Average Dust Concentration Research Articles

Investigation on dust pollution and pneumoconiosis incidence in a steel enterprise

Objective: To analyze the change trend of underground dust concentration, the incidence and survival status of pneumoconiosis patients, and provide reference for improving the working environment of dust-exposed workers and the prevention and treatment of pneumoconiosis patients in the future. Methods: In February 2020, a retrospective investigation was conducted on the dust data of underground mining operations in a steel enterprise in Jiangsu Province from 1991 to 2019, and the case data of patients diagnosed with pneumoconiosis from 1956 to 2019 were collected. The time trends of the number of pneumoconiosis patients and dust concentration, the stage of pneumoconiosis and survival status of patients were analyzed. Results: From 1956 to 2019, a total of 241 patients with pneumoconiosis were diagnosed in the steel enterprise. From 1991 to 2019, the annual average dust concentration in the mine showed a downward trend as a whole. Compared with the transportation platform (14.28%, 1447/10132) , the average dust concentration exceeding rate of the mining platform (43.68%, 8415/19263) was significantly higher (χ(2)=2674.84, P<0.01) . The average age of pneumoconiosis patients was (73.54±10.42) years old, and the average working age of dust exposure was (21.41±8.68) years, of which 85 cases (35.27%) survived and 156 cases (64.73%) died. The main type of pneumoconiosis was silicosis (90.46%, 218/241) , and the main stage of pneumoconiosis was the stage I (96.68%, 233/241) ; The higher the stage of pneumoconiosis, the younger the diagnosis age (P<0.01) . The average survival time of patients was (27.264±1.982) years, and the median survival time was 28 years. The cumulative survival rates of patients with pneumoconiosis in different diagnosis time periods were significantly different (χ(2)=35.57, P<0.01) . Conclusion: The improved dust-proof measures have a significant effect on reducing the concentration of underground dust. We need to focus on the dust control of underground mining platforms and the treatment of patients with stage Ⅲ pneumoconiosis.

Transient analysis of dust exposure under different supply airflow angle in a blasting tunnel based on CFD

In recent years, with the rapid development of metro tunnels, many scholars have paid attention to the serious dust environment during blasting construction. To efficiently alleviate the dust pollution in working zone and reduce the ventilation time after blasting, this study adopted the CFD numerical simulation method to investigate the effect of supply airflow angle on the dust removal performance of 3 m breathing height within the working zone in an entrance and exit metro tunnel. The supply airflow angle corresponding to the optimal dust removal performance and minimum ventilation energy consumption was determined after in-depth analysis of four kinds of supply airflow angles. The simulation results showed that when the supply airflow angle was 30°, the minimum ventilation time was obtained in the breathing zone 5 m away from the driving face; while in the breathing zone 10 m, 15 m and 20 m away from the driving face, the minimum ventilation time was achieved when the supply airflow angle was 10°. From the view of the weighted average dust concentration and ventilation time in the working zone, the supply airflow angle of 10° could obtain the optimal dust removal performance and minimum ventilation energy consumption, with dust removal performance improved by 67.6% and ventilation energy consumption reduced by 20.46%.

Simulation study on gas-bearing dust and its application combined with air curtain in development heading, a case study

In view of the problems caused by the overrun of gas and dust in the tunneling process of 7703 rock roadway in Zouzhuang Coal Mine, the risk control technology research was carried out by combining numerical analysis, research and development of new automatic wall-attached duct and field test, and the dust closed control within low gas concentration was realized. The results show that the gas concentration in the local area exceeded the legal or regulation limit of 1% under the conditions of forced ventilation, axial-to-radial flow ratio 1:9 and 2:8 mixed ventilation. When the axial-to-radial flow ratios were 3:7 and 4:6, the gas concentration was low, approximately 0.5%. Additionally, when the axial-to-radial flow ratio was 4:6, the dust concentration was still maintained at approximately 150 mg/m3 until 20 m away from the head. When the axial-to-radial flow ratio was 3:7, the dust pollution was effectively controlled. At approximately 17 m from the head, the average dust concentration was gradually brought lower than 4 mg/m3.

