MEMORANDUM
To:	Docket ID No. EPA-HQ-OAR-2017-0664
From:	David Putney, US EPA/OAQPS/SPPD
         Chris Sarsony, US EPA/OAQPS/HEID
Date:	August 22, 2019
Subject:	EPA's Analysis of Elongated Mineral Particulate
______________________________________________________________________________

 BACKGROUND
The EPA promulgated the original Taconite Iron Ore Processing NESHAP (i.e., 40 CFR part 63, subpart RRRRR) in October of 2003. In 2004, the National Wildlife Federation filed a petition for review of that regulation with the United States Court of Appeals for the District of Columbia Circuit (Case No. 03-1458). In their petition, the National Wildlife Federation alleged that the EPA had failed to set standards for what they believed were emissions of asbestos, or asbestos-like fibers, from taconite iron ore processing plants. The compounds in question result from the crushing and processing of the taconite iron ore, which produces short, blocky particulate emissions. Those emissions are referred to as non-asbestiform amphibole elongated mineral particulate (EMP) within this document. The EPA subsequently requested a partial voluntary remand to further investigate the EMP emissions and consider possible options to address the issue, as appropriate. This request was granted by the United States Court of Appeals for the District of Columbia Circuit.
This memorandum summarizes our analysis of the available information and provides the rationale for our conclusion that the EMP emissions from taconite iron ore processing plants are neither asbestos, nor any other hazardous air pollutant (HAP) listed in section 112(b)(1) of the Clean Air Act (CAA).
 CLEAN AIR ACT LIST OF HAZARDOUS AIR POLLUTANTS
Section 112(b)(1) of the CAA contains the list of regulated HAP. Only two of the HAP in that list were considered possible candidates to include the subject EMP emissions  -  specifically, "asbestos" and "fine mineral fibers."
 Asbestos
 History of Taconite Fiber Emissions
The basis for the belief that asbestos, or asbestos-like fibers, may be emitted from taconite iron ore processing facilities was the case brought against the Reserve Mining Company (now the Northshore Mining Company) in the United States District Court for the District of Minnesota (litigated from 1973 through 1982). It was alleged that the emissions from the associated taconite iron ore processing facility contained an amphibole mineral called cummingtonite-grunerite, which is chemically indistinguishable from a certain type of asbestos called amosite. There is only one taconite iron ore processing facility that utilizes ore known to contain amphibole minerals, i.e., the Northshore facility. This is because the Northshore facility is the only facility that obtains iron ore from the eastern end of the Mesabi Range, which was metamorphosed by the Duluth Gabbro Complex (the intrusive rock formation which comprises much of the basement bedrock in northeastern Minnesota), resulting in the presence of amphibole minerals. However, the presence of amphibole minerals alone is not sufficient to determine that asbestos is present, as amphiboles develop in either the asbestiform or non-asbestiform geologic forms and the non-asbestiform form of amphibole minerals are not considered asbestos, as explained below.
 Clean Air Act HAP Definition of Asbestos
CAA section 112(b)(1) lists "Asbestos  -  CAS Number 1332214" as a HAP. However, the CAA does not provide a definition of the term "asbestos." Therefore, we have referred to how asbestos has been defined in other EPA CAA regulations to inform the definition of asbestos in the context of the CAA HAP list, as follows:
          Subpart M "National Emission Standards for Asbestos" (§61.141 of 40 CFR part 61)
         "Asbestos means the asbestiform varieties of serpentine (chrysotile), riebeckite (crocidolite), cummingtonite-grunerite, anthophyllite, and actinolite-tremolite." (emphasis added)
          Subpart E "Asbestos-Containing Materials in Schools" (§763.83 of 40 CFR part 763) "Asbestos means the asbestiform varieties of: chrysotile (serpentine); crocidolite (riebeckite); amosite (cummingtonite-grunerite); anthophyllite; tremolite; and actinolite." (emphasis added)
          Subpart I "Prohibition of the Manufacture, Importation, Processing, and Distribution in Commerce of Certain Asbestos-Containing Products; Labeling Requirements" (§763.163 of 40 CFR part 763)
         "Asbestos means the asbestiform varieties of: chrysotile (serpentine); crocidolite (riebeckite); amosite (cummingtonite-grunerite); tremolite; anthophyllite; and actinolite." (emphasis added)
Note that all definitions previously used in CAA actions define asbestos to include only the asbestiform varieties of certain minerals. Definitions of "asbestiform" are provided by the Agency for Toxic Substances and Disease Registry (ATSDR) and the EPA, as follows:
          "Asbestiform: A habit of crystal aggregates displaying the characteristics of asbestos: groups of separable, long, thin, strong, and flexible fibers often arranged in parallel in a column or in matted masses (Veblen and Wylie 1993; Zoltai 1979, 1981)." "Mineralogists call asbestiform amphibole minerals by their mineral name followed by "asbestos" (Leake 1978). Thus, asbestiform tremolite is called tremolite asbestos." Found in Appendix F of the ASTDR document Toxicological Profile for Asbestos, dated September 2001.
