chemical safety during preparation

[Michael Gochfeld]

	It don't know much about genitalia but I do deal with chemical 
safety.  The interesting post on techniques includes mention of xylene, 
euparal, and cellosolve. 

------------------------------excerpt from original message----------
"Main exceptions are the substitution of Xylene with 95-100% Isopropyl
alcohol, and the substitution of Canada Balsam with Euparal (avail from
Bioquip, as is the Cellosolve). Only drawback with these substitutions 
is that Euparal takes far far longer to dry, and slides must be kept 
flat for months. Plus side is that it is far less carcinogenic than 
xylene."

-------------------------end of original message---------------

I was somewhat confused as to exactly what is substituted for which, 
since it seems that the tradeoff is between Euparal (long-drying) and 
"xylene" (toxic). 

Nonetheless, I should point out that although xylene is toxic to the 
nervous system, it is not currently classified as a carcinogen (see 
documentation below) and if future research should detect 
carcinogenicity, it is certainly not a potent carcinogen, since cancer 
has not turned up in any studies of xylene in humans thus far.  However, 
it is toxic and needs to be treated with respect. Perhaps the confusion 
lies in the fact that industrial grade xylene may have a trace of 
unreacted benzene, which is indeed a carcinogen (leukemia). However, the 
metabolism of xylene (dimethyl-benzene) does not go through benzene, but 
rather to hippuric acid which is excreted by the kidney. 

On the other hand cellosolve is also quite toxic and absorbable through 
the skin.  Cellosolve has lower volatility than xylene, but is not 
appreciably less toxic to the nervous system.  And it is somewhat 
volatile (it is a derivative of ethylene glycol which is a common 
antifreeze). At very high doses it is toxic to the kidney.  This would 
not affect entomology users, but would be a hazard if a small child took 
a swig from an open bottle. 

Good ventilation and care in handling are important for ALL of these 
materials. 

========XYLENE AND CANCER
Information from EPA's Integrated Risk Information System (IRIS) 
  ___II.A.1.  WEIGHT-OF-EVIDENCE CLASSIFICATION
  Classification -- D; not classifiable as to human carcinogenicity.

  Basis -- Orally administered technical xylene mixtures did not result 
in   significant increases in incidences in tumor responses in rats or 
mice of both sexes.

  ___II.A.2.  HUMAN CARCINOGENICITY DATA
      None.

  ___II.A.3.  ANIMAL CARCINOGENICITY DATA
      Inadequate.  
  ___II.A.4.  SUPPORTING DATA FOR CARCINOGENICITY
      The frequency of sister chromatid exchanges and chromosomal 
aberrations   were nearly identical between a group of 17 paint industry 
workers exposed to  xylene and their respective referents (Haglund et 
al., 1980).  In vitro,  xylene caused no increase in the number of 
sister chromatid exchanges in human lymphocytes (Gerner-Smidt and 
Friedrich, 1978).  Studies indicate that xylene isomers, technical grade 
xylene or mixed xylene are not mutagenic in tests with Salmonella 
typhimurium (Florin et al., 1980; NTP, 1986; Bos et al., 1981) 
  nor in mutant reversion assays with Escherichia coli (McCarroll et 
al., 1981).  
  Technical grade xylene, but not o- and m-xylene, was weakly mutagenic 
in   Drosophila recessive lethal tests.  Chromosomal aberrations were 
not increased  in bone marrow cells of rats exposed to xylenes by 
inhalation (Donner et al.,  1980). 

  __II.B.  QUANTITATIVE ESTIMATE OF CARCINOGENIC RISK FROM ORAL EXPOSURE
      Not available.
  __II.C.  QUANTITATIVE ESTIMATE OF CARCINOGENIC RISK FROM INHALATION 
EXPOSURE
      Not available.


To see for yourself

for XYLENE: http://www.epa.gov/ngispgm3/iris/subst/0270.htm#II.
For the entire data base: http://www.epa.gov/ngispgm3/iris/index.html

Mike Gochfeld 
=============================================================
Michael Gochfeld, MD PhD
Environmental and Occupational Health Sciences Institute
170 Frelinghuysen Road
Piscataway, NJ 08854
gochfeld at eohsi.rutgers.edu