Published on February 13, 2008
An Evaluation of a Workplace Hazard: Carbon Monoxide : An Evaluation of a Workplace Hazard: Carbon Monoxide University of Central Florida, Introduction to Industrial Hygiene EIN 6264 April 1998 Submitted by, Tim Wallace, R.S email@example.com Identification of Workplace Hazard: Identification of Workplace Hazard Carbon Monoxide (CO) = a chemical compound consisting of one carbon and one oxygen. CO is a colorless and odorless gas at room temperature. Therefore, it has no WARNING properties!!!! The most likely route of exposure is through inhalation. Extent of Hazard-OSHA Says:: Extent of Hazard-OSHA Says: “Some 2,000 persons a year are killed out right by CO gas exposure” “At least 10,000 more workers suffer from exposure to debilitating levels of CO” “One of the most dangerous industrial hazards” “One of the most widespread” Nature of Hazard: Nature of Hazard Primarily known as an asphixiant or chemical anoxiant. This means that the CO causes absence or abnormally low amounts of oxygen in the body CO simply disrupts the oxygen transport to all tissues in the body. CO combines with hemoglobin in blood to form carboxyhemoglobin (COHb) Nature of Hazard II: Nature of Hazard II CO has an affinity for the oxygen binding site in the blood; 200 times more so than oxygen Other Potential Hazards (Atypical): highly flammable, may form explosive mixtures when mixed in air, may react to finely dispersed metal powders to form toxic and flammable carbonyls, may react vigorously w/ oxygen, acetylene, chlorine, fluorine, nitrous oxide. Other Physical Properties: BP -191ºC, MP -205°C, Explosive Limits (volume % in air) 12.5-74.2 Health Effects (Target Organs or Systems): Health Effects (Target Organs or Systems) Blood Cardiovascular System Lungs Central Nervous System Tissues with the highest oxygen need are first affected: myocardium brain exercising muscles Symptoms of Exposure: Symptoms of Exposure Particularly Susceptible Populations: Particularly Susceptible Populations Elderly Pregnant Women and Young Children Smokers Persons with existing illnesses: WHY??? a. cardiovascular disease (heart disease, coronary artery disease) b. pulmonary disease (asthma, emphysema, chronic bronchitis) c. blood disorders (sickle cell anemia, lassemia, others) Sources of CO: Sources of CO Incomplete combustion of anything containing carbon (fossil fuels, wood, tobacco) - Especially high in exhaust from internal combustion engines. CO is a metabolic product of methylene chloride (common ingredient in paints and solvents) may be be produced within the body by catabolism (breakdown) of hemoglobin Typical Occupations that May Experience CO Hazard: Typical Occupations that May Experience CO Hazard fire fighters garage mechanics aircraft refuelers truck Drivers Kiln and furnace operators forklift operators lawn care workers janitorial staff disaster relief workers miners parking garage attendants toll collectors agricultural workers Standard Methods of Measurement/Assessment: Standard Methods of Measurement/Assessment Direct reading CO Detector (electro-chemical voltimetric sensor) - dataloger and calibration to known gas concentration required sampling with calibrated vacuum pump through adsorption tube - laboratory analysis detector tubes certified by NIOSH all samples or measurements should be in the worker’s “breathing zone” Other Methods (EPA Outside Air Methods): Other Methods (EPA Outside Air Methods) Gas Filter Correlation (GFC) - relies on infrared absorbency properties of CO at 4.7, High accuracy, greater sensitivity, more complex equipment, stationary measurement Nondispersive Infrared (NDIR) - CO has a characteristic spectrum that allows it to be measured with reference to IR energy absorbed. Sensitive to drift, allows continuous datalogging, requires warm-up time, operable by non-technical personnel Applicable IH Standards : Applicable IH Standards OSHA PEL=50 ppm TWA NIOSH REL=35 ppm TWA; 200 ppm ceiling NIOSH IDLH=1,200 ppm ACGIH TLV=25 ppm TWA EPA NAAQS (Primary Standard) for outside air=9 ppm (TWA 8 hrs), =35 ppm (TWA 1 hr). This was established to protect public health (susceptible populations) Still More TLV’s (International Flavor): Still More TLV’s (International Flavor) DFG MAK (Germany) TWA = 30 ppm PEAK = 60 ppm (30 min) Japan (JSOH) TWA = 50 ppm HSE OES (United Kingdom) TWA = 50 ppm STEL = 300 ppm Reference: “TLVs and Other Occupational Exposure Values” Other Guidelines: Other Guidelines NRC (1987) EEGLs: 10 min = 1,500 ppm 30 min = 800 ppm 60 min = 400 ppm 24 hrs = 50 ppm NRC = National Research Council EEGL is Emergency Exposure Guidance Levels Canadian IAQ Residential Exposure Guidelines: <11 ppm for 8 hrs, <25 ppm for 1hr (ASTER) WHO Concentration of Concern is >30 ppm CO Study, Occupation: Lawn Care Worker: CO Study, Occupation: Lawn Care Worker My project was a simulation of lawn care worker. 