In March 2007, the National Institute for Occupational Safety and Health (NIOSH) was asked to evaluate the noise exposure of employees in the Nutrition and Food Services Department of a large hospital, because of noise concerns raised after the installation of the PowerSoak® dishwashing system. Eleven employees (two cooks, eight food service workers, and a materials handler) contributed 13 full-shift and two task-based personal noise dosimetry measures over two days. The noise levels for two food service workers assigned to the pots and pans room (85.1 and 85.2dBA), a cook working in the food preparation area (85.9 dBA), and a food service worker assigned to the dishwashing room (89.5 dBA) exceeded the NIOSH Recommended Exposure Limit (REL); however, none of the measures exceeded the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL). The noise level from the PowerSoak® dishwashing system alone was not excessive, but additional noise from the food preparation area (primarily from blenders and utensils), and from metal-to-metal contact between stainless steel pots and pans and metal racks, may explain exposures above the NIOSH REL for employees in the pots and pans room. The cooks were exposed to many intermittent impact noise sources, such as, metal-to-metal contact between utensils and the use of industrial-size blenders. We recommended that metal-to-metal contact be reduced as much as possible throughout the Nutrition and Food Services Department, and hearing protectors be provided to employees in the dishwashing room until engineering controls were in place.
Keywords: Noise exposures, dosimetery, hospital kitchen, dishwasher
|How to cite this article:|
Achutan C. Assessment of noise exposure in a hospital kitchen. Noise Health 2009;11:145-50
| Introduction|| |
On March 21, 2007, the National Institute for Occupational Safety and Health (NIOSH) received a management request from a hospital to assess employee noise levels in the Nutrition and Food Services Department. The request stated that employees were concerned about noise exposures in the kitchen's pots and pans room after the installation of a PowerSoak® continuous dishwashing system. On March 27 and 28, 2007, a NIOSH researcher conducted a noise assessment in the hospital's Nutrition and Food Services Department.
The Nutrition and Food Services Department prepares and provides meals to hospital inpatients. The department employs approximately 30 full-time and part-time food service workers, three cooks, and one materials handler. Full-time food service employees work from 6:00 a.m. to 2:30 p.m. or from 11:00 a.m. to 7:30 p.m.; part-time employees work from 6:00 a.m. to 10:00 a.m. or from 3:30 p.m. to 7:30 p.m. Cooks work from 6:00 a.m. to 2:30 p.m. or from 8:00 a.m. to 4:30 p.m. The materials handler typically works from 8:00 a.m. to 4:30 p.m.
Meals are prepared by the cooks approximately two-to-three days in advance and stored in plastic storage containers in freezers. Work activities during meal preparation include slicing meat, opening food cans with a metal can opener, pureeing food in industrial-size blenders, and cooking. Ingredients and other materials needed for food preparation are transported by the materials handler on carts from freezers in the hospital basement. Every day, food service workers warm the pre-cooked meals and place them on carts, which are then transported to the patients' rooms. Diet aides, a job classification within the food service workers, alert the staff preparing patient food carts when patients require special diets.
In the dishwashing room, one or two food service workers remove utensils (cups, plates, trays, and silverware) from carts and place them on a mechanical stainless steel dishwashing table. While the empty carts are being power-washed, leftover food from patient rooms is scraped from the plates and placed in a drain with running water that is part of the dishwashing table [Figure 1]. This food/water mix is fed into a "pulper," a machine designed to reduce waste by removing the water and cutting up the dried food into small sizes. The pulper is attached to the dishwashing table. Except for the trays, the utensils are placed in plastic racks or containers before they are placed in a dishwasher. The dishwasher washes, rinses, sanitizes, and dries the utensils, which are then put away by the food services workers.
Oversized metal trays, pots, and pans that are used in food preparation, and plastic food storage containers, are cleaned in the pots and pans room using the PowerSoak® continuous dishwashing system, and air-dried on metal racks in this room [Figure 2].
| Materials and Methods|| |
The objectives of this study are as follows: (1) to evaluate personal noise levels for employees in the kitchen area, (2) to identify specific sources of loud noise, and (3) to identify potentially hazardous noise sources through spectral analysis.
