Institute of Labor, Occupational Safety And Health, Ministry of Labor

Safety concerns have been raised over the extensive applications of silver nanoparticles (AgNPs) because nano dimensions make them highly bioactive, being potentially harmful to the exposed humans. Surface physico-chemistry (shape, surface charge, chemical composition, etc.) that mainly dictates nano-bio interactions is relevant for influencing their biocompatibility and toxicity. Although the hazardousness of AgNPs has been demonstrated in vitro and in vivo, mechanistic understanding of the toxicity particularly at the molecular and organismal levels, in addition to oxidative stress and silver ion dissolution, has remained unclear. A growing body of research has elucidated that autophagy, being activated in response to exposure to various nanomaterials, may serve as a cellular defense mechanism against nanotoxicity. Recently, autophagy activation was shown to correlate with AgNPs exposure; however, the subsequent autophagosome-lysosome fusion was defective. As autophagy plays a crucial role in selective removal of stress-mediated protein aggregates and injured organelles, AgNPs-induced autophagic flux defect may consequently lead to aggravated cytotoxic responses. Furthermore, we suggest that p62 accumulation resulting from defective autophagy may also potentially account for AgNPs cytotoxicity. Intriguingly, AgNPs have been shown to interfere with ubiquitin modifications, either via upregulating levels of enzymes participating in ubiquitination, or through impairing the biological reactivity of ubiquitin (due to formation of AgNPs-ubiquitin corona). Ubiquitination both confers selectivity to autophagy as well as modulates stabilization, activation, and trafficking of proteins involved in autophagic clearance pathways. In this regard, we offer a new perspective that interference of AgNPs with ubiquitination may account for AgNPs-induced defective autophagy and cytotoxic effects.

Nanoparticles (NPs) have been used to produce a wide range of products that have applications in imaging and drug delivery in medicine. Due to their chemical stability, well-controlled sizes and surface charges, polystyrene (PS) NPs have been developed as biosensors and drug delivery carriers. However, the possible adverse biological effects and underlying mechanisms are still unclear. Recently, autophagy has been implicated in the regulation of cell death. In this study, we evaluated a library of PS NPs with different surface charges. We found that NH2-labeled polystyrene (NH2-PS) nanospheres were highly toxic with enhanced uptake in macrophage (RAW 264.7) and lung epithelial (BEAS-2B) cells. Furthermore, NH2-PS could induce autophagic cell death. NH2-PS increased autophagic flux due to reactive oxygen species (ROS) generation and endoplasmic reticulum (ER) stress caused by misfolded protein aggregation. The inhibition of ER stress decreased cytotoxicity and autophagy in the NH2-PS-treated cells. In addition, the Akt/mTOR and AMPK signaling pathways were involved in the regulation of NH2-PS-triggered autophagic cell death. These results suggest an important role of autophagy in cationic NP-induced cell death and provide mechanistic insights into the inhibition of the toxicity and safe material design.

In healthcare settings, nurses' workload, burnout, and job satisfaction are associated to the patient-nurse ratio. Whether this ratio also affects their intention to leave the nursing profession, along with the underlying stress pathway, remains unclear. This study aimed to investigate the effects of the patient-nurse ratio on nurses' intention to leave and considering the mediating roles of burnout and job dissatisfaction. The study analyzed the data of two pooled cross-sectional surveys collected in 2013 and 2014. Measures were obtained by a structure questionnaire, which queried the average daily patient-nurse ratio (ADPNR), nurses' personal burnout, client-related burnout, job dissatisfaction, intention to leave, and other demographics. ADPNRs were standardized according to hospital levels. Multiple regression models examined mediation hypotheses, and a percentile bootstrap confidence interval was applied to determine the significance of indirect effects. A total of 1409 full-time registered nurses in medical and surgical wards of 24 secondary or tertiary hospitals in Taiwan completed self-administered questionnaires. Most of the participants were female (97.2%), and the mean age was 29.9 years. The association between the standardized ADPNR and intention to leave their job was significantly mediated by personal burnout, client-related burnout, and job dissatisfaction. Higher standardized ADPNRs predicted higher levels of personal burnout, client-related burnout, and job dissatisfaction, each of which resulted in higher levels of intention to leave the current job. The results highlight that appropriate patient-nurse ratio standards may be further discussed by selecting personal burnout, client-related burnout, and job dissatisfaction as indicators.

