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Occupational Medicine Advance Access originally published online on February 1, 2007
Occupational Medicine 2007 57(3):203-209; doi:10.1093/occmed/kql180
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© The Author 2007. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Hearing loss, accidents, near misses and job losses in firefighters

Christopher Ide

Salus Occupational Health & Safety, Centrum Park, Hagmill Road, Coatbridge ML5 4TD, UK

Correspondence to: Christopher Ide, Salus Occupational Health & Safety, Centrum Park, Hagmill Road, Coatbridge ML5 4TD, UK. Tel: +44 1236 438203; fax: +44 1236 438180; e-mail: christopher_ide{at}yahoo.co.uk


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 
Background The hearing losses of workers exposed to occupational noise have been extensively documented, but no information exists on the level of hearing loss which results in job loss.

Aim To define levels of hearing loss associated with ill-health retirement (IHR), comparing them with existing standards and assessing the extent to which poor hearing contributes to accidents and near misses to assist the development of rational standards for retention.

Methods All UK local authority fire brigades were approached for information on IHRs due to audiological problems, accident/near-miss totals and the numbers thought to be due to poor hearing in a 60-month period beginning in 1997.

Results Only 15/59 (25%) of brigades provided all information requested, although 50 (85%) and 32 (52%) supplied medical and safety information, respectively, which was used for analysis. Of 3366 IHRs, 135 (4%) were due to audiological problems. When compared to a control group of firefighters of similar age, those taking IHR had worse mean and median hearing losses in all grouped frequencies in both ears than the controls, and this difference always reached statistical significance (P < 0.001), but there was considerable overlap in terms of range of hearing loss in each group. Only 41/31 274 (0.13%) of accidents/near misses reported were believed to result from hearing problems, and seven of these were related to device failure.

Conclusions Retention criteria based on audiometric grounds alone may result in unnecessary IHRs. Poor hearing is only responsible for a small proportion of accidents and near misses.

Keywords      Acoustic neuroma; deafness; ENT; local government; NIHL; noise induced hearing loss; occupational deafness; occupational noise


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conflicts of interest
 References
 
The firefighters' working environment is frequently unpredictable, and sensory deprivation may increase the hazards. Over 90% of ~230 firefighters agreed that good hearing was essential for the majority of fireground tasks [1].

Until the mid 1990s, UK fire brigades used voice tests to assess potential recruits' hearing, as prescribed by the Appointment and Promotion Regulations 1950 [2]. When the benefits of audiometry were mentioned 37 years later [3], there was discussion about what standard should be applied. The PULHHEEMS system used by the armed services was eventually adopted, with H1 being the standard for recruitment to the fire service [4], later modified to H2 [5].

Hearing loss is a normal part of ageing, progression differing between individuals, and various factors accelerate it. External causes include toxins and trauma, both potentially present during firefighting. The most widespread cause, also found in the leisure environment, is excessive noise exposure.

In 1995, Tubbs described hearing impairment in American firefighters, first noted in the late 1970s [6–8]. These demonstrated noise-induced hearing loss. Noise surveys showed that firefighters were frequently exposed to high peak levels, sometimes to 120 dBA, although when averaged over a shift, the recommended Occupational Safety & Health Administration (OSHA) exposure limit (then 90 dBA) was rarely exceeded. Hearing conservation advice was published by the Federal Emergency Services Agency in 1992 [9]. Nonetheless, in 2001, Kales et al. [10] found that some firefighters were still losing hearing faster than expected, implying factors identified by earlier workers had been inadequately addressed, assuming they caused the hearing loss. Clark and Bohl [11] found no evidence of accelerated deafness, attributing differences to the fact that their study was longitudinal (practically all the others were cross-sectional), the use of alternative reference populations and the presence of hearing conservation programmes throughout the survey.

