Introduction:
Heated tobacco products have been recently marketed as harm reduction products, but the scientific literature is mostly comprised of industry funded studies. The aim of this independently-funded study was to compare carbonyl emissions from a novel heated tobacco product (IQOS) in comparison with a commercial tobacco cigarette and a new generation e-cigarette.

Methods:
Aerosol and smoke was collected using an automated machine in 2 impingers connected in series that contained DNPH. The e-cigarette was tested at 2 power settings (10 W and 14 W). Health Canada Intense (HCI) and two more intense puffing regimes were tested. Analysis was performed using HPLC, using a previously validated method.

Results:
IQOS regular and menthol IQOS emitted 6.4 and 5.0 μg/stick formaldehyde, 144.1 and 176.7 μg/stick acetaldehyde, 10.8 and 10.4 μg/stick acrolein, 12.8 and 11.0 μg/stick propionaldehyde and 2.0 and 1.9 μg/stick crotonaldehyde. IQOS products emitted approximately 10-fold less formaldehyde, 7-fold less acetaldehyde, 10-fold less acrolein, 9-fold less propionaldehyde and 20-fold less crotonaldehyde compared to the tobacco cigarette. The e-cigarette emitted approximately 65 to 130-fold less formaldehyde, 1000-fold less acetaldehyde and 300-fold less acrolein compared to the tobacco cigarette. Propionaldehyde and crotonaldehyde were not detected in the e-cigarette aerosol. At more intense puffing regimes, only formaldehyde was observed to be increased in IQOS products, while all other carbonyls were emitted at levels similar to the HCI regime. The levels of carbonyls emitted from IQOS were similar to those reported by the manufacturer in the literature.

Conclusions:
IQOS emits substantially lower levels of carbonyls compared to a commercial tobacco cigarette but higher levels compared to an e-cigarette. There seems to be a risk continuum between different harm reduction products.

Funding:
The study was funded by Mayo Clinic.