The impact of housing type on low-income asthmatic children receiving multifaceted home interventions.

OBJECTIVES: This study sought to evaluate whether government-assisted vs market-rate housing type influences the frequency of asthma symptoms or the quality of life scores among low-income urban children. In addition, the study sought to evaluate whether housing type influenced the success of in-home environmental and educational interventions in improving children's asthma symptoms or quality of life scores. STUDY DESIGN: This was a before-and-after intervention design. Comprehensive health and environmental assessments and subsequent interventions were completed in 176 low-income households with 257 asthmatic children living in government-assisted housing and market-rate housing in Lowell, Massachusetts. METHODS: We collected environmental and health data with questionnaires at a baseline and a 12-month follow-up visit using the Children's Health Survey for Asthma and a walk-through environmental checklist. Education, tools to remove asthma triggers from the home, and home repairs and remediation were included in the interventions. RESULTS: As in other studies of multifaceted home interventions, there were significant improvements in all asthma symptoms, reductions in healthcare utilization related to asthma, and improvements in quality of life domains for children in both housing types. Environmental indices also improved from the baseline to the final assessment for both housing types. However, the housing type was an important factor in predicting a child's asthma status at the start of the study, with children living in government-assisted housing having significantly better physical health scores (76.8 of 100) and family emotional health scores (74.8 of 100) and fewer overnight hospital stays (mean of 0.02 in the previous 4 weeks) than children living in market-rate housing (67.6, 71.6, and 0.06, respectively). Examination of the change in the health status over the 1-year study period found that children living in market-rate housing had significantly larger reductions in the number of asthma attacks (0.43 in the previous 4 weeks versus 0.24 in assisted housing) and overnight hospital stays (0.06 in the previous 4 weeks versus 0.01 in assisted housing) and larger improvements in physical health quality of life scores (54% improved versus 25.5% in assisted housing). CONCLUSIONS: Public assistance for low-income urban housing is associated with better health among children with asthma, and may influence the impact the in-home interventions have on health outcomes because children in market-rate housing have more prospects for improvement in their asthma-related health.

Reducing silica and dust exposures in construction during use of powered concrete-cutting hand tools: efficacy of local exhaust ventilation on hammer drills.

Concrete cutting in construction is a major source of exposure to respirable crystalline silica. To reduce exposures, local exhaust ventilation (LEV) may be integrated into the hand tools used in concrete cutting. Volunteers from the New England Laborers Training Center participated in a field study focused on the use of LEV on concrete-cutting hammer drills. A randomized block design field experiment employing four workers measured the efficacy of four hood-vacuum source combinations compared with no LEV in reducing dust and silica exposures. Using four-stage personal cascade impactors (Marple 294) to measure dust exposure, a total of 18 personal samples were collected. Reductions of over 80% in all three biologically relevant size fractions of dust (inhalable, thoracic, and respirable) were obtained by using any combination of hood and vacuum source. This study found that respirable dust concentrations were reduced from 3.77 mg/m(3) to a range of 0.242 to 0.370 mg/m(3); thoracic dust concentrations from 12.5 mg/m(3) to a range of 0.774 to 1.23 mg/m(3); and inhalable dust concentration from 47.2 mg/m(3) to a range of 2.13 to 6.09 mg/m(3). Silica concentrations were reduced from 0.308 mg/m(3) to a range of 0.006 to 0.028 mg/m(3) in the respirable size fraction, from 0.821 mg/m(3) to a range of 0.043 to 0.090 mg/m(3) in the thoracic size fraction, and from 2.71 mg/m(3) to a range of 0.124 to 0.403 mg/m(3) in the inhalable size fraction. Reductions in dust concentrations while using the four LEV systems were not statistically significantly different from each other.

Estimation of compressive forces on lumbar spine from categorical posture data.

