Researchers have gathered evidence which shows that combined chronic exposure to noise and carbon monoxide in the
workplace induces hearing loss. Adriana Lacerda, researcher at the ecole d'orthophonie et d'audiologie of the Universite de
Montreal, presents her findings at the annual meeting of the Acoustical Society of America in Vancouver on Wednesday. Those
findings are the result of a study conducted with over 8,600 workers exposed to both noise and carbon monoxide in the
workplace. Among the riskier professions are welders, firefighters, garage mechanics, truckers, forklift operators and
miners.
The correlation between carbon monoxide exposure and hearing loss had been established in previous animal studies but never
in humans. Based on data gathered by the National Institute of Occupational Safety and Health, Lacerda compared the hearing
of workers exposed to noise levels lower than 90 decibels for 8 hours to another group of workers exposed to noise levels
above 90 decibels. In both groups, a sample of workers was also exposed to carbon monoxide.
The results revealed that the workers who were exposed to carbon monoxide and to noise levels above 90 decibels displayed
significantly poorer hearing thresholds at high frequencies (from 3 to 6 kiloHertz). A larger shift was observed among
workers with 25-29 years of noise exposure in the workplace.
"Based on these results, we recommend that such risks as chronic exposure to carbon monoxide be considered when assessing the
risk of developing a noise-induced hearing loss," said Lacerda. One of several hypotheses to explain this phenomenon is that
the reduction of oxygen in the blood stream accelerates the deterioration of the sensory cells of the inner ear.
Adriana Lacerda is currently finishing her doctoral thesis under the supervision of Professor Tony Leroux and Jean-Pierre
Gagne of the ecole d'orthophonie et d'audiologie at the Universite de Montreal. She is the recipient of the Brazilian
government's CAPES bursary (Coordena de Aperfeioamento de Persoal de Nivel Superior), Universidade Tuiuti do Parana
bursary and also the recipient of a bursary of excellence from the Universite de Montreal.
About Universite de Montreal
Founded in 1878, the Universite de Montreal counts 13 faculties and, along with its two affiliated schools, HEC Montreal and
l'ecole Polytechnique, is Quebec's largest institution of higher learning, second in Canada, and among the most active in
North America. With a faculty of 2,400 professors and researchers, the university has a student population of more than
55,000, offers more than 550 undergraduate and graduate programs and awards some 3,000 Master's and PhD degrees each year.
University of Montreal
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