Applied occupational and environmental hygiene最新文献

Hypersensitivity pneumonitis (HP) was identified among employees in an automobile parts manufacturing facility. Mycobacteria immunogenum (MI) was identified as a metal removal fluid (MRF) contaminant at this facility and had been identified as a contaminant in other facilities where HP had occurred. We therefore questioned whether measurement of MI-specific cell-mediated immunity would be associated with HP in this facility. We also questioned whether measures of cell-mediated immunity would be more informative about the presence of HP than evaluation of serum anti-MI antibody levels. Workers were categorized for exposure and disease status by questionnaire and review of medical records. Cell-mediated immunity to MI was assessed by measuring in vitro secretion of cytokines (interleukin 8, tumor necrosis factor alpha, and interferon-gamma) from peripheral blood mononuclear cells or anticoagulated whole blood induced by culture with MI antigen. Serum antibodies against MI were also measured. Six study participants met our survey definition for HP and 48 did not. As has been reported for various agents causing HP, serum antibody levels against MI were increased in both exposed workers and workers with HP. Serum antibodies did not distinguish between the two. When expressed as a percentage of secretion induced by lipopolysaccharide, MI induced a significant increase in interleukin-8 secretion in exposed participants' whole blood cultures. There were trends for increased MI-induced secretion of interferon-gamma by peripheral blood mononuclear cells from both exposed workers and workers with HP. However, these trends did not attain statistical significance. Thus, several measures of immunity to MI distinguished between exposed and unexposed workers but not between workers with and without HP. These evaluations of cell-mediated immunity were not more informative than measurement of serum antibodies. As was done at this facility, institution of a comprehensive safety and health plan for MRF is necessary to eliminate (or minimize) health effects related to occupational exposures in the machining environment.

Since 1985, a number of North American researchers have evaluated the association between worker exposure to metalworking fluids (MWFs) and cancer mortality or respiratory morbidity. The studies have used different methods to measure the MWF aerosol concentration and to evaluate the exposures to the specific components of the MWF aerosol (bacteria, endotoxin, elements, metals, ethanolamines, polyaromatic hydrocarbons). This diversity of approaches makes comparison of study results difficult and has impeded the development of an occupational exposure limit (OEL) for metalworking fluids. This article summarizes the exposures measured in these North American epidemiologic studies by estimating their thoracic and inhalable MWF particulate levels. In addition, issues that must be resolved before a universal sampling and analysis method for MWF can be recommended are reviewed, including: the use of gravimetric versus extractable analysis; whether the analytical limit of detection can support a lower occupational exposure limit; if the volatile components of mineral oils should also be collected; and whether there are components of specific concern in MWFs that should be regulated separately. Finally, recommendations for future directions in MWF exposure assessment and control are suggested.

In a reported study, mists of selected synthetic metalworking fluids were generated in laboratory experiments by two processes, nebulization (atomization) and air sparging (bubbling). Short-chain fatty acid species were determined by in situ trimethylsilyl derivatization. Comparison of relative amounts of the short-chain acids collected from mists generated by nebulization with those generated by sparging showed that the sparged mists had significantly higher amounts of neodecanoic, nonanoic, and dodecanedioic acids. Comparison of the amounts of acids collected by the resin cartridges to amounts found on the filters showed that significant losses of octanoic and isononanoic acids occurred over 8 hours of collection and that only dodecanedioic acid was not lost from the filter over a 22-hour sampling period. In another reported metalworking mist study, contaminants of metalworking fluids, e.g., tramp oils, were shown in laboratory experiments to increase the misting potential of water-based metalworking fluids. Significantly, tramp oil contamination caused less misting in synthetic fluids than soluble and semi-synthetic fluids.

Early subchronic and chronic inhalation toxicology studies on various petroleum mineral oils and formulated lubricants supported the ACGIH TLV of 5 mg/m(3) for mineral oil mist. Additional subchronic studies with aerosolized mineral base oils and lubricants during the last 15 years demonstrated that exposures to aerosols of mineral base oils (often >100 mg/m(3)) resulted mainly in concentration-related accumulation in the lung of alveolar macrophages laden with oil droplets. Inflammatory cells were observed with higher aerosol concentrations, consistent with the clinical literature from highly exposed workers. These pulmonary changes appeared to be a nonspecific response to the presence of deposited aerosol. Studies on sensory irritation during exposures of lab animals to mineral oils indicate possible effects only with very high aerosol concentrations. Coupled with changes in refining to remove carcinogenic polynuclear aromatic hydrocarbons from mineral oils several decades ago, this information indicates that current aerosols of mineral oils have a profile of low toxicity from acute to long-term exposures. Available information suggests that additives in some formulated products and/or maintenance of mineral-based metalworking fluids may play a much more significant role in potential health effects.

