Risk Assessment of Noise Pollution in a Cement Plant: Perspectives and Recommendations

: Introduction : noise is an acoustic phenomenon producing an auditory sensation considered unpleasant or annoying.Exposure to high sound levels over 85 dB(A) can affect the auditory system and other extra-auditory systems Our study


Introduction:
Noise is an acoustic phenomenon producing an auditory sensation considered unpleasant or annoying 1 .It is a nuisance present in many economic sectors and professional activities.In most industrial sectors, noise is a determining factor in working conditions, employee health and company performance 2 .
Exposure to high noise levels can affect the auditory system and other extra-auditory systems.The auditory effects of noise damage include posttraumatic deafness, auditory fatigue and occupational deafness 3 .As for extra-auditory damage, generally linked to chronic exposure, it is attributed to the stressful effect of noise and can also impair our attention span, degrade the quality of communication, and even impair quality of life 4 .
According to the WHO in 2017 in World Hearing Report one in four people, will suffer from hearing loss to varying degrees by 2050 5 .
In Canada in 2010 in Noise from Machinery in the Workplace, around 9,000 workers developed some form of hearing impairment, caused by overexposure to noise in the workplace 6 .
In the United States, according to the ILO, 9 million workers are exposed to daily levels of 85 dB(A), and 5.2 million of these come from manufacturing industries 7 .
The European Agency for Safety and Health at Work states that the cost of hearing loss accounted for around 10% of the total cost of occupational diseases between 1999 and 2000 8 .
The Sumer 2010 survey in France on long-term exposure of more than 20 hours a week to high levels of 85 dB(A) concerns 4.8% of employees.
In Tunisia in 2011, Habib Nouaigui and Coll reported that around 25% of the working population is exposed to high noise levels exceeding 85 dB.
In Côte d'Ivoire, decree no.01164 of November 04, 2008, sets national environmental standards for noise exposure levels in industrial zones at 75dB(A) during the day and 60dB(A) at night.
The risk assessment process identifies workstations at risk and the equipment that is the main source of noise.In the field of acoustics, risk assessment can start with a sound level estimate, followed by noise measurement, as per ISO 9612.
It was in this context that we initiated this study, the general aim of which was to assess the impact of exposure to noise.

Methodology:
Study setting: our study setting was the Lafarge Holcim Guinea plant.
The plant covers an area of 5.04 km2 and consists of an administrative building, a refectory, 02 crushers and several material installations.
Our study focused on the employees of the Lafarge Holcim plant.
We used the following to collect data: A pre-established survey sheet including: Socio-professional data Workers' medical data; Sound level meter

Methods:
Type and duration of study: this was a prospective descriptive study lasting 06 months, from 01 March 2022 to 01 September 2022.
Target population: Our study covered LafargeHolcim employees and their workstations.

Selection criteria
Inclusion criteria: all workers hired by the Lafarge Holcim plant The following work areas: Storage hall; Bagging area, BULK loading area, Maintenance workshop; Power station, Mixer operator, Laboratory, Weighing operator, Shipping area, Unloading area.

Non-inclusion criteria:
Hygiene and administration workers were included.Results:   The good qualification of the employees, the type of contract and the social insurance and pecuniary benefits linked to the contract would justify these results.
Work zone measurements ranged from 55. 2  Dia S.A. et al 13 noise levels exceeded 85 dB(A) in all areas except the laboratory, the storage area, the micro-packaging room, the flour store and the production manager's offices.
In some work areas, noise levels exceeded the set standards, exposing plant workers to various noise-related risks: auditory (hearing fatigue, reduced hearing acuity, deafness), extra-auditory stress-related (hypertension, sleep disturbance, impaired concentration and quality of life).
In terms of frequency of use, 48.9% of workers wore anti-noise Epi regularly, and the most frequently used type of PPE was earplugs.
Dia S.A. et al 13 in Dakar in 2014 in Evaluation des risques professionnels chez les travailleurs dans une meunerie showed that 45.45% of workers regularly used anti-noise PPE.
Hinson A.V. et al 14 in Benin in 2017 Evaluation of noise nuisance among workers in a steel production company reported that 21% of workers regularly wore hearing protection equipment .
Amadou Oury 15 in Guinea in 2020 in Evaluation des nuisances sonores chez les travailleurs de la SOGEAC found that 74.56% of workers used earplugs followed by 25.44% using helmets .
This result shows that, despite the CHS's efforts to raise awareness of the need to wear anti-noise PPE, many employees are not using them.This would be detrimental to their hearing health.
In addition, workers' preference for earplugs may be linked to the fact that they are lighter and more compatible with other PPE, and thus meet noise attenuation requirements.
Nicolas Derumaux et al 13 in their 2013 study of airport noise in France reported 37% tinnitus, 18% hearing loss and 7% vertigo at the end of a working day.
According to the literature, prolonged exposure to noise leads to clinical manifestations of repeated acoustic trauma, otosclerosis and vestibulocochlear nerve damage.
The audiograms carried out showed that 25.6% of workers had an abnormal audiogram, i.e. one worker in 4 had an abnormal audiogram.
Hinson A.V. et al 14 showed that 26% of workers' audiograms were abnormal.
Arip Amel Ep et al 15 in Algeria in 2011 in their study Evaluation of average hearing loss among workers in an Electrical Household Appliances industry found that 20.2% of workers had hearing loss.
Exposure to noise in different departments at sound levels exceeding 85dB(A) such as (Grinding area, Bagging machine, Bulk loading) are harmful to the auditory system and can lead to hearing deficits ranging from hypoacusis to deafness.In our context, this exposure combined with failure to wear PPE could explain the proportion of workers with abnormal audiograms.
Sensorineural hearing loss accounted for 61.9% of abnormal audiograms, followed by conductive hearing loss at 28.6%, and mixed hearing loss was the least represented at 9.5%.
The study carried out by the Observatoire Régional de la Santé de Midi Pyrénées in Enquête Audience in 2010 among young people aged 16-25 15 reported that hearing losses greater than 20 dB were located in the left ear (OG) with a frequency of 36.1%, followed by 34% in the right ear (OD) and 29.9% were bilateral.Bachy A. et al 16 in France in 2014 showed in their study Evaluation of a rapid audiometric screening test(DARDA) reported that 15 out of 35 patients had sensorineural hearing loss(42.85%).
The occurrence of these different types of deafness can confirm the negative effect on the ENT sphere.These include presbycusis, damage to Corti's apparatus (barotrauma) and auditory nerve disorders (acoustic neuroma).
In terms of hearing loss, 66.7% of audiograms revealed mild hearing loss, 23.8% moderate and 9.5% severe.
Chakroun A. et al 16 Tunisia in 2013 showed in their work "Evaluation of occupational deafness in a department of southern Tunisia" that 38.5% of workers had mild deafness and 48% had moderate deafness.
High noise exposure, ototoxic drugs (Gentamicin, Streptomycin, Cis platinum and Quinine) and certain pathologies such as Meniere's disease could explain these results.

Conclusion :
Exposure to noise represents a real risk in the workplace.Workers at the LafargeHolcim plant are highly exposed to it; hearing loss was mainly sensorineural, with a frequency of 61.9%.48.9% of workers regularly used noise protection equipment; 66.4% of PPE used was earplugs.
In addition to the effects on the auditory system, noise has an impact on extra-auditory systems, such as impaired communication and attention.However, noise mitigation measures must be implemented and reinforced to limit the risk and avoid these effects.

Figure 1 :
Figure 1: Distribution of workers according to selection criteria

Figure 2 :
Figure 2: Breakdown of workers by audiogram