Hearing Loss Hazards for Industrial Workers
Chemicals as Well as Noise Pose Potential Risks to Inner Ears
Oct 27, 2009
It has been discovered that hearing loss and difficulties with balance can be caused on workplaces by exposure of people to any of a range of chemicals known as "ototoxins." The Canadian Centre for Occupational Health and Safety (CCOHS) states in a recent newsletter that this hazard to hearing health has been suggested by tests on both people and animals.
The concentrations of the chemicals that are considered dangerous to the ears are high, the CCOHS states. If exposure occurs in the presence of high levels of noise, the risk of damage increases. Exposure to either noise or an ototoxin chemical can increase the susceptibility of the ear to damage. When noise is at a normally acceptable level, the presence of a chemical can render the noise level hazardous, and vice-versa.
It is thought the chemicals, once absorbed into the bloodstream, can affect the auditory nerve and cause the same type of damage to the hair cells in the cochlear (inner ear) that sense sound as is caused by high noise. It can result in not only hearing loss but also ringing in the ears and problems with balance.
Hearing Loss Hazards
The substances most commonly identified as ototoxins by CCOHS and NIOSH (National Institute for Occupational Health and Safety) are organic solvents. Others are some metals (lead and mercury) and a range of chemicals.
CCOSH's website lists chemicals associated with hearing loss. Among them are:
- Benzene, one of the top 20 chemicals produced by volume in the U.S.; used in the plastics, synthetic fibers, detergent, pharmaceutical and pesticide industries.
- Xylene, one of the 30 top chemicals produced by volume in the U.S., used as a degreasing agent, thinner and solvent.
- Ethylbenzene, used to make styrene, paints, solvents and fuels.
- Hydrogen cyanide, used for production of other chemicals, synthetic fibers, plastics, dyes, and pesticides as well as in fumigation, electroplating and mining.
- n-Hexane, mixed with other chemicals to form solvents.
- Styrene, used to make polystyrene for insulation, fiberglass, pipes, automobile parts, food containers, and carpet backing.
- Trichloroethylene, used as a solvent to remove grease and in adhesives, paint removers and spot removers.
- Toluene used in production of paints, paint thinners, fingernail polish, lacquers and adhesives.
Work Places With Potential Hearing Loss Hazards
Work environments and occupations where chemicals and noise levels can be combined to result in potential hazards include the industries mentioned above as well as:
- construction,
- firefighting,
- furniture manufacture,
- painting,
- printing,
- boat building and
- weapons firing.
Because workers are exposed to various chemicals, it is difficult to determine the ototoxic effects in any particular circumstance or environment,. the CCOHS says. Also, it is difficult to distinguish between the effect of the chemical and the noise on hearing loss.
Prevention of Hearing Loss
CCOHS suggests a number of steps to lessen hazards, summarized here:
- Assessment of hazards in a workplace;
- Removal of hazards as much as practical;
- Substitution of ototoxins with less hazardous chemicals;
- Change of processes, improve ventilation and personal protection to minimize potential inhalation, ingestion or absorption of ototoxins through the skin.
- Reduction of noise levels;
- Use of hearing protection even in low noise levels to prevent the combined effects of noise and ototoxins;
- Hearing conservation programs for workers exposed to ototoxins, whether exposed to noise or not.
The CCOHS warns that, although there is "no firm guidance" on limits of exposure to solvents, current exposure limits and hearing conservation for workers exposed to solvents "may not be adequate." The information available from the CCOHS and NIOSH provides valuable guidance to employers and unions in protecting workers from hearing loss.
Sources: Agency for Toxic Substances and Disease Registry (ATSDR), Atlanta, GA, an agency of the U.S. Department of Health and Human Services; Centers for Disease Control and prevention.
Associated articles: Workplace health hazards are part of the practice of ergonomics. For other articles on ergonomics, see Cost Benefits of Ergonomic Chairs; Office Chairs That Ease Back Pain; Chairs for Pain-Free Computer Work.
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