A powerful preventive against pneumonia, influenza and other respiratory
diseases may be promised by a brilliant series of experiments conducted
during the last three years at the University of Chicago's Billings
Hospital. Dr. Oswald Hope Robertson last week was making final tests
with a new germicidal vapor—propylene glycol—to sterilize air. If the
results so far obtained are confirmed, one of the age-old searches of
man will finally achieve its goal. The idea of sterilizing the air is not new —London's great fire of
1666, for example, was touched off by the countless fires which
townsmen lit to purge the air of plague. Use of chemical sprays to
control air contamination was first attempted in 1928 by three doctors
who tried a fine mist of sea water containing sodium hypochlorite.
This venture gave promising results, but all such research lapsed for
another decade. Within the last few years, several research groups
again began testing various sprays. Many chemicals were
found to kill airborne micro-organisms quickly, even in concentrations
as low as one gram of chemical per 500 cu. ft. of air. Trouble was that
all these air germicides smelled bad, or were toxic, or irritated the
respiratory tract. Dr. Robertson's propylene glycol vapor is odorless,
tasteless, nontoxic, non-irritating, cheap, highly bactericidal. Its discovery was accidental. Dr. Robertson and his colleagues were
trying out another possible germicide—a detergent or “soapless soap”
. Water solutions of the detergent were only mildly
effective, so the researchers tried solutions of detergents in
propylene glycol, which is a sort of thin glycerine. Results were much
better. Then the researchers found that the propylene glycol itself was
a potent germicide. One part of glycol in 2,000,000 parts of air
would—within a few seconds—kill concentrations of air-suspended
pneumococci, streptococci and other bacteria numbering millions to the
cubic foot. How did it work? Respiratory disease bacteria float about in tiny
droplets of water breathed, sneezed and coughed from human beings. The
germicidal glycol also floats in infinitesimally small particles.
Calculations showed that if droplet had to hit droplet, it would take
two to 200 hours for sterilization of sprayed air to take place. Since
sterilization took place in seconds, Dr. Robertson concluded that the
glycol droplets must give off gas molecules which dissolve in the water
droplets and kill the germs within them. Dr. Robertson placed groups of mice in a chamber and sprayed its air
first with propylene glycol, then with influenza virus. All the mice
lived. Then he sprayed the chamber with virus alone. All the mice died.