          "Asbestiform (morphology) - Said of a mineral that is like asbestos, i.e., crystallized with the habit of asbestos. Some asbestiform minerals may lack the properties which make asbestos commercially valuable, such as long fiber length and high tensile strength. With the light microscope, the asbestiform habit is generally recognized by the following characteristics:
             Mean aspect ratios ranging from 20:1 to 100:1 or higher for fibers longer than 5 ug. Aspect ratios should be determined for fibers, not bundles;
             Very thin fibrils, usually less than 0.5 micrometers in width; and
             Two or more of the following:
                Parallel fibers occurring in bundles,
                Fiber bundles displaying splayed ends,
                Matted masses of individual fibers, and
                Fibers showing curvature.
         These characteristics refer to the population of fibers as observed in a bulk sample. It is not unusual to observe occasional particles having aspect rations of 10:1 or less, but it is unlikely that the asbestos component(s) would be dominated by particles (individual fibers) having aspect ratios of < 20:1 for fibers longer than 5ug. If a sample contains a fibrous component of which most of the fibers have aspect ratios of < 20:1 and that do not display the additional asbestiform characteristics, by definition the component should not be considered asbestos." Found in Appendix A of the EPA document Test Method - Method for the Determination of Asbestos in Bulk Building Materials (EPA/600/R-93/116, dated July 1993).
 Characterization of Fiber Emissions from the Northshore Taconite Facility
Fiber emissions from Northshore's Peter Mitchell Mine were characterized in a study by Ross, et. al., The search for asbestos within the Peter Mitchell Taconite iron ore mine, near Babbitt, Minnesota. During this study Ross et. al. analyzed 53 samples from 30 sites within the mine where fibrous minerals were thought to potentially occur. Samples were analyzed using transmission electron microscopes and other state-of-the-art equipment. Their findings included:
          "The fibrous ferroactinolite is a low temperature alteration product of non-fibrous amphibole; it does not occur in the manner of true asbestos which crystallizes as a primary mineral from hydrothermal solutions into open veins within deformed rock. The ropy mats of ferrian sepiolite are composed of inter-woven sub-micrometer sepiolite fibers. Due to interweaving of the fibers within the mats, individual fibers will be released only with great difficulty."
          "The fibers collected during ambient air sampling at the taconite mill where the Northshore iron ore is processed and at the town of Silver Bay are not asbestos, but rather are non-asbestiform ferroactinolite and grunerite."
          "No asbestos of any type was found in the mine pit."
In another study by Wilson et. al., ambient air samples from monitors at the taconite mill and in a nearby town were analyzed. It was found that the fibers collected by the ambient air monitors were non-asbestiform ferroactinolite and grunerite, not asbestos. (Wilson et. al., 2008)
After reviewing and evaluating available information, we have determined that the EMP emissions from the Northshore taconite facility do not meet the definition of "asbestos" found in EPA regulations and technical documents. This conclusion is supported by:
          The fact that asbestos is always defined as the asbestiform varieties of certain minerals (see 40 CFR sections 61.141, 763.83, and 763.163), whereas the EMP in question developed in the non-asbestiform geologic form;
          A study by Ross et. al. which found no asbestos in the Peter Mitchell Mine after analyzing over 50 samples from sites within the mine where fibrous minerals were thought to potentially occur; and
          A study by Wilson et. al., wherein ambient air samples indicated that the fibers collected by ambient air monitors located near the Northshore taconite processing facility were non-asbestiform ferroactinolite and grunerite, not asbestos.