In the present study, a theoretical model was used to examine factors affecting the filtration characteristics of filters used for respiratory protection. This work was designed to support the particulate filter test requirements established in 1996. The major operating parameters examined in this work include face velocity, fiber diameter, packing density, filter thickness, and fiber charge density. Characteristics of the most penetrating particle size were also modeled with the same operating parameters. The results showed that aerosol penetration through electret filter media increases with increasing face velocity and increasing fiber diameter, and decreases as packing density, filter thickness or fiber charge density increase. Face velocity and fiber charge density have more significant effects on filter quality than the other factors. Filter quality increases with decreasing face velocity or increasing fiber charge density. For electret filters, (1) the most penetrating particle size increases with increasing fiber diameter; (2) an increase in packing density, thickness, or fiber charge density would cause the most penetrating particle size to decrease, and (3) the most penetrating particle size through electret filters increases with increasing face velocity and decreasing filter thickness. On the other hand, for non-electret filter media, the most penetrating particle size increases with decreasing face velocity, and the filter quality factor is not affected by filter thickness.

This study was conducted to investigate the protection of disposable filtering half-facepiece respirators of different grades against particles between 0.093 and 1.61 μm. A personal sampling system was used to particle size-selectively assess the protection of respirators. The results show that about 10.9% of FFP2 respirators and 28.2% of FFP3 respirators demonstrate assigned protection factors (APFs) below 10 and 20, which are the levels assigned for these respirators by the British Standard. On average, the protection factors of FFP respirators were 11.5 to 15.9 times greater than those of surgical masks. The minimum protection factors (PFs) were observed for particles between 0.263 and 0.384 μm. No significant difference in PF results was found among FFP respirator categories and particle size. A strong association between fit factors and protection factors was found. The study indicates that FFP respirators may not achieve the expected protection level and the APFs may need to be revised for these classes of respirators.

OBJECTIVES: We evaluated the association between exposure to polycyclic aromatic hydrocarbons (PAHs) and immunological measurements using blood samples from coke oven workers exposed to high and low PAH levels. METHODS: A population-based cross-sectional study was conducted from 2008-2009 with coke oven workers and steel-rolling workers as the exposed and control groups, respectively. Questionnaires on basic demographic information were administered. Personal breathing zone and urine samples were collected to quantify personal PAH intake and biological response doses. Immunological and cytokine parameters in serum were analysed. Urinary malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were analysed to determine oxidative stress induced by PAHs in relation to altered humoural immunological status. RESULTS: Mean levels of serum immunoglobulin A (IgA) and TNF-α were significantly increased in coke oven workers compared to steel-rolling workers who had no or minimal PAH exposure (p=0.0033 and p<0.0001, respectively). There were no significant differences in mean levels of IL-4 and IL-10 between coke oven workers and steel-rolling workers. Moderate activation of lipid peroxidation and oxidative damage as determined by plasma MDA and 8-OHdG levels were detected simultaneously with significant alterations in IgA and IgE levels. Multiple regression analyses demonstrated that PAHs with high molecular weights >252 (dibenzo(a,h)anthracene, benzo(a)pyrene, benzo(a)anthracene and/or indeno(1,2,3-cd)pyrene) correlated with IgA and IgE levels. CONCLUSIONS: This study showed that coke oven workers with chronic exposure to PAHs may develop immunological alteration. Oxidative stress and lipid peroxidation induced by PAHs may partly explain the alteration in immunological parameters.

The aim of this study was to identify the health hazards and possible exposure surveillance markers of workers exposed to nanoparticles during manufacturing and application in comparison to a group of unexposed workers. For this longitudinal study, we recruited 158 nanomaterial-handling workers and 104 non-exposed workers from 14 manufacturing plants in Taiwan (baseline). Among them, 124 nanomaterial-handling workers and 77 unexposed workers were monitored 6 months later. We investigated pulmonary and cardiovascular disease markers, inflammation and oxidative stress markers, antioxidant enzymes and genotoxicity markers. Antioxidant enzymes (superoxide dismutase, glutathione peroxidase) and cardiovascular markers (vascular cell adhesion molecule, paraoxonase) were significantly associated with nanomaterial-handling during the 6-month follow-up period. In addition, the small airway damage marker (Clara cell protein 16) and lung function test parameters were also significantly associated with handling nanomaterials. The study markers and lung function tests are possible markers that could be useful for surveillance of nanomaterial-handling workers.

