4-Golmohammdi

JRHS 2008; 8(2): 21-27

Copyright © Journal of Research in Health Sciences

A Rapid Method for Estimating of Noise Exposure in Work­places

Golmohammadi R (PhD)a, Atari SQ (Msc)b, Arefian S (Bsc)b, Golchobian R (Bsc)b

a Department  of Occupational Health, School of Public Health and Center for Health Research, Hamadan University of Medical Sciences, Iran. 

b Department of Occupational Health, School of Public Health, Hamadan University of Medical Sciences, Iran

*Corresponding Author: Dr Rostam Golmohammadi, E-mail: golmohamadi@umsha.ac.ir

Received :2 September 2008; Accepted: 18 October 2008

Abstract

Background: Noise pollution is one of the important issues of pollutant in workplaces and is almost one of the harmful agents for workers. At present, instrumental based inspections for determining the index levels of noise in workshops is performed. This method is requiring a time consuming and ex­pensive in large scale inspection for workplaces. Classification of workplaces based on noise pollution is one of the necessaries for macro programming view of monitoring and controlling of noise. The Propose of this study was to submit a simply scientifically screening method for inspection of noise pollution in workplaces.

Methods: In this experimental study, the results of instrument based and checklist based of noise in­vestigation was compared. For designing of proposed screening checklist and instrumental measuring based, 30 workplaces with more than 20 workers in Hamadan industrial area (west of Iran) were stud­ied. The suggested screening checklist containing a 3×10 matrix can use for recognition step of noise as­sessment in a large scale investigations.

Results: Comparison of the results of the noise screening test with the outcome of a noise measure­ment by sound level meter, gave a sensitivity of 50% and specificity of 85%.

Conclusion: The screening test will be useable, if we only want to estimate the global noise pollution in workplaces.

Keywords: Noise, Screening, Noise exposure, Workplaces, Iran

Introduction

Nowadays, however development of indus­try and technology and using industrial new techniques have apparently presented a com­fortable life for human being. But that has followed negative aspects and has caused workers to expose to numerous harmful fac­tors that reckon on inseparable portion of in­dustry and production, they consist threaten the health of workers. Noise pollu­tion is one of the important issues of pollut­ant in work­places and is almost one of the harmful agents

for workers. At present, in­strumental based inspections for determining the index levels of noise in workshops is performed.

Screening is defined as, the presumptive iden­tifi­cation of unrecognized agent or de­fect by the application of tests, question­naire, exami­nation or other procedures which can be ap­plied rapidly (1). The valid­ity of a test or questionnaire is defined as the ability of the test to distinguish between in­fected and un­infected people or safe and un­safe conditions (2). To make appropriate recommendation for the development of standards for compre­hen­sive noise screening of workplaces, atten­tion to the efficacy of present system is needed.

Classification of workplaces based on noise pollution is one of the necessaries for macro programming view of monitoring and con­trolling of noise. According to the data based statistics in census of industrial workplaces with more than 10 workers, the health min­istry of Iran in 1999, about 11002 work­places had been covered by health delivery system. In theses places and other work­places that have not covered yet, considera­tion the condition of harmful agents consist of noise with administration way, needs to the specialist personals, equipments and time that has not the possibility and explanation in the existing circumstances. Therefore, us­ing a simple method base on screening check­list can be helpful to reduce the ex­pense and time in inspection of noise pollu­tion in work­places. 

Screening method is a valid way for early de­tection of disease and epidemiology stud­ies (3-7), also in other studies screening is a com­mon method for early investigations for sepa­ration of study popular (8-12).

The Propose of this study was to submit a simply scientifically screening method for in­spection of noise pollution in workplaces. In this study, the results of instrument based and checklist based of noise investigation was compared. The suggested method can be used for recognition step of noise assessment in large scale investigations. This method is a proper way for exploiting and reducing the expenses by separation of workplaces that hasn't the problem of noise pollution.

