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Can you still hear safety or did you lack of safety take way your ability to listen, even GHS ototoxic chemicals!

Hearing conservation at  work is a critical component of your system and programs not just for your workers but for claim management and prevention.   In the USA, Occupational hearing loss is one of the most common work-related illnesses in the United States. Approximately 22 million U.S. workers are exposed to hazardous noise levels at work, and an additional 9 million are exposed to ototoxic chemicals.An estimated $242 million is spent annually on worker’s compensation for hearing loss disability.

When the safety person, supervisor or your safety manual covers hearing and hearing loss we usually note sound and prevention items like ear plugs or muffs associated to PPE requirement but what about the OTHER risks you are not seeing like OTOTOXICTY issues in both GHS produces and Dangerous Goods!!!

GHS Ototoxicity is the property of being toxic to the ear (oto-), specifically the cochlea or auditory nerve and sometimes the vestibular system, for example, as a side effect of a drug. The effects of ototoxicity can be reversible and temporary, or irreversible and permanent. It has been recognized since the 19th century. There are many well-known ototoxic drugs used in clinical situations, and they are prescribed, despite the risk of hearing disorders, to very serious health conditions. Ototoxic drugs include antibiotics such as gentamicin, loop diuretics such as furosemide and platinum-based chemotherapy agents such as cisplatin.   noise-induced hearing loss (NIHL) and we have the National Exposure Standard for Occupational Noise to deal with this.  It is less well known that a substantial number of medications and common industrial chemicals can also cause hearing loss themselves or exacerbate the effects of noise.  These chemicals are said to be ototoxic (oto = ear, toxic = poisonous).    Drugs and chemicals can effect auditory brainstem response results, demonstrate balance and equilibrium problems, result in abnormal acoustic reflexes, demonstrate hearing loss initially above 8K Hz, often do not show recruitment and are capable of demonstrating measurable auditory processing difficulties to staggered word tests. Tinnitus is often present and may disappear or be reduced when medication or exposure ceases.

Noise induced hearing loss results primarily in cochlear dysfunction, does not show abnormal auditory brainstem responses, does not usually effect balance, demonstrates recruitment, shows the presence of acoustic reflexes within measurable threshold ranges, shows a dip in hearing at 3, 4, and/or 6 K Hz in the initial stages, does have recruitment and most often results in speech discrimination problems not necessarily auditory processing difficulties. Tinnitus may not be reported in noise induced (continuous exposure to high levels of noise) but a ringing is associated with blast wave exposure (as gunfire). Noise is not associated with a roaring, buzzing or pulsating tinnitus.

Prevention starts in the workplace with but not limited too; Increased Occupational Hygiene Interventions in workplaces through:

  • Regulation Development/amendments
  • Enforcement of Regulations, Occupational Exposure Limits (OELs), and Federal/Provincial WHMIS Legislation
  • Inspections and Investigations
  • GHS classification criteria
    • Health and Environmental Hazards
    • Physical Hazards
  • Canada is working towards GHS implementation for:

Health Canada

  • Workplace Chemicals (WHMIS)
  • Consumer Chemical Products
  • Pest Control Products

Transport Canada

  • Transportation of Dangerous Goods

They may damage the cochlea in the inner ear and/or the auditory neurological pathways leading to hearing loss, tinnitus and vertigo.  Hearing damage is more likely if exposure is to a combination of chemicals or a combination of the chemicals and noise.

In relation to chemicals, a hazard is a set of inherent properties of the substance, mixture, article or process that may cause adverse effects to organisms or the environment. There are two broad types of hazards associated with hazardous chemicals which may present an immediate or long term injury or illness to people. These are:

  • Health hazards – These are properties of a chemical that have the potential to cause adverse health effects. Exposure usually occurs through inhalation, skin contact or ingestion. Adverse health effects can be acute (short term) or chronic (long term). Typical acute health effects include headaches, nausea or vomiting and skin corrosion, while chronic health effects include asthma, dermatitis, nerve damage or cancer.
  • Physicochemical hazards – These are physical or chemical properties of the substance, mixture or article that pose risks to workers other than health risks, as they do not occur as a consequence of the biological interaction of the chemical with people. They arise through inappropriate handling or use and can often result in injury to people and/or damage to property as a result of the intrinsic physical hazard. Examples of physicochemical hazards include flammable, corrosive, explosive, chemically reactive and oxidising chemicals.

Workers can come in contact with a hazardous chemical and any waste, intermediate or product generated from the use of the substance if they: • work with it directly • are in the vicinity of where it is used or likely to be generated • enter an enclosed space where it might be present • disturb deposits of the substance on surfaces (for example, during cleaning) and make them airborne • come into contact with contaminated surfaces.

You should consider all people at the workplace, including those who may not be directly involved in using, handling, storing or generating a hazardous chemical, such as: • ancillary or support/services workers (be aware that cleaners, maintenance and laboratory staff are often exposed to both the hazardous chemicals they use in the course of their work, such as cleaning products, and the hazardous chemicals used in the workplace by other workers) • contractors • visitors • supervisors and managers.

You should consider: • how specific tasks or processes are actually carried out in the workplace (for example, decanting, spraying, heating). By observing and consulting workers you can find out if they are not adhering strictly to standard procedures or if procedures are not adequately providing protection to workers. • the quantity of the chemicals being used. Use of larger quantities could result in greater potential for exposure • the risk controls in place and their effectiveness. For example, a ventilation system may be in use but when poorly designed, installed or maintained it may not achieve the correct level of protection (such as if filters are not regularly cleaned), • whether each worker’s work technique has a significant bearing on their level of exposure – poor techniques can lead to greater exposure • workers who may be working alone with hazardous chemicals and if any additional precautions or checks may be necessary in case they become incapacitated.

