Rock Magnetic Characterization of Fine Particles from Car Engines, Brake Pads and Tobacco: An Environmental Pilot Study on Oahu, Hawaii, USA

Today, it is well known that small airborne particles are very harmful to human health. For the first time in Hawaii we have conducted an environmental pilot study of fine magnetic particles on the island of Oahu, Hawaii, of particulate matter (PM) PM = 60, PM = 10, and PM = 2.5. In order to do a rock magnetic characterization we have performed low field susceptibility vs. temperature [k-T] experiments to determine the Curie points of small particles collected from exhaust pipes, as well as from brake pads of four different types of car engines using gasoline octane ratings of 87, 89, and 92. The Curie point determinations are very well defined and range from 292˚C through 393˚C and up to 660˚C. In addition, we have conducted magnetic granulometry experiments on raw tobacco, burnt tobacco ashes, as well as on automotive engine exhaust, and brake pads in question. The results of the experiments show ferro and ferrimagnetic hysteresis loops with magnetic grain sizes ranging from superparamagnetic-multidomain [SP-MD], multi-domain [MD] and pseudo-single domain [PSD] shown on the modified Day et al., diagram of Dunlop (2002). Thus far, the results we have obtained from this pilot study are in agreement with other studies conducted from cigarette ashes from Bulgaria. Our results could be correlated to the traffic-related PM in Rome, Italy where the


Introduction
Airborne pollution is an ever-increasing issue and cause for numerous human health conditions such as respiratory and cardiovascular ailments. Especially prominent in our urban areas, airborne pollution consists of a wide array of particulate sizes and compositions. An often overlooked aspect of our daily lives is our contribution to airborne pollution.
The simple act of driving one's vehicle creates a plethora of airborne pollutants and furthermore these pollutants are often magnetized. Our vehicle does not make gasoline simply vanish. Our fuel is stored in a metal tank, sent through a mechanical pump to your engine where it is combusted in a hot mass of various different types of moving metal and then as a gaseous mixture, it is sent out of the engine through a hot pipe and into the air. Our brake pads and our tires do not simply disappear either. These wearable items also contain metals that are slowly ground down through normal use contributing to airborne pollution. Even the act of smoking a cigarette can contribute to magnetic particulates in the air.
Medical science is just beginning to understand the impact that ingested or inhaled magnetic pollution can have on the human body. A recent study showed that iron oxide (Fe 3 O 4 ) magnetite nanoparticles in the human brain may be the cause of Alzheimer's disease (Curtis et al., 2006;Plascencia-Villa et al., 2016).
The aim of this study is to utilize rock magnetic measurement techniques to characterize the airborne pollution created by normal automotive use as well as by cigarettes. The exhaust particulate built up in different vehicles tailpipes as well as in vehicles utilizing different octane gas will be tested as well as brake pad dust and cigarette tobacco and its ashes.
Through the environmental study and characterization of these sources of airborne pollution the resultant information may provide the medical community with better knowledge of just what exactly we as human beings face as airborne pollution. The aim of this study is to investigate the magnetic properties of traffic-produced airborne particulate matter (PM) and by raw tobacco and burnt ashes of cigarettes (e.g. Jordanova et al., 2006;Sagnotti & Winkler, 2012), for the first time in the city Honolulu, Hawaii, USA. wheel area. In addition, we have also recovered cigarette tobacco as well as ashes from a smoked cigarette in order to analyze the possible magnetic properties of such materials.

Rock Magnetic Experiments
Magnetic susceptibility and mineralogy Magnetic properties were analyzed to identify the magnetic carriers of the natural remanent magnetization (NRM) and to investigate the origin of the NRM. Studies of magnetic mineralogy were performed first using 10 specimens of very small pieces of fragments of brake pads, particles of fumes in the exhaust tail pipes of vehicles as well as raw tobacco and burnt ashes of cigarettes (Sagnotti & Winkler, 2012;Jordanova et al., 2006). The first experiment was to determine the magnetic susceptibility χ (×10 8 m 3 /kg) of the ten specimens in question (see Table 1). The values obtained range from very low values of 0.4 up to ~192 × 10 8 m 3 /kg.
Low-field susceptibility versus temperature (k-T) experiments was conducted in air using a Multi-Function Kappabridge MFK-1 with a CS-3 attachment in order to determine the Curie temperature of the samples. Nine specimens were progressively heated from room temperature up to 700˚C and subsequently cooled down using a CS3 apparatus (Hrouda, 1994;Hrouda et al., 1997)  phases. We have found that ALL the specimens studied had reversible and irreversible heating and cooling results, with single inflection points, indicating Curie temperatures between low (i.e. 250˚C) and very high (i.e. 675˚C) temperatures (see Table 1). We have interpreted these data to indicate the presence of low-Ti magnetite, pure magnetite as well as hematite as the primary magnetic minerals in these samples (see Figure 1) as shown by the inflection points of the Curie point diagrams.