8 hour work day (~ 6 hrs of mowing) work equipment varied some CO exposure expected Mowed two properties. One property was approximately 1 acre and was mowed with push mower 2nd property was about 2.5 acres and was mowed by riding mower Specific Job Duties of Worker During Study Period: Specific Job Duties of Worker During Study Period To operate gasoline powered mowers to mow two properties Edging not included To obtain gas for mower if empty Subject of Study:: Subject of Study: Question: Will CO Exposure exceed any standards or guidelines during a simulated average 8-hour work shift for an Lawn Care Worker? There seems to be few published reports on this type of a study. Some reports focus on small gasoline engines used inside buildings where the CO is easily concentrated. Equipment in Use: Equipment in Use Push mower riding lawn tractor automobile (to move between sites) IH Equipment Used for Hazard Assessment: IH Equipment Used for Hazard Assessment Metrosonics PIM 1100 Industrial Hygiene Personal Monitor - Courtesy of Metrosonics, Inc. CO Electrochemical Oxidation Sensor with a Heat Stress Monitor (core temperature and heart beats per minute) with Noise monitor (slow, A-weight) Findings: Findings Minimum 0 ppm Average 5 ppm Maximum 150 ppm 15 min STEL 13 ppm TWA 5 ppm Comparison to Exposure Guidelines and Standards: Comparison to Exposure Guidelines and Standards The OSHA PEL TWA was not exceeded. The NIOSH REL TWA was not exceeded. The NIOSH Ceiling was not exceeded. The ACGIH TLV was not exceeded. None of the other suggested guidelines were exceeded. Comments on Data: Comments on Data The momentary CO level measured during the start-up of the riding mower was elevated, however the duration of the exposure was short. Graph of Data (available as handout) Breaks and Lunch are distinct on data graph Possible CO Hazard Control Measures (if needed): Possible CO Hazard Control Measures (if needed) Eliminate - ex. Substitute gas mower with electric or manual mower. Control Source - ex. Adjust equipment to control emissions (catalytic converters) or improve efficiency of combustion process Apply appropriate ventilation or exhaust mechanism (only inside enclosures), ensure proper operation of exhausts More CO Hazard Control Measures: More CO Hazard Control Measures Provide appropriate personal protective equipment (PPE) to workers, when sources can not be controlled or eliminated and levels are suspected as hazardous. SCBA (NIOSH specified) is often specified. Definitely applies to fire/rescue personnel. Summary of Key Points: Summary of Key Points Carbon Monoxide exposure is a serious health and safety hazard. CO is especially a hazard in enclosed spaces CO did not seem to be a serious hazard during normal mowing operations. If CO levels were high and exceeded applicable TLVs, Control measures could be effectively instituted. Conclusion: No CO Standards or Guidelines Exceeded: Conclusion: No CO Standards or Guidelines Exceeded If this simulation was representative of a normal workday of a lawn care worker, then it appears that CO does not pose a serious threat to normal healthy adults. It is conceivable that that these low level exposures may cause measurable effects in susceptible individuals. More data is needed. Note: Other Potential Hazards Associated w/ Featured Occupation: Note: Other Potential Hazards Associated w/ Featured Occupation Heat Stress Noise/Vibration Injuries (overturned tractors, cuts, eye injuries, thrown debris) fire (burns) UV radiation exposure exposure to bioaerosols (mold spores, pollen) - a problem for asthmatics and allergy sufferers Note: CO can be a Hazard in Nonoccupational Settings: Note: CO can be a Hazard in Nonoccupational Settings Schools Homes Commuting Hospitals Nursing Homes Electronic Resources: Electronic Resources Internet: www.osha.gov/ www.cdc.gov/niosh/homepage.html www.epa.gov/iaq/ www.safety-fl.org/ www.acgih.org/ Acknowledgements: Acknowledgements Thanks goes to: Jennifer, Ed Williams and Mary Gestaldi for use of their property (land and work equipment) James Slattery from Metrosonics, Inc. for use of IH equipment
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