When this project was conceived, noise exposure of workers in the UK was governed by the Noise at Work Regulations (NAW) 1989 [12], setting three action levels of 85, 90 and 140 dBA. The first two refer to noise exposure as assessed over an 8-h working day, and the third concerns impact or impulse noise. The legislation also stipulates steps to be taken if the action levels are exceeded. As far as is known, only one brigade has organized a comprehensive evaluation of the noise environment of firefighting, including workshops and offices. The first action level was often exceeded and, occasionally, the second [13]. The NAW were superseded by the Control of Noise at Work Regulations 2005 [14]. Essentially, these regulations reduce the first and second action levels of NAW by 5 dBA, creating peak exposure levels of 135 and 137 dBC, respectively, for each action level. The third action level is unchanged, with an additional daily or weekly exposure limit of 87 dBA.

In 2001, Palmer et al. [15] assessed the prevalence of hearing loss in ~21 000 British adults of working age, with an overall response rate of ~60%. Ninety-five per cent of those aged 45–54 (the age of firefighters approaching the end of their careers) believed their hearing in the better ear acceptable. Under 2% required a hearing aid. However, their survey was questionnaire based, uncorroborated by audiometry. Although detailed information regarding job and noise exposure was sought, no questions were put about unemployment.

While the PULHEEMS system has a level at which hearing is incompatible with military service, there is no standard for retention in the UK fire service [5]. When assessed audiometrically, hearing impairment begins when hearing losses pass 25–30 dBA, but handicap (and potential benefit from hearing aids) only occur if losses exceed 45 dB [16]. Since there are problems associated with the use of hearing aids at incidents, a firefighter requiring one may well take ill-health retirement (IHR).

This study aimed to

(i) observe levels of hearing loss associated with IHR,
(ii) compare these levels with various population norms and
(iii) determine the extent to which hearing problems are associated with accidents and near misses involving wholetime firefighters.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conflicts of interest
 References
 
The Edinburgh-based Multicentre Research Ethics Committee raised no objections to the protocol which required approaches to the Occupational Health (OH) and Health & Safety (H&S) Units of all 59 local authority fire brigades.

The OH units were asked for anonymized information regarding numbers of wholetime firefighters granted IHR following hearing problems during a 60-month period beginning in 1997. Nil returns were specifically requested, but brigades which incurred IHRs due to hearing problems were asked to give for each individual

(i) age and length of service at retirement,
(ii) hearing losses in both ears at 0.25, 0.5, 1.0, 2.0, 3.0, 4.0, 6.0 and 8.0 kHz and
(iii) any relevant clinical information.
Hearing losses at 0.5, 1.0 and 2.0 kHz (low frequencies); 3.0, 4.0 and 6.0 kHz (higher frequencies) and 4.0, 6.0 and 8.0 kHz (highest frequencies) were calculated. Descriptive and hypothesis testing statistical analysis was performed using ‘Minitab’ release 14. Differences between means and medians were explored using two-sample t-test and Mann–Whitney U-tests, respectively. This information was compared with the Health & Safety Executive's publication MS26 [17] and ‘Hearing in adults’ [18].

The first document assists with the interpretation of the results of screening audiometry performed on workers potentially exposed to hazardous levels of occupational noise. The tester adds the hearing loss in the lower frequencies, and then the higher frequencies in both ears. The total hearing losses are compared with figures for high- and low-frequency losses tabulated by quinquennial age groups from 20 to 65 years old. Should hearing loss exceed a minimum level for that quinquennium, the subject is warned that it may be necessary to re-test hearing sooner than normal, since there may be early damage to hearing. If a higher loss is incurred, referral for specialist evaluation is recommended.

The second publication describes audiometric testing of 2708 adults who believed that they had normal hearing. The results are tabulated as a series of cross-sectional surveys arranged by decade from 21 years upwards displayed for each ear, both sexes and for manual and non-manual workers. Hearing losses at eight frequencies from 0.25 to 8.0 kHz and six combinations of frequencies are displayed as means and centiles from 5 to 95 kHz.

