas respirable mass concentrations did not vary noticeably with season, they were greater in areas with poorly fitting enclosures (0.12 mg/m3) than in areas where state-of-the-art enclosures were used (0.03 mg/m3). These differences were attributed to metalworking fluid mist that escaped from poorly fitting enclosures. Particles generated from direct-fire natural gas heater operation were very small, with a number size distribution modal diameter of less than 0.023 μ m. Aerosols generated by machining operations had number size distributions modes in the 0.023 μ m to 0.1 μ m range. However, multiple modes in the mass size distributions estimated from OPC measurements occurred in the 2–20 μ m range. Although elevated, very fine particle concentrations and respirable mass concentrations were both associated with poorly enclosed machining operations; the operation of the direct-fire natural gas heaters resulted in the greatest very fine particle concentrations without elevating the respirable mass concentration. These results suggest that respirable mass concentration may not be an adequate indicator for very fine particle exposure.

Do Long Workhours Impact Health, Safety, and Productivity at a Heavy Manufacturer?

Objectives: To test the health, safety, and productivity effects of long workhours. Methods: Secondary analyses of a longitudinal employee panel (n = 2746). Average hours worked during spring 2001 were assessed relative to health, safety, and productivity outcomes spanning summer 2001 through spring 2002. Results: Employees working overtime were no more likely to incur adverse physical or mental health, presenteeism, or disability outcomes. Those working 60+ hours were more likely to report new injuries and diagnoses, but these effects were overwhelmed by prior health, demographics, and compensation type. Conclusions: Much previous work has suggested that long workhours generate a wide range of adverse outcomes across the employee continuum. This study found no evidence for pervasive workhour effects. Rather, long workhours—especially weekly schedules at the 60 hour or above mark—can lead to problems in certain areas of health and safety. More research is needed that tests group differences across segmented characteristics (eg, poor versus good health) but keeps workhour impact in perspective.

A Reevaluation of the Literature Regarding the Health Assessment of Diesel Engine Exhaust

While the International Agency for Research on Cancer (IARC) classified diesel exhaust (DE) as a “probable” carcinogen in 1989 based primarily on “sufficient” animal data, other investigators have since concluded that the lung tumors found in the rat studies were a result of particle overloading. Subsequent health risk assessments of DE have not used the rat cancer data. The U.S. Environmental Protection Agency (EPA), in developing its 2002 Health Assessment Document (HAD) for DE, primarily considered the epidemiology studies of railroad workers and truck drivers to develop health risk assessments of DE. However, both sets of epidemiology studies have serious weaknesses that make them unsuitable for cancer risk assessment. Major shortcomings were the lack of contemporaneous measurements of exposures to DE, difficulties with exposure history reconstruction, and adequately accounting for other exposures such as gasoline exhaust and cigarette smoke. To compound these problems, there was not, and there is still not, a specific exposure marker for DE. Interestingly, in the underground mining industry, where diesel exposures are much higher than observed in railroad workers and truck drivers, there was no increase in lung cancer. These problems and concerns led the U.S. EPA to conclude that while DE was a “likely” carcinogen, a unit risk value or range of risk cannot be calculated from existing data and that the risk could be zero. In addition, the DE emissions have changed and continue to change with the implementation of new emission control technologies. The HAD recognized this fact and noted that further studies are needed to assess new diesel engine emissions. Recent chemical characterization studies on low-emitting diesel engines with catalyzed particulate filters have shown emissions rates for several chemicals of concern that are even lower than comparable compressed natural gas (CNG)-fueled engines. With lower emissions, better fire safety, and improved cost-effectiveness of new low-emitting diesels compared to CNG, current efforts to restrict use of low-emitting diesels seems misguided.

An intervention to promote appropriate management of allergies in a heavy manufacturing workforce: Evaluating health and productivity outcomes

This work presents the evaluation of a first-of-its-kind intervention to improve the management of allergies among workers in a largely blue-collar industrial setting. This intervention implemented eight educational strategies focusing on appropriate medication use in the context of a controlled, nonrandomized, pre-post quasi-experimental study design. Program implementation occurred during summer 2001, with change assessed by means of measures of health and productivity, developed from employee surveys timed to occur at the height of the spring and fall allergy seasons, and measures of contemporaneous adverse events developed from administrative databases. Evidence of improvement was found at one experimental site but not at the other experimental sites or the control site. Tests using exploratory and confirmatory analyses were conducted of two hypotheses linking the gains of this site’s allergy group to 1) intervention process changes and 2) changes in allergy severity caused by seasonality. Neither hypothesis is found to fully account for the explained variation between sites. Similar pre-post productivity gains for other disease groups at this site relative to the other sites suggest that the inclusion of other unmeasured variables would improve explanation; e.g., the responses of employees with chronic disease to notably challenging labor negotiations at this site. The implications for promoting behavioral change in the management of the impact of disease on productivity are explored.