To combine estimates of trunk posture and force into an integrated measure of load on the low back, continuous variables for body angles were estimated by assuming specified distributions within corresponding posture categories with Monte-Carlo (MC) simulation. The estimated posture angles were compared with reference measurements from the Lumbar Motion Monitor and inclinometers. The lumbar compression estimates, generated from simulated posture angles and from direct measurement, were compared. Trunk flexion showed high correlation between direct measurements and simulated angles, as did L5/S1 compression. The MC approach to extracting continuous posture angles from categorized observations did not appear to introduce large error in the variables used to estimate spinal compressive forces. When instrumentation methods of postural assessment are not feasible, a simulation approach combined with biomechanical modelling could be used to integrate multiple external exposure variables into estimates of compressive forces acting on the low back.

Determinants of isocyanate exposures in auto body repair and refinishing shops.

As part of the Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), the determinants of isocyanate exposure in auto body repair shops were evaluated. Measurements (n = 380) of hexamethylene diisocyanate-based monomer and polyisocyanate and isophorone diisocyanate-based polyisocyanate were collected from 33 auto body shops. The median total reactive isocyanate concentrations expressed as mass concentration of the NCO functional group were: 206 microg NCO/m3 for spray operations; 0.93 microg NCO/m3 for samples collected in the vicinity of spray operations done on the shop floor (near spray); 0.05 microg NCO/m3 for office or other shop areas adjacent to spray areas (workplace background); 0.17 microg NCO/m3 for paint mixing and gun cleaning operations (mixing); 0.27 microg NCO/m3 for sanding operations. Exposure determinants for the sample NCO mass load were identified using linear regression, tobit regression and logistic regression models. For spray samples in a spray booth the significant determinants were the number of milliliters of NCO applied, the gallons of clear coat used by the shop each month and the type of spray booth used (custom built crossdraft, prefabricated crossdraft or downdraft/semi-downdraft). For near spray (bystander) samples, outdoor temperature >65 degrees F (18 degrees C) and shop size >5000 feet2 (465 m2) were significant determinants of exposure levels. For workplace background samples the shop annual income was the most important determinant. For sanding samples, the shop annual income and outdoor temperature >65 degrees F (18 degrees C) were the most significant determinants. Identification of these key exposure determinants will be useful in targeting exposure evaluation and control efforts to reduce isocyanate exposures.

Evaluation of the NIOSH draft method 5525 for determination of the total reactive isocyanate group (TRIG) for aliphatic isocyanates in autobody repair shops. National Institute for Occupational Safety and Health.

This paper evaluates the performance of the NIOSH draft method 5525 for analysis of monomeric and TRIG aliphatic isocyanates in autobody repair shops. It was found that an optimized pH gradient enhanced noticeably the resolution and, therefore, identification of aliphatic isocyanates. Samples proved to be very stable for at least a year when stored at -13 degrees C in the freezer, and no major stability problems were found for the MAP reagent. The detector response factor RSD for selected MAP ureas was 40% in the fluorescence (FLD), 3% in the UV at 254 nm (UV254), and 1% in the UV at 370 nm (UV370). The mean FLD/UV254 and UV254/UV370 detector response ratios of standards were 31.7 (RSD = 37.8) and 17.1 (RSD = 5.4), respectively. The FLD/UV254 ratio in bulks varied from 0.41 to 1.97 times the HDI monomer ratio. The mean UV254/UV370 ratio in bulks was 16.1 (range 14.1 to 19.2, N = 38). Mean (range) recovery of 92 (91.2-93.2)% was found for the N3300 (isocyanurate) spiked on 25 mm quartz fiber filters in the range 0.07 to 2.2 microg NCO ml(-1). Mean (range) recovery for impingers was 100.7 (91.7-106.0)% for N3300 in the concentration range of 0.018 to 2.5 microg NCO ml(-1) and 81.0 (76.1-89.1)% for IPDI in the concentration range of 0.016 to 1.87 microg NCO ml(-1). Analytical method precision was 3.4% and mean bias 7.4% (range = 0-25%). The NIOSH draft method 5525 provides flexibility, enhanced sensitivity and specificity, powerful resolution, and very small compound-to-compound variability in the UV254, resulting in a more reliable identification and quantification of aliphatic isocyanates.