At least two OH units spontaneously volunteered they had serving firefighters with worse hearing than those granted IHR. Therefore, another control group was drawn from Strathclyde Fire Brigade, consisting of all firefighters aged at least 49 who were attending the OH unit for a routine examination (unless absent due to hearing problems) and who would be eligible to retire within the next 3 years. Before the test, all were asked ‘Is your hearing satisfactory for day-to-day purposes, or not?’ Hearing was checked by a single experienced operator in a quiet room using an Amplivox 116 Screening Audiometer (Amplivox, UK).

While it was not possible to measure background noise levels in the office concerned during this testing, the accuracy of the operator's testing was checked by comparing the operator's audiometry results with those obtained by competent technicians using soundproofed booths in various National Health Service and private hospitals in the west of Scotland, testing the same subjects. Spearman's rank correlation coefficient was calculated, since it was unlikely that the hearing losses would be normally distributed.

H&S units were asked for information regarding numbers of accidents and near misses involving wholetime firefighters reported during the same 60-month period, how many had been thought to be due to failure of the firefighters concerned to hear an audible warning and if the firefighter concerned had been referred for OH review.

Information about wholetime establishment, actual strengths and IHRs of fire brigades during this period came from the Office of the Deputy Prime Minister (for England, Wales and Northern Ireland) and the Scottish Executive (Scottish Brigades). Since the strengths were very stable, the number of firefighters in all brigades on 31 March 2000—the study mid-point—constituted the denominator.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conflicts of interest
 References
 
Fifty of 59 local authority fire brigades (85% of UK fire brigades) provided medical information. They employed 35 737 wholetime firefighters accumulating 3366 IHRs, representing 93% of wholetime UK firefighter strength and 91% of all IHRs during this period.

Of the 3366 IHRs, 135 (4%) resulted from hearing loss. Twenty-three brigades attributed no IHR to this cause, 11 had 1 case, 6 had 2 cases, 9 reported between 3 and 10 cases each, while 1 had 61 cases. Because of the 60-fold difference in strength between the smallest and largest brigades in this study, the numbers were converted to a rate per 1000 wholetime firefighters over the study period. This ranged from 0 to 24/1000, mean 2.88 ± 3.79 SD, median 1.14 and interquartile range (IQR) 0–3.45.

Age was known for 132 (98%), ranging from 29 to 59 years, mean 49 years ± 4.7 SD, median 50 years and IQR 47–52 years. Length of service was available for 130 (96%), range 5–37 years, mean 24.9 years ± 4.8 SD, median 26 years and IQR 23–27 years. Audiometric information was present for 123 personnel (91%).

In 30 cases (23%), the hearing loss was attributed to firefighting duty. Only once did this result from a specific incident—an explosion. Other identified causes of deafness included the following: past occupational history of noisy job (14), accelerated presbyacusis (13), noisy hobbies and leisure trauma (10), family history and genetic syndromes (6), conductive defects (6), chronic suppurative otitis media problems (4), Meniere's disease, head injury and childhood problems (3 each), acoustic neuroma (2) and stroke (1).

Table 1 summarizes the types of hearing loss giving rise to IHR. Bilateral generalized hearing loss (31) was most common, and then bilateral high frequency (29). With unilateral loss, the left ear was more commonly affected. Eighty-seven cases had hearing loss severe enough to merit referral, and 34 warning. Two had normal hearing, and their problems leading to IHR were tinnitus and vertigo.


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  		Table 1. Audiometric classification of firefighters taking IHR as a result of audiological disease and a control population using the criteria of the Health & Safety Executive's publication MS26

 
The firefighter control group comprised 112 consecutive individuals. Seventy had hearing losses deserving the ‘warning’ category, and nine merited referral. None admitted any significant hearing impairment. The operator's audiometry was validated by a group of 39 consecutive individuals who met the criteria specified. Spearman's rank correlation coefficient varied from 0.89 to 0.94, median 0.92.

