Sales in the U.S. of electronic cigarettes (a.k.a. e-cigarettes) have more than doubled since 2014 to 3.6 billion dollars in 2018 with currently 4 to 6 million units being sold every year. Teens are now more likely to use e-cigarettes than cigarettes with 9.5% of 8th graders and 16.2% of 12 graders using e-cigarettes according to www.drugabuse.gov. In the U.S. new products are put on the market with only limited short-term safety testing and no long term testing on the health effects of chronic usage. In the case of e-cigarettes this results in primary and secondary exposure to aluminum vapor that may become a risk to mental health after years of chronic exposure. In this review what is known about aluminum vapor’s toxicity in aluminum welders and narcotics users who “chase the dragon” is applied to what is known about using aluminum containing Kanthal wire as a heated filament in e-cigarettes.
Aluminum Neurotoxicity - Aluminum kills neurons and causes a variety of neurological problems including death. Aluminum accumulates over a period of years in areas of the brain resulting in aluminum hotspots. The olfactory bulb is both responsible for the sense of smell in the brain and is an aluminum hotspot1. If aluminum is ingested with food or drink it must cross the gut-blood-barrier and then cross the blood-brain-barrier in order to get inside the brain. Both of these barriers together exclude most of ingested aluminum from entering the brain unless there has been traumatic brain injury,
However, if aluminum is inhaled from the nose or mouth these two barriers are skipped as aluminum goes directly to the olfactory bulb of the brain by axonal transport from nasal passages2-5. Once in the olfactory bulb the aluminum finds its way into both the entorhinal and frontal cortexes and the hippocampus6 causing shrinkage of the brain and impaired memory7. In addition, inhaled aluminum has been found in the myelin rich white matter region of the brain3. Shrinkage of the brain and damage of myelin due to inhaled aluminum is a likely cause of toxic leukoencephalopathy that can result in death. Therefore avoid inhaling aluminum by making the following lifestyle choices:
· Avoid Inhaling Aluminum Vapor while Welding
· Avoid “Chasing the Dragon”
· Avoid e-cigarettes with Kanthal heater coils
Inhaling Aluminum through the Nose and Mouth
The human nose and mouth are connected by the retronasal passageway as diagrammed in the following figure. This passageway allows us to smell food in our mouth even with our nose plugged. Therefore any vapor that reaches our olfactory receptors either from inhaling ‘out-there’ orthonasally or ‘in-the-mouth’ retronasally can be axonally transported directly to the olfactory bulb of the brain by-passing the blood-brain-barrier. In other words inhaling e-cigarette vapor by either the nose or mouth exposes the olfactory receptors and olfactory bulb of the brain to vapors.
Aluminum Welding – Welding aluminum in an inert atmosphere results in aluminum rich vapors that when inhaled cause high levels of aluminum in the urine and a decrease in cognitive and motor (i.e. muscular) performance. This was confirmed with two studies one in Finland in 1996 and one in Sweden in 20008,9. In both studies aluminum welders had much higher levels of aluminum in their urine than did steel welders. The welders in both studies were categorized into 3 sub-groups based upon urinary aluminum levels. Testing the welder’s cognition revealed a dose dependent correlation between urinary aluminum levels and declining cognitive performance. Also analysis of electro-encephalography (EEG) testing revealed abnormalities only in the aluminum welders with a higher frequency of abnormalities in those aluminum welders with high levels of aluminum in their urine8,9. In addition, disturbed central nervous system driven motor (i.e. muscular) function was observed only in the aluminum welders with higher levels of aluminum in their urine8.
Aluminum tops the list of metals that cause oxidative damage to the brain with manganese being third on the list with less than half the oxidizing power of aluminum10. Vapor exposure to these metals is common when welding either aluminum alloys or steel and nickel alloys that contain manganese. Manganese has a vapor pressure of 1x10-5 bar at 955oC while aluminum has the same vapor pressure at 1,200oC11,12. Note that in aluminum containing alloys of iron, chromium, and aluminum, such as Kanthal and PM2000, all the aluminum is vaporized after 70 hours at 1,200oC in an oxygen and moisture rich atmosphere13.
No MRI has been reported of an aluminum welder’s brain. However, inhaled organo-aluminum compounds and aluminum ions and particles have been found to be axonally transported into the olfactory bulb and beyond into the hippocampus and white matter regions of the brain bypassing the protective blood-brain-barrier2-5.
Chronic exposure to levels of manganese in air greater than 5mcg/m3 can lead to a variety of psychiatric and motor (i.e. muscular) disturbances called manganism. Unlike aluminum, manganese can be detected by T1 weighted MRI scans of the brain. It has been shown by T1 weighted MRI scans that manganese accumulates in the olfactory bulb of the brain of steel alloy welders at much higher than normal levels14. In addition, it has been shown that both soluble manganese ions15-17 and insoluble manganese particles18 are transported along the olfactory nerve directly into the olfactory bulb and cortex and further into the brain (i.e. the amygdala) bypassing the protective blood-brain-barrier.
Therefore whenever welding aluminum alloys or manganese containing steel alloys always wear protective breathing gear or weld with just arms inside a fume hood with adequate ventilation for brain protection.
