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2008| April-June | Volume 10 | Issue 39
May 20, 2008
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Occupational noise in rice mills
GV Prasanna Kumar, KN Dewangan, Amaresh Sarkar, Amrita Kumari, Banani Kar
April-June 2008, 10(39):55-67
A major occupational hazard for the workers in rice mills is the noise during the operation of various machines. A noise survey was conducted in the workrooms of eight renowned rice mills of the north-eastern region of India established during the period between 1980 and 1985. The rice mills were selected on the basis of the outcome of a walk-through noise survey involving several rice mills of the region. A noise survey map of each rice mill was drawn to identify the predominant noise sources and the causes of high noise in the workrooms of the rice mill. The sound-pressure level (SPL) in the workrooms of the rice mill varied from 78 to 92 dBA. The paddy cleaner, rubber roll sheller, compartment separator, rice cleaner, auxiliary sieve shaker and an electric motor without enclosure were found to be the predominant noise sources in the workrooms of the mill. The causes of high noise in the rice mills may be attributed to the use of a long flat belt drive, crank-and-pitman mechanism, absence of an electric motor enclosure, poor machine maintenance and inadequate acoustic design of the workroom of the rice mill. About 26% of the total labourers were found to be exposed to higher levels of noise than 85 dBA. Subjective response indicated that about 26% of the total labourers felt noise interferes in their work and about 49% labourers were of opinion that noise interferes with their conversation. Context: Noise from machines in the rice mills was found to be the major occupational hazard for the rice mill workers. The predominant noise sources need to be identified and the causes of high noise need to be studied to undertake the appropriate measures to reduce the noise level.
To identify the predominant noise sources and their distributions in rice mills, to study the causes of high levels of noise in rice mills and to examine the response of the workers towards noise. Settings and Design: A noise survey was conducted in eight renowned rice mills of the north-eastern region of India. The mills were selected based on a walk-through survey conducted for the identification of rice mills with high noise. A noise survey map of each rice mill was collected by following the guidelines of Canadian Centre for Occupational Health and Safety (CCOHS). The distribution of high noise in rice mills was studied and the causes of high noise were identified. The subjective response to noise in rice mills was assessed by conducting personal interview with all the workers of the rice mills using a structured form.
Methods and Material:
The guidelines of CCOHS were followed during the noise survey. A sound level meter (SLM; Model-824) was used to record the noise level at each grid point marked at 1 m × 1 m. SPL in weighting scale "A" and the noise spectrum were recorded at each grid point for 30 s and data were stored in SLM. A noise survey map of equivalent SPL was drawn for each rice mill by drawing contour lines on the sketch of the rice mill between the points of equal SPL. The floor area in the rice mill where SPL exceeded 85 dBA was identified from the noise survey map of each rice mill to determine the causes of high levels of noise. In order to study the variation in SPL in the workroom of the rice mill throughout the shift, equivalent SPL was measured at six locations in each rice mill. The subjective response to noise in rice mills was assessed by conducting personal interview with all the workers of the rice mills using a structured form. Demographic information, nature of work, working hours, rest period, experience of working in mill, degree of noise annoyance, activity interference, and psychological and physiological effects of machine noise on the worker were asked during the interview. Statistical Analysis Used: Nil.
The noise survey in eight select rice mills of the major paddy-growing regions of India revealed that the workrooms of five rice mills had SPL more than 85 dBA in the locations where workers were engaged for most of the time. The predominant noise sources in the rice mills were paddy cleaner, rubber roll sheller, compartment separator, rice cleaner, sieve shaker and an electric motor without enclosure. The causes of high noise in the rice mills may be due to the use of a long flat belt drive, crank-and-pitman mechanism, absence of an electric motor enclosure, poor machine maintenance and inadequate acoustic design of the workroom in the rice mill. In general, a well-maintained rice mill with each machine being run individually using an electric motor produced less noise than that being run using a single electric motor along with flat belt drives. The normal working period in the rice mill was 48 h/week and it was 56 h/week during the peak season of rice milling. About 26% of the total workers were exposed to noise of more than 85 dBA. Subjective response indicated that about 26% of the total workers felt noise interferes in their work and about 49% workers were of opinion that noise interferes with their conversation.
The workers in the rice mills are exposed to high noise, which will have detrimental effect on their health. Apart from undertaking appropriate noise control measures, preventive maintenance of machines needs to be given due importance in all the rice mills.
Hospital contacts for noise-related hearing loss among Danish seafarers and fishermen: A population-based cohort study
Linda Kaerlev, Anker Jensen, Per Sabro Nielsen, Jorn Olsen, Harald Hannerz, Finn Tuchsen
April-June 2008, 10(39):41-45
Noise-induced hearing loss (NIHL) is a leading occupational disease and some seafarers and fishermen may be at high risk. We present here standardized hospital contact ratios (SHCRs) for hearing loss among Danish seafarers and fishermen.
Materials and Methods:
Cohorts of all Danish seafarers registered by the Danish Maritime Authority (DMA) and fishermen retrieved from a 1989-1998 pension registry were linked to the nationwide Occupational Hospitalisation Registry (OHR) with follow-up for NIHL from 1994 to 2003, using rates specific for age and calendar time for the entire Danish workforce as a reference.
We found high SHCRs for NIHL: 165 [95% confidence interval (CI) 131-206] among officers, 113 (79-157) for nonofficers and 119 (85-162) for fishermen. The increased SHCR for hearing impairment among seafarers was solely found in engine room personnel (SHCR = 222; 95% CI 178-277). Compared to other seafarers, the engine room personnel had a relative risk ratio of 2.39 (95% CI: 1.74-3.26). Short-term employment is common in many trades. No duration response pattern was observed which may suggest a secondary healthy worker effect.
These findings indicate that hearing problems are frequent among men who work in the engine rooms on ships. Long-term cumulative effects of employment were not shown.
Monetary value of undisturbed sleep
Sebastian Riethmuller, Ruedi Muller-Wenk, Andreas Knoblauch, Otto D Schoch
April-June 2008, 10(39):46-54
To design a national antinoise policy, we need to know the monetary value that people attach to the reduction of sleep disturbance due to road traffic noise.
Patients with obstructive sleep apnea syndrome (OSAS) controlled by nasal continuous positive airway pressure (nCPAP) underwent one-to-one structured interviews to determine the monetary value of their resultant undisturbed sleep. This was then converted into a value for sleep undisturbed by noise, using a severity ratio. Setting: Outpatient interviews in 67 OSAS patients (54 males, 28 to 73 years old) managed by the Center for Sleep Medicine, Kantonsspital, St. Gallen, Switzerland.
Materials and Methods:
The interview questions addressed the outcome and difficulties of nCPAP therapy, the self-rated severity of pretreatment sleep disturbance and self-rated monetary value of sleep improvement. Thirteen OSAS patients who had also experienced noise-related sleep disturbance rated its severity on a visual analogue scale (VAS).
The mean monetary value of nCPAP-controlled sleep disturbance was Swiss francs (CHF) 70/night (CHF1 = US$ 0.877, year end 2004; 25
percentiles: CHF 35 and CHF 100). Interviewees maintained this high estimate after learning that the actual treatment costs were only approximately 6 CHF/night. A severity ratio ranging from 2.3:1 to 4.7:1 for sleep disturbance resulting from OSAS or from noise was derived from patients' responses and literature. The value of noise-free sleep was CHF 7.45-23.81 per night.
Sleep undisturbed by noise has a remarkably high monetary value for people, which should be considered in political decision-making.
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