Numerical analysis of dust pollution evolution law caused by ascensional/descensional ventilation in fully mechanized coal mining face based on DPM-DEM model

To understand the problem of differences in the dust migration law of ascensional and descensional ventilation, this study numerically simulates the dust migration law under the condition of ascensional and descensional ventilation, and proposes corresponding automatic spray control schemes. The results show that under the influence of wind flow, the migration distance of dust under ascensional ventilation was longer than that under descensional ventilation at the same time, and the distance difference of dust migration between ascensional and descensional ventilation also increased with the evolution of time. Among them, the distance differences at 10 s, 25 s, 50 s and 75 s were 2 m, 7 m, 9 m and 14 m respectively. The lift of the ascensional wind hindered dust deposition, which caused the dust at 0–15 m on the downwind side of the shearer to seriously affect the breathing belt, with an average dust concentration of 1683.3 mg/m³ . The thrust of the descensional wind caused the roof near the moving support to seriously affect the breathing belt, with an average dust concentration of 1435.1 mg/m³ .

Reducing Construction Dust Pollution by Planning Construction Site Layout

Many construction activities generate fine particles and severely threaten the physical health of construction workers. Although many dust control measures are implemented in the industry, the occupational health risks still exist. In order to improve the occupational health level, this study proposes a new method of reducing the construction dust pollution through a reasonable site layout plan. This method is based on the field measurement and dust diffusion law. The dust diffusion law can be fitted based on the field monitoring data. With diffusion law, the average dust concentration exposed to workers of different site layouts can be simulated. In addition, the cost of the dust control method is a concern for site managers. Therefore, the total transportation cost reduction is another optimization objective. Finally, the multi-objective particle swarm optimization (MOPSO) algorithm is used to search for an optimized site layout that can reduce dust pollution and transportation cost simultaneously. The result shows that average dust concentration exposed to workers and total transportation cost are significantly reduced by 60.62% and 44.3%, respectively. This paper quantifies the construction dust pollution and provides site managers with a practical solution to reduce the construction dust pollution at low cost.

Analysis and Forecasting of PM2.5, PM4, and PM10 Dust Concentrations, Based on In Situ Tests in Hard Coal Mines

The method of analyzing the results of dust concentration measurements in mine workings that was conducted within the ROCD (Reducing risks from Occupational exposure to Coal Dust) European project using the developed dust prediction algorithm is presented. The analysis was based on the measurements of average dust concentration with the use of the CIP-10R gravimetric dust meters, for the respirable PM4 dust concentration, and IPSQ analyzer for instantaneous concentration measurements (including PM2.5 dust) and with the use of Pł-2 optical dust meters for instantaneous concentration measurements of PM10 dust. Based on the analyses of the measurement results, the characteristics of the distribution of PM10, PM4, and PM2.5 dust particles were developed for the tested dust sources. Then, functional models based on power functions were developed. The determined models (functions) allow predicting the dust distribution in such conditions (and places) for which we do not have empirical data. The developed models were implemented in a specially developed online tool, which enables predicting the concentration of PM10, PM4, and PM2.5 dust (on the basis of dust concentration of one source) at any distance from the dust source.

Levels, Sources, and Health Damage of Dust in Grain Transportation and Storage: A Case Study of Chinese Grain Storage Companies

A large amount of mixed dust exists in grain, which can easily stimulate the respiratory system and cause diseases. This study explored contamination levels and health effects of this grain dust. A total of 616 dust samples from different stages and types of grain were collected in China—in Hefei (Anhui), Shenzhen (Guangdong), Chengdu (Sichuan), Changchun (Jilin), and Shunyi (Beijing)—and analyzed using the filter membrane method and a laser particle size analyzer. A probabilistic risk assessment model was developed to explore the health effects of grain dust on workers in the grain storage industry based on the United States Environmental Protection Agency risk assessment model and the Monte Carlo simulation method. Sensitivity analysis methods were used to analyze the various exposure parameters and influencing factors that affect the health risk assessment results. This assessment model was applied to translate health risks into disability-adjusted life years (DALY). The results revealed that the concentration of dust ranged from 25 to 70 mg/m3, which followed normal distribution and the proportion of dust with a particle size of less than 10 μm exceeded 10%. Workers in the transporting stage were exposed to the largest health risk, which followed a lognormal distribution. The average health risks for workers in the entering and exiting zones were slightly below 2.5 × 10−5. The sensitivity analysis indicated that average time, exposure duration, inhalation rate, and dust concentration made great contributions to dust health risk. Workers in the grain storage and transportation stage had the health damage, and the average DALY exceeded 0.4 years.