Methods

This essay contains investigations result that introduces an innovative method for ridding in inspection of workplaces noise without need to the measurement's system. The study was based on designing a worksheet check­list of any major factor that affected on noise pollution in workplaces (13, 14). In this study 30 workplaces that contained above of 20 workers in Hamadan Province (west of Iran) were studied. In the secondary step of the study, designed checklist containing of 13 items was filled by observation method. In this step, sound pressure level in indus­tries based on instrument on girding method by a calibrated sound level meter (Lutron SL4011) was measured. In the third step, mean of sound pressure levels by results of checklists were compared. Statistical analy­sis was performed using a best regression between items of check­list. In this step the checklist proportional of measurements was modified. Therefore, final checklist con­sisted of 10 important items ac­cepted. In this checklist the parameters are inspected that can affect in increasing of noise pollution in a workplace contain follows:

  1. The quality of wall sound absorption
  2. The quality of ceiling sound absorption
  3. The quality of roof sound absorption
  4. Mean of noise sources life
  5. The quality of maintenance of equip­ments
  6. The rotation and duration of noise pro­duce noise sources
  7. The quantity of noise sources
  8. Time duration of worker exposure in a shift
  9. Clearness of conversation in the distance of one meter
  10. The volume of workplaces

For each mentioned items, three characteris­tics were defined that contained grade coef­ficients 1, 2 and 3. As well as, regarding to the rate of their effect on noise aggravation, for each item a modified constant was con­sidered. Determining of these constants was based on best multiple regression analysis on SPSS package. Total rank of noise pollution for each workplace was based on sum of the multiplying grade number to constant coeffi­cients. Minimum rank in this method was considered 32, and the maximum 96.

In the final step for comparison of two meth­ods, the sensitivity, specificity, positive pre­dictive value and negative predictive value were calculated.  Sensitivity is the ability of the screening test to give a positive finding when the workplace tested truly has the noise pol­lution, a/(a+c).  Specificity is the ability of the test to give a negative finding when the subjects tested are truly free of the noise pollution, d/(b+d). The proportion of positive tests that are truly positive, a/(a+b)  is called the predictive value of a positive test. The pro­portion of negative tests that are truly nega­tive d/(c+d) is called the predictive value of a negative test (6). The general represen­tation of the screening evaluation is shown in Ta­ble 1.

Table 1: The general representation of the screening matrix



Measurement by sound level meter




high pollution*

low pollution

Total

Screening by the noise pollution checklist

Positive**

True positive (a)

False positive (b)

(a+b)


Negative

False negative (c)

True negative (d)

(c+d)


Total

(a+c)

(b+d)

(a+b+c+d)

* Mean sound pressure level 85 dB(A) and above

** Rank number 72.5 and above

Results

Table 2 shows the descriptive analysis com­parison between mean sound pressures lev­els and the rank numbers of screening test in studied workplaces. The statistic analysis showed that a Pearson's regression between two assess­ment scales was 0.771 and this results was a significant correlation (P= 0.0001).

Table 2: Descriptive analysis of mean sound pressures levels and rank numbers of screening test


Ranking number in screening checklist

Mean sound level meter dB(A)

Mean

66.33

81.59

Median

66.50

81.80

Mode

66.00

80.23

SD

12.27

8.30

Range

41.00

41.56

Minimum

47.00

54.00

Maximum

88.00

95.56

 

Total rank of noise pollution for each work­place was based on sum of the multiplying grade number to constant coefficients. Mini­mum rank in this method is considered 32, and the maximum 96. In this suggested scr­eening checklist, the noise pollution bound­ary of 72.48 (= 72.5) was determined. This criteria was based on the noise pollu­tion level of 85 dB(A) in same measurement results. In this essay, pollutant workplace (positive test) is a ranking of 72.5 or above. Table 3 showed the suggested screening checklist. Also Figure 1 showed the scatter re­lation between mean SPL values and noise ranking number in study workplaces.