Field comparison of impingers and treated filters for sampling of total aliphatic isocyanates with the MAP reagent.

Results of a comparative field study on the performance of 25-mm inhalable samplers (Institute of Occupational Medicine [IOM]) and midget impingers for the collection of total isocyanates in air using the 1-(9-anthracenylmethyl)piperazine (MAP) reagent are presented. Air sampling and analysis was performed according to the National Institute for Occupational Safety and Health MAP draft method 5525. Midget impingers filled with 15 mL of 1 x 10(-4) M MAP in butyl benzoate were operated at 1 L/min. IOM cassettes loaded with 25-mm quartz fiber filters impregnated with 500 microg MAP, were operated at 2 L/min. Filters were field extracted with 10 mL of 1 x 10(-4) M MAP in acetonitrile. Thirty-four impinger-IOM pairs were collected in three autobody shops during spray painting tasks. Regression analysis [Ln (IOM) = 1.0 Ln (impinger), R2 = 0.98] and a paired t-test (Pr > 0.9) demonstrated that impingers and IOMs perform equally in their collection efficiency for the monomer and total oligomeric hexamethylene diisocyanate (HDI). IOM performance did not deteriorate at longer sampling times compared with the impinger performance. Within-sampler variability was calculated from the individual coefficients of variation (CV) of the 17 pairs of like samplers. The mean of CVs (SD)% for the monomer and total oligomeric HDI was approximately 12 (12)% and 15 (13)% for the IOM and the impinger sampler, respectively. Poor correlation (Pearson correlation coefficient < 0.3) and statistically nonsignificant differences (P > 0.74 two-sided) were found for the between-sampler CVs. Factors that might have influenced the observed sampler agreement are also discussed. It is concluded that MAP impregnated filters can be successfully used for sampling of slow curing total aliphatic isocyanates in air.

Exposure-response models based on extended follow-up of a cohort mortality study in the automobile industry.

OBJECTIVE: This report describes the extended follow-up of a cohort of 46 399 automobile manufacturing workers with potential exposure to metalworking fluids (MWF). The outcomes of interest were cancers of the esophagus, stomach, colon, rectum, liver, pancreas, larynx, skin, prostate, and brain, as well as leukemia. Additional follow-up increased the power to detect modest elevations in mortality rates in association with specific types of MWF, including synthetic fluids not in widespread use until the 1970s. METHODS: Standardized mortality ratios (SMR) were computed for the most recent 10 years of follow-up, as well as for the entire study period. Adjusted relative risks (RR) were estimated in Poisson regression models with categorical variables for cumulative exposure to each type of MWF and in proportional hazards models with continuous exposure variables. RESULTS: Associations were found between straight MWF and esophageal, laryngeal and rectal cancer; soluble MWF and cancer of the esophagus, larynx, skin, and brain; synthetic MWF and cancer of the esophagus, liver, and prostate. The elevated RR values were modest in magnitude (1.5 to 2.0). SMR values were increased for stomach, liver, and pancreatic cancer and also for leukemia in the last 10 years of follow-up. The SMR values were also elevated for stomach and liver cancer among the persons recently hired. CONCLUSIONS: The results provide further evidence that exposure to metalworking fluids causes cancer among workers in automobile manufacturing. Although airborne exposures declined over the study period, this study suggests that modest risk of several digestive cancers, as well as prostatic cancer and leukemia, may persist at current levels of exposure to water-based metalworking fluids.

Subclinical immunologic and physiologic responses in hexamethylene diisocyanate-exposed auto body shop workers.