Design of pulse cleaning device for single-filter cartridge dust collector by multi-factor orthogonal method based numerical simulation

To solve the problem of difficulty in dust removal from single-filter cartridge dust collector equipment in confined space, an orthogonal experimental design and numerical simulation methods were adopted to optimize the ash-cleaning device. The study found that the diameter of the cone base has a greater impact on the pulse cleaning performance of the dust collector than the angle of the cone, and the installation height L has the least impact. When the optimal parameters θ = 55°, D = 80 mm, L = 0 mm, compared with the traditional dust collector, the average dust concentration at the outlet of the equipment is reduced by 11.5%, the number of cleanings is reduced by 37.5%, and the pressure at the lower part of the filter cartridge is reduced. 34.7%, the upper part increased by about 53.9%. The problem of uneven cleaning of filter cartridges in confined spaces is solved, and equipment performance is improved.

Compliance Testing and Homogenous Exposure Group Assessment in the South African Coal Mining Industry.

Globally, several strategies for compliance testing and within-group exposure variability have been suggested. This study aimed to evaluate the performance of the South African Mining Industry Code of Practice (SAMI CoP) approach for grouping and compliance testing against international standards. A total of 28 homogenous exposure groups (HEGs) with 728 underground coal mine workers' eight-hour time-weighted average coal dust concentration data were obtained. Compliance testing was assessed using 10% exceedance above occupational exposure limit (OEL) for SAMI CoP, and the 95th percentile of the lognormal distribution was computed for the European Standardization Committee (CEN) and American Industrial Hygiene Association (AIHA). Comparison of the homogeneity of the HEGs was done between SAMI CoP which mandates that both the arithmetic mean (AM) and 90th percentile must fall in the same exposure band to certify homogeneity and the global geometric standard deviation (GSD) and Rappaport ratio (R-ratio) with specific acceptability criteria. To test the homogeneity of exposure within job titles, eight non-homogenous HEGs that have two or more job titles with three measurements were investigated using GSD and the SAMI CoP criteria. A total of 21 HEGs out of 28 were non-compliant to the OEL across SAMI CoP, CEN, and AIHA criteria. Compliance to the OEL was observed for seven HEGs according to the SAMI CoP approach, whereas only one HEG was compliant according to both the SAMI CoP and CEN approaches. The GSD criterion and SAMI CoP revealed that 11 and 6 HEGs were homogenous, respectively, and only on 4 occasions, the 2 approaches agreed. The job titles of the majority of non-homogenous HEGs in both SAMI CoP and GSD were actually homogenous. Five out of 10 sub-groups have their AM above that of HEG B. Other HEGs had at least one of their AM and 90th percentile values above that of their respective parent HEGs. All three approaches mainly confirmed non-compliance of HEGs. SAMI CoP tended to show compliance of HEGs more than CEN. Non-homogenous HEGs had many job titles that were homogenous according to both SAMI CoP and GSD criteria. There was no perfect agreement of homogeneity by all the indicators. For both future constitutions of HEGs as well as a retrospective assessment of high exposure groups, homogeneity can be improved by using job titles.

Black carbon and dust in the Third Pole glaciers: Revaluated concentrations, mass absorption cross-sections and contributions to glacier ablation

In snow and ice, light-absorbing particles (LAPs), such as black carbon (BC) and dust, accelerate the melting of Third Pole glaciers (TPGs). In this study, we revaluated LAP concentrations in the snow pits of TPGs (SP-TPGs), measured LAP mass absorption cross-sections (MACs), and simulated their effects on glacier darkening and melting based on the Spectral Albedo Model for Dirty Snow and a surface energy and mass balance model. The results indicated that because of their short distances to emission sources, the average BC concentrations measured in snow pits in the periphery of Third Pole were much higher than those measured in the inland Tibetan Plateau, and the average dust concentrations generally decreased from north to south. The average MACs of BC in the SP-TPGs varied from 3.1 to 7.7 m2 g−1 at 550 nm, most of the average spectral values were comparable in the visible and near-infrared bands to those calculated by Mie theory, except those in Urumqi Glacier No. 1 (UR), Syek Zapadniy Glacier (SZ), and Laohugou Glacier No.12 (LH), while the average spectral MACs of dust in the SP-TPGs were considerably smaller in magnitude than most of the variations measured in other regions. Compared with the pure snow surfaces, BC and dust played comparable roles in reducing albedo in UR, SZ, LH, and Renlongba Glacier, whereas BC was the most prominent absorber in the other glaciers. The combined effect of BC and dust accelerated melting by 30.4–345.9 mm w.e. (19.7–45.3% of the total mass balance) through surface albedo darkening (0.06–0.17) and increased radiation absorption (25.8–65.7 W m−2) within one month of the ablation season. This study provides a new data set of LAP concentrations and MACs and helps to clarify the roles of these factors in the cryospheric environment of the Third Pole.

