IQOS exposes you to significantly fewer toxic chemicals than cigarettes, but that doesn’t mean it’s safe. The FDA has authorized IQOS to claim it “significantly reduces” exposure to harmful chemicals compared to cigarettes, while explicitly stating this is not the same as reducing your health risk. The distinction matters more than it might seem, because lower chemical exposure doesn’t automatically translate into better health outcomes.
How Chemical Exposure Compares
IQOS heats tobacco to around 350°C instead of burning it at 600°C or higher. This eliminates most of the combustion process, which is where the bulk of cigarette toxins originate. The reductions in specific chemicals are dramatic: carbon monoxide drops by about 99%, acrolein (a potent lung irritant) by over 90%, and formaldehyde by 77% to 85%, depending on the testing method. Across 54 harmful compounds tracked by the FDA, reductions range from 54% to 99.9% per unit compared to a cigarette.
The FDA’s own lab found somewhat higher levels of certain chemicals than the manufacturer reported, but still confirmed the reductions were substantial relative to cigarettes. That said, the World Health Organization has pointed out that some toxins are actually present at higher levels in IQOS aerosol than in cigarette smoke, and the aerosol contains additional chemicals not found in cigarette smoke at all. The health effects of these unique compounds remain unknown.
What Happens Inside Your Body
Here’s where the picture gets more complicated. Despite the large drop in chemical exposure, short-term cardiovascular effects look surprisingly similar. A study of current smokers found that IQOS and traditional cigarettes produced comparable acute effects on heart rate, blood pressure, and arterial stiffness. In animal studies, rats exposed to IQOS aerosol showed similar impairment in blood vessel function as those exposed to cigarette smoke. IQOS did produce less oxidative stress in immune cells than cigarettes, but it still triggered a measurable stress response.
The respiratory picture is even more surprising. A study measuring airway obstruction found that IQOS caused greater short-term narrowing of small airways than cigarettes. Central airway obstruction increased by 22% after using IQOS, compared to 10.5% after a cigarette. Peripheral obstruction, which affects the smaller, deeper airways, jumped by as much as 144% with IQOS versus 93% with a cigarette. These effects persisted for at least 60 minutes. Animal models have also shown that heated tobacco products trigger inflammatory responses in lung tissue, including the kind of airway remodeling seen in emphysema and pathways linked to cancer development.
This disconnect between lower chemical exposure and similar (or sometimes worse) short-term physiological effects is one reason health authorities remain cautious. Fewer toxins entering your body is clearly preferable in theory, but the body’s actual response to the aerosol you inhale doesn’t neatly follow those numbers.
Indoor Air and Secondhand Exposure
If you’re concerned about the people around you, IQOS does produce far less secondhand pollution than cigarettes. A study measuring air quality inside passenger cars found that IQOS had almost no effect on fine particle concentrations or PM2.5 levels in the cabin. Cigarettes, by contrast, produced PM2.5 levels between 64 and 1,988 micrograms per cubic meter. Nicotine levels from IQOS were comparable to those from e-cigarettes and far lower than the 8 to 140 micrograms per cubic meter generated by cigarettes. Cigarettes also released measurable formaldehyde and acetaldehyde into room air, while IQOS produced negligible amounts.
The Dual Use Problem
One of the biggest practical challenges with IQOS is that most people don’t fully switch. In a pilot study tracking smokers given IQOS as a substitute, 80% were unable to completely stop cigarettes within two weeks. On average, participants initially replaced about 59% of their daily cigarettes with IQOS, eventually reaching 87% substitution. But for most, that still meant smoking some conventional cigarettes alongside IQOS use.
Only about 20% of smokers in the study fully switched, and these tended to be people who already found cigarettes less rewarding. Those who did switch completely ended up using more IQOS HeatSticks per day than they had smoked cigarettes, suggesting the product may not deliver nicotine as efficiently as a cigarette. If you’re using both products simultaneously, you’re getting the full harm of cigarettes plus whatever additional effects IQOS contributes, which defeats the purpose of switching.
What the FDA Actually Authorized
The FDA classified IQOS as a “modified risk tobacco product” but only with exposure modification claims. The authorized language states that IQOS “significantly reduces the production of harmful and potentially harmful chemicals” and that switching completely “significantly reduces your body’s exposure to harmful or potentially harmful chemicals.” That’s a statement about exposure, not about health outcomes.
The FDA was explicit that this authorization does not mean the product is safe, endorsed, or approved for consumer health. It cannot be marketed with claims suggesting reduced disease risk. The agency’s position is that no tobacco product is safe, and people who don’t currently use tobacco should not start.
The Bottom Line on “Better”
IQOS delivers nicotine with far fewer combustion-related toxins, produces less indoor air pollution, and reduces your exposure to dozens of harmful chemicals by large margins. By the measure of chemical exposure alone, it is meaningfully less toxic than a cigarette. But the clinical evidence so far shows that your heart and lungs still react to IQOS aerosol in ways that closely resemble their reaction to cigarette smoke, and in some airway measurements, the reaction is actually more pronounced. Long-term disease outcomes in humans simply haven’t been studied for long enough to know whether the chemical reductions lead to fewer cancers, heart attacks, or cases of COPD.
If you currently smoke and cannot quit nicotine entirely, switching completely to IQOS reduces your chemical exposure. If you end up using both, which is the more common outcome, the benefit shrinks dramatically. And if you don’t currently smoke, IQOS is not a safe product to start with. The WHO’s summary remains the clearest framing: reduced exposure to harmful chemicals does not automatically mean reduced risk to your health.