termine the safety of this chemical. Many of these studies have been published as references at the end of
this bulletin. This summary only lists some of the results found, but in-depth details are reported in the original
publications. A substantial dossier of data was submitted to the EPA for the HPV "High Production Volume"
program by a consortium of producers including Gaylord Chemical. This data is available on the EPA website
at
by those who request it.
DMSO is a commercially manufactured dipolar aprotic solvent which is also a naturally occurring substance.
It is apparently a part of earth's complex sulfur cycle. DMSO is created in the atmosphere at a rate of 20-60 bil-
lion pounds per year from dimethyl sulfide, which is produced by metabolic processes in soil and sediments.
DMSO is also found in natural waters and soil. Metabolism of DMSO in soil by microorganisms results in
the formation of sulfur and dimethyl sulfide. DMSO is also reported to be present at low concentrations
(<0.05-3.7 ppm) in food products such as sauerkraut, tomato paste, milk, beer, coffee, tea and in forage crops
such as alfalfa and corn silage.
DMSO has low acute and chronic toxicity for animal, plant and aquatic life. Exposure to test organisms at
high concentrations by contact, ingestion or inhalation consistently show low toxicity. DMSO is not listed as a
carcinogen by regulatory authorities and is actually used as a neutral solvent in the Ames mutagenicity
tests. DMSO is not a teratogen in mice, rats or rabbits. Because of this low potential for toxicity, the EPA
has approved DMSO as a solvent or a cosolvent, in pesticides which are applied before crop emergence or prior
to the formation of edible parts of food plants
In 1978, the FDA approved the use of DMSO in a 50/50 mixture with water as an effective treatment for the symp-
toms of interstitial cystitis. Since then, a large number of people have received this treatment. The product is
marketed today by Edwards Life Sciences under the trade name of Rimso-50TM. DMSO has been approved
for use in other pharmaceutical formulations in the U.S. and other countries. In addition, in 1998, the FDA en-
dorsed the recommendation of the expert working group of the International Conference on Harmonization
relative to the residual solvents in pharmaceuticals. DMSO was placed in the safest category, class 3 solvents,
with low toxic potential. Class 3 includes no solvent known as a human health hazard at levels normally ac-
cepted in pharmaceuticals. Solvents in Class 3 (Table 1) may be regarded as less toxic and of lower risk to
human health. Available data indicate that they are less toxic in acute or short-term studies and negative in
genotoxicity studies. It is considered that amounts of these residual solvents of 50 mg per day or less
(corresponding to 5,000 ppm or 0.5 percent under Option 1) would be acceptable without justification. Higher
amounts may also be acceptable provided they are realistic in relation to manufacturing capability and good
manufacturing practice (GMP).
considered regarding possible exposure routes. Skin contact, the most likely exposure, has been extensively
studied with humans and animals. Large dosages over prolonged periods showed only minor toxic effects
such as minor skin irritation, itching and burning Although DMSO is absorbed rapidly through the skin, it has a
low degree of toxicity via dermal route of administration. Also, it has been found that the molecular weight of
chemical compounds can preclude their transdermal penetration by DMSO. For instance, DMSO enhances
the penetration of butyl acetate in solution, while octyl acetate is a "nonpermeator".
when working with all solvents. Table 2 provides relative permeability data for some common solvents.