Eleven employees (two cooks, eight food service workers, and a materials handler) contributed 13 full-shift and two task-based personal noise measures over two days. NoisePro™ noise dosimeters (from Quest Technologies, Oconomowoc, Wisconsin) were worn by the employees while they performed their daily activities. The noise dosimeters were attached to the wearer's belt and a small remote microphone was fastened to the wearer's shirt at a point midway between the ear and the outside of the employee's shoulder. A windscreen provided by the manufacturer of the dosimeter was placed over the microphone during recordings. At the end of an inspection, the dosimeter was removed and paused to stop data collection. The information stored in the dosimeters was downloaded to a personal computer for interpretation with QuestSuite® Professional II computer software. The dosimeters were calibrated before and after the measurement periods according to the manufacturer's instructions.
The Quest dosimeters collect data so that one can directly compare the information with three different noise criteria used in this survey: The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) and Action Level (AL), and the NIOSH Recommended Exposure Limit (REL). The OSHA standard for occupational exposure to noise (29 CFR 1910.95)  specifies a maximum limit of 90 dBA for a duration of 8 hours per day, using a 5 dB time/intensity trading relationship. The NIOSH REL uses an exposure criterion of 85 dBA for 8 hours.  The REL uses a more conservative 3 dB time/intensity trading relationship for calculating exposure limits. The OSHA and NIOSH criteria provide a formula based on the above limits for calculating the daily dose. During any 24-hour period, a worker is allowed up to 100% of his daily noise dose. An employer is required to administer a continuing, effective hearing conservation program when the OSHA standard AL of 50% dose is exceeded. The instrument parameters used to calculate noise levels by the OSHA and NIOSH criteria are listed in [Table 1].
Spot-checks of area noise and spectral analysis was measured with a SoundPro® (Quest Technologies, Oconomowoc, Wisconsin) handheld sound level meter (SLM and real-time frequency analyzer). The instrument was set to measure noise levels between 70 and 140 dBA, on an A-weighted scale. The SLM was calibrated before and after the measurement periods according to the manufacturer's instructions.
| Results|| |
[Table 2] shows the full-shift personal noise dosimetry results. None of the employees exceeded the OSHA criteria for noise
In the pots and pans room, noise levels for two food service workers exceeded the NIOSH REL. In addition, the level for a cook in the food preparation area also exceeded the NIOSH REL. The cook's exposure was 85.9 dBA, and the food service workers' exposures were 85.1 and 85.2 dBA for the actual time worked. The noise exposures from the pots and pans room alone were not enough to explain employees' exposures exceeding the NIOSH REL.
The continuous noise level from the PowerSoak® machine was 77 dBA, and although the noise levels from metal-to-metal contact between steel pans and racks were occasionally high (80-90 dBA), they were intermittent and of short duration. The noise levels for various activities in the Nutrition and Food Services Department are provided in [Table 3]. The close proximity of the pots and pans room to the kitchen area suggested that the pots and pans room employees were exposed to noise from the kitchen area, primarily when cooking was in progress. Evidence of this is shown in Graph 1 - [Additional file 1] and Graph 2 - [Additional file 2]. In Graph 1, noise exposure profiles for a pots and pans room employee is compared with that of a cook working in the same shift. The noise exposure profiles of these employees are similar.
In Graph 2, noise profiles for two part-time pots and pans employees are compared. One employee worked the morning shift (6:00 a.m. to 10:00 a.m.), and the other worked the evening shift (3:30 p.m. to 7:30 p.m.). Graph 2 indicates that the morning worker had higher noise exposures than the evening worker. This difference might be explained by the fact that cooking ceased at 2:30 p.m. on the days of the study.
Graph 3 - [Additional file 3]compares the noise profiles of two part-time pots and pans employees with that of a full-time employee. The part-time employees' exposure profiles were similar to the full-time employee's for the comparable time that they worked in the pots and pans room. This suggests that employees working in the pots and pans room have uniform noise exposures.
