2'2 OCCUPATIONAL HEALTH STANDARDS

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2.2 OCCUPATIONAL HEALTH STANDARDS
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SCOPE

• Types of Exposures
• Definition
• Threshold Limit Value
• Limitation
• Duration of Exposure
• Biological Standard
• Malaysian Occupational Exposure Standard

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Types Of Standard

• Voluntary Standard
• - American Conference of Governmental
• Industrial Hygienist (ACGIH)
• - Threshold Limit Value (TLVs)
• Compulsory Standard
• - Permissible Exposure Limit

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Threshold Limit Value (TLV)

• Threshold limit values (TLVs)refer to airborne
  concentrations of substances and represent
  conditions under which it is believed that nearly
  all workers may be repeatedly exposed day after
  day without adverse health effects
• Because of wide variation in individual
  susceptibility, however, a small percentage of
  workers may experience discomfort from some
  substances at concentrations at or below the TLV
• A smaller percentage may be affected more
  seriously by aggravation of a pre-existing
  condition or by development of an occupational
  illness

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TLV (USA)

• Published by ACGIH
• Established in 1946 (updated annually)
• Approximately 750 chemicals covered
• Guidelines not law
• Documentation of TLVs and BEIs
• Method of adoption
• Balancing of health considerations and cost to
  industryACGIH 1948

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Examples of TLV
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Definition (from USECHH 2000)

• "permissible exposure limit" means a ceiling
  limit or an eight-hour time-weighted average
  airborne concentration or the maximum exposure
  limit
• "ceiling limit" means the airborne concentration
  that should not be exceeded during any part of
  the working day
• "time-weighted average" in relation to airborne
  concentration, means an average airborne
  concentration over a specified period of time
• "maximum exposure limit" means a fifteen-minute
  time-weighted average airborne concentration
  which is three times the eight-hour time-weighted
  average airborne concentration of the chemicals
  specified in Schedule I - same as STEL (ACGIH)

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Threshold Limit Value (ACGIH)

• TLV-TWA Threshold Limit Value Time Weighted
  Average (TLV-TWA) 8 Hour time weighted average
• Time Weighted Average Short Term Exposure Limit
  (TLV-STEL) TLV for short term exposure,
  Contaminant concentration averaged over a
  15-minute period
• Threshold Limit Value-Ceiling (TLV-C) maximum
  concentration that cannot be exceeded at any time
  / location at work. This is an instantaneous
  concentration or concentration averaged over a
  15 minute period if technology does not exist to
  measure instantaneous concentrations

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General Formula for TWA
ci is concentration during ith interval ti is
duration of the ith interval
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Evaluating Exposure to Volatile Toxicant by
Monitoring

• Worker exposures using online continuous
  monitoring of air concentrations of toxicants
  (C), the measured timeweighted average
  concentration is,

TWA is time weighted average C(t) is
concentration in ppm or mg/m3 of chemical in
air tw is the worker shift time in hours
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For workers exposed for more than 8 hour

• Since the computation is normalized to 8 hours,
  if workers are exposed to TLVTWA level for 12
  continuous hours, then TWA(12/8)(TWA8)
• Thus higher TLV is tolerated ? Think

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8-hour Time Weighted Average
For a worker who works at various locations in
the plant, his/her exposure is measured using
intermittent samples at fixed points,
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Example

• PEL for the chemical involved is 12 ppm
• Partial period samples
• 4 hours _at_ 11 ppm, 2 hours _at_ 14 ppm, 2 hours _at_ 20
  ppm
• TWA calculation

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Another example

• PEL for the chemical involved is 12 ppm
• Partial period samples
• 4 hours _at_ 11 ppm, 2 hours _at_ 14 ppm
• TWA calculation

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Another Example

• PEL for the chemical involved is 12 ppm
• Partial period samples
• 4 hours _at_ 11 ppm, 2 hours _at_ 14 ppm, 2 hour not
  sampled
• TWA calculation

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TLV for Mixture
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Evaluation of Exposure to Volatile Toxicant by
Monitoring
For exposure to mixture of toxicants (assuming
the effects are additive), the TWA for mixture is,
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Compliance of mixture
For exposure to mixture of toxicants (assuming
the effects are additive)
C is the measured 8-hour TWA concentration EL is
the exposure limit for substance
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TLV for MixtureExposure Limit for working greater
that 8 hours
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Workers of extended hours

• Many worker work longer than 8 hour per day or 40
  hours per week
• Apply adjustments to Els with caution
• Should not be used to justify very high exposures
  as allowablewhere exposure periods are short

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EL for gt 8 hour shift

• Adjustments dont have the benefit of historical
  use and long term observation
• Medical supervision during early adjustment use
  advisable

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EL for gt 8 hour shift

• Simplest form, dose (concentration x time) is
  held constant and new allowable concentration is
  calculated

Other more complicated adjustment calculations
can account for pharmacokinetic behaviour
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Example

• What is the PEL for benzene over a 12-hour shift
  given an 8-hour PEL of 1.0ppm?