In response to worker and union representative concerns, the association between metalworking fluid exposure and respiratory symptoms was investigated in a cross-sectional survey, in a large automotive machining location. A self-administered respiratory symptom-screening questionnaire was sent to 2935 current employees. MWF exposure levels were assigned to respondents on a departmental basis based on average and "peak" area aerosol measurements. MWF exposure, years in the plant, and smoking status were regressed on presence or absence of daily or weekly respiratory symptoms, as well as upper and lower respiratory symptom groupings derived from principal components factor analysis. The response rate was 81 percent. Symptom prevalence was high: 29 percent of subjects reported weekly or daily phlegm; 23 percent, dry cough; 42 percent, runny or plugged nose. Average aerosol concentration in departments with exposure ranged from 0.02 to 0.84 mg/m(3), and peak levels from 0.02 to 2.85 mg/m(3). Average exposures ranging from 0.25 to 0.84 mg/m(3), as compared to exposures in the range of 0.02 to 0.09 mg/m(3), were statistically significantly associated with wheezing, chest tightness, sore throat, and hoarse throat, as well as with the upper respiratory symptom grouping. When peak exposure was included in the regression, it exerted a stronger effect than average exposure level on dry cough, phlegm, wheezing, fever/chills, and hoarse throat, as well as on upper and lower respiratory symptom groupings. These effects were independent of smoking status. Exposure-symptom trends for the average and peak departmental area concentration categories were statistically significant for the upper and lower respiratory symptom groupings and for most individual symptoms. We have observed an association of increasing upper and lower respiratory symptoms with estimated MWF exposure, measured independently, at average departmental aerosol concentrations well below the NIOSH recommended personal exposure level of 0.5 mg/m(3). The results have been used to prioritize exposure reduction efforts in the workplace.

The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that the threshold limit value (TLV) for mineral oil mists be dramatically lowered, based on epidemiological evidence of respiratory health effects among machinists exposed to various metalworking fluid mists. A review of the literature regarding respiratory health effects from either metalworking or non-metalworking fluids suggest that machinists may have experienced slightly higher prevalence of common respiratory symptoms and mild and reversible cross-shift changes in some measures of pulmonary function. However, the inconsistency and potential for both random and systematic error in this body of literature argue against drawing definitive conclusions. There is also no substantive evidence that any of these effects led to permanent disease or impairment. The most likely causal agents for respiratory effects in these workers are microbial contaminants in water-based metalworking fluids, not straight mineral oils. This is consistent with the epidemic outbreaks of hypersensitivity pneumonitis, bronchitis, and asthma reported at some work sites using water-based metalworking fluids. This highlights the importance of frequent cleaning and fluid changes for metalworking fluid reservoirs, as part of a systematic approach to managing metalworking fluid aerosol exposures. A dramatic drop in the TLV for mineral oil mists would not resolve this problem.

Recent outbreaks of hypersensitivity pneumonitis (HP) have been associated with exposures to metalworking (MWF) fluid aerosols. Mycobacteria present in mismanaged fluids have been suggested as the likely culprit. In January 2001, three machinists at a machining plant were hospitalized with HP. Subsequently, additional HP cases developed as well as cases of bronchitis and occupational asthma. In October 2001, an aerosol concentration map was constructed to advise on priorities for corrective actions. In April 2002 after installation of mist collectors, a second map was generated. Mist reductions varied from about 75 percent to an increase of about 20 percent. Mist concentrations increased in the areas near an uncontrolled transfer line. Subsequent to the first mapping exercise, the exposures of 30 HP cases were classified as low, medium, and high based on job location and the map. There were 6 cases among low exposure jobs (4% of exposed), 14 cases among medium exposure jobs (19% of exposed), and 10 cases among high exposure jobs (34% of exposed), suggesting a relation between exposure to contaminated metalworking fluid mist and the development of HP. A combination of interventions (fluid management, mist control, improved fresh air ventilation, and medical surveillance/restriction) eliminated any new cases 11 months after the first diagnosis of HP.

The purpose of the study was to determine whether hexahydrotriazine ("triazine") bactericides increase the likelihood of elevated mycobacteria growth in metal removal fluids (MRFs). In reaction to an outbreak of hypersensitivity pneumonitis (HP) at a transmission manufacturing facility, machining plants of a large automobile manufacturer were directed to increase the testing of MRF, especially testing for mycobacteria. A working hypothesis was developed that triazine bactericides cause an increase in mycobacteria contamination, which in turn may lead to an increased risk of HP for workers exposed to MRF aerosols. Test results for 277 central MRF systems from nine machining facilities were analyzed for various MRF properties including the presence and type of both bactericide in the MRF formula and bacterial contamination of the MRF. The study included data reflecting usual operating conditions of all of the 277 large MRF systems in the company. The study does not evaluate the effect of tank-side biocide addition. The results show that soluble oils, semi-synthetic, and synthetic MRFs are all capable of supporting mycobacterial growth. The results also demonstrate a highly significant association between routine use of triazine bactericides and mycobacterial contamination of MRF. Based on the hypothesis that mycobacteria are a likely causative agent of hypersensitivity pneumonitis from MRF exposure, it is concluded that elimination of triazines from MRF formulae may be protective against HP in the machining environment.