BACKGROUND: Diisocyanates are potent sensitizing agents and currently the most commonly identified cause of occupational asthma in industrialized countries. However, diisocyanate asthma is difficult to diagnose and exposure and host risk factors are unclear. Auto body shops, one of the most common hexamethylene diisocyanate (HDI) exposure settings, are particularly difficult to study due to their small size and episodic exposures. Surveillance studies of such workers are limited. OBJECTIVES: We have initiated a cross-sectional field epidemiologic study, Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), to characterize the effects of diisocyanate exposures on actively employed auto body shop workers. Methods and Results We present here questionnaire, physiologic, immunologic, and exposure data on 75 subjects enrolled in the study. No overt cases of clinically apparent diisocyanate asthma were identified based on spirometry, methacholine challenge, peak flows, and symptoms. HDI-specific lymphocyte proliferation was present in 30% of HDI-exposed workers and HDI-specific IgG in 34% of HDI-exposed workers, but they were not associated. HDI-specific IgE was detected in two workers. HDI-specific lymphocyte proliferation, increased methacholine responsiveness, and symptoms of chest tightness and shortness of breath were more common in the most heavily HDI-exposed workers, the painters. More long-term follow-up of this cohort should clarify the significance of these HDI-specific immunologic responses, physiologic changes, and symptoms. CONCLUSIONS: These findings demonstrate the presence of HDI-specific immune responses in a large proportion of healthy HDI-exposed workers.

Respiratory health of automobile workers and exposures to metal-working fluid aerosols: lung spirometry.

BACKGROUND: Despite substantial evidence that workers exposed to metal-working fluids (MWF) have increased respiratory morbidity, the few studies of chronic effects on lung function have not been conclusive. METHODS: Lung spirometry was measured and both current and past exposures to metal-working fluid (MWF) aerosols were estimated in this cross-sectional cohort of 1,811 male automobile workers. Satisfactory exposure data were available for 1,745 (96%): 239 assemblers (never-exposed to MWF), 487 assemblers (previously exposed), 352 machinists currently exposed to straight oils, 441 to soluble oils, and 226 to synthetic fluids. Operations were classified as either grinding or non-grinding machining. RESULTS: Current exposure was not found to be associated with either forced expiratory volume in 1 second (FEV(1)) or forced ventilatory capacity (FVC). Nor was past exposure to water-based fluids (soluble or synthetic MWF) related to pulmonary function. Past exposure to straight oils, however, was significantly associated with FVC. This association was more obvious among older workers and among workers who had never transferred from MWF exposed jobs to assembly. CONCLUSIONS: The magnitude of the association between FVC and lifetime exposure to straight MWF was slightly larger than the estimated cigarette effect, suggesting that the impact of an additional year of exposure to 1 mg/m(3) of mineral oil particulate in the thoracic particle size range, has the same impact on FVC as smoking one pack per day for one more year.

Short-term effects of formaldehyde on peak expiratory flow and irritant symptoms.

The authors studied the respiratory effects of formaldehyde exposure among students who dissected cadavers in a gross anatomy laboratory. Peak expiratory flow and respiratory symptoms were measured before and after each weekly laboratory session. Each of 38 students was exposed to formaldehyde for 2.5 hr/wk for 14 wk. Individual, daily formaldehyde measurements averaged 1.1 ppm (standard deviation = 0.56 ppm). Multivariate models demonstrated two different time scales of effect of formaldehyde on peak expiratory flow: (1) exposure during the previous 2.5 hr reduced peak expiratory flow by -1.0% per ppm, and (2) average exposure during all preceding weeks reduced peak expiratory flow by an additional -0.5% per ppm of formaldehyde. However, the short-term exposure effect was diminished during the first 4 wk, suggesting at least partial acclimatization. Symptom reporting was also associated with exposure during the previous 2.5 hr, and similar evidence of acclimatization was observed. These results suggest that there are two different time scales of response to formaldehyde, and they emphasize the need for longitudinal studies, characterized by quantitative exposure characterization, and frequent measurements of outcome.

A nested case-control study of stomach cancer mortality among automobile machinists exposed to metalworking fluid.