The inner ear also has primary responsibility for balance function. Ototoxic compounds can affect all of the inner ear structures—not just the hearing part—putting a person at risk for falls from dizziness and vertigo. Even if noise levels alone don’t seem loud enough to cause hearing damage (e.g., < 80 dBA), the synergy with chemicals makes hearing loss more likely with lower noise levels. In any environment where chemicals are being used, wearing hearing protection is good practice even when noise is just below the action level (an earplug with moderate attenuation,), especially where the use of a respirator is required. Wearing a respirator can be as important as wearing hearing protection when it comes to working with ototoxins.  Ototoxic chemicals can be divided into two general classes: workplace chemicals and medication. Currently it is thought that more than 750 different groups of chemicals are potentially ototoxic.

In the RISK world and understanding your chances of not knowing this subject!!!

Drug and Chemical Ototoxicity

Synergistic Effects

Noise and drugs (chemicals) have been shown to be synergistic in their damaging effects to the balance/hearing mechanisms. Synergistic damage is multiples of the expected damage of either agent alone.

Noise Alone                              4.1 risk factor

Solvent Mixture Alone            5.0 risk factor

Noise and Toluene                 10 to 27.5 risk factor

High Frequency Hearing Loss

Many chemicals and most drugs will affect the higher frequencies first. The recognized range of human hearing is 20 to 20,000Hz. Current industrial and clinical hearing testing includes the frequencies ranging from 125 Hz to 8,000Hz. The initial hearing loss may well be in frequencies above 8,000Hz.

It is possible to monitor hearing loss caused by drugs and chemicals. This is usually done with children undergoing chemotherapy treatment. Pre, during, and post hearing testing of the extreme high frequencies to monitor the highest five-frequencies the patient can respond to, provides a clinical procedure to identify changes caused by drugs and chemicals. These frequencies are above the standard 500Hz to 8,000Hz testing done in industry. They include 1/6 octaves above 8,000Hz up to 20,000Hz.

Ototoxic chemicals can cause hearing loss on their own, however when combined with noise exposure, the effects can be even more severe. Organic solvents are the most commonly identified chemicals, but others may also be involved (e.g. metals and chemical asphyxiants). The hearing frequencies affected by solvent exposure are different than those affected by noise. Research suggests that solvents may interact synergistically with noise. Even when noise and chemicals are at permissible exposure levels, the impact of a combined exposure can do more damage than a higher exposure to either hazard alone.

Some chemicals associated with hearing loss

  • Benzene
  • Carbon disulfide
  • Carbon monoxide
  • Ethylbenzene
  • Hydrogen cyanide
  • Lead
  • Mercury
  • n-Hexane
  • Solvent mixtures
  • Styrene
  • Trichloroethylene
  • Toluene
  • Xylene

Organic solvents are widely used: in automotive and aviation fuels; in plastics industries; as thinners for paints, lacquers and dyes; in the manufacture of detergents, medicines, perfumes, fabric and paper coatings, printing inks, spray surface coatings; and in insect repellents.

An effective hearing conservation program must be implemented by employers in general industry whenever worker noise exposure is equal to or greater than 85 dBA for an 8 hour exposure or in the construction industry when exposures exceed 90 dBA for an 8 hour exposure. This program strives to prevent initial occupational hearing loss, preserve and protect remaining hearing, and equip workers with the knowledge and hearing protection devices necessary to protect them. Key elements of an effective hearing conservation program include:

  • Workplace noise sampling including personal noise monitoring which identifies which employees are at risk from hazardous levels of noise.
  • Informing workers at risk from hazardous levels of noise exposure of the results of their noise monitoring.
  • Providing affected workers or their authorized representatives with an opportunity to observe any noise measurements conducted.
  • Maintaining a worker audiometric testing program (hearing tests) which is a professional evaluation of the health effects of noise upon individual worker’s hearing.
  • Implementing comprehensive hearing protection follow-up procedures for workers who show a loss of hearing (standard threshold shift) after completing baseline (first) and yearly audiometric testing.
  • Proper selection of hearing protection based upon individual fit and manufacturer’s quality testing indicating the likely protection that they will provide to a properly trained wearer.
  • Evaluate the hearing protectors attenuation and effectiveness for the specific workplace noise.
  • Training and information that ensures the workers are aware of the hazard from excessive noise exposures and how to properly use the protective equipment that has been provided.
  • Data management of and worker access to records regarding monitoring and noise sampling.

Review your GHS chemical products on site and know the risks.  How to protect workers; Conduct a hazard assessment as the first step in a hearing loss prevention program to learn if and what hazardous exposures exist in the workplace.

  • Remove the source of hazardous exposures from the workplace (the most effective way to prevent hearing disorders from noise or chemical exposure, but may not be possible).
  • Substitute ototoxins with less hazardous chemicals.
  • Take steps to minimize potential ototoxin exposures through inhalation, ingestion, and/or skin absorption.
  • Minimize exposure to these chemicals through process changes, ventilation, and/or skin or respiratory protection.
  • Reduce noise levels through engineering or administrative controls.
  • Wear hearing protection when exposed to noise, or when exposed to ototoxins – even when noise levels are below the threshold – to prevent the combined effects of noise and solvent exposure.
  • Start a hearing conservation program for workers at lower levels of noise exposure than is required by occupational health and safety legislation.
  • Include workers exposed to chemicals in hearing conservation programs, whether or not they are exposed to noise. These programs should consider the possible combined effects of exposure to both solvents and noise.

Each of these elements is critical to ensure that workers are being protected where noise levels are unable to be reduced below the O H & S  required levels.

Terry Penney

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