?????Lab safety series

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?????Lab safety series
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Toxic Chemical Hazards
All chemicals can be toxic, but few actually hurt
us. WHY? Its the dose that makes the poison
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• ?????
• ????
• ????
• ???????? (???) ?????? (???)

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Dose-Response Model
The higher the dose of a chemical, the more
severe the response
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Dose-Response Model
???????????? ??????? ?? ???? (????????????,??????
?)
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Relative Toxicity
Some chemicals are more toxic than others at the
same quantity, so toxicity indexes were developed
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LD50

• Refers to dose fed to an animal population
• The lethal dose to 50 of an animal population
• Given in mg/kg of body weight(?????????)

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LC50

• Refers to the concentration of chemical in the
  air inhaled by an animal population
• The lethal concentration to 50 of an animal
  population
• Given in mg/m3 (????)

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LD50 LC50

• Remember that these are lethal doses to animals,
  not people
• Still the best method for relative toxicity

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???? LD50 (lethal) gt TD50 (toxic) gt ED50
(effective) gt ED10
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???????????,????????
From Crowl Louvar
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TLV

• The Threshold Limit Value (TLV) is a guideline
  concentration developed by the American Council
  of Governmental Industrial Hygienists (ACGIH)
• TLVs are recommendations and should be used as
  guidelines for good practices??????????????????

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TLV

• TLVs refer to airborne concentrations of
  substances
• TLVs represent conditions under which it is
  believed that nearly all workers may be
  repeatedly exposed to day after day without
  adverse health effects

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TLV

• TLVs are based on available information from
• industrial experience
• experimental human studies
• experimental animal studies
• The amount and nature of the information varies
  from substance to substance consequently, the
  precision of the estimated TLV is also subject to
  variation

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TLV-TWA

• Threshold Limit Value-Time Weighted Average
• The time-weighted average concentration for a
  normal 8-hour workday and a 40-hour workweek
• Nearly all workers may be repeatedly exposed,
  day after day, without adverse effect
• TWA 1/8 ?C(t) dt (t 0 ? tw) where tw worker
  shift time in hours

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????

• ??????, ????, ????????????, ??????????
• PEL permissible exposure limit
• OEL occupational exposure limits
• TLV threshold limiting value
• REL recommended exposure limit
• ???? TLV in mg/m3 (TLV in ppm) x
  (?????/??????????in Liter)
• 25oC, 1 atm ???24.45 L
• ? ??????????? design control limit ???OEL?0.1
  0.5 (I.e. ??????????????????)

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TLV-STEL

• Threshold Limit Value-Short Term Exposure Limit
• The concentrations to which workers can be
  exposed continuously for a short period of time
  without suffering from
• irritation
• chronic or irreversible tissue damage
• narcosis of sufficient degree to increase the
  likelihood of accidental injury, impair
  self-rescue, or materially reduce work efficiency

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Ceiling Limit
The concentration that should not be exceeded
during any part of the working exposure
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STEL

• Short Term Exposure Limit
• A 15 minute TWA exposure which should not be
  exceeded at any time during a workday even if the
  8 hour TWA is within the TLV-TWA
• Exposures above the TLV-TWA up to the STEL
  should not be longer than 15 minutes and should
  not occur more than four times per day

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STEL

• There should be at least 60 minutes between
  successive exposures in this range
• Excursions in worker exposure levels may exceed
  3 times the TLV-TWA for no more than a total of
  30 minutes during a work day
• Under no circumstances should they exceed 5
  times the TLV-TWA, provided that the TLV-TWA is
  not exceeded

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PEL

• Permissible Exposure Limit
• PEL is an exposure limit set by OSHA
• Similar to TLVs, the PEL refers to
  concentrations to which the employee may be
  exposed
• PELs are legally binding

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IDLH
Immediately Dangerous to Life or Health
Specifically refers to the acute respiratory
exposure that poses an immediate threat of loss
of life, immediate or delayed irreversible
adverse effects on health, or acute eye exposure
that would prevent escape from a hazardous
atmosphere
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Relative Toxicity
The LD50, LC50, TLV, PEL, STEL, Ceiling, and IDLH
provide a good index of the toxicity of the
chemical
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????

• ?LD50??
• ??? LD50 lt 500 mg/Kg
• ?? 500 lt LD50 lt 5000
• ??? 5000 lt LD50 lt 50,000
• ??? 50,000 lt LD50 lt 150,000
• ????? (LC50 x exposure time)
• ??? ?? lt500
• ?? 500 lt ?? lt 5,000
• ??? 5,000 lt ?? lt 50,000
• ??? 50,000 lt ?? lt 150,000

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Concentration

• The higher the concentration or dose of the
  chemical, the higher the risk of harmful effects
• Nitrogen at 78 concentration in the air is
  healthy, but at over 85, it asphyxiates humans

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Concentration
Probable Oral Dose for Humans Toxicity
Rating Dose For Average Adult Practically
nontoxic gt15 g/kg more than 1 quart Slightly
toxic 5-15 g/kg between pint and
quart Moderately toxic .5-5 g/kg between ounce
and pint Very toxic 50-500 mg/kg between tsp.
and ounce Extremely toxic 1-50 mg/kg between 7
drips and tsp. Super toxic lt1 mg/kg a taste
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????????
?? ???? TWA? 4 ?? 1ppm
or less 3 ???? gt 110ppm 2
???? gt10100ppm 1 ????
gt1001000ppm 0 ?? gt1000ppm
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Time of Exposure