Filtration of submicron dust by a dual-layer granular bed filter with an external electric field.

To improve the filtration efficiency of submicron dust by dual-layer granular bed filters, filtration experiments for micro-silica powder were conducted for removing particles smaller than 1 μm that account for more than 96% (by volume) using a dual-layer granular bed filter with an external electric field. Electrostatic enhancement methods, including dust pre-charging, application of an electric field to the lower filter layer, and that to both the upper and lower filter layers, were examined. Results showed that the average filtration efficiency of a dual-layer granular bed filter for micro-silica powder without electric field was 76.52%, the average outlet dust concentration was 263.53 mg/m3, and the filtration cycle time was 73 min. With pre-charged dust, the average outlet dust concentration dropped to 82.51 mg/m3. A decrease in the thickness of the lower filter layer from 45 to 25 mm with electric field reduced the pressure drop from 2570 to 1770 Pa. Meanwhile, the application of an electric field to the lower/upper filter layer reduced the average outlet dust concentration to 25.98 mg/m3. Increasing the initial face velocity from 0.25 to 0.45 m/s increased the average outlet dust concentration from 25.98 to 30.27 mg/m3 and increased the pressure drop from 2570 to 3500 Pa.

Numerical research on airflow-dust migration behavior and optimal forced air duct installation position in a subway tunnel during drilling operation

In order to efficiently control the severe dust pollution ahead of the driving face during drilling operation, this study combined the numerical simulation with field measurements to analyze the effect of installation position of the forced air duct on the airflow-dust migration behavior in a subway tunnel. Nine schemes of installation position of the forced air duct were chosen to in-depth investigate the dynamic variation of dust concentration in four personnel breathing zones, then the optimal installation position of the forced air duct with regard to the efficient dust suppression performance was determined. The numerical simulation results showed that from the perspective of the static excavation process, the optimal dust suppression performance was achieved when the forced air duct was installed in the bottom arch of 30 m from the driving face, and the average dust concentration in four personnel breathing zones was 31.78 mg/m3. While, from the perspective of 10 m dynamic excavation process, the optimal dust suppression performance was achieved when the forced air duct was installed in the bottom arch of 20 m from the driving face, and the average dust concentration in four personnel breathing zones was 33.21 mg/m3. Finally, the accuracy of the numerical simulation results was validated by field measurement.

Aridity Index Variations and Dust Events in Iran from 1990 to 2018

This study was carried out to determine whether the changes in dust concentration (DC) in Iran were attributed to changes in aridity index (AI) from 1990 to 2018. Long-term precipitation and potential evapotranspiration were used to compute the United Nations Environment Program AI and horizontal visibility data were used to calculate the DC in the study area. The DC spatial distribution maps were prepared to better identify areas affected by sand-dust events. Pearson’s correlation analysis was performed to explore the association between DC and AI in Iran and study stations during the monitoring period. Spatiotemporal variations in DC showed that more than 60 percent of Iran’s area experienced severe wind erosion events in 2001, 2008, and 1990 when AI was less than 0.2. The results also showed that approximately 45 percent of Iran’s area has suffered from the average DC over the study period (565 µg/m3). The incremental changes in DC were observed in almost half of the entire area of Iran during the second period (2000–2008) and one third of this area during the third period (2009–2018). Areas affected by decreasing changes in AI during the second and third periods were 90 percent and 73 percent of the area affected during the previous period, respectively. Overall, there was a significant negative correlation between AI and DC in Iran over the monitoring period (r = −0.51, p value < 0.01). Insignificant positive correlations were observed in humid regions, whereas negative correlations were mostly detected in arid and semiarid regions of Iran.

