Deuterated methylene chloride used as a solvent to reduce toxicity

Deuterated methylene chloride is used to replace methylene chloride in a solvent system to reduce the overall toxicity of the composition.

BACKGROUND OF THE INVENTION 
Methylene chloride is a colorless, volatile liquid which is widely used as 
a solvent for various processes including applications in the 
pharmaceutical and food processing industry. The chemical also is used as 
a constituent of aerosols and as a blowing agent in the production of 
foam. 
In many of the above-mentioned applications, the user is exposed either 
through skin contact or inhalation to the methylene chloride. Although 
methylene chloride is not highly toxic, excessive exposure to the liquid 
or vapors has been shown to result in an increase in the amount of 
carboxyhemoglobin present in the blood resulting from the metabolism of 
the molecule in the body. Therefore, prolonged exposure to the compound 
may result in a health hazard to users of the chemical. 
SUMMARY OF THE INVENTION 
The present invention is directed to a method and compositions for reducing 
the health hazard associated with the exposure of methylene chloride to 
users or bystanders during applications when it is difficult to control 
the amount of vapor inhaled or the amount of liquid in contact with the 
skin. Such applications would include, but are not limited to, use as a 
volatile component in aerosols, as a paint solvent, as an ingredient in 
degreasing compositions, as a spotting agent, and as a blowing agent in 
the production of foam. 
The present invention is directed to the replacement of methylene chloride 
by its deuterated analogue, CD.sub.2 Cl.sub.2, in applications where there 
is the possibility of exposure to mammals or man of the vapor or liquid. 
It has been found that deuterated methylene chloride is less likely to be 
metabolized by an animal exposed thereto as compared to an animal exposed 
to methylene chloride. The physical and chemical properties of deuterated 
methylene chloride are very similar to those of methylene chloride, 
therefore the deuterated analogue may be used to replace methylene 
chloride in those compositions which contain methylene chloride and are 
used in such a way that animals or man may be exposed. Such compositions 
would be especially useful in consumer products where the compositions may 
not be used under carefully controlled conditions. Speciality solvents 
intended for use in small shops would be a further example. Examples of 
such products have already been listed above and would be formulated using 
methods well known to the appropriate art. Such solvent compositions 
usually will contain from about 1% to 95% methylene chloride; generally, 
the deuterated analogue would simply be substituted for methylene chloride 
on a volume to volume basis. However, in some situations where exposure of 
the methylene chloride vapors or liquid to man or animals is minimal only 
a portion of the methylene chloride may be replaced with the deuterated 
methylene chloride. 
DETAILED DESCRIPTION OF THE INVENTION 
The effect of inhaling the vapors of the deuterated material as compared to 
methylene chloride illustratively was demonstrated in rats as follows: 
Deuterated methylene chloride and methylene chloride were vaporized by 
metering the liquid compounds at a controlled rate in a 
temperature-regulated vaporization flask held at 120.degree. C. The vapor 
was swept into the air inlet of a 30 liter glass exposure chamber at a 
rate of 6 liters/minute. The concentration of the vapors in the exposure 
chamber was monitored by gas-liquid chromatography using direct gas 
sampling loops. 
Three groups of 9 male Sprague-Dawley rats (8 months of age, 200-300 grams) 
were exposed to room air, methylene chloride 0.05% v/v and deuterated 
methylene chloride 0.05% v/v, respectively for a period of three hours. 
Following exposure, each animal was anesthetized with methoxyflurane, and 
5 cc of blood was collected via cardiac puncture. Sequester-Sol.RTM. 
(Cambridge Chemical Products, Inc.) 0.1 ml was added to the blood sample 
as an anti-coagulant. Carboxyhemoglobin readings were made using an IL 182 
Co-oximeter.RTM. (Instrumentation Laboratory, Inc.). The diluent supplied 
for use with the Co-oximeter.RTM. was modified for use with rat blood by 
adjusting the pH to 1.64 using 1 N HCl. 
The comparative carboxyhemoglobin levels of the three groups of animals 
were as follows: 
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Control (Room Air 
Only) 0.0% carboxyhemoglobin 
Methylene Chloride 
6.2% .+-. 1.3 carboxyhemoglobin 
Deuterated 
Methylene Chloride 
1.8% .+-. 0.5 carboxyhemoglobin 
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Statistical differences between the above values were found to be 
significant at p&lt;0.001. The instrument was calibrated to read zero percent 
carboxyhemoglobin on the control rat blood, therefore the values do not 
represent absolute amounts of carboxyhemoglobin present. The results 
indicate inhalation of the deuterated methylene chloride resulted in 
significantly lower carboxyhemoglobin contents in the blood of exposed 
rats as compared to rats exposed to methylene chloride. 
Examples of specific embodiments of the present invention are illustrated 
below to further clarify the invention as already outlined above but such 
examples are not to be construed as a limitation on the scope of the 
invention.