PURPOSE: In this study, we examined whether the associations between working hours, job satisfaction, and work-life balance are mediated by occupational stress. In addition, we tested whether perceived time control helps moderate the effects of working hours and occupational stress. METHODOLOGY: Questionnaires were administered to 369 respondents working in the high-tech and banking industries. Analyses were then conducted on the data. FINDINGS: The analysis revealed significant correlations between long working hours and both occupational stress and work-life balance, as well as between occupational stress and both work-life balance and job satisfaction. In addition, the relationship between working hours and occupational stress exhibited a significantly positive interaction with perceived time control. VALUE: The results indicate the importance of giving workers greater control over working hours. We therefore recommend that labor laws should be revised as necessary to prevent excessive working hours and enhance work-time flexibility.

A highly sensitive and selective method, using isotope-dilution liquid chromatography with tandem mass spectrometry (LC/MS/MS), for quantification of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), an important biomarker of oxidative stress, was developed and compared with a method using an enzyme-linked immunosorbent assay (ELISA). The synthesis of (15)N(5)-8-OHdG is described. In this study, 140 urine samples were collected from workers in a coke oven plant, including samples from 49 control workers and 91 workers who had been occupationally exposed to polyaromatic hydrocarbons (PAHs). The major urinary metabolite of PAHs, 1-hydroxypyrene (1-OHP), was measured for the exposed workers. Results from the present study showed a significant correlation between these two measurements for determination of 8-OHdG (p < 0.05, r(2) = 0.70). However, only the LC/MS/MS measurements of urinary levels of 8-OHdG showed a significant difference between the exposed and the control subjects (p < 0.05). The ELISA method failed to demonstrate this difference. Furthermore, only by using the LC/MS/MS method was a significant correlation observed between the urinary levels of 1-OHP and 8-OHdG. These findings suggest that a highly specific and sensitive analytical method such as isotope-dilution LC/MS/MS is extremely important and necessary for accurate measurement and a comprehensive study of oxidative stress in human subjects.

This study evaluates oxidative DNA damage in workers who are exposed to cooking oil fumes (COFs) in Chinese restaurants. The study participants were 387 nonsmoking Chinese restaurant workers, 202 kitchen staff, and 185 service staff at 23 Chinese restaurants in Taiwan. Airborne particulate matter and particulate polycyclic aromatic hydrocarbon levels were monitored in kitchens and dining areas. Urinary 1-hydroxypyrene (1-OHP) was used as an internal dose of exposure to COFs, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) was used as an oxidative DNA damage marker. The relationship between workers' 8-OHdG and 1-OHP levels was estimated using linear mixed-effects models. Airborne particulate matter and polycyclic aromatic hydrocarbons levels in kitchens significantly exceeded those in dining areas. The kitchen staff's geometric mean levels of urinary 8-OHdG (7.9 microg/g creatinine) and 1-OHP (4.5 microg/g creatinine) were significantly higher than those of the service staff, which were 5.4 and 2.7 microg/g creatinine, respectively. Urinary 1-OHP level, work in kitchens, gender, and work hours per day were four significant predictors of urinary 8-OHdG levels after adjustments are made for covariates. Oxidative DNA damage was associated with exposure of Chinese restaurant workers to COFs. Female restaurant workers had a greater oxidative stress response to COFs than male restaurant workers, providing additional evidence of the link between lung cancer in Chinese women and exposure to COFs.

AIMS: To assess the relations between exposure to traffic exhausts and indicators of oxidative DNA damage among highway toll station workers. METHODS: Cross-sectional study of 47 female highway toll station workers exposed to traffic exhausts and 27 female office workers as a reference group. Exposure assessment was based on average and cumulative traffic density and a biomarker of exposure, urinary 1-hydroxypyrene-glucuronide (1-OHPG). Urinary 8-hydroxydeoxyguanosine (8-OHdG) was used as a biomarker of oxidative DNA damage. Plasma nitric oxide (NO) was measured as an indicator of oxidative stress related to traffic exhaust exposure. RESULTS: The mean concentration of urinary 8-OHdG was substantially higher among the exposed non-smokers (13.6 microg/g creatinine) compared with the reference non-smokers (7.3 microg/g creatinine; difference 6.3, 95% CI 3.0 to 9.6). The mean concentration of NO among the exposed (48.0 micromol/l) was also higher compared with the reference non-smokers (37.6 micromol/l; difference 10.4, 95% CI -0.4 to 21.2). In linear regression adjusting for confounding, a change in log(8-OHdG) was statistically significantly related to a unit change in log(1-OHPG) (beta = 0.372, 95% CI 0.081 to 0.663). CONCLUSIONS: Results indicate that exposure to traffic exhausts increases oxidative DNA damage. Urinary 8-OHdG is a promising biomarker of traffic exhaust induced oxidative stress.

