Download Chemicals and Hearing Loss - California Industrial Hygiene Council

Chemicals and Hearing Loss
California Industrial Hygiene Conference
December 4, 2006
LT Anne M. Jarrett, M.A., CCC-A
Occupational Audiologist, MSC, USN
Hearing Conservation Program
Naval Medical Center San Diego
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Hearing in the Work Environment
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Important for understanding:
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Individually and others in the work environment
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Productivity
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critical orders
warning and alerting signals (including listening to equipment
sounds)
general directions
Job related communication between coworkers
Hearing can be difficult in the work environment
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poor acoustical environments
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noise, distance, reverberation, distractions
work space, intercoms, meetings, telephones, walkie-talkie
Compounded by any underlying hearing loss
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Workers in the United States
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30 million individuals in the labor force who are exposed
to hazardous noise
9.5 million individuals who may be exposed to organic
solvents
1988 – Nat. Institute for Occup. Safety & Heath (NIOSH)
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1998 - National Occupational Research Agenda (NORA)
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included noise + chemicals topic
2001 - NIOSH
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began studying the solvents and HL
made available grants for investigating
2002 - NIOSH Best Practices Workshop
(Effects of Chemicals & Noise on Hearing)
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Work Environments with Solvents
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Painting
Printing
Boat Building
Construction
Furniture Making
Manufacturing of metal, leather, and petroleum
products
Cause: Spills, explosions/fires, industrial wastes, water
contamination, occupational environment, etc.
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Ototoxins
Organic
solvents
Metals
Drugs
Toluene (printing)
* Mercury and derivatives  Aminoglycosides
 Loop diuretics
* Lead and derivatives
** Xylenes (plastics)
 Anti-neoplastic agents
* Arsenic (atoxyl)
** Styrenes (plastics)
 ASA
** Trichloroethylene (degrease) * Manganese
 Trimethyltin (organic tin)  Quinine compounds
* Carbon Disulfide (textile)
 Cobalt
* Stoddard/white spirits
* N-hexane
Others
Asphyxiants
 Fuels (JP-8 fuel)
 Chem. warfare nerve agents
** Carbon Monoxide
 Ethyl benzene
 Organophosphate (pesticide)
* Cyanide
 Perchloroethylene
 Paraquat (pesticide)
**
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Butyl Nitrite
Methylene chloride
Army ID:
* potential
** high-priority
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Morata,TC., Dunn,DE., Kretschmer, LW., Lemasters, GK., Keith,
RW., Scandinavian Journal of Work, Environment & Health,
19(4): 245-54, 1993 Aug.
 Paint
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and print industries - risk of hearing loss
Unexposed (no noise or solvent)
Noise exposed only – hearing loss risk 4x
Toluene solvent only – hearing loss risk 5x
Toluene solvents and noise –hearing loss risk 11x
Controls: previous exposure to noise and/or chemicals,
medical and audiological history, age, length of
employment, recreational exposure, and military service
Tests: puretones, immittance (tympanograms, reflexes, reflex
decay)
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Problems caused by solvents
 Hearing
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Sensorineural Hearing Loss - Inner Ear
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Loss
Tuning (clarity and loudness)
Testing: common audiometric procedures (Puretones, Speech, Other)
Central/Retrocochlear Hearing Loss - Brainstem and Cortex
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Processing (transmission, cognition, varying degrees of tuning and loudness)
Testing:
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Speech Processing (interrupted speech, speech in noise, temporal integration)
Evoked Potentials (brainstem or cortical potentials),
DPOAE: Contra-lateral suppression (efferent testing)
Reflex and Reflex Decay
Modified Puretone: masking level difference, gap detection, duration pattern, pitch
pattern, temporal integration, high frequency audiometry, step size less 5dB
Questionnaire on speech discrimination difficulties or other auditory problems that
are inconsistent with thresholds
 Disequilibrium,
Headaches, Vision Problems, Neurological
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Many other causes of Hearing Loss
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Accumulative noise exposure
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Disease Processes
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occupational and recreational
outer, middle, inner ear and combinations
Accidents
Ototoxic exposure that are medical
Aging
Genetics: anatomical and sensitivity/susceptibility
Medical contributions to poor hearing health
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Hearing Conservation Programs (HCP)
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Most HCP have no mandate for chemical
exposure
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American Conference of Industrial Hygienists
(ACGIH)
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Advise Monitoring
US Army (1998):
Initiation enrollment when there is excessive exposures
to ototoxins (1 of 13 solvents)
 Monitoring (same as noise exposure)
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Questions with integrating into
solvent exposure in HCP
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Which solvents to include?
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Excessive exposure levels?
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Best audiometric test battery?
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Location of damage - Retrocochlear hearing loss
Efficient Monitoring Program
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2002 Best Practices Workshop
Comb. Effects of Chem. & Noise on Hearing
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NORA – Nat. Occupational Research Agenda
NIOSH – Nat. Institute for Occupational Safety and Health
NHCA – Nat. Hearing Conservation Association
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Goal:
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Review current knowledge
Determine how to address chemical exposures in hearing loss
prevention efforts
Next Slides:
Main Results of the Workshop
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Current knowledge
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Yes, enough evidence that solvents alone
and solvents combined with noise exposure
cause hearing, but more research is needed
Research does not capture all
conditions/questions to outline a new
national guideline for Hearing
Conservation Programs
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Mechanistic Research
guide research to determine auditory risk - affect
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Understand the mechanisms by which chemicals
affect the auditory system. Lead to a prediction of
which chemicals to target by preventive efforts
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Issues:
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Species respond differently – clues to the mechanism of
ototoxicity
Toxic interactions – manipulate exposure parameters
Physical or other factors considerations
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Health status, genetics, and age of participants
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Rationale for Inclusion of Chemicals
guide research on specific solvents and establish recommendations
for best practices
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Magnitude of exposed population
Evidence of chemical's ototoxicity, general
toxicity, and neurotoxicity
Chemical produces reactive oxygen species
(free radicals) or glutathione depletion cellular injury
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Glutathione –antioxidant that limits cell damage
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Exposure Issues
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Methods for administering chemicals
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inhalation, dermal, injection sites
Methods for evaluating exposures
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Task-based exposures assessments
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experienced, specifically trained control variables)
Comprehensive noise measurements
Biomarkers for type of cell damage in the ear
Personal protective use
Target workers who have held their jobs
Methods for assessing auditory effects
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Approach that discerns peripheral vs. central systems
No gold standard auditory test battery
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Response Level and Action
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Concentration level at which protective action
(i.e.. enrolled in HCP) should be initiated
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What actions for various solvents
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Intervals between testing
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Alert/Criteria signal
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HCP = puretones significant threshold shift
Alternatives Evaluation/control exposure
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HCP= annually
HCP = NIOSH 8 hour TWA =>85dB A SPL, hearing
protection, remove from noise
New training needs for exposed population
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HCP = initial and annual (effects, purpose testing & protection)
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Other Issues Identified
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Information Dissemination
Database (IH, HCP)
Other research questions
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Development of standardized case history
Interactions that modify the effects (smoking)
Occurrence of tinnitus
Incorporating neurological tests periodical
medical evaluations
Antioxidant therapy impact on preventive
strategies
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Key points – Take home message
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Keep updated on new research findings and
guidelines
Review exposures in current work area and workers
No standard yet but it is coming
Hearing is:
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Complex (when damaged causes many problems)
Painless (often taken for granted)
Effects others (not just the hearing impaired)
Permanent (except for many OM and ME problems)
Accumulative and Progressive
Often preventable
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