From: whenry@leland.Stanford.EDU (homo obsolescensis)
Subject: Re: the TRUTH about Methylene Chloride
Organization: Stanford University Libraries
Date: Tue, 18 Aug 92 20:55:52 GMT

I am not a chemist and will not presume to comment on the toxicity of
Methylene Chloride, but would like to offer a little data that I have
lying around.

From _Handbook of Organic Industrial Solvents_ 5th edition [Alliance
of American Insurers, Technical Guide No. 6, 1980], which is not the
most recent edition.

  TWA: 100 ppm (AIC)
  STEL: 500 ppm (AIC)

  Methylene Chloride:  One of the least toxic of the chlorinated
  hydrocarbons.  Metabolized to carboxyhemoblogin; thus, additive to
  carbon monoxide exposures.  Concentrations of ten times threshold
  limit required to cause even slight narcosis.  Inhalation.
  Inhalation of highly excessive concentrations can cause chronic
  poisoning of the liver.  Odor detectable at 500 ppm.


From Clydesdale, Amanda. _Chemicals in Conservation:  A guide to
possible hazards and safe use_.  Edinburgh, 1982, which is not the
most recent edition:

  Effects of exposure
  Skin: burns on contact; degreases skin
  Eyes: eye damage
  Inhalation: narcotic; causes headache; dizziness; digestive
  disturbances

From a Fisher MSDS 1/19/86

  Exposure Limits:
  500 ppm OSHA TWA: 1000 ppm OSHA CEILING; 2000 ppm/5 Min OSHA peak;
  75 ppm NIOSH Recommended TWA; 500 ppm/15 Min NIOSH Recommended Ceiling
  100 ppm (500 MG/M3) ACGIH TWA; 500 pm (1740 Mg/M3) ACGIH STEL (Notice
  of intended change 1984-1985)
  
  
  Toxicity:  10 MG Eye-Rabbit Mild Irritation;  88,000 Mg/M3/30 Minutes
  inhalation-RAT LC50; 14.400 ppm/7 Hours inhalation-Mouse-LC50; 1900
  Mg/Kg Oral Rabit LDLO; 500 ppm/8 Hours Inhalation-Human TCLO; 2524
  Mg/Kg Oral-Rat LD50; Mutagenic Data (RTECS): Tumorigenic Data (RTECS);
  Reproductive Effects Data (RTECS)l Indefinite animal carcinogen
  (IARC).  Available data do not perman an evaluation of the
  carginogenicity of Methylene Chloride to be made.
  
  Methylene Chloride is a skin irritant and central nervous system
  depressant.  Exposure may irritate the eyes, and mucous membranes.
  Poisoning may affect (sic) the liver and kidneys.  Metabolism of
  Methylene Chloride by humans leads to an elevation  of
  carboxyhemoglobin (Methemoglobinemia), resulting in decreased oxygen
  carrying capacity in the blood.  This may present an increased risk to
  people with heart problems.
  
  In an inhalation study by the National Toxicology Program (NTP),
  Methylene Chloride caused an increasse in lung and liver cancer in
  mice.  In a similar study in rats, methylene chloride caused an
  increase in benign mammary tumors.  To data (sic), there is no evidence
  that methylene chloride has caused increased cancer in humans.
  
  ...
  Inhalation
  ...

  Chronic Exposure- Repeated expusure to concentrations from 500-3600
  ppm for one year has caused toxic encaphalosis with hearing and
  visual delusions and hallucinations.  Liver damage is possible....
  ...


From a local database:

  Chemical Safety / Search: Find NAME METHYLENE CHLORIDE
  Result: 3 records
  
  Record 1 -------------------------------------------------------
  CAS Number:  75-09-2                           SU Number:    6611
        Name: Dichloromethane
  
   Storage Group: L: Non-Reactive Flammables and Combustibles, including
   Solvents
  
       UN Number: UN1593        DOT Class:               UBC Class: B3
  
  Physical State:  Liquid
   Melting Point:  - 97.C   Boiling Point: 40.C        Flash Point:
  
   Hazards: 10 Other Hazards
            12 Slight Poisons
            15 Suspect carcinogen, mutagen, or reproductive hazard
            17 Halogenated solvent
            28 Skin irritant
            33 Hepatotoxin
            
            36 Blood and hemapoetic system toxin
            37 Lung irritant
            38 Eye irritant
            51 EPA list of priority pollutants
            52 AB 1803 well monitoring chemicals
            53 SARA section 313 toxic chemicals
            56 AB 2588 toxic hot spots A-I
            57 DHS drinking water action levels
            58 AB 1807 toxic air contaminants
            65 Prop. 65 Carcinogen
  
  Synonyms: DCM
            Freon 30
            Methane dichloride
            Methylene chloride
            Methylene dichloride
            PA8050000
            RCRA waste # U080
                                        Last Update: 07/06/90
  
  
  
I hope the above is of some use.
Walter Henry
Conservation Lab
Stanford University Libraries 
Newsgroups: sci.chem