(See: Williams M, Villarreal A, Bozhilov K, Lin S, Talbot P. Metal and silicate particles including nanoparticles are present in electronic cigarette cartomizer fluid and aerosol. PLos ONE 2013; 8(3): e57987.)
The study reported that: "The aerosol contained particles greater than 1 micrometer comprised of tin, silver, iron, nickel, aluminum, and silicate and nanoparticles (less than 100 nanometers) of tin, chromium and nickel. The concentrations of nine of eleven elements in EC aerosol were higher than or equal to the corresponding concentrations in conventional cigarette smoke. Many of the elements identified in EC aerosol are known to cause respiratory distress and disease."
While the article scared many vapers by comparing the metal levels in e-cigarette vapor to that in cigarette smoke, it failed to inform readers that the levels of metals in electronic cigarettes are generally comparablle to those in nicotine inhalers. Today, I compare the levels of metals reported by Williams et al. to the USP standards for metals in inhalation medicines.
The Rest of the Story
The Williams et al. article reported the following levels of metals in 10 puffs of an electronic cigarette (all are in micrograms):
Since 10 puffs is equivalent to about 1 cigarette, and assuming that a vaper inhales the equivalent of 2 packs of cigarettes per day, that would be a total of 200 puffs per day. We can then multiply each of the above values by 20 to determine the total daily intake of each metal, in micrograms, as follows:
Now, here are the USP standards for the maximum allowable daily exposures for each of these metals from inhalation medicines, in micrograms (from the United States Pharmacopeial Convention, Revision Bulletin, Elemental Impurities--Limits, February 1, 2013) :
You can see that the total daily intake of these metals from the electronic cigarette brand tested by Williams et al. is far below the USP standard for each of the metals. The elemental impurities table does not contain values for the other metals reported in the article, but it does appear that for the ones listed, there don't seem to be safety concerns.
Once again, there is no question that the presence of trace levels of metals in electronic cigarette vapor needs to be addressed. Quality control measures need to be in place to minimize the presence of metals in electronic cigarette aerosol. However, there is no reason to sound the alarm from the data reported in the present study because it fails to compare the detected levels with regulatory standards for pharmaceutical products, including FDA-approved nicotine inhalers.
(Special thanks to Bill Godshall for providing the USP standards.)