Impacts of El Niño-Southern Oscillation on surface dust levels across the world during 1982–2019

Dust pollution has become a significant concern worldwide. Both human activities and climate conditions affect dust levels. This study investigates the influence of El Niño–Southern Oscillation (ENSO), an important large-scale climate phenomenon, on surface dust levels in different regions. We used surface dust concentrations from Retrospective analysis for Research and Applications version 2 reanalysis and Southern Oscillation index (SOI) as dust and ENSO indicators, respectively. First, we first described characteristics of the global surface dust concentrations spanning a period of 37 years (1982–2019). Subsequently, we investigated the associations between monthly surface dust concentrations and SOI in regions with relative high dust levels, (i.e., North Africa, Northwest China and Mongolia, the Middle East, and South Australia) using time-series generalized additive models, controlled for meteorological variables and normalized difference vegetation index (NDVI). In order to capture the delayed effects of ENSO on dust, we fitted the model for SOI with 13 different moving averages starting from 12 months before. The highest average surface dust concentration for our study regions was 306.68 μg/m3, observed in North Africa. The average dust concentrations in the Middle East, Northwest China, and South Australia were 193.18, 113.64, and 77.19 μg/m3, respectively. Our results showed that dust concentrations were positively related with SOI. The associations between dust and SOI were more significant and higher for North Africa and the Middle East. Our results indicated that for regions with high dust pollution, La Niña episodes are associated with increased dust concentrations, while El Niño events are associated with decreased dust concentrations.

Refined Dust Fine Control Method of Bulk Cargo Yard Based on Whole-field Monitoring

The fine dust control method and control system of bulk cargo yard based on whole-site monitoring are realized through the following paths. Firstly, the extinction coefficient of the whole area of the storage yard is obtained by using lidar, and the proportion relationship between the extinction coefficient and the dust concentration data measured at the same position is obtained to obtain the dust concentration distribution in the whole area. Secondly, the radar scanning plane is divided into N grids with the control range of each spray head as a grid unit, and the average dust concentration in each grid is calculated. Thirdly, the critical value of the average dust concentration and the critical value of dust contribution rate are set to judge the grid that needs to start the sprinkler head. Repeat the above process to achieve continuous fine control of dust in bulk cargo yard. The system not only improves the efficiency of dust suppression, but also reduces the amount of sprayed water, achieves the purpose of improving the efficiency of environmental protection effects, reducing the labor intensity of workers, and maximizing the utilization of water resources while effectively removing dust.

Seoul bike trip duration prediction using data mining techniques

Trip duration is the most fundamental measure in all modes of transportation. Hence, it is crucial to predict the trip-time precisely for the advancement of Intelligent Transport Systems and traveller information systems. To predict the trip duration, data mining techniques are employed in this study to predict the trip duration of rental bikes in Seoul Bike sharing system. The prediction is carried out with the combination of Seoul Bike data and weather data. The data used include trip duration, trip distance, pickup and dropoff latitude and longitude, temperature, precipitation, wind speed, humidity, solar radiation, snowfall, ground temperature and 1-hour average dust concentration. Feature engineering is done to extract additional features from the data. Four statistical models are used to predict the trip duration. (a) Linear regression, (b) Gradient boosting machines, (c) k nearest neighbour and (d) Random Forest (RF). Four performance metrics root mean squared error, coefficient of variance, mean absolute error and median absolute error is used to determine the efficiency of the models. In comparison with the other models, the best model RF can explain the variance of 93% in the testing set and 98% (R 2) in the training set. The outcome proves that RF is effective to be employed for the prediction of trip duration.