Table 2 summarizes the audiometry results of those taking IHR. Hearing in the left ear was slightly worse than the right, but was not statistically significant. The firefighter controls demonstrated a similar finding. Henceforth, analysis is confined to the better (right) ear. For the Medical Research Council (MRC) controls, hearing was a little better on the left side. When the comparison was made between the hearing losses in the ipsilateral ears of the ill-health retirees and the firefighter control group, the differences in each frequency group were more striking, reaching statistical significance in each case (P < 0.001).


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  		Table 2. Differences in hearing loss at frequencies in right and left ears between ill-health retirees and controls

 
Of the 123 audiograms of those taking IHR, 84 (68%) had at least one frequency in which the hearing loss exceeded 45 dB—the point at which a hearing aid becomes of benefit—compared to 18/112 (16%) for the controls. This difference reached statistical significance (P < 0.001, 95% CIs –0.63, –0.42).

Comparison of hearing losses between those whose retirement was attributed to fire service duties, and others whose hearing loss was non-occupational, showed the differences between mean and median age (48.8 and 49.2 years; 49.5 and 50.0 years, respectively) and length of service (23.7 and 25.2 years; 46.8 and 47 years, respectively) were small, not reaching statistical significance. The mean (49.2 versus 83.3 dB) and median (43.0 versus 63.0 dB) hearing losses at low frequencies were markedly less in those who took IHR following service injury; these differences reached statistical significance (P < 0.001). For the higher and highest frequencies, the differences in each ear were much less, and not significant.

The control group was initially compared to the 51–60 decade, since their median age was 50.6 years (IQR 50.0–53.5) and mean 51.6 years (±2.1 SD); 58 firefighters (52%) were <51 years old, so the results were re-analysed using the values of the 41–50 decade. This made no difference (Table 3).


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  		Table 3. Comparing hearing losses in decibels hearing level in the right ear in firefighters retiring with hearing loss aged 41–50 years (n = 57) and 51–60 years (n = 53)

 
Table 4 compares hearing losses of those taking IHR and the firefighter controls with the population values with regards to the low and highest frequencies in each of the decade groups. For both the low and highest frequencies in the 31–40 decade, the mean values fell between 80th–85th and 85th–90th percentiles for low and highest frequencies, respectively, in the right ear. In the older cohorts, the mean hearing loss in each of the categories becomes comparatively less, insofar as it corresponds with a lesser centile/quartile.


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  		Table 4. Mean hearing losses in ill-health retirees and firefighter control population compared with general male population (Davis [18])

 
The crude numbers of accidents and near misses were presented as a number of events per firefighter over the duration of the study. For the 15 brigades who provided both accident and near-miss data for the entire study period, this produced a range from 0.22 to 4.6 events per firefighter, mean 1.99 (±1.08 SD) and median 1.59 (IQR 1.4–2.55). For the 25 brigades who could produce 5 years complete accident data, the figures ranged from 0.14 to 3.57, mean 1.38 (±0.69 SD) and median 1.28 (IQR 1.01–1.62). These brigades incurred 25 267 of the 32 274 accidents and near misses involving the firefighters of the 32 brigades who provided some health and safety information.

Forty-one of 32 274 (0.13%) accidents and near misses were ascribed to the inability of a firefighter to hear an audible signal. Of these, seven were attributed to device breakdown, e.g. malfunctions of transmitters/receivers, etc., and 31 were due to failure of a driver to hear the command ‘Stop!’ while reversing vehicles. Thus, just three (0.09%) were likely to be due to persistently defective hearing. Only one was referred to the brigade's OH unit; his hearing was normal. None of the 135 taking IHR as a result of hearing loss attended their occupational health unit due to problems identified by their commanders arising while training or at an incident.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conflicts of interest
 References
 
The overall proportion of firefighters taking IHR due to hearing loss was 4%, comparable to the 3% found in Ide's survey [19]. These proportions are not large, but IHR is expensive, so even small reductions can yield worthwhile benefits.

