The desktop slot exhaust hood has been widely used, but it is calculated by empirical formula. Axial velocity change rule of desktop slot exhaust hood can effectively provide the basis of the wind speed needed in order to control the poison. According to gas motion mathematical model, the geometry model and boundary conditions of desktop slot exhaust hood was established, and the influence of the hood sizes to axial velocity were analyzed by Fluent simulation. The changes of relationship between the axial velocity (V) and the distance from the hood mouth (L), the short edge of the hood mouth (a), the long edge of the hood mouth (b), the equivalent diameter of the hood mouth (d) and the square root of the hood mouth area (√A) were comparative analyzed by dimensionless processing. The result is the V/V0 with L/d have better change rule. The axial velocity change rule of different axial velocity were also analyzed using V/V0 with L/d change rule, and the change rule of V/V0 with L/d of desktop slot exhaust hood was obtained, which was verified by experiment.
With economic growth, the use of chemicals has continually increased, resulting in an increase of chemical accidents. Chemical accidents pose a life threat and can lead to many health problems among the residents living in close proximity to chemical plants. This study aimed to investigate the awareness of the residents living near chemical plants about hazardous chemicals, as well as to survey the awareness of workers who do not directly handle chemicals at chemical plants (WNHCs). To this end, a questionnaire survey was conducted among a total of 600 residents and 160 WNHCs. The questionnaire was composed of three items: awareness of chemical risk, awareness of countermeasures in chemical accidents, and imperious necessity of PPE (personal protective equipment). Statistical analysis of the data was performed with the Statistical Package for Social Sciences (SPSS) version 18.0. The results show that the government needs to complement the notification system of chemical risk for residents who live close to chemical plants. The highest priority of PPE which residents want to prepare for chemical accidents was respiratory protective equipment (RPE). They responded that, if necessary to purchase PPE, they could bear a portion of the expenses (up to US $30). This study provides basic data for the development of programs and policies on chemical safety relevant for the residents living in close proximity to chemical plants in South Korea.
Working and walking environments often involve standing positions on different surfaces with inclination and different friction. In this study, standing balance of thirteen participants during sudden and irregular external perturbation to calf muscles was investigated. The aim of the study was to evaluate the combined effect of surface inclination and friction on standing balance. The main findings when eyes closed revealed that the standing utilised coefficient of friction (μSUCOF) increased when the surface was inclined for both high and low friction materials. The anterior-posterior torque increased more anteriorly when the surface was inclined toes down and when the surface friction was low. The results indicate that the anterior-posterior torque is a sensitive parameter when evaluating standing balance ability and slip risk. On inclined surface, particularly on the surface with lower friction, the potential slip and fall risk is higher due to the increase of standing utilised coefficient of friction and increased forward turning torque.
Occupational trichloroethylene (TCE) exposure can induce life-threatening generalized dermatitis accompanied by hepatitis: TCE hypersensitivity syndrome (HS). Since the patients’ exposure levels have not been fully clarified, this study estimated end-of-shift urinary concentrations of trichloroacetic acid (TCA) and their lower limit below which the disease occurrence was rare. TCA concentration was measured in 78 TCE HS patients whose urine was collected at admission between 2nd and 14th d after their last shift. Then a linear regression model was used to calculate the mean TCA concentration with 95% confidence interval (95% CI) and 95% prediction interval (95% PI) in the end-of-shift urine. The estimated mean concentration was 83 (95% CI, 49–140) mg/l with 95% PI 9.6–720 mg/l. TCA concentrations were also measured in the end-of-shift urine of 38 healthy workers involved in the same job as were the patients. The geometric mean and its 95% CI were 127 mg/l and 16–984 mg/l, respectively. The exposure levels in HS patients might have thus overlapped with those in workers without HS. Accordingly, it was suggested that HS occurred in the environment where the workers were exposed to the TCE concentration corresponding to the urinary TCA concentration as low as 10 mg/l.
In Iran-Shiraz, municipal solid waste is collected manually requiring strenuous physical activities. This study was conducted to determine the prevalence rate of musculoskeletal disorders (MSDs) and its associated risk factors. Two hundred male waste collectors participated in this cross-sectional study, in which task analysis followed by motion and timeline analysis were performed. The data were collected using demographic, occupation-specific physical and organizational demands, and Nordic musculoskeletal questionnaires. Logistic regression analysis was used for identifying independent risk factors for MSDs. Ten motions observed during waste collection, and the most physical and organizational demands were related to the running along with bag carriage, and the time pressure, respectively. About 39% and 36.5% of the workers reported very high physical and psychological workloads, respectively. Totally, 92.5% of waste collectors reported MSDs symptom at least in one body region during the last 12 months. Lower back and knee injuries were more prevalent and more severe. Some individual factors (age, body weight, and waste collecting duration), physical demands (lifting bag/bucket, pulling/pushing waste container, walking along with bag/bucket carriage, and jumping up/down on the garbage truck), and organizational demands (low vacation and high decision authority) were the most important risk factors for developing MSDs.