• The dose-response model teaches the toxicity risk
  increases as
• relative toxicity increases
• concentration increases
• length of exposure increases

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Effects

• Acute
• a rapid, sudden exposure
• the harmful effects are immediate
• Chronic
• repeated, small exposures
• the harmful effects are delayed
• sometimes as long as 40 years
• Latency Period
• the time between the exposure and the effect

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Probit

• Probit probability unit ?????response-dose?????,
  ???????,?????
• P probability 1/(2?) 1/2 ? exp(-u2/2) du
  from Y-5 to -? ??P ?probit??Y????
• Y k1 k2 lnV k1, k2???,V????dose (caustic
  factor) Y probit variable k1, k2??????????????

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?????probit??????
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(No Transcript)
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???????????

• ????? benzene, carbon bisulfide, CCl4,
  formaldehyde, methyl alcohol, phenol,
  tetrachloroethane, etc.
• ????? amyl acetate, cumene, butyl alcohol,
  cycloheptane, nitroethane, toluene, xylene, etc.
• ????? ethyl alcohol, ethyl acetate, ethyl ether,
  heptane, hexane, petroleum ether, etc.

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????????
5 min 30 min ??????? ?? ??????? ?? CO
6000ppm 12000 1000
2500 HCN 150ppm 250
90 170 HCl
500ppm 16000 200
lt12 ?????? ?????????, p.31, sep./oct. 2002
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ROUTES OF ENTRY
How do chemicals enter our bodies to cause harm?
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Routes of Entry

• Four routes of entry are recognized
• Inhalation ??
• Absorption ??(??)
• Ingestion ??(????)
• Injection ??
• ? ???????, ??????

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Inhalation
Inhalation is the most common form of
occupational exposure to chemicals
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????????421?, p.27
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Inhalation

• Minimize inhalation of hazardous chemicals
  through
• good ventilation
• use of fume hoods/glove-box
• respirator
• Always try to engineer out the hazard BEFORE
  resorting to a respirator

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Inhalation

• Respirators can pose additional hazards to the
  user
• Punctured eardrums also provide an inhalation
  route of entry

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Absorption
The most frequently reported occupational
injuries are chemical effects to the skin
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Absorption

• Not all chemicals are absorbed through the skin
  many defat the skin and cause injury
• How do we minimize chemical absorption through
  the skin?
• Gloves provide a good barrier when the
  appropriate glove materials are used

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Ingestion
We probably do not eat our lab chemicals so how
do we sometimes swallow them?
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Ingestion

• Minimize the ingestion route of entry by
• NO eating or drinking in the lab
• NO smoking in the lab
• ALWAYS wash your hands when leaving the lab

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Injection
Very few, if any, accidents occur in the
laboratory as a result of accidental injection of
a chemical filled syringe
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Injection

• How can this happen?
• cleaning up contaminated broken glass
• cutting self on contaminated sharps
• leak in high pressure hoses
• puncturing self with a contaminated syringe

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Injection

• How can this route of entry be minimized?
• use only a broom and dust pan for cleaning up
  broken glass
• dispose of used syringes, do not recap them
• wear puncture resistant gloves

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???????

• ????(exposure dose) ???????????
• ????(potential dose) ???????
• ????(applied dose) ???????????
• ????(internal dose) ??????????
• ??????(biologically effective dose) ?????????

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? ? ?
Intake Rate ???? x ??? ??? (????,??,???)
f(????,????,???)
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???????

• ????? ??????? ? ???? ? ???? ? ?????? ? ????
• ?????? ???? ? ???? ? ???? ? ???? ? ??? ? ??????
  ? ?????? ? ????

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?????

• ?????? ??(carcinogen),????(mutagen),??????(reprod
  uctive hazard),??(teratogen)
• ??(???)??? ??,??,??,??,????,???

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?????????

• Biological exposure indices BEI
• ????????????,?????????,????????????
• ????????????,??????
• ?????????????
• ????????????
• ??????
• ?????? ??,??,???
• ?????? ??,??
• ???????? ???????

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Various Responses to Toxicants
Effects that are irreversible Carcinogen causes
cancer Mutagen causes chromosome
Reproductive hazard causes damage to reproductive
system Teratogen causes birth defects
?? Effects that may or not may not be reversible
Dermatotoxic affect skin Hemotoxic affect
blood Hepatotoxic affect liver Nephrotoxic
affect kidney Neurotoxic affect nerous system
Pulmonotoxic affect lungs
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SUMMARY
??????????????????????
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SUMMARY
If the toxicity of a chemical is unknown, treat
it as toxic
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SUMMARY
Use a fume hood or glove box when the chemical
could become a vapor or dust
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SUMMARY

• Always wear the proper personal protective
  equipment
• eye protection
• gloves
• lab coat

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SUMMARY
Change protective garments as required
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SUMMARY
Decontaminate before eating, drinking, smoking,
or going to the bathroom
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SUMMARY
Minimize the time of exposure
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SUMMARY
Become familiar with the Standard Operating
Procedures for safe handling of toxic materials
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Toxics
Knowledge of a chemicals toxic properties and
the correct handling precautions can prevent
adverse health effects (e.g. read MSDS)