Two task-based personal dosimetry samples were taken in the dishwashing room. An employee who was unloading utensils from the carts and onto dishwashing racks had a 4-hour exposure of 89.5 dBA. He exceeded his daily allowable noise dose of 100% as determined by the NIOSH criterion. This employee's noise exposures came from the pulper (93 dBA), china-to-china contact (97 dBA), power washing of carts (80-83 dBA), and contact between utensils and the wash area (85 dBA). An employee mentioned that the pulper often gets clogged, and during maintenance of the machine, it is common for the food/water mix to be strewn in the dishwashing room, creating an unsanitary situation.
Spectral measurements, averaged over 60 seconds, were collected in the pots and pans room, to determine frequencies at which the highest sound levels occurred (Graph 4 - [Additional file 4]). The loudest exposures in the pots and pans room occurred at 315 Hz. This frequency at the levels measured was not typically associated with NIHL, which usually occurred between 2000-6000 Hz.
In the dishwashing room, spectral measurements were compared with the dishwashing Table switched ON and switched OFF. The pulper was on in both instances. The data, averaged over 20-40 seconds, as shown in Graph 5 - [Additional file 5]. As expected, the noise levels were higher with the dishwashing table switched ON, but only at frequencies from 1250-20000 Hz. At lower frequencies (less than 1000 Hz), the average noise levels were higher with only the pulper switched ON. The maximum noise levels were 93.4 dBA with the dishwashing Table switched OFF and 110 dBA with the dishwashing Table switched ON. The frequencies associated with high noise levels when the dishwashing table was switched OFF were 630 and 1250 Hz. Frequencies associated with high noise levels when the dishwashing table was switched ON were between 2500-6300 Hz, which was in the range where NIHL most typically occurs.
Materials handlers and food service workers who are assigned as diet aides were unlikely to exceed any regulatory or recommended noise criteria. The materials handler does not spend long periods at any specific part of the Nutrition and Food Services Department. The diet aides spend most of their time in a fully enclosed office with the doors closed.
| Discussion|| |
Engineering and administrative controls are the preferred ways of reducing work place hazards. In the dishwashing room, noise exposures could probably be reduced by replacing the pulper with a garbage disposal system. This may reduce the noise exposure to the employees, in addition to preventing unsanitary working conditions when the pulper becomes clogged. It would be helpful to reduce metal-to-metal contact as much as possible. This can be accomplished by replacing metal racks with plastic racks, and replacing stainless steel utensils (for example ladles and tongs) with plastic materials. Also, noise reduction enclosures are available for the blenders used in the Nutrition and Food Services Department of the hospital in this study.
Upon implementation of any engineering, administrative, or process changes, personal noise dosimetry should be conducted throughout the Nutrition and Food Services Department. If employee personal noise exposures continue to exceed the NIOSH REL, or if these changes cause employee exposures to exceed the OSHA AL, employees must be enrolled in a hearing conservation program. The basic elements of the program should at a minimum, meet the requirements of the OSHA hearing conservation amendment.  Other sources for defining effective hearing conservation programs are also available. ,, Until engineering and administrative controls are in place, employees in the dishwashing room should be provided with hearing protection devices (HPD) and trained on their proper use.
| Conclusions|| |
Some employees in the Nutrition and Food Services Department at a hospital were exposed to excessive noise levels. These employees included cooks and food service workers assigned to the pots and pans and dishwashing rooms. Food service workers who were assigned as diet aides and materials handlers were not likely to exceed any regulatory or recommended noise criteria. Hearing protectors should be provided to employees in the dishwashing room until engineering controls were implemented.
| References|| |
|1.||OSHA. Occupational Noise Exposure: Hearing Conservation Amendment; final rule. U.S. Dept. Labor, Occupational Safety and Health Administration, 48 Fed. Reg.; 1983. p. 9738-84. |
|2.||NIOSH. Preventing occupational hearing loss-a practical guide. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No.; 1996. p. 96-110. |
|3.||Royster JD, Royster LH. Hearing conservation programs: practical guidelines for success. Chelsea, MI: Lewis Publishers; 1990. |
|4.||Suter AH. Hearing conservation manual. 4th ed. Milwaukee, WI: Council for Accreditation in Occupational Hearing Conservation; 2002. |
Department of Environmental, Agricultural, and Occupational Health College of Public Health, 985840 Nebraska Medical Center, Omaha, NE 68198
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]