In this study we investigated the risk of hearing loss among workers exposed to both toluene and noise. We recruited 58 workers at an adhesive materials manufacturing plant who were exposured to both toluene and noise [78.6-87.1 A-weighted decibels; dB(A)], 58 workers exposed to noise only [83.5-90.1 dB(A)], and 58 administrative clerks [67.9-72.6 dB(A)] at the same company. We interviewed participants to obtain sociodemographic and employment information and performed physical examinations, including pure-tone audiometry tests between 0.5 and 6 kHz. A contracted laboratory certified by the Council of Labor in Taiwan conducted on-site toluene and noise exposure measurements. The prevalence of hearing loss of >or=25 dB in the toluene plus noise group (86.2%) was much greater than that in the noise-only group (44.8%) and the administrative clerks (5.0%) (p<0.001). The prevalence rates were 67.2, 32.8, and 8.3% (p<0.001), respectively, when 0.5 kHz was excluded from the estimation. Multivariate logistic regression analysis showed that the toluene plus noise group had an estimated risk for hearing loss>or=25 dB, 10.9 times higher than that of the noise-only group. The risk ratio dropped to 5.8 when 0.5 kHz was excluded from the risk estimation. Hearing impairment was greater for the pure-tone frequency of 1 kHz than for that of 2 kHz. However, the mean hearing threshold was the poorest for 6 kHz, and the least effect was observed for 2 kHz. Our results suggest that toluene exacerbates hearing loss in a noisy environment, with the main impact on the lower frequencies.

This study determines the relative survival (RS) of Bacillus subtilis spores loaded on an N95 filtering facepiece respirator (FFR) after decontamination by five methods under worst-case conditions. Relative survival was obtained by testing after decontamination and after storing the FFRs at 37°C and 95% relative humidity for 24 hours. The decontamination methods involved ethanol, bleach, ultraviolet irradiation (UVA 365 nm, UVC 254 nm), an autoclave, and a traditional electric rice cooker (TERC) that was made in Taiwan. Without decontamination, 59 ± 8% of the loaded spores survived for 24 hours. When 70% ethanol was added to the N95 FFR at a packing density of 0.23, the RS was 73 ± 5% initially and decayed to 22 ± 8% in 24 hours. Relative survival remained above 20% after 20 minutes of UVA irradiation. The other four decontamination measures achieved 99%-100% biocidal efficacy, as measured immediately after the methods were applied to the test FFRs. Relative survival is a useful parameter for measuring sterilization or degree of disinfection. Bleach, UVC, an autoclave, and a TERC provide better biocidal efficacy than ethanol and UVA. Not only a higher filter quality but also a lower value of RS produced the most decontaminated FFR.

A novel active personal nanoparticle sampler (PENS), which enables the collection of both respirable particulate mass (RPM) and nanoparticles (NPs) simultaneously, was developed to meet the critical demand for personal sampling of engineered nanomaterials (ENMs) in workplaces. The PENS consists of a respirable cyclone and a micro-orifice impactor with the cutoff aerodynamic diameter (d(pa50)) of 4 μm and 100 nm, respectively. The micro-orifice impactor has a fixed micro-orifice plate (137 nozzles of 55 μm in the inner diameter) and a rotating, silicone oil-coated Teflon filter substrate at 1 rpm to achieve a uniform particle deposition and avoid solid particle bounce. A final filter is used after the impactor to collect the NPs. Calibration results show that the d(pa50) of the respirable cyclone and the micro-orifice impactor are 3.92 ± 0.22 μm and 101.4 ± 0.1 nm, respectively. The d(pa50) at the loaded micro-Al(2)O(3) mass of 0.36-3.18 mg is shifted to 102.9-101.2 nm, respectively, while it is shifted to 98.9-97.8 nm at the loaded nano-TiO(2) mass of 0.92-1.78 mg, respectively. That is, the shift of d(pa50) due to solid particle loading is small if the PENS is not overloaded. Both NPs and RPM concentrations were found to agree well with those of the IOSH respirable cyclone and MOUDI. By using the present PENS, the collected samples can be further analyzed for chemical species concentrations besides gravimetric analysis to determine the actual exposure concentrations of ENMs in both RPM and NPs fractions in workplaces, which are often influenced by the background or incident pollution sources.

