Chemicals And Hearing Loss


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Chemicals And Hearing Loss

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