Chasing the Dragon – In order to avoid diseases transferred by using needles to inject narcotics, many users switched to inhaling narcotics. The most common method is called “chasing the dragon” which involves heating by flame from below the narcotic on a small piece of aluminum foil while inhaling the vapor with a straw19. Depending upon the heat produced by the flame some aluminum foil is burned, vaporized, and inhaled along with the narcotic. In those cases where the user’s brain was examined by CAT and MRI scans, voids were found in the myelin that makes up the white matter region of the brain due to a decreased number of neurons and oligodendrites20,21. Bilateral and symmetrical hyper-intensities in cerebral white matter and middle cerebellar peduncles were found using T2 weighted MRI20. The white matter in these brain regions has the appearance of Swiss cheese. The symptoms of this disease include mental deterioration, vison loss, speech disturbances, paralysis, and coma. This condition has been named both progressive and acute toxic leukoencephalopathy, multifocal leukoencephalopathy, and spongiform leukoencephalopathy.
Myelin is the preferential target of aluminum-mediated oxidative damage22. In 2008 the link between aluminum accumulation and progressive toxic leukoencephalopathy was reported in a 20 year old woman in whose brain aluminum deposits were found in the myelin sheath making up the white matter region of her brain after autopsy23. As in the cases of “chasing the dragon”, bilateral and symmetrical hyper-intensities in cerebral white matter and middle cerebellar peduncles were found using T2 weighted MRI scans23. In this women’s case the cause of aluminum accumulation was possibly due to a prior traumatic brain injury that made her blood-brain-barrier more permeable to aluminum but “chasing the dragon” was not ruled out23.
It has been suggested that acute toxic leukoencephalopathy can be clinically reversed by removing the casual toxin24. For instance, by both avoiding “chasing the dragon” and drinking OSA rich silica water could potentially reverse the disease and heal the brain by removing aluminum25. Drinking silica water has been shown to selectively remove aluminum from five lobes of the brain, including the olfactory bulb1.
E-cigarettes with Kanthal Heating Coils - E-cigarettes (a.k.a. e-cigs) are handheld devices for vaporizing liquids (a.k.a. e-liquids) in order for the user to inhale the vapor. Inside each e-cigarette are one or more coils of resistance wire (a.k.a. vape wire) that are heated either at constant temperature or constant wattage (i.e. constant power mode) with an internal battery. There are five different types of vape wires generally used: Kanthal (an iron-chromium-aluminum alloy), NiChrome (e.g. nickel-chromium alloy), stainless steel, nickel (e.g. nickel-manganese alloy), and titanium. The vape wire coils are filled with a wicking material (e.g. cotton, wool, silica, or rayon fibers) saturated with the e-liquid mixture primarily containing glycerol and/or propane-1,2-diol26.
Kanthal vape wire has a stable resistance regardless of coil temperature and for this reason must be heated at a controlled wattage (i.e. power mode) not a controlled temperature27. Therefore the temperature of Kanthal vape wire coils will rise above normal in the absence of sufficient e-liquid being wicked to the coil. This is called getting “dry hits” during which the temperature of the vape wire rises to temperatures that allow aluminum to be vaporized more readily from Kanthal vape wire.
Nickel vape wire has a predictable change in resistance with temperature (i.e. temperature coefficient)27. Therefore nickel-manganese alloy vape wire coils, such as in the T3 eGo e-cigarette26, are heated at a controlled temperature by detecting the resistance in order to control the coil temperature. This keeps the coil temperature from rising higher than normal. Temperature control prevents manganese from being vaporized from nickel-manganese alloy vape wire. Only a very small amount (i.e. one nanogram) of manganese has been found in T3-eGo e-cigarette aerosol26.
Kanthal alloy is the most popular vape wire as it is easy to work with, has good resistance to oxidation, it’s not springy so it holds shape, and it’s inexpensive. In addition it holds shape well when re-wicking. The main problems with Kanthal alloy are that it must be heated at constant wattage and not constant temperature and it contains 4% to 7% aluminum that is not thermally stable. When Kanthal wire was heated for 70 hours at 1,200oC all the aluminum is vaporized13.
There have been three studies that have found aluminum in e-cigarette aerosols but in two studies the vape wire was not Kanthal and in the third study the type of vape wire was undiscolosed26,28,29. Heating Kanthal wire at a constant wattage (i.e. constant power) and not a constant temperature allows the temperature to rise significantly when the wick can’t supply e-liquid quick enough (i.e. “dry hit”). This is because the thermal conductivity of an e-liquid containing propane-1,2-diol and/or glycerol is more than ten times higher than moist air at 25oC (e.g. 0.20-0.29W/mK versus 0.018W/mK) 30-32. For brain health aluminum containing vape wire, such as Kanthal, should not be used for heater coils in e-cigarettes. Since there are many other safer vape wire choices, do not use e-cigarettes in power mode with Kanthal vape wire coils.
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26. Palazzolo, D.L.; Trace metals derived from electronic cigarette (ECIG) generated aerosol: Potential problem of ECIG devices that contain nickel; Jan.; Frontiers in Physiol.; 7(Article 663):1-17 (2017) Note: vape wire did not contain aluminum but did contain 9% manganese. 1.2mcg of aluminum and 0.001mcg of manganese were trapped from the aerosol. Source of aluminum is unknown but could be from a woven around the core.
28. Williams, M., et al.; Metal and silicate particles including nanoparticles are present in electronic cigarette cartomizer fluid and aerosol; PLOSone; Mar.; 8(3)1-11 (2013) Note: vape wire did not contain aluminum or manganese. Source of aluminum containing particles is unknown but could be either aluminosilicate beads or aluminosilicate containing fiberglass.
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