          Therefore, we conclude the appropriate term for these particles is "non-asbestiform amphibole EMP."
             Fine Mineral Fibers
We also evaluated whether these non-asbestiform amphibole EMP emitted by taconite iron ore processing facilities might meet the definition of "fine mineral fibers." The HAP "fine mineral fibers" is defined in footnote 3 of the HAP list in CAA section 112(b)(1) as follows: "[f]ine mineral fibers includes mineral fiber emissions from facilities manufacturing or processing glass, rock or slag fibers (or other mineral derived fibers) of average diameter 1 micrometer or less." The EPA Health Effects Notebook (available at https://www.epa.gov/haps/health-effects-notebook-hazardous-air-pollutants) further explains that the term "fine mineral fibers" was intended to apply to the synthetic vitreous fibers glasswool, rockwool, slagwool, glass filaments, and refractory ceramic fibers.
We conclude that the non-asbestiform amphibole EMP emitted by taconite facilities do not meet the HAP definition of "fine mineral fibers" found in CAA section 112(b)(1) because the taconite iron ore processing facilities are not manufacturing or processing glass, rock or slag fibers (or other mineral derived fibers) or synthetic vitreous fibers such as rockwool, glasswool, slagwool, glass filaments, and refractory ceramic fibers.
 CONCLUSIONS/SUMMARY
          The EMP emissions resulting from Northshore Mining Company's taconite mining and processing do not meet the HAP definition of "asbestos" because they are not "asbestiform." This conclusion is supported by studies by Ross et. al. and Wilson et. al. Therefore, we conclude that these emissions should be characterized as non-asbestiform amphibole EMP, as opposed to asbestos.
          The EMP emissions resulting from taconite iron ore processing also do not meet the HAP definition of "fine mineral fibers" for purposes of CAA section 112 as that term refers to the manufacturing or processing of glass, rocks or slag fibers or the listed synthetic vitreous fibers.
          Nevertheless, we note that the EMP are a component of PM which are currently subject to a MACT level of control by the NESHAP as a surrogate for metal HAP and acid gases. We also note that the Minnesota Pollution Control Agency requires the Northshore Mining facility to monitor the EMP and ensure ambient levels of EMP near the facility are no higher than levels found in a non-affected location (i.e., St. Paul, Minnesota).

 REFERENCES (all available in Docket ID No. EPA-HQ-OAR-2017-0664)
          Minnesota Pollution Control Agency (MPCA) memorandum to the MPCA Advisory Committee Members, dated August 2, 2016, with the subject Proposal Regarding Airborne Mineral Fibers Emitted by Northshore Mining Company.
          The search for asbestos within the Peter Mitchell Taconite iron ore mine, near Babbitt, Minnesota (Malcolm Ross, Robert P. Nolan, and Gordon L. Nord). Elsevier, Inc., 2007.
          October 20, 2016 email from Eric Alma of the MPCA.
          American Iron and Steel Institute memorandum to the EPA, dated February 25, 2019, titled Information for EPA regarding Amphiboles on the Mesabi Iron Range.
          Wilson, R., McConnell, E.E., Nolan, R.P., Axten, C.W., Ross, M., 2008. Risk assessment due to environmental exposures to fibrous particulates associated with taconite ore. Reg. Tox. Pharm. 52, S232-S245.
          Toxicological Profile for Asbestos (September 2001). U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry (ATSDR).
          Test Method  -  Method for the Determination of Asbestos in Bulk Building Materials (EPA/600/R-93/116, dated July 1993).
          January 30, 2019 email from Eric Alma of the MPCA.