Table 3: The suggested screening checklist

Screening checklist for estimating of noise exposure

Workplace Name:                                                 

Number of worker:                                                 Main production:

Workplace code:

Date:                                                                       Name of  screener:

Row

Effective items

Trait -A

3

Trait -B

2

Trait -C

1

Constant

coefficient

1

Quality of wall sound absorption

Hard surface (like cement or tile)


Medium hardness(like gypsum)


Soft (like wood or fiber board)


2

2

Quality of ceiling sound absorption

Hard surface (like metal or cement)


Medium hardness (like gypsum)


Soft (like wood or fiber board)


1

3

Quality of roof sound absorption

Hard surface (like cement or tile)


Medium hardness (like brick)


Soft (like wood or fiber board)


1

4

Mean of noise sources life

More than 10 years


5-9 years


Less than 5 years


1

5

Quality of maintenance of equipments

Suitable


Little suitable


Unsuitable


1

6

Rotation and duration of noise produce noise sources

All of shift


Half of a shift


Less than a half shift


2

7

Quantity of noise sources

More than 10 sources


5-9 sources


Less than 5 sources


2

8

Time duration of worker exposure in a shift

More than 8 hours


4-7 hours


Less than 4 hours


1

9

Clearness of conversation in the distance of one meter

Isn't heard at all


It should be shouted


It is heard easily


15

10

Volume of workplaces (m3)

Less than 100


100-1000


More than 1000


6

Total ranking number (Sum of the multiplying grade number to constant coefficients)


Name of  screener:                                             Signature:

Figure 1: Relation between mean SPL values and noise ranking number in study workplaces

Table 4 shows the general representation of the screening matrix. The calculated values of the noise screening checklist were; sensi­tivity 50%; specificity, 85%; positive pre­dictive value, 62.5%; and negative predictive value, 73.9%.

Table 4: The general representation of the screening matrix



Measurement by sound level meter




High pollution*

Low pollution

Total

Screening by the noise exposure checklist

Positive**

5

3

8

Negative

5

17

23


Total

10

20

30

      * Mean sound pressure level 85 dB(A) and above

     ** Rank number 72.5 and above

Discussion

The Propose of this study was to submit a simply scientifically method for inspection of noise in work places. In this study, the results of instrument based and checklist based of noise investigation was compared.

Comparison of the results of the noise scr­eening test with the outcome of a noise meas­urement by sound level meter, gave a low sensitivity of 50% but a high specificity of 85%. An ideal screening test would be 100% sensitive and 100% specific. In prac­tice this dose not occurs; sensitivity and specificity are usually inversely related (15). Any other studies had similar results for specificity to obtain a reliable test for screening. Sadri and Mahjub gave a low sen­sitivity of 44.8% but a high sensitivity of 98.9% in Evaluation of the Vision Screening test (E-chart) in School Children (3). Riedar et al. reported 38.9% true positives, 4.4% true negatives, 56.7% false positives and 0% false negatives in the K2 Asbestos Screening Test (10). Also, Yeagar DE et al. reported a sensitivity of 52.63% and a specificity of 94.90% for Posttrau­matic stress disorder (PTSD) Checklist and SPAN in Vet­erans Affairs primary care settings (16). In this study, the positive predictive value was 62.5% and negative predictive value as 73.9%. According to the results, use of sug­gested noi­se screening test to estimate of noise pollu­tion is insensitive and highly spe­cific. When we added 5 true positive to 17 true negative cells to all of 30 studied work­places in Table 3 we obtained a 76.67% of true answer by the screening method. This finding shows that the screening test will be useable if we only want to estimate the global noise pollu­tion in workplaces. Con­stant coefficient of Clearness of conversation in the distance of one meter in the row No.9 of suggested check­list showed a noticeable coefficient equal to15, therefore it must need to add any other personal effect variables that affected in this coefficient, such as heart rate of workers, noise annoyance rate, and hearing loss  in the future studies.

In conclusion, these results showed that, us­ing proposed screening checklist for noise inspection can be used with a high reliance before of noise measuring without necessity to use the instrument in workplaces. There­fore, this method is a proper rapid method for exploiting and reducing the expenses by separation of workplaces that has not the problem of noise pollution in the occupa­tional health inspection systems.

Acknowledgements

This paper is based on the third and forth au­thor in BSc project which was conducted in Department of Occupational Health, School of Public Health, Hamadan Uni­ver­sity of Medi­cal Sciences, Iran.

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