Asbestos and zeolites are silicate-based
minerals, linked inextricably
via paradoxical similarities and differences which have emanated from
different geological epochs. Both have been employed in the service
of humanity through millennia: asbestos, for its “inextinguishable”
quality of being an insulator against heat and fire; zeolite, a “boiling
stone” with its volcanic and marine sedimentary rock origins,
for its propensity to adsorb water and remove metals and toxins. Serious
adverse health effects observed in asbestos miners as long ago as
the 1st Century AD did not halt the rising popularity of asbestos.
As the miracle material of the 1900s, asbestos production and consumption
exploded, culminating in its ubiquity in ships, vehicles, homes, commercial
buildings, and over 3000 different industrial and household products.
Through the 1940s and 1950s, epidemiological studies concluded that
asbestos was a likely cause of asbestosis, lung cancer, and malignant
mesothelioma, and it is now banned in many but far from all countries.
The long latency between exposure to asbestos and the occurrence of
cancer has obscured the deadly consequences of asbestos exposure for
centuries. Even today, a considerable part of the world population
is insufficiently aware of the dangers of asbestos, and millions of
tons of this carcinogen continue to be mined and used worldwide. Zeolites,
both natural and synthetic, are microporous aluminosilicate minerals
commonly used in a myriad of processes, in the petrochemical industry,
in domestic appliances and cleaning agents, as commercial adsorbents
and exchangers for toxins and pollutants, and as catalysts. Zeolites
are found in agriculture, veterinary science, and human health. More
recently, new materials such as carbon nanotubes are being employed
in materials requiring durability and thermal and electrical conductivity,
yet nanotubes are now joining the ranks of more established particulates
such as asbestos and silica, in causing human disease. In this review,
we compare and contrast the similarities and differences of these
two groups of silicate minerals and their waxing and waning use in
the employ of humanity.