PURPOSE: In a nested case-control study of 140 stomach cancer deaths (1941-1984) among 46,384 automobile workers, we examined risk in relation to lifetime exposure to metalworking fluid (MWF) in machining and grinding operations.METHODS: Exposure was defined during varying windows of biologic time (<10 years before death, 10-20 years before death, and > 20 years before death) and evaluated using a nonparametric smoothing technique and conditional logistic regression. Exposure was measured by duration, intensity (mg/m(3)), and cumulative exposure (mg/m(3)-years) to each MWF type (straight, soluble, or synthetic), as well as by duration of exposure to selected metals, additives, and components of the fluids.RESULTS: When data from three plants were combined, grinding with water-based synthetic or soluble MWF increased the risk of stomach cancer mortality. Those grinding with synthetic MWF with more than 1.3 mg/m(3)-years exposure during the 10 years just prior to death experienced a 4.4-fold risk of stomach cancer (95% CI 1.5-13.1). Increased risk was also observed among those in the highest category of soluble grinding grading exposure (OR 1.9; 85% CI 1.0-3.6). In plant-specific analysis, there was evidence of increased risk of stomach cancer associated with exposure to straight MWF and iron, as well as the water-based fluids.CONCLUSIONS: Study findings suggest that stomach cancer mortality was associated with exposure to each MWF type. Results suggesting that synthetic MWF may act as a stomach cancer promoter are of particular concern because this MWF is widely used in today's high speed grinding operations.

Personal fluoride and solvent exposures, and their determinants, in semiconductor manufacturing.

Personal air sampling for fluorides and solvents was done at 35 semiconductor fabrication facilities in the United States. Fluoride compounds were used in etching and cleaning operations, and solvents were used in photoresist and developing operations. All personal solvent and fluoride levels were less than 2 percent of current Occupational Safety and Health Administration (OSHA) standards. Statistical models of the exposure determinants for the target agents found production level, as indicated by number of semiconductor wafer cassettes loaded/unloaded from the target machines or baths, was predictive of fluoride, xylene and 1-methoxy-2-propyl acetate exposures. The percent of fresh air ventilation and the percent of xylene in the photoresist were also significant determinants in the statistical model predicting personal xylene exposure levels.

Qualitative assessment of isocyanate skin exposure in auto body shops: a pilot study.

BACKGROUND: Little is known about the extent of human isocyanate skin exposure in auto body shops and the effectiveness of personal protective equipment. Animal studies have suggested that skin exposure to isocyanates may be an important risk factor for respiratory sensitization leading to asthma. This study provides initial data on hexamethylene diisocyanate skin exposure in three auto body shops. METHODS: Three auto body shops of different size which use different paint systems were examined for the presence of aliphatic isocyanates on environmental surfaces and workers' skin and for breakthrough of personal protective equipment. Qualitative detection of contamination by isocyanates was conducted using a wipe-sampling technique. Assessment focused on the painters and their tasks, although other auto body repairers were also evaluated. RESULTS: Environmental surfaces such as painters' workbenches, spray equipment, and cleaning tools were found contaminated with isocyanates. Painters had frequent contact with contaminated surfaces, often without wearing gloves. Moderate to heavy contamination of some skin surfaces was found with painters from two of the three auto body shops. Latex gloves used for skin protection showed significant penetrations by isocyanates even after a single painting session. CONCLUSIONS: Contaminated environmental surfaces and skin exposure to isocyanates were documented in several auto body shops. Latex gloves were not adequate protection for workers using isocyanate paints. Further research which would better quantify skin exposure, and its potential relationship to respiratory sensitization and asthma is warranted.

Identifying the determinants of viable microorganisms in the air and bulk metalworking fluids.

Exposure assessment was conducted for an epidemiologic study of the respiratory effects of exposure to metalworking fluids (MWF). As part of the study, airborne microorganisms were collected with a two-stage microbial impactor, and a sample of the bulk soluble MWF was collected from each machine sump, as well as information about the work environment. These data were then used to develop multivariate statistical models of the determinants bulk MWF and airborne microbial levels. Microbial concentrations in the bulk MWF ranged from 5 x 10(4) to 5 x 10(10) colony-forming units (CFU)/mL, with a geometric mean of 3.4 x 10(7) CFU/mL. The geometric mean airborne microbial level was 182 CFU/m3 (for particles size <8 microm) with a range of 1 to 8,308 CFU/m3. In modeling the determinants of bulk microorganisms, fluid-related factors were the most important characteristics associated with microbial levels, followed by process-related and environmental factors. The final full multivariate model predicted a significant reduction in bulk microbial levels by increasing pH of the fluid and reducing the amount of tramp oil leaking into the fluid. For the airborne microbial models, process-related factors were the major characteristics associated with microbial levels, followed by factors related to worker activities and environmental factors. The final full multivariate model predicted a significant control of airborne microorganisms by increasing worker distance from the machine, reducing the number of machines within 10 feet of the worker, decreasing the bulk microbial levels, and adding machine enclosures. These models can be used to prioritize nonbiocidal interventions to control microbial contamination of the bulk MWF and the air.