Detection and comparison of fiber count concentration in processing environment of asbestos and man-made mineral fiber

Objective: To connect with the measurement data of asbestos dust fiber concentration in foreign countries, improve the accuracy of asbestos fiber detection in China, and understand the dust exposure in the working environment of asbestos and man-made mineral fiber production and processing sites in Zhejiang Province. The fiber count concentrations of working environment in glass fiber, ceramic fiber and asbestos processing plants were measured and compared. Methods: The dust concentration in the working environment of two glass fiber factories, one ceramic fiber factory and eight asbestos products processing factories was measured. The total dust mass concentration was measured according to GBZ/T 192.1-2007, and the fiber count concentration was measured by phase contrast microscope. Kruskal Wallis was used to test and compare the dust concentration in the working environment of each post. The correlation between asbestos mass concentration and fiber count concentration was analyzed by Spearman correlation. Results: Under the phase contrast microscope, there were many short and fine asbestos fibers in the field of vision, and there were many impurities around. The average dust concentration of asbestos processing plant was 3.2 f/ml, and the dust concentration of cotton ginning was the highest (6.68 f/ml) . There was a significantly positive correlation between asbestos fiber count concentration and mass concentration (r=0.535, P=0.033) . The average fiber count concentration of glass fiber factory was 0.001 f/ml, and the highest was 0.005 f/ml. The average fiber count concentration of ceramic fiber factory was 0.001 f/ml, and the highest was 0.006 f/ml. Conclusion: The fiber count concentration in the working environment of asbestos factory in Zhejiang Province is obviously over the standard, which is one of the important reasons for the high incidence of mesothelioma in this area. Short and small asbestos fibers are easy to be ignored when counting. It is necessary to improve the actual operation process of fiber counting to form a laboratory standard in China.

Predicting the Risk of Developing Silicosis in Refractory Workers

We conducted a study of refractory workers exposed to multiple occupational hazards, the most important of which being dust aerosols of predominantly fibrogenic action. Our objective was to identify the spectrum of predictors of the occupational disease in refractory workers and to build a predictive mathematical model using multivariate analysis to assess the likelihood of developing silicosis. Materials and methods: The case reports of 172 refractory production workers were analyzed. The main group consisted of 75 silicosis patients and the control cohort consisted of 97 experienced workers without this occupational disease. The groups were comparable in gender (p=0.052), dust exposure (p=0.862), and the severity of the work process (p=0.147). We assessed a wide specter of factors related to refractory workers’ health and occupational conditions significantly affecting the timing of developing occupational pulmonary fibrosis. Results: In the silicosis patients, arterial hypertension (p=0.005), left ventricular myocardial hypertrophy (p=0.002), coronary heart disease (p=0.010), chronic circulatory depression (p=0.010), low hemoglobin level (p=0.022), and low speed and volume criteria of external respiration function were significantly more prevalent. We established four important independent factors associated with the development of silicosis in refractory workers including age, time-weighted average and maximum one-time dust concentrations, and the forced expiratory volume in the first second. Conclusions: We observed a medium work-relatedness of hypertension, a strong work-relatedness of left ventricular myocardial hypertrophy, sinus node tachycardia syndrome and obesity, and a very strong work-relatedness of impaired fasting glycemia. Using a logistic regression, we built a silicosis development predictive model having high predictive ability (82.8 %), sufficient sensitivity (85.2 %) and specificity (80.0 %). The model was tested and verified on clinical examples and can be used to predict the probability of silicosis in refractory workers.

Field comparison of a roof bolter dry dust collection system with an original designed wet collection system for dust control.

Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box, the average respirable dust concentration was 1.188 mg/m3, a 60% reduction in respirable dust concentration. The quartz content of the roof material was high, ranging from 28.9 to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60% when cleaning the collector boxes.

Respiratory Health and Inflammatory Markers-Exposure to Cobalt in the Swedish Hard Metal Industry.

To study the relationship between inhalable dust and cobalt, and respiratory symptoms, lung function, exhaled nitric oxide in expired air, and CC16 in the Swedish hard metal industry. Personal sampling of inhalable dust and cobalt, and medical examination including blood sampling was performed for 72 workers. Exposure-response relationships were determined using logistic, linear, and mixed-model analysis. The average inhalable dust and cobalt concentrations were 0.079 and 0.0017 mg/m, respectively. Statistically significant increased serum levels of CC16 were determined when the high and low cumulative exposures for cobalt were compared. Nonsignificant exposure-response relationships were observed between cross-shift inhalable dust or cobalt exposures and asthma, nose dripping, and bronchitis. Our findings suggest an exposure-response relationship between inhalable cumulative cobalt exposure and CC16 levels in blood, which may reflect an injury or a reparation process in the lungs.