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LIMITATION

• Data based on TLVs are limited
• Variations in data
• Difficulty in measuring existing exposure
• Difficulty in getting sample that are
  representative on the breathing zone
• Uncertainty in actual amount inhaled.

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CARCINOGEN

• Category
• A1 Confirmed human carcinogen
• A2 Suspected human carcinogen
• A3 Confirmed animal carcinogen with unknown
  relevance to humans
• A4 Not classifiable as a human carcinogen
• A5 Not suspected as a human carcinogen

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Duration of Exposure

• TWA standard of exposure for air pollution
• Variation in standard of exposure is affected by
  factors including acute effect and removal of
  metabolite substances
• Factors that require expert scrutiny is
  considered in modification/adjustment of standard
  of exposure.

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BIOLOGICAL STANDARD

• Analysis of substances that do not change in body
  tissues
• Analysis for metabolite
• Analysis of variation of enzyme or biochemical
  levels

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Biological Exposure Indices (BEI)

• Measurement of chemical determinant in a
  biological media
• Examples
• Acetone in urine
• S-Phenylmercapturic acid (metabolite of benzene)
  in urine
• n-Hexane in end-exhaled air
• Lead in blood

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Occupational Standard of Exposure in Malaysia

• AKTA KILANG JENTERA 1967
• Peraturan-Peraturan Kilang dan Jentera (Timah
  Hitam) 1984
• Peraturan-Peraturan Kilang dan Jentera (Proses
  Asbestos) 1986
• Peraturan-Peraturan Kilang dan Jentera (Habuk
  Galian) 1989
• Peraturan-Peraturan Kilang dan Jentera
  (Pendedahan Bising) 1989
• AKTA KESELAMATAN KESIHATAN PEKERJAAN 1994
• Peraturan-Peraturan Keselamatan dan Kesihatan
  Pekerjaan (Penggunaan Standard Pendedahan
  Kepada Bahan Kimia Berbahaya Kepada Kesihatan)
  2000

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Occupational Exposure Standard (FMA 1967)

• Permissible Exposure Limit
• Lead 150 microgram per cubic meter of air
• Asbestos 1 fiber per mililiter of air
• Mineral Dust
• 5 mg/m3 for respirable dust)
• 10 mg/m3 for total dust
• 0.1 mg/m3 for respirable quartz)

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Occupational Exposure Standard (FMA 1967)

• Permissible Exposure Limit for Noise
• 90 dB(A) for 8 hours
• Limits as specified in schedule 1 for exposure
  other that 8 hours
• 115dB(A) maximum
• 140 dB peak for impulse noise

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Occupational Exposure Standard (OSHA 1994)

• Permissible Exposure Limit(PEL)
• Peraturan-Peraturan Keselamatan dan Kesihatan
  Pekerjaan (Penggunaan dan Standard Pendedahan
  Bahan Kimia Berbahaya Kepada Kesihatan) 2000
• Ceiling Limit
• Airborne TWA-8
• Maximul Exposure Limit

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Occupational Exposure Standard (OSHA 1994)

• Permissible Exposure Limit Unit
• Miligram per cubic meter of air (mg/m3)
• Parts per million(ppm)
• Fiber per mililiter of air Gentian per militer of
  air (f/ml)

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Occupational Exposure Standard (OSHA 1994)

• Example of Ceiling Limit
• Formaldehyde 0.3 ppm
• Hydrogen bromide 3 ppm
• Hydrogen Chloride 5 ppm

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Occupational Exposure Standard (OSHA 1994)

• "maximum exposure limit" means a fifteen-minute
  time-weighted average airborne concentration
  which is three times the eight-hour time-weighted
  average airborne concentration of the chemicals
  specified in Schedule I
• Example
• Acetic Acid 30 ppm (TWA 8-hour10 ppm)
• Ammonia 75 ppm (TWA 8-hour25 ppm)

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Occupational Exposure Standard (OSHA 1994)

• "time-weighted average" in relation to airborne
  concentration, means an average airborne
  concentration over a specified period of time
• Example of TWA-8
• Acetic Acid 10 ppm
• Asbestos 0.1 f/ml
• Lead 0.05 mg/m3