An Outbreak of nHexane Neuropathy among Workers in a LCD Manufacturer

1
An Outbreak of n-Hexane Neuropathy among Workers
in a LCD Manufacturer
September 26, 2005

• Seong-Kyu Kang, Eun A Kim, Jee-Yeon Jeong,
  Gwang-Yong Yi, Byung-Kyu Kim, Mi-Young Lee

Korea Occupational Safety and Health Agency
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N-Hexane

• Aliphatic hydrocarbons
• Mostly non toxic
• Except n-hexane
• Use
• Cleaning agents in the printing, textile,
  furniture, shoemaking industry
• Special glue quick drying glue
• Extract vegetable oils from crops such as
  soybeans, flax, peanuts, and safflower seed.
• Paint/pharmacy/cosmetic/solvents
• Binding books/non mercury thermometer/
• alcohol preparations,

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Metabolism

• Absorption
• respiratory excrete in exhaled air (10 )
• No dermal absorption
• Linear correlation between air level and
  absorption up to 200 ppm
• Distribution
• Adipose and nerve tissues
• Metabolism
• Excrete in urine with 2,5 hexanedione
• Maximal urinary level after 4-7hour inhalation
• Detected in non exposed humane

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Physical Chemical properties of n-Hexane
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Health effects by n-Hexane

• Exposure to high level
• Mild irritation
• No sensitization
• Optic nerve decrease visual field, optic
  neuritis, macula degeneration, abnormal color
  vision
• Neurotoxicity
• Peripheral neuropathy caused by 2,5 hexanedione
• Multiple, bilateral, centripedal (distal to
  proximal)
• Both sensory and motor nerve involvement
• Numbness and weakness of lower extremities
  muscle atrophy
• Decreased DTR reflex and NCV
• Biopsy Axonal edema and demyelination
• Prognosis
• Recovered slowly after cessation of exposure
• May persist disability of extremities

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What is the problem?

• The n-hexane toxicity is well known.
• Using n-Hexane has been almost disappeared
  because of peripheral neuropathy
• Use of n-Hexane is increasing recently
• It is increasing in use to clean plastics in IT
  industry
• Why??

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Historical Reports in Korea

• Leather in shoe making factories(1974)
• 13 among 17 workers, loss of sense, muscle
  weakness, gait, motor disturbance
• 15hours work a day
• Air level 220-655 ppm (detector)
• Tire manufacture(1999)
• Automobile supplier factories(2002)
• Cleaning workers/ high exposure
• LCD frame manufacture(2002)
• 3 Immigrant Chinese workers
• 500 kg per month, 8.7 ppm (post investigation)
• Manufacture frame for mobile phone(2004)

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N-Hexane investigation in 2003

• Database of Work Environment Survey(1998)
• Manufacture in 6 factories with 45 workers
• Use in 373 factories with 4076 workers
• Generate in 9 factories with 47 workers
• Reviewed 450 factories
• Survey 390 added 60
• Site visit survey for 97 factories
• Investigated 17 factories
• Air-level 0.1-47.8 ppm

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Outbreak in Korea
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Introduction

• November 2004
• Polyneuropathy in 8 workers at the inspection
  process
• Used n-Hexane as degreasing solvents
• Illegal immigrant workers from Thailand
• Inspection by local office of KOSHA
• No awareness of using n-Hexane of the workers
• Improper ventilation system
• No personal protection equipment

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Polyneuropathy

• Age 19-37year-old
• Employed in 2001-2004
• Exposure duration 4-32 months
• Develop symptoms Aug to Nov 2004

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Polyneuropathy

• Progress
• general fatigue-weakness legs-gait disturbance-
• Numbness and paralysis of both extremities
• Muscle power
• Decrease to 50 in 7 workers
• To 10 in leg and 25 in arm
• EMG
• decrease NCV in both extremities
• Nerve biopsy
• Axonal degeneration, demyelination

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Work Process

• Extrusion
• plastic frame for notebook computer
• Grinding
• Ultrasonic cleaning - drying
• Inspection
• inspect blemish/dust and remove it by n-hexane
• Packing

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General information

• Workers
• Total/production line 50/30
• Plastic frame for notebook computer

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Inspection room

• Established since late 2001
• Confined space with poor ventilation

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Transport after Ultrasonic washing
Take out frames from dryer for cleaning
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Inspection

• Inspect frames to find blemish at the level of
  respiration
• Clean it with n-Hexane before and after
  Ultrasonic washing

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Cleaning

• Remove dust and blemish using n-Hexane
• Use half-cut plastic bottle for keeping n-hexane
• No respiratory protection
• Use cotton glove

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Packing
Packing five frames with one
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Investigation by Occupational Safety and Health
Research Institute

• 2005.1.-2.
• Investigation of the disease process
• Review the medical record, interview workers
• Medical examination to workers in neighbor
• Review the amount of consumption of n-Hexane
• Analysis the solvents known to n-Hexane
• Check air level with same work
• Check the ventilation system

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Work condition

• Estimated amount of monthly consumption
• 4 liter
• Number of workers 4-8
• Amount of work 5,000 frames per day
• Work hours per day
• 10-12 hours per day
• 1-2 days off per month

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History of the work environment measurement

• 2000 2001
• Mixed solvents 0.04-0.54 (OEL 1)
• 2002
• Mixed solvents 1.28 n-Hexane 50.96, 51.59 ppm
• n-Hexane 16.83, 46.92 ppm
• 2003
• n-Hexane 12.48 ppm
• n-Hexane 54.26 ppm
• 2004
• n-Hexane 59.7 ppm
• n-Hexane ND ppm

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Replicate same work

• Volunteers worked as it was.
• 4 volunteers with ventilation
• 4 volunteers without ventilation
• 8 volunteers with ventilation
• 8 volunteers without ventilation
• Use same amount of solvents estimated
• Mask and glove
• No protection at all in a volunteer

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Result(personal)
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Result(area)
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Ventilation efficiency during operating a fan
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Trend of air concentration at the level of
respiration
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Biological monitoring

• Methods
• Urine 2,5 hexanedione before and after shift.
• Results
• Internal absorption was markedly decreased with
  respiratory protection
• Without PPE, the exposure level was OEL value
  with just 4 hours work.

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Biological monitoring(urine 2,5 Hexanedion, mg/g
cr)
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(No Transcript)
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Component of the solvents
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Summary

• Air concentration of n-hexane is 1.5-6 times
  higher than regular measurement
• The highest level by real time monitoring was 800
  ppm.
• Big difference occurred between operating and not
  operating a fan(simple ventilation)
• Number of workers affected a little to the air
  concentration.
• PPE is very effective to prevent internal
  absorption.

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Lesson learned

• Employer
• Not awareness for work environment in small
  scaled-enterprise
• Production manage was in charge of all work
  process
• Work Environment
• Some cases do not reflex the practical value
• Health management
• Occupational Health Service did not work well
• Because of illegal workers
• No smell, no irritation
• Should be careful for the circulating air in case
  of operating air condition
• Health Examination
• Not taken because of illegal immigrant workers

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Actions taken

• Information in their language
• Published information sheets in 10 different
  language
• Enforce inspection to workplace where foreign
  workers are employed
• Reform the work environment evaluation system
• Need to setup a communication among Asian
  countries or between developed and developing
  countries