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Occupational Exposures BY BILL EVANS – INDUSTRIAL HYGIENIST Understanding Occupational Exposure Dose – Response Curves are different for all toxic agents. The most disconcerting factor is that the most harmful exposures come from particles, fibers and gases smaller than the human eye can see. “Targets” of OSHA Compliance Updating of OSHA PELs Status – 11th Cir. Court gutted PELs by vacating standards for 212 substances in 1991 moving back to levels of 1971 OSHA LEPs – Local Emphasis Programs vary slightly by Region, but the items called out below are consistent Noise, Hazard Communication/GHS, Gut-Rehab, Silica, Lead, Asbestos, Hexavalent Chromium, Cadmium and Carbon Monoxide Industrial Hygiene Method of Assessment Unhealthy noise exposure is used as an example to show: Pathway of Exposure Body System Affected Mode of Transmission Symptoms of Exposure Acute Effects Chronic Effects Health Codes: Legal Exposure Limits (PELs) & Guidelines (TLVs, RELs, OELs) Video of Hazardous Noise Objectives 29 CFR 1910.95 Distinguish between sound and noise Discuss types of hearing loss Become familiar with types of noise measuring equipment Understand the requirements of 29 CFR 1910.95 Sound Versus Noise Sound is a pressure change detectable by the human ear. Pitch/frequency ranges between 20 to 20,000 Hertz (cycles/sec) Volume ranges between 0 to 140 dB Noise is a type of sound. Generally described as undesirable or unwanted sound Types of Hearing Loss Middle ear hearing loss results from lack of conduction. Impacted wax Broken ear drum Inner ear hearing loss results from lack of neural connections. Naturally due to aging Loud noises Disease Occupational Noise Loss Cannot be treated or corrected medically Initially affects high frequencies Progresses to lower frequencies Threshold Shift Temporary Threshold Shift (TTS) Hearing returns to normal after noise exposure Permanent Threshold Shift (PTS) Repeated noise exposure without a return to normal OSHA Standard Threshold Shift (STS) > 10 dB average loss of hearing ability at 2000, 3000, & 4000 Hz in either ear Non-Auditory Effects of Noise Affects cardiovascular & nervous systems Interferes with speech and concentration Causes annoyance, stress, and fatigue Reduces work efficiency Lowers morale Masks warning sounds Noise Measuring Equipment Sound level meters Basic instrument to measure sound pressure variations in air Noise dosimeter Combines sound pressure and time for employee exposure monitoring Permissible Exposure Limits 1910.95(b) No employee can be exposed above the permissible exposure limit (PEL) w/o hearing protection. OSHA PEL = 90 dBA for a 8-hour time-weighted average (TWA) Feasible administrative or engineering controls are required. Hearing protection provided and used to reduce sound to within levels of Table G -16. Table G-16 - Permissible Noise Exposures Duration per day, hours Sound level dBA slow response 8 90 6 92 4 95 3 97 2 100 1½ 102 1 105 ½ 110 ¼ or less 115 Footnote(1) When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractions: C(1)/T(1) + C(2)/T(2) C(n)/T(n) exceeds unity, then, the mixed exposure should be considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, and Tn indicates the total time of exposure permitted at that level. Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level. 90 dBA PEL? 90 1910.95(c)-(d) dBA PEL (early 1970s) not protective enough Recommended TLV = 85 dBA for 8 hrs is better Noise Action Level OSHA Action Level (AL) = 85 dBA for a 8-hour TWA 1910.95(c)-(d) Determined without regard to hearing protector reduction Hearing Conservation Program (HCP) required at this level Audiometric testing Baseline & Annual Tests A qualified person performs the hearing test (e.g., audiometric tech, audiologist). Compare annual test to baseline test to check for STS Example of Audiogram STS Notification 1910.95(g) Recall standard threshold shift definition: > 10 dB avg. loss @ 2000, 3000 & 4000 Hz Employer may retest within 30 days to verify the STS. Employer shall notify the employee of the STS in writing within 21 days. STS Requirements 1910.95(g) If STS is work-related: Employee is fitted for hearing protection and trained Refitted and retrained if already wearing hearing protection Referred for audiological or otological exam, if necessary. Hearing Protectors Must be available to “action level” employees Must be required for those employees: 1910.95(i) Exposed at or above 90 dbA Exposed at or above 85 dbA (without an audiometric baseline) Who have an STS Hearing Protectors Provided at no cost to the employee Selected from a variety of types and brands Properly fitted 1910.95(i) Noise Reduction Rating (NRR) Appendix B Laboratory-based reduction in decibels that the hearing protector will provide. NRR specified on hearing protector packages. NRR example for A-weighted exposure data Estimated exposure (dBA) = TWA (dBA) - (NRR - 7)/2 3M Fit Test System – example of Field Attenuation Estimation System (FAES); use the term Personal Attenuation Rating (PAR) Some research, particularly in Europe, suggest links between hazardous noise and diabetes, arthritis and cardiovascular ailments. Carbon Monoxide Chemical asphyxiant CO binds to hemoglobin forming carboxyhemoglobin (COHb). Hemoglobin has affinity for CO 240X greater than that for oxygen. COHb decreases oxygen saturation and shifts the O2 hemoglobin dissociation curve to the left. COHb At levels of 6% may cause impairment. 40-60%, alterations in mental status and death may occur. Silica 29 CFR 1910.1000 Table Z - 3 Basic component of soil, sand, granite, and many other minerals Exposure only when crystalline silica particles are in the air If materials containing silica do not generate dust, there is little chance of inhaling the silica 29 CFR 1910.1000 Table Z-3 OSHA PEL (mg/m³) = (10 mg/m³)/(2+% respirable quartz) Lead – 29 CFR 1910.1025/1926.62 In bloodstream, lead is bound to red blood cells. Distributed to soft tissue (liver, kidney, brain, Eventually deposits in the bone muscle) Half-life of 10-30 years (bone) Asbestos 1910.1001 1926.1101 Airborne fibers range in size from 0.1 to 10 µm in length. ACM: “asbestos-containing material,” any material containing >1% asbestos. PACM: “presumed asbestos-containing material” – thermal system insulation and surfacing material found in buildings constructed no later than 1980. Hierarchy of Protection Engineering Mechanical ventilation (e.g., draw bad air away from BZ) Work practice/administrative controls Equipment Housekeeping Hygiene facilities Employee information and training PPE (last because it puts onus on employees) Respiratory protection Protective work clothing