Exposure characterization for highway construction. Part I: Cut and cover and tunnel finish stages.

The purpose of this study was to characterize respirable dust, crystalline silica, diesel, and noise exposures to construction workers on a large highway construction project in Boston, Massachusetts. The study primarily focused on operating engineers and laborers, and to a lesser extent on ironworkers and carpenters during the tunnel finish and cut and cover stages. Full and partial shift noise dosimeter measurements were collected. Eighty percent of the 40 noise measurements were at or above 85 dBA, with the operating engineers averaging 91 dBA. Sample collection for respirable dust, crystalline silica, and diesel particulates measured as elemental carbon was done using cyclones and personal cascade impactors. Exposure to respirable dust ranged from 0.06 to 21.77 mg/m3 for the 77 workers sampled, with the laborers having the highest mean concentration of 2.85 mg/m3. The respirable quartz measurements for the 32 samples collected ranged from the detection limit of 0.008 mg/m3 to 1.64 mg/m3, with the highest mean concentration of 0.31 mg/m3 attributed to the laborers. The use of drills, when compared to other machine types, produced the highest exposures to respirable quartz. The levels for elemental carbon ranged from 4 to 178 micrograms/m3 (mean of 41 micrograms/m3) inside enclosed work spaces, compared with 0.5 to 53 micrograms/m3 (mean of 10 micrograms/m3) for samples collected in unenclosed work sites. Statistical modeling of the factors influencing the elemental carbon exposures showed that machine type, worker distance from the diesel source, the number of other diesel sources in the work area, and site enclosure were all significant exposure determinants. The results indicate that high exposures to noise, respirable dust, and crystalline silica are common in the highway construction industry.

Worker sensitivity and reactivity: indicators of worker susceptibility to nasal irritation.

This study examines the determinants of susceptibility to the irritant effects of sodium borate in 18 responsive workers identified through repeated self-reports of nasal irritation. For each worker, susceptibility was characterized by two features; reactivity and sensitivity, as estimated from the slope and intercept parameters from their individual exposure-response regression model. Individual estimates of reactivity and sensitivity were then examined to evaluate the importance of personal and environmental characteristics in determining susceptibility. The use of nasal sprays, current smoking and allergies were associated with lower reactivity, while high exposures to borate dust were associated with higher sensitivity. To examine possible biologic mechanisms for the irritant response, a toxicokinetic dose model was used to calculate nasal osmolarity during symptom intervals. The estimated levels suggest that osmolar activation of mast cells to release histamine and other mediators is a plausible mechanism by which these workers may experience nasal irritation.

Mortality studies of metalworking fluid exposure in the automobile industry: VI. A case-control study of esophageal cancer.

