What is the Potential Harm from these Asbestos Fibers?
Inhalation of dust containing these fibers is known to cause a number of lung diseases. The kidneys, throat and digestive system may
also be affected by either inhalation or ingestion. The USEPA has researched the potency of taconite mining fibers in NE MN relative to
known carcinogenic fibers since 1978. The fibers have been found to be toxic to a varying degree. Results have been presented in
various papers and seminars since 1982.

Retention of these fibers in the lungs is the problem.
Given the characteristics of theses fibers, their presence in the lungs and other body organs over an extended period of time is directly
related to the risk of contracting disease. The EPA studies conducted at the Duluth Laboratory show that the number and sizes of
these fibers retained in the lungs is more important that the number of fibers inhaled. Although short, thin amphibole fibers are more
toxic than longer fibers, risk is a function of cumulative exposure to all sizes of fibers. The shorter fibers travel deeper into the lungs.

Exposure at an early age increases the health risk.
A recent EPA summary statement on risk factors for contracting disease when exposed to asbestos fibers lists

•        high levels of fibers in the ambient air
•        high frequency of exposure
•        longer duration of exposure and
•        more elapsed time after exposure

as being most significant. The effects of exposure are difficult to quantify but health risk is greater when the exposure occurs at an early
age. One such study was conducted at El Dorado Hills, CA in 2005.

Some of the Fibers being released Along the North Shore are Very Potent.
Although all fibers with the asbestos characteristics are potentially harmful, one of the most potent, according to the EPA tests, is the
ferroactinolite fiber. It takes far fewer of these fibers to create a given number of tumors in laboratory tests. Ferroactinolite is even
worse than the classic amosite and crocidolite fibers. Serpentine chrysotile fibers have been found less toxic than equivalent doses of
the asbestos fibers found in the ore processed at the Silver Bay and other locations on the Iron Range.

How do we Know When the Air is Safe to Breathe?
Since asbestos fibers are a naturally occurring material as well as a material produced by mining activity, some exposure to them is at
a low risk level. But the cliché that natural fibers and mining dust are not harmful is harmfully wrong. Low risk “reference” fiber
concentration levels have been recorded in El Dorado Hills, CA and St. Paul, MN for use in comparative testing.   

The “total” of both amphibole and chrysotile fibers, have been recorded as part of sampling for personal exposures in activity-based
analyses on school campuses. Fiber concentrations in ambient air surrounding mining activity have also been sampled. The test data
has been taken with up-to-date monitoring equipment for analysis using Transmission Electron Microscopy.
Location
Time frame
and source
Arithmetic
Average
Geometric
Mean
Eldorado Hills, CA
2005
USEPA
1000-2000
1000-2000
St Paul, MN
3/2006 - 3/2007
MPCA
  1146
Silver Bay, MN
3/2006 - 3/2007
MPCA
5998
3399
Beaver Bay, MN
3/2006 - 3/2007
MPCA
4407
2116
Total “Reference” Fibers per Cubic Meter Ambient Air
This data shows that the average ambient fiber concentrations in cities near the Silver Bay plant and the inland waste tailings basin,
factors such as wind speed and wind direction or plant production levels at the time of the tests. These factors have been shown to
have a significant effect on data comparisons among monitor sites and at individual sites over a period of time. Under these
conditions the arithmetic averages affect the recorded data the least of all methods of analysis.

The Federal District Court Imposed “Control City Standard” Provides a Practical and Effective Measure of and Limit for the Level
of Asbestos fibers in Ambient Air.
This standard was imposed during the 1975 Reserve Mining Case and continues as the only control of asbestos fiber air emissions
from the Silver Bay plant and waste tailings basin. Based upon the latest comparative test data from St. Paul and Silver Bay/Beaver
Bay, the “safe” ambient fiber concentration limit would be 1146 fibers per cubic meter (geometric mean) or about 2113 fibers per cubic
meter (arithmetic average). The data was taken over a one year time period.


The Majority of the Asbestos Fibers in the Air along the North Shore are of the More Potent Amphibole Variety.
Using the same data base as was used for the “total” fibers values above, the asbestos fibers gathered in both Silver Bay and Beaver
Bay, MN are predominantly amphibole asbestos. St. Paul fibers are of the less toxic serpentine chrysotile variety.
Location
Time Frame
and source
Amphibole
(Fibers per cubic
meter)
Chrysotile
(Fibers per
Cubic Meter)
Amphibole
/Chrysotile
St Paul, MN
3/25/2007
MPCA
558
1555
0.36
Silver Bay,
MN
1/11/2006-
1/24/2007
MPCA
5370
663
8.10
Beaver Bay,
MN
1/11/2006-
1/24/2007
MPCA
4329
583
7.43
Bay taconite processing plant.
Many Factors affect Fiber Concentration Levels.
Factors such as wind direction and velocity, precipitation, season and taconite production levels affect asbestos fiber
concentrations in ambient air near the plant in Silver Bay and the tailings basin near Beaver Bay. As noted in the video on our History
Page, Judge Miles Lord suspected that precipitation had a very significant effect on fiber levels reported during the 1975 Reserve
Mining trial.

Strong northwest and northeast winds along the North Shore can increase the fiber concentration in ambient air by 5 to 10 times the
average ambient levels shown in the table. This concentration of fibers could indeed be considered dangerous even on a short
term basis on a typical windy day.

The Concentration of Asbestos Fibers in Local Soil and Water Increases each Day.
Fiber concentrations increase in surface soils and surface water on a cumulative basis as mining and processing of taconite ore
continue over time. Any disturbance of loose soil in areas of human activity will increase the number of fibers in the immediate air
for inhalation. The USEPA conducts activity-based personal monitoring tests to assess asbestos exposure in public areas such as
school playgrounds and ball fields. The asbestos in schools regulation (AHERA) is the basis for most of these studies. In the case
of El Dorado Hills, CA the EPA found asbestos present in almost all of the test air samples.

Save Lake Superior Association continues to be concerned about the countless fibers both in the water near the Shores of Lake
Superior and in the 6.8 million fibers per each liter of the 7.5 million gallons of water released into the Beaver River from Mile Post 7
Basin drainage each day. These waterborne fibers combined with the ever increasing fiber concentration in the air and in the soil is
cause for concern for the health of our members and of the general public inhabiting and visiting the North Shore of Lake Superior.
Save Lake Superior Association
Fibers - Chapter 2