This study assessed fatigue in electric arc melting workers (ER) and continuous casting workers (CC) in a steel plant and evaluated their physiological response to different levels of heat stress. Fifty-five men participated in the study. The ER group (mean, standard deviation [SD]=41.6, 7.4 years) was significantly older than the CC group (34.9, 6.4 years). The wet bulb globe temperature (WBGT) index of the workplace was measured. Workers' subjective fatigue symptoms were investigated by a 30-item constructive questionnaire, and physiological conditions and response time were measured before and after work for 2 consecutive days. WBGT ranged from 25.4 approximately 28.7 degrees C and 30.0 approximately 33.2 degrees C for the CC and ER areas, respectively. After age adjustment the ER group had significantly higher prevalence rates in subjective symptoms and slower response time than the CC group. The response "thirsty" was the highest after work (75 and 60% for the 2 ER interview days, respectively). A high prevalence (over 40%) of "eyes feel strained," "perception of shoulders stiff," or "feel waist pain" also was observed. Average pre- and postwork ER group systolic pressures were 129.1+/-11.4 mmHg (mean+/-SD) and 126.1+/-12.1 mmHg, 132.5+/-11.4 and 130.6+/-11.2 mmHg for the CC group. Continuous heat-strain monitoring data from one ER and one CC worker indicated that average working heart rate and body temperature were well below 150 beats/min and 38 degrees C. Faster response in critical flicker fusion was found after work than before work, but the differences were not statistically significant (p>.05). Response time for the falling bar grasp was faster at the beginning of work, declined with working time, and rebounded at the end of work. Workers exposed to a hot environment are inclined to subjective fatigue, and their fatigue symptoms increase with the heat exposure levels. However, low resting heart rate and systolic pressure are two characteristics for high heat exposure workers.

BACKGROUND: Lead-exposed workers may suffer adverse health effects under the currently regulated blood lead (BPb) levels. However, a probabilistic assessment about lead exposure-associated anemia risk is lacking. The goal of this study was to examine the association between lead exposure and anemia risk among factory workers in Taiwan. METHODS: We first collated BPb and indicators of hematopoietic function data via health examination records that included 533 male and 218 female lead-exposed workers between 2012 and 2014. We used benchmark dose (BMD) modeling to estimate the critical effect doses for detection of abnormal indicators. A risk-based probabilistic model was used to characterize the potential hazard of lead poisoning for job-specific workers by hazard index (HI). We applied Bayesian decision analysis to determine whether BMD could be implicated as a suitable BPb standard. RESULTS: Our results indicated that HI for total lead-exposed workers was 0.78 (95% confidence interval: 0.50-1.26) with risk occurrence probability of 11.1%. The abnormal risk of anemia indicators for male and female workers could be reduced, respectively, by 67-77% and 86-95% by adopting the suggested BPb standards of 25 and 15 μg/dL. CONCLUSIONS: We conclude that cumulative exposure to lead in the workplace was significantly associated with anemia risk. This study suggests that current BPb standard needs to be better understood for the application of lead-exposed population protection in different scenarios to provide a novel standard for health management. Low-level lead exposure risk is an occupational and public health problem that should be paid more attention.

The role of ventilation in preventing tuberculosis (TB) transmission has been widely proposed in infection control guidance. However, conclusive evidence is lacking. Modeling suggested the threshold of ventilation rate to reduce effective reproductive ratio (ratio between new secondary infectious cases and source cases) of TB to below 1 is corresponding to a carbon dioxide (CO2) level of 1000 parts per million (ppm). Here, we measured the effect of improving ventilation rate on a TB outbreak involving 27 TB cases and 1665 contacts in underventilated university buildings. Ventilation engineering decreased the maximum CO2 levels from 3204 ± 50 ppm to 591-603 ppm. Thereafter, the secondary attack rate of new contacts in university dropped to zero (mean follow-up duration: 5.9 years). Exposure to source TB cases under CO2 >1000 ppm indoor environment was a significant risk factor for contacts to become new infectious TB cases (P < .001). After adjusting for effects of contact investigation and latent TB infection treatment, improving ventilation rate to levels with CO2 <1000 ppm was independently associated with a 97% decrease (95% CI: 50%-99.9%) in the incidence of TB among contacts. These results show that maintaining adequate indoor ventilation could be a highly effective strategy for controlling TB outbreaks.