There was a considerable overlap in the ranges of hearing loss, and when the hearing losses of the entire 235 firefighters were ranked, the firefighters with the second and third worst losses belonged to the control group. Therefore, the arbitrary imposition of a standard might result in considerable numbers of firefighters being inappropriately retired. It might also conflict with the Disability Discrimination Act [20].

While high-frequency hearing losses predominated among the ill-health retirees (56/121, 42%), low-frequency deficits were most common within the control group (34/79, 43%). This difference did not reach statistical significance (P = 0.65). One possible reason for the widespread low-frequency losses might be eustachian tube dysfunction. In the 34 cases where the audiometric finding was solely a low-frequency loss, 15 might be attributable to this. Three occurred in the months of December–February, when upper respiratory tract infections are common, but 12 were detected in June–August, when hay fever would be most likely. Unfortunately, subjects were not asked whether or not they suffered from these afflictions.

As hearing loss generally increases with age, it was not surprising that this tended to occur more often with older firefighters. Length of service varied from 5 to 37 years, mean 24.9 years. Since this distribution is skewed, the median length of service might be a more appropriate measure. This is 26 years, roughly coinciding with the point at which the maximum enhancement of pension incurred at IHR produces a full pension. This implies factors other than the inability to perform the job may, in some cases, make the firefighter declare the problem at that point.

The firefighters retiring with the shortest length of service, i.e. the youngest, had the greatest hearing loss when compared to Davis's findings—not less than the 80th centile over all frequencies [18]. They may have become more rapidly aware of hearing handicap, while older firefighters lost hearing more gradually, possibly compounded by presbyacusis.

Although 30 IHRs occurred due to the effects of an injury on duty, 27 (90%) occurred in just two brigades. While the hearing loss in the low frequencies in both ears was significantly worse in those taking retirement due to this cause (P < 0.001 for mean and P = 0.005 for median loss), there was no such difference apparent over the other frequencies.

Two firefighters had acoustic neuromas. For such a rare tumour to occur twice in a population of 3366 is unexpected [21] but Rajaraman et al. [22] found no evidence of increased risk involving firefighters in their survey, although Preston-Martin et al. [23] reported a roughly doubled risk of acoustic neuromas, but this only referred to men working in ‘extremely noisy’ jobs for at least 20 years. Known neurotoxins, such as carbon monoxide, might act synergistically with noise to produce hearing loss. Ferrite and Santana [24] found hearing loss more marked in smokers. While the smoking history of the subjects and controls in this survey was not specifically sought, in a study of factors involved in IHR, Ide [25] noted that those firefighters who took IHR were much more likely to be current smokers than those who had completed maximum service.


Key points

  • Attempts to define criteria for retention solely on audiometric grounds might result in the unnecessary retirement of otherwise fit firefighters. A functional hearing test is essential.
  • Hearing impairment appears responsible for a tiny proportion of work-related accidents and near misses.

 


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
References
 
None declared.


   Acknowledgements
 
I thank G. G. Browning and A. M. M. Ide for helpful comment, the Fire Service Medical Advisers, Occupational Health Advisers, Health and Safety and Personnel Officers who provided the information and the Chief Fire Officer of Lothian and Borders Fire and Rescue Service for permission to quote from the noise survey.


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conflicts of interest
 References
 

  1. Medical and Occupational Evidence for Recruitment and Retention in the Fire & Rescue Service. London. Office of the Deputy Prime Minister, 2004; 2–15. http://www.communities.gov.uk/pub/796/MedicalandOccupationalEvidenceforRecruitmentandRetention/PDF1599Kb_id1124796.pdf (date last accessed 22 September 2006).

  2. Fire Service Circular No. 19/1950, 25 April 1950.

  3. Central Fire Brigades Advisory Council for England & Wales; Scottish Central Fire Brigades Advisory Council. Joint Working Party on Appointments and Promotion. Final Report, Parts I, II, IV & V. Home Office, 1987.

  4. Jones CM, Hughes KB. Hearing and vestibular disorders. In: Fitness for Work: The Medical Aspects—Cox RAF, Edwards FC, Palmer K, eds. (2000) Chapter 10, 3rd edn. Oxford: Oxford University Press. 182–209.

