Journal of School of Public Health and

Background and Aim: In the initial preparation stage, before feeding worms with organic wastes, the wastes are pre-composted for some time. This was done so that the thermophilic phase of organic wastes degradation is passed, no harm is done to the worms which are sensitive to high temperatures, production of fertilizer faster is quicker, and biological contamination is reduced. The length of this preparation time is important with regard to the quality of the compost obtained, the vermicomposting process, and space and facilities needed. The purpose of this study was to determine the effect of preparation time of food wastes on the vermicomposting process without any preliminary action or continuous aeration.

Materials and Methods: The Eisenia Foetida species was used for vermicomposting. Food waste preparation times of 0,6,12 and 18 days were attempted, and factors such as pH, C%, N%, C/N ratio, and the process rate were monitored during the process.

Results: The lowest and highest final C/N ratios were seen on days 6 and 18 of preparation, respectively. The data also showed that the highest reduction (64.93) in this ratio was observed on 6 day and the lowest (36.56) on day18.

Conclusion: On the basis of these findings it can be concluded that there is a significant difference among various food waste preparation times with regard to C/N ratio (p-value<0.05), the preparation time is effective on the C/N ratio, and the most appropriate length of time for preparation is 6-12 days.

Background and Aim: In the raw furniture preparation workshops, in which the workers usually have an undesirable postures when at work, ergonomic assessment and the work environment improvement seem essential. Developing checklists and calculating ergonomic indices would be useful in this assessment. This study was conducted with the objectives of assessing musculoskeletal disorders (MSDs) risk factors and determining types of corrective measures in raw furniture preparation workshops.

Materials and methods: After conducting task analysis, 268 workers were assessed using an ergonomic checklist developed for the purpose and ergonomic indices were calculated. The Nordic musculoskeletal disorders questionnaire was used to determine the prevalence rate of MSDs among the workers. Data were analyzed using the t-test and the test of proportions.

Results: The highest prevalence was in the lower back (38.4%) and the knees 36.2%). Statistical analysis revealed that there were significant associations between MSDs and calculated ergonomic indices (p<0.001). In addition, calculation of OR revealed that ergonomic conditions were associated with MSDs in different body parts (OR=2.90-9.49, p<0.001). On the whole, the working conditions of 32.46% of the workers studied were poor from an ergonomic point of view.

Conclusion: The checklist developed was found to be an appropriate and low-cost tool for ergonomic assessment. The most important problems in the workshops were due to inappropriate general working conditions, inappropriate organization, and unsuitable work stations.

  Background and Aim: The aim of this study was to assess exposure of workers in a metal industry to nickel and lead.

  Materials and Methods: Extraction was done using the solid-phase extraction on Chromosorb-102 resin to prepare, concentrate and purify biological samples of urine, hair and nails of workers working in metal industries. The variables influencing response (pH, loading flow rate, elution solvent, and amount of resins, elution volume, and sample volume) were examined and the procedure was optimized. The optimized procedure was, then, validated based on the “within-day” and “day-to-day” reproducibility experiments, using low, medium and high concentrations, leading to a satisfactory accuracy and precision. Finally, lead and nickel samples were taken from the workers and their concentrations determined voltammetrically.

  Results: The optimum values for the examined parameters were as follows: pH = 9, ligand concentration = 0.05%, loading flow rate = 5 ml/min, elution solvent = 2M HNO₃, amount of resins = 500 mg, elution volume = 15 ml, and sample volume up to 500 ml. A good reproducibility and repeatability was obtained for the optimized method under the existing conditions. Lead and nickel could be extracted with recoveries in the range of 94-100%. On the whole, the concentrations of nickel and lead in the workers’ biological samples were above the respective maximum permitted levels.

  Conclusion: Solid-phase extraction procedure is a fast and simple method for preconcentrating and isolating analytes from biological samples. Considering the low concentrations of the analytes and presence of confounding factors in such samples, the procedure can be very effective for their preparation. The application of the developed method indicates that trace metal ions can be effectively purified and preconcentrated from different matrices like urine, hair and nail samples to assess occupational exposures.