Magnetic granulometry from hysteresis experiments
Magnetic hysteresis measurements were performed on very small particles sampled from vehicles (i.e. brake pads, gasoline remains on the exhaust tail pipes), cigarettes and their ashes (i.e. a few milligrams) in order to determine their hysteresis properties and eventually their magnetic grain sizes. To achieve such tasks we used a variable field translation balance (VFTB) up to 1.2 T. Saturation remanent magnetization (Mr), saturation magnetization (Ms), and coercive force (Hc) were calculated after removing the paramagnetic contribution.
We have determined the hysteresis loops and the back-field demagnetization curve of the saturation isothermal remanent magnetization (SIRM). The variable field translation balance (VFTB) instrument has a measuring range of 10 −8 -10 −2 Am 2 . The coercivity of remanence (Hcr) suggests that the Isothermal Remanent Magnetization (IRM) is carried by low-coercivity grains (see Figure 2), which is E. Herrero-Bervera et al. Figure 1. Results of nine low-field magnetic susceptibility versus temperature (k-T) Curie point curves obtained from small particles of brake pads, gasoline fuels (i.e. octane 87, 89 and 92, tobacco cigarettes and burnt tobacco ashes). Notice the diverse reversibility and irreversibility of the specimens tested as well as the variety of Curie point determinations. Table 1. Magnetic characteristics of the studied gasolines, brake pads, tobacco and burnt ashes data. Hcr remanence coercivity field, Hc coercivity field, Ms saturation magnetization, Mrs/Ms ratio of remanence saturation relative to saturation magnetization, Hcr/Hc ratio of remanence coercivity field to field coercivity, Magnetic domains, SD single domain, PSD pseudosingle domain, MD multidomain; (χ) bulk magnetic susceptibility (10 −6 m 3 /kg), Curie point determinations in degree centigrades.  case for the ten specimens shown in Figure 2 (Tauxe et al., 1996). The ratios of hysteresis parameters were plotted in Figure 3 and Table 1 as a Day diagram (Day et al., 1977) following modifications by Dunlop (Dunlop, 2002) for type curves and regions that have been defined for pure magnetite. Most grain sizes are scattered within the pseudo-single domain range (PSD) for the nine specimens under question (Tauxe et al., 1996). If we do not consider the influence of grain sizes, it is interesting to associate this distribution with the magnetic phases that are present in the sample. The hysteresis parameters have been initially defined from synthetic crystals of magnetite (Dunlop & Özdemir, 1997). However we must keep in mind that we are dealing with samples that contain magnetic grains associated with different mineralogical phases. We wonder whether the characteristic values that separate the grain size domains for pure magnetite are fully appropriate in the presence of several mineralogical components with overlapping coercivity spectra and magnetizations (see Figure  3(b)). This would probably explain why most studies deal with samples that are actually found within the pseudo-single domain range (e.g. Herrero-Bervera & Valet, 2009;Tauxe et al., 1996).

Discussion
One of the objectives of this very rudimentary, elementary and simple magnetic experiment(s) is to test the hypothesis that in the city of Honolulu, Hawaii there are traffic-related particulate matter (PM), see Figure 4, as well as cigarette tobacco and burnt ashes (Jordanova et al., 2006) that pose a real threat to the health of the inhabitants of the city.
As it has been published in the recent past, airborne particulate matter is composed of a mixture of a variety of chemical and physical characteristics that harm the respiratory, cardiovascular, immunological, hematological, neurological and reproductive/developmental systems (e.g. Plascencia-Villa et al., 2016;Sagnotti & Winkler, 2012;Thompson & Oldfield, 1986) (Figure 5 and Figure 6).
As commented and published by (Curtis et al., 2006) magnetic susceptibility (χ) is a property of matter, that reflects substantially the concentration of the different iron-containing minerals, mostly iron oxides and sulfides in natural systems (WHO, 2006), assuming that the mineralogy does not vary.
The other magnetic properties studied here such as the Curie point determinations and the hysteresis loops are also results that in a very initial phase, E. Herrero-Bervera et al. Figure 4. The atmosphere, in addition to gaseous pollulants is characterized by additional particles either in suspension, fluid or in solid state that have different compositions and sizes that are also called aerosols. Sometimes those particles are classified and called "floating dust" but in reality they are known as particulate matter (PM). The figure on the left side depicts the comparison with the thickness of a human hair (i.e. 50 -70 µm), and 90 µm of fine beach sand and PM 2.5 (i.e. <2.5µm) and PM 10 (i.e. 10 µm). The figure on the right hand side depicts light blue ball particles from combustion processes; the pink particles are minerals, and the green cubes salts. Image courtesy of the US EPA.   indicate that presence of magnetic particles occurring in ALL the specimens under question.

Conclusion
Our study of the magnetic properties such as magnetic susceptibility (χ), Curie point determination as well as hysteresis loops experiments to determine magnetic grain sizes is in reality constraints to assess the production of traffic-related airborne particulate matter (PM) in the City and County of Honolulu, Hawaii as well as the content of magnetic particles both in cigarettes and burnt ashes.
The results of the induced magnetization experiments such as the magnetic hysteresis loops are shown in Figure 2. The most salient features of such determinations are the very small and narrow coercivities of the loops or the so called "wasp-waisted loops" diagrams (Tauxe et al., 1996) that indicate such geometries are generated from populations of Single Domain (SD) and super paramagnetic (SP) grains; these cases are represented by the octane 87 gasoline small particles and the rear and front brake pad particles of the vehicles analyzed. Six of the hysteresis loop diagrams correspond to the Toyota SUV octane 87, Toyota Echo octane 92 and the tobacco and ashes of the Japanese and Marlboro cigarettes depicted in Figure 2. These six loop diagrams in addition show a ferro-ferri-magnetic contribution (i.e. the Ulvospinel-Magnetite magnetic minerals solid solution).
They are also characterized by paramagnetic contributions to the hysteresis curves.
The final conclusion about this research note is to point out that vehicles, cigarettes and their smoked ashes have produced very fine magnetic particles that no matter what their sizes are they potentially will cause illnesses that can severely harm the human body (i.e. brain, lungs, heart, liver, see Figure 5 and