  5. Medical and Occupational Evidence for Recruitment and Retention in the Fire & Rescue Service. (2004) 5. London: Office of the Deputy Prime Minister. 23–26.

  6. Tubbs RL. Noise and hearing loss in firefighting. In: Occupational Medicine: State of the Art Reviews (1995) Vol. 10. Philadelphia: Hanley & Belfus Inc. 843–856.[Web of Science]

  7. Reischl U, Bair HS, Reischl P. Firefighter noise exposure. Am Ind Hyg Assoc J (1979) 40:482–489.[Web of Science][Medline]

  8. Reischl U, Hanks TG, Reischl P. Occupational related firefighter hearing loss. Am Ind Hyg Assoc J (1981) 42:656–662.[Web of Science][Medline]

  9. Fire & Emergency Service. Hearing Conservation Programm Manual. (1992) Emmitsburg, MD: Federal Emergency Services Agency/United States Fire Administration.

  10. Kales SN, Freyman RL, Hill JM, Polyhronopoulos GN, Aldrich JM, Christiani DC. Firefighters' hearing: a comparison with population databases from the International Standards Organisation. J Occup Environ Med (2001) 43:650–656.[CrossRef][Web of Science][Medline]

  11. Clark WG, Bohl CD. Hearing levels of firefighters: risk of ocupational noise-induced hearing loss assessed by cross-sectional and longitudinal data. Ear Hearing (2005) 26:327–340.[CrossRef][Web of Science][Medline]

  12. Noise At Work Regulations 1989. Statutory Instrument 1989 No. 1790.

  13. Sewell C, Johnston P. Report to Client—Noise Exposure Assessment for Lothian and Borders Fire Brigade. Institute of Occupational Medicine, Edinburgh Contract No. 403/ 1711, Report No. OH1711.

  14. Control of Noise at Work Regulations 2005. Statutory Instrument No. 1643. (2005) London: The Stationery Office.

  15. Palmer KT, Coggon D, Syndall HE, Pannell B, Griffin MJ. Occupational exposure to noise and hearing difficulties in Great Britain. HSE Contract Research Report 361/2001. (2001) London: HSE.

  16. Browning GG. Clinical Otology and Audiology. (2001) Chapter 1, 2nd edn. London: Arnold. 3–4.

  17. Guidance Note MS 26. A guide to audiometric testing programmes. Health and Safety Executive, 1995.

  18. Davis A. Hearing in adults. Tables 323, 341, 449, 467. (1995) London: MRC Institute of Hearing Research, Nottingham Whurr Publications Ltd.

  19. Ide CW. Failing firefighters. A survey of the causes of death and ill-health retirement of serving firefighters in Strathclyde, Scotland. Occup Med (Lond) (1998) 48:381–388.[CrossRef][Medline]

  20. Disability Discrimination Act 1995. London: The Stationery Office.

  21. Schuknechkt HF. Pathology of the Ear. (1993) 2nd edn. Philadelphia: Lea & Febiger. 447–498.

  22. Rajaraman P, De Roos AJ, Stewart PA, et al. Occupation and risk of meningioma and acoustic neuroma in the United States. Am J Ind Med (2004) 45:395–407.[CrossRef][Web of Science][Medline]

  23. Preston-Martin S, Thomas DC, Wright WE, Henderson BE. Noise trauma in the aetiology of acoustic neuromas in men in Los Angeles County 1978 –1985. Br J Cancer (1989) 59:783–786.[Web of Science][Medline]

  24. Ferrite S, Santana V. Joint effects of smoking, noise exposure and age on hearing loss. Occup Med (Lond) (2005) 55:48–53.[CrossRef][Medline]

  25. Ide CW. Toothless tests–associations between the results of routine screening examinations and ill-health retirement of serving firefighters in Strathclyde, Scotland. Occup Med (Lond) (2000) 5:353–365.


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