BACKGROUND: Results are reported from a nested case-control study of 60 esophageal cancer deaths among 46,384 automobile manufacturing workers potentially exposed to metalworking fluids (MWF) in machining and grinding operations. METHODS: By using incidence-density sampling, controls were selected with a sampling ratio of 20:1 from among co-workers who remained at risk by the age of death of the case, matched on race, gender, plant, and year of birth. Conditional logistic regression was used to evaluate the risk associated with cumulative exposure (mg/m3-years) to each of three types of metalworking fluid (straight, soluble, and synthetic MWF), as well as with years of exposure to selected components of MWF, including nitrosamines, sulfur, biocides, and several metals. RESULTS: Esophageal cancer was found to be significantly associated with exposure to both soluble and synthetic MWF in grinding operations. The odds ratios (ORs) for grinding with soluble MWF were elevated at 2.5 or greater in all categories of cumulative exposure, although the exposure-response trend was statistically significant only when exposure was measured as duration. Those with 12 or more years exposure to soluble MWF in grinding operations experienced a 9.3-fold relative risk of esophageal cancer mortality (95% CI = 2.1-42.1). The OR for ever grinding with synthetic MWF was 4.1 (95% CI = 1.1-15.0). Elevated risk was also associated with two agents found in both synthetic and soluble fluids, nitrosamines, and biocides. For exposure to nitrosamines, the OR was 5.4 (95% CI = 1.5-19.9); for biocides the OR was 3.8 (95% CI = 0.8-18.9). However, because the same workers were exposed to grinding with synthetics, nitrosamines and biocides, it was not possible to separate the specific risks associated with these components.

Respiratory health of automobile workers exposed to metal-working fluid aerosols: respiratory symptoms.

A total of 1,811 automobile workers at three General Motors facilities were evaluated by questionnaire for possible respiratory effects resulting from airborne exposures to metal-working fluids (MWF): 1,042 currently worked as machinists and were exposed to one of three types of MWF aerosols (straight mineral oils, soluble oil emulsions, or water-based synthetic fluids that contained no oils); 769 assembly workers, without direct exposure, served as an internal reference group (of these, 239 had never worked as machinists). Symptoms of usual cough, usual phlegm, wheezing, chest tightness, and breathlessness, as well as physician-diagnosed asthma, and chronic bronchitis were the primary outcomes examined. Machinists as a whole had higher prevalence of cough, phlegm, wheezing, and breathlessness than that of assembly workers. Adjusting for confounding, phlegm and wheeze were associated with increasing levels of current exposure to straight oils; cough, phlegm, wheeze, chest tightness, and chronic bronchitis were associated with increasing levels of current exposure to synthetics. In models that included both past and current exposure, only current exposures to straight and synthetic fluids were associated with current symptoms.

Mortality studies of machining fluid exposure in the automobile industry. V: A case-control study of pancreatic cancer.

Results are presented from a case-control study of 97 cases of pancreatic cancer nested in a cohort of workers from three automobile manufacturing plants. Risk was examined for lifetime exposure to straight, soluble, and synthetic metalworking fluids, as used in specific machining or grinding operations, as well as for constituents of the fluids. Pancreatic cancer was associated with exposure to synthetic fluids in grinding operations, with an odds ratio of 3.0 (95% CI: 1.2-7.5) among those with more than 1.4 mg/m3-years of exposure. We were unable to examine synthetic exposure in the absence of grinding because there was virtually no exposure to synthetics in machining operations in this study population. Although a disproportionately high percent of the cases were black, no black workers had any exposure to synthetic fluids, and no other measured exposure was found to be related to risk. Thus, the previously documented excess risk of pancreatic cancer among blacks in this cohort remains unexplained.

A strategy to reduce healthy worker effect in a cross-sectional study of asthma and metalworking fluids.

This report describes the reanalysis of a cross-sectional study of asthma in a large cohort of autoworkers with exposure to metalworking fluids (MWF). There is strong evidence from case reports, clinical studies, and medical surveillance data that exposure to MWF can cause asthma, yet no association was found in the original analysis. The central hypothesis of the reanalysis was that the absence of an association between asthma and MWF exposure was the result of bias caused by the self-selection of asthmatics out of exposed jobs. We addressed the potential job transfer bias by redefining exposure and disease status at the time of asthma onset, rather than at the time of the health survey. This permitted us to treat the cross-sectional study as if it were a historical cohort study, despite the fact that the population was a biased sample of the full cohort. This approach resulted in a significantly elevated incidence rate ratio of 3.2 (95% CI: 1.2-8.3) for synthetic MWF estimated in a Cox proportional hazards model. Although the cross-sectional design makes it impossible to document or control for differential selection out of the workforce, the approach described here provides a strategy for reducing the healthy-worker effect due to job transfer bias in cross-sectional studies.