||Vermiculite Mountain in Libby, Montana discovered.
||Commercial mining begins at Libby.
||Montana State Board of Health defines dust at the Libby plant as "nuisance dust."
Measurements are well below 50 mppcf (million particles per cubic foot) for total
dust, indicating "no dust hazard."
||Zonolite production reaches 150,000 tons per year.
||First "wet" mill is installed at Libby mine.
||U.S. Department of Health scientist informs Montana Health Department there is no
reliable way of analyzing asbestos content, estimating 10% of Libby ore is asbestos
and recommending a 50 mppcf limit of total dust. He adds, "If the company will cooperate
and actually attain dust control of this order, the asbestos and silicosis hazard
would certainly be minimal."
||Zonolite requests chest x-rays of all Libby employees. Of 130 mine employees, 48
show abnormalities. Results are sent to each employee's family physician.
||Montana State Board of Health survey shows extremely high and substantial concentrations
of asbestos dust in the first report to identify tremolite asbestos at the Libby
||Grace, unaware of the extent of hazards of mining and milling vermiculite, purchases
||Grace initiates annual x-ray testing of Libby employees, reporting results to each
employee's family physician.
||Grace begins moving employees with breathing concerns to less dusty areas of the
plants. Dismayed by former mine owner Zonolite's slowness to react to State Board
of Health recommendations, Grace explores "wet" mill technology to reduce dust.
||Montana Board of Health reports total dust concentrations at Libby plant between
8.0 and 52 mppcf, noting, "Some good work has been made and housekeeping has substantially
improved over previous times. But, other engineering changes need to be implemented
to further reduce dust." Grace responds with plans to further reduce dust through
purchase of high-load fans, application of oil on mine roads and research to develop
wet mill technology. Grace installs 50-foot stack, plus additional exhaust fans
and cyclones to further reduce dust.
||Libby mineworkers' union files first asbestosis claim. State Board of Health reports,
"Our view of the operation of the plant and the dust samples taken in the dry mill
during these two periods indicated that, in general, the dustiness in the dry mill
had been reduced substantially from previous periods and the systematic review of
the dust concentration showed a reduction over previous periods." While 96% of all
dust counts are within the State's imposed "safe" threshold--not requiring a respirator--Grace
still requires respirator use in most locations throughout the mill.
||Grace installs stronger filters in cyclones to further reduce dust.
||Engineering work gets underway for construction of new wet mill to significantly
reduce dust. Grace commences air sampling and initiates dust control measures, such
as bag houses, enclosed silos, improvements in furnace and ventilation systems and
improved work practices at its vermiculite expanding plants.
||U.S. Bureau of Mines reports, "Work on alleviating dust conditions proceeding,"
when Grace installs air-filtered hoods for tractor loader, air filter systems on
trucks, cabs and skipper's shack and new respirator sterilization center. Wet mill
||Grace initiates annual x-ray testing in all vermiculite expanding plants.
||Grace begins wet mill construction in Libby at a cost of $14 million. Grace initiates
membrane filter air-sampling program at Libby.
||New wet mill becomes operational, significantly reducing airborne mill asbestos
dust to levels considered safe by government agencies--several thousand times lower
than when Grace purchased the mine from Zonolite in 1963. Grace implements lung
function tests for Libby employees.
||Grace continues improvements in ventilation system and work practices to reduce
fiber exposures at plant. Grace implements intensified air-sampling program.
||Grace no longer hires smokers.
||Grace implements employee health questionnaire. Grace bans smoking on premises,
prompting mine workers' union to file a grievance, despite Company educational program
citing substantial health risk to smokers exposed to asbestos dust.
||Grace files notice under Section 8(e) of the Toxic Substances Control Act, reporting
possible health effects from exposure to tremolite at Libby. Grace visits NIOSH
to discuss health studies by McGill University. McGill begins health studies for
||McGill presents study findings to current and former employee participants, reporting
levels of tremolite fiber exposure at Libby are 20 times lower than federal regulations
require. Grace requires employees to wear removable coveralls to prevent dust traveling
||Grace closes Libby mine and mill. Land reclamation work begins.
||Grace initiates sweeping three-part medical program to provide immediate medical
coverage to any and all Libby residents diagnosed with asbestos-related illness.
Plan includes annual donation of $250,000 to St. Johns Lutheran Hospital for independent
testing, plus additional sums for purchase of state-of-the-art equipment, staffing