This cross sectional study developed and validated a LBP risk-factor screening scale for use with sugarcane farmers. The scale was developed from a synthesis of LBP risk factors, pretested with 30 sugarcane farmers and administered to five hundred and forty sugarcane farmers to test its psychometric properties. Results indicated construct validity for three factors; physical factors (19 items) with factor loadings of 0.406 to 0.881 and communalities between 0.471 and 0.991; psychological factors (7 items) with factor loadings of 0.635 to 0.821 and communalities between 0.444 and 0.714, and third, working environment factors (2 items), with factor loadings between 0.345 and 0.347 and communalities between 0.946 and 0.953. The content validity index was 0.90 with reliability index of 0.87. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 82.02%, 30.49%, 62.65% and 54.40% respectively. The area under the receiver operating characteristic was 0.56. The scale’s high specificity and sensitivity and comprehensive three risk-factor dimensions should make it a very useful screening tool in primary health care for early detection of LBP and for LBP risk-reduction and prevention advice. Future studies could focus on confirming content and predictive validity in other settings to assess generality of its usage.
In 2011, load limits for manual lifting were adopted in Iran to protect workers from low back injury without prior testing of accuracy with Iranian workers. This investigation examined how accurate the adopted ACGIH TLVs at the allowable limits predict risk for LBP disorders for a group of Iranian workers using biomechanical criteria. Testing took place in the laboratory with participants completing a series of 2-handed lifting tasks as defined in the Iranian Guideline for Manual Lifting. To test accuracy, both compression and shear forces were estimated for fifteen male Iranian workers who completed 25 lift combinations that varied in height and reach with the maximal allowable load. The findings, when compared to a risk threshold of 3400 N compression and 700 N shear, showed above-threshold forces for compression and little-to-no safety margins with repetitive lifting for most lifts at torso height and below. Since Government, employers and workers use these guidelines to decide on work/workplace design; these guidelines require further review and revision based on the anthropometrics of Iranian people.
This study aimed to examine the cross-sectional association of non-standard employment with cardiovascular disease risk factors. Five yr of data from the Comprehensive Survey of Living Conditions and National Health and Nutritional Survey were combined. We used logistic regression to examine the association of employment contract (non-standard [part-time, dispatched, or contract] vs. standard [full-time and permanent]) with eight cardiovascular disease risk factors among 1,636 men and 2,067 women aged 40–60 yr. There were significant associations between non-standard employment and cardiovascular disease risk factors such as current smoking among men (odds ratio [OR] 1.39; 95% confidential interval [CI], 1.13–1.86) and diabetes among women (OR 1.83; 95% CI, 1.10–3.09). Non-standard employment was associated with a few cardiovascular disease risk factors in this middle-aged cohort in Japan.
Previous studies have shown that biomarkers of chemicals with long half-lives may be better surrogates of exposure for epidemiological analyses, leading to less attenuation of the exposure-disease association, than personal air samples. However, chemicals with short half-lives have shown inconsistent results. In the present study, we compared pairs of personal air benzene and its short-half-life urinary metabolite trans,trans-muconic acid (t,t-MA), and predicted attenuation bias of theoretical exposure-disease association. Total 669 pairs of personal air benzene and urine t,t-MA samples were taken from 474 male workers during turnaround maintenance operations held in seven petrochemical plants. Maintenance jobs were classified into 13 groups. Variance components were calculated for personal air benzene and urine t,t-MA separately to estimate the attenuation of the theoretical exposure-disease association. Personal air benzene and urine t,t-MA showed similar attenuation of the theoretical exposure-disease association. Analyses for repeated measurements showed similar results, while in analyses for values above the limits of detection (LODs), urine t,t-MA showed less attenuation of the theoretical exposure-disease association than personal air benzene. Our findings suggest that there may be no significant difference in attenuation bias when personal air benzene or urine t,t-MA is used as a surrogate for benzene exposure.
We investigate exposure to welding fume metals in pipeline construction, which are responsible for severe respiratory problems. We analyzed air samples obtained using size-fractioning cascade impactors that were attached to the welders performing shielded metal and gas tungsten arc welding outdoors. Iron, aluminum, zinc, chromium, manganese, copper, nickel, and lead concentrations in the water-soluble (WS) and water-insoluble (WI) portions were determined separately, using inductively coupled plasma mass spectrometry. The mass-size distribution of welding fume matches a log-normal distribution with two modes. The metal concentrations in the welding fume were ranked as follows: Fe>Al>Zn>Cr>Mn>Ni>Cu>Pb. In the WS portion, the capacities of metals dissolving in water are correlated with the metal species but particle sizes. Particularly, Zn, Mn, and Pb exhibit relatively higher capacities than Cu, Cr, Al, Fe, and Ni. Exposure of the gas-exchange region of the lungs to WS metals were in the range of 4.9% to 34.6% of the corresponding metals in air by considering the particle-size selection in lungs, metal composition by particle size, and the capacities of each metal dissolving in water.