Comments on the Diesel Exhaust in Miners Study

We are writing in response to four recent articles describing the historical reconstruction of diesel exhaust exposures in underground mines (Diesel Exhaust in Miners Study or DEMS) for use in epidemiological analyses of exposure–response relationships between mining-associated diesel exposure and health effects, e.g. lung cancer (Coble et al., 2010; Stewart et al., 2010; Vermeulen et al., 2010a,b). We have particular concerns about the estimation of historical respirable elemental carbon (REC) levels for underground miners. Those estimates were back extrapolated using historical carbon monoxide (CO) area measurements and estimated levels of historical ‘adjusted horsepower (HP)’ of diesel fleets to estimate levels of CO as surrogates of diesel exhaust (DE). As discussed below, those measures are at best imprecise and may not be valid measures of DE. Accordingly, we have concerns about the validity of the articles’ conclusions, which we believe are insufficiently justified. The following communication briefly describes those concerns. 1. Measurements of CO by colorimetric tubes are imprecise and may be unreliable. The historical reconstruction relied on CO data obtained in the DEMS survey, a 1994 Feasibility study, and a compilation of MSHA data from 1976 to 2001 (MIDAS). In the DEMS and Feasibility studies, CO measurements were obtained using long-term (i.e. 8 h) colorimetric tubes. The MIDAS surveys used short-term colorimetric tubes (i.e. 5–15 min) or gas chromatography, but the numbers determined by each of those methods were not described. The precision of CO colorimetric tubes is limited, especially at low exposure levels. Prior to the NIOSH certification program, colorimetric and length-ofstain detector tubes were considered ‘inaccurate’ (Perkins, 1997). Early studies reported that over the range from 25 to 100 p.p.m., all commercially available CO detector tubes were worse than –25% of the true value, while only some brands yielded results within –50% of the true value (Morgenstern et al., 1970). CO tubes are currently required to yield results –35% the true value at 12.5 p.p.m., but precision and accuracy decline as concentrations approach the limit of their recommend use ( 5 p.p.m.). Because of imprecision, inaccuracy, and observer variability, historical and current authorities agree that CO colorimetric tubes should only be used to detect the presence of CO and for range finding purposes, not for quantitative measurements (WHO, 1976; Stern and Mansdorf, 1999; Todd, 2003) and that after CO detection ‘a more accurate . . . method’ should be used (Lodge, 1988). In 1976, the year MIDAS surveys began, WHO recommended that detector tubes only be used ‘for estimating the concentration of CO at concentrations above 5 mg/ m, (i.e. 4.35 p.p.m.) (WHO, 1976). Accordingly, it is notable that the great majority of CO measurements in the DEMS reports were below 4.35 p.p.m.. We are also concerned by a table footnote indicating that some CO values were ‘corrected for measurement technique (detector tube versus bistable)’, but the reports described neither the method for and effects of such ‘correction’, nor the number of samples so ‘corrected’. Thus, the CO measurements are subject to still further uncertainty. 2. The majority of CO measurements were below the recommended range for use of colorimetric tubes. The reports do not describe the actual CO measurements across the seven mines, but summary statistics were provided for samples obtained at the underground production face. Across the seven mines in the DEMS survey, the geometric means of CO samples ranged from 0.8 to 4.5 p.p.m.. Among historical production face CO measurements, the geometric means across all mines grouped by decade ‘typically’ ranged from 1 to 3 p.p.m..

Sustainability at Navistar: a model distinguished by sustainable innovation, proactive product stewardship, and sound science

While corporate sustainability is interpreted broadly to mean ensuring success in the present without compromising the future, a well-accepted workable definition has remained elusive. Sustainability is often defined using a set of criteria or metrics that address the recognised environmental, social, and economic pillars of sustainability. However, standard metrics fail to account for how companies deal with operational challenges to their sustainability and viability. As a 175 year old diesel engine manufacturer, Navistar, Inc. has developed a model to address not only the three pillars of sustainability but also its significant business challenges, including those related to health concerns over its diesel products and environmental and employee legacies. Featuring a commitment to sustainable innovation and product stewardship and reliance on sound science, Navistar’s sustainability model has evolved in response to its unique operating environment. This model illustrates the benefits of designing sustainability strategies to address specific business challenges rather than a standard set of criteria.