To identify a set of important WBV predictors that could be used to develop a statistical instrument for exposure assessment in a large epidemiologic study, a total of 432 WBV measures were taken from a sample of 247 male drivers in Taipei City, Taiwan. In accordance with the ISO 2631-1 (1997) methods, we measured the frequency-weighted vertical acceleration (z-axis) over drivers' seat surface, under conditions representing different types of rides (vacant vs. short vs. long) assigned to random destinations. Mixed effect models were used to analyse the WBV data including repeated measures. For this group of urban taxi drivers regularly exposed to WBV of low intensity (mean = 0.31 ms( - 2), ranging from 0.17 to 0.55 ms( - 2) r.m.s.), our analyses indicated that average driving speed was the primary predictor (p < 0.0001). As average driving speed increased, measured vertical acceleration increased in a quadratic-linear manner (p < 0.0001). Other WBV predictors, after adjusting for the effects of other covariates, included automobile manufacturer (p = 0.02), engine size (p = 0.04), body weight (p = 0.002), age (p = 0.02), use of seat cushion (p = 0.03), and traffic period (p = 0.02). Our study suggests that a similar statistical approach could be employed in future studies to improve the quality and efficiency of WBV exposure assessment in professional drivers.

Abstract Cooking-related emissions are associated with environmental pollution and adverse health effects. Of the various chemical species emitted during cooking, polycyclic aromatic hydrocarbons (PAHs) and aldehydes are two chemical species with carcinogenic or tumor promoting characteristics. Although PAH exposure has been studied in commercial kitchen workers, few studies have investigated simultaneous exposure to PAHs and aldehydes in these workers. The aims of this study were to compare personal concentrations of PAH and aldehyde in three commercial cooking workplaces and to estimate their corresponding cancer risks. The three cooking workplaces included western fast food restaurant kitchens, Chinese cafeteria kitchens, and street food carts. Comparisons showed that workers in western fast food restaurant kitchens and Chinese cafeteria kitchens tended to have lower personal concentrations of these pollutants compared to workers in street food carts. The geometric mean (95% CI) cancer risks in the three workplaces were, from lowest to highest, 1.36 (1.12–1.67) × 10−5 for western fast food restaurant kitchens, 1.52 (1.01–2.28) × 10−5 for Chinese cafeteria kitchens, and 3.14 (2.45–4.01) × 10−5 for street food carts. The percentage contributions of aldehyde species to cancer risk were very high (74.9–99.7%). Street food cart workers had high personal exposure to aldehyde probably due to lack of effective exhaust systems. Thus, their cancer risk was significantly higher than those of workers in western fast food restaurant kitchens (p < 0.001) and Chinese cafeteria kitchens (p = 0.013).

PURPOSE: The aim of this study was to investigate whether rotating shift work increases occupational stress in nurses. METHODS: This study measured shift work scheduling and occupational stress by using the Effort-Reward Imbalance model with self-reported questionnaires in a sample of 654 female nurses. RESULTS: Overcommitment risk was higher in nurses who worked rotating shifts than in those who worked day/non-night shifts (OR, 2.16; 95% CI, 1.03-4.66). However, an effort/reward imbalance was not directly associated with work schedules (OR, 1.88; 95% CI, 0.87-4.35). Among nurses working rotation rotating shifts, those who had 2 days off after their most recent night shifts showed an alleviated risk of overcommitment (OR, 0.52; 95% CI, 0.32-0.82), but those who had worked for at least one series of 7 consecutive work days per month had an increased risk of effort/reward imbalance (OR, 2.75; 95% CI, 1.69-4.48). Additionally, those who had little or no participation in planning working hours and shift scheduling and worked overtime at least three times per week during the preceding 2 months tended to have high stress. CONCLUSIONS: The nurses who worked rotating shifts tended to experience work-related stress, but their stress levels improved if they had at least 2 days off after their most recent night shift and if they were not scheduled to work 7 consecutive days. These empirical data can be used to optimize work schedules for nurses to alleviate work stress.