An Evaluation of a Workplace Hazard: Carbon Monoxide

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An Evaluation of a Workplace Hazard Carbon
Monoxide
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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.

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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

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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)

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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
  -205C, Explosive Limits (volume in air)
  12.5-74.2

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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

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Symptoms of Exposure
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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)

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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

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Typical Occupations that May Experience CO Hazard

• lawn care workers
• janitorial staff
• disaster relief workers
• miners
• parking garage attendants
• toll collectors
• agricultural workers

• fire fighters
• garage mechanics
• aircraft refuelers
• truck Drivers
• Kiln and furnace operators
• forklift operators

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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
  workers breathing zone

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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

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Applicable IH Standards

• ACGIH TLV25 ppm TWA
• EPA NAAQS (Primary Standard) for outside air9
  ppm (TWA 8 hrs), 35 ppm (TWA 1 hr). This was
  established to protect public health (susceptible
  populations)

• OSHA PEL50 ppm TWA
• NIOSH REL35 ppm TWA 200 ppm ceiling
• NIOSH IDLH1,200 ppm

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Still More TLVs (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

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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
  lt11 ppm for 8 hrs, lt25 ppm for 1hr (ASTER)
• WHO Concentration of Concern is gt30 ppm

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CO Study, Occupation Lawn Care Worker

• 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

• My project was a simulation of lawn care worker.
• 8 hour work day ( 6 hrs of mowing)
• work equipment varied
• some CO exposure expected

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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

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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.

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Equipment in Use

• Push mower
• riding lawn tractor
• automobile (to move between sites)

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IH Equipment Used for Hazard Assessment

• Metrosonics PIM 1100 Industrial Hygiene Personal
  Monitor - Courtesy of Metrosonics, Inc.CO
  Electrochemical Oxidation Sensorwith a Heat
  Stress Monitor (core temperature and heart beats
  per minute)with Noise monitor (slow, A-weight)

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Findings

• Minimum 0 ppm
• Average 5 ppm
• Maximum 150 ppm
• 15 min STEL 13 ppm
• TWA 5 ppm

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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.

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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

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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

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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.

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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.

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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.

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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

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Note CO can be a Hazard in Nonoccupational
Settings

• Schools
• Homes
• Commuting
• Hospitals
• Nursing Homes

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Electronic Resources

• Internet
• www.osha.gov/
• www.cdc.gov/niosh/homepage.html
• www.epa.gov/iaq/
• www.safety-fl.org/
• www.acgih.org/

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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