If you've spent any time researching vaping, you've probably come across the acronym HPHCs. You'll also notice that we talk about HPHCs frequently here at Kai's Virgin Vapor and encourage customers to take a look at our HPHC lab test results to review the data for themselves.
But what exactly are HPHCs? Why do regulators and researchers care about them? And what does it mean when a vape product tests for low—or even non-detectable—levels of these compounds?
Let's take a closer look.
HPHC stands for Harmful and Potentially Harmful Constituents.
Quick Definition: HPHCs (Harmful and Potentially Harmful Constituents) are chemicals identified by the FDA that may contribute to disease or other adverse health effects. Scientists often test for these compounds when evaluating tobacco and nicotine products.
The term comes from the U.S. Food and Drug Administration (FDA), which uses it to describe chemicals that are known—or strongly suspected—to contribute to disease, toxicity, or other negative health effects.
Many HPHCs are associated with cigarette smoke, but they can also be present in aerosol generated from some vaping products depending on ingredients, device design, operating temperature, and manufacturing quality.
In simple terms, HPHCs are substances researchers would generally prefer not to find in anything you inhale.
The FDA created an official list of harmful and potentially harmful constituents to help researchers, manufacturers, and regulators evaluate tobacco and nicotine products.
The list contains dozens of compounds from several categories, including:
Carcinogens (cancer-causing substances)
Respiratory toxicants
Cardiovascular toxicants
Heavy metals
Volatile organic compounds (VOCs)
Tobacco-specific nitrosamines (TSNAs)
Carbonyl compounds such as formaldehyde and acetaldehyde
Not every HPHC is equally dangerous, and not every product contains every HPHC. The purpose of the list is to identify substances that deserve special attention because of their known or suspected health risks.
Here are a few HPHCs that are commonly discussed in vaping research:
| HPHC Category | Examples | Why It's Monitored |
|---|---|---|
| Carbonyls | Formaldehyde, Acetaldehyde, Acrolein | Can form during overheating and may pose respiratory or toxicological concerns |
| TSNAs | NNK, NNN | Tobacco-specific carcinogens |
| Heavy Metals | Lead, Nickel, Cadmium, Chromium | May originate from device components or manufacturing |
| VOCs | Benzene, Acrylonitrile | Associated with toxicity and long-term health concerns |
| PAHs | Benzo[a]pyrene | Known carcinogenic compounds |
Formaldehyde is a carbonyl compound and a known human carcinogen.
In vaping, formaldehyde is generally associated with overheating e-liquid or operating devices under conditions that produce "dry puffs." Under normal use conditions, levels are often dramatically lower than those found in cigarette smoke, but researchers still monitor it closely.
Acetaldehyde occurs naturally in many foods and beverages but can also be produced during combustion and thermal degradation.
Like formaldehyde, it is commonly included in emissions testing because elevated exposure may pose health risks.
Acrolein is a respiratory irritant that can form when glycerin-based liquids are overheated.
Researchers frequently test for acrolein because it may contribute to irritation and inflammation of the respiratory tract.
TSNAs are among the most significant carcinogens associated with tobacco products.
Because nicotine is often derived from tobacco, researchers carefully monitor TSNA levels in nicotine-containing products.
Testing may also look for metals such as:
Lead
Cadmium
Nickel
Chromium
Arsenic
These substances are not typically ingredients in e-liquid. Instead, when present, they may originate from manufacturing processes, device components, or heating elements.
Many consumers assume all vape products are essentially the same.
They are not.
Differences in ingredients, manufacturing practices, flavoring systems, hardware, and quality control can produce meaningful differences in product chemistry.
This is one reason independent laboratory testing matters.
Testing allows manufacturers and consumers to move beyond assumptions and look at actual data.
Rather than simply claiming a product is "clean" or "high quality," laboratory analysis can identify whether specific harmful compounds are present and at what levels. Rather than relying solely on opinions or marketing claims, analytical testing provides objective data about specific compounds under defined testing conditions.
One question many people naturally ask is:
If HPHCs can be found in some vape products, how does that compare to smoking?
This is an important question because HPHCs were originally identified and studied largely in the context of cigarette smoke.
When a cigarette burns tobacco, it creates smoke containing thousands of chemicals, including many of the HPHCs on the FDA's list. The combustion process itself generates substantial quantities of compounds such as formaldehyde, acetaldehyde, acrolein, benzene, and numerous other toxicants.
Vapor products work differently. Instead of burning tobacco, they heat a liquid to create an aerosol. Researchers frequently study how HPHC levels compare between cigarette smoke and vapor product aerosols in order to better understand the presence of specific compounds across different nicotine products.
Those differences do not mean all vape products are identical, nor does it mean vaping is risk-free or safe. Product design, ingredients, manufacturing quality, and operating conditions can all influence emissions.
For consumers, the key takeaway is that HPHC testing is not simply about whether a compound is present or absent. Equally important is understanding which compounds are present, at what levels, and how those levels compare to known sources of exposure such as cigarette smoke.
You may sometimes see laboratory reports showing that a compound was "not detected".
This does not necessarily mean the compound is absolutely absent.
Instead, it means that if the compound is present, it is below the laboratory's ability to reliably measure it using the testing method employed.
In practical terms, "non-detectable" generally means levels are extremely low—below the test's established detection threshold.
One of the most effective ways to reduce unwanted constituents is to start with carefully selected ingredients. As unglamorous as it sounds, at Kai's Virgin Vapor, the decision about what flavors we manufacture was primarily made in a lab. You can also learn more in our Clean Vaping Guide.
Researchers have found that flavoring compounds can vary significantly in their chemistry and thermal behavior. For that reason, ingredient transparency, supplier qualification, and formulation practices play an important role in product quality.
Not all flavor systems are created equal.
Long before laboratory testing became common in the vaping industry, we invested heavily in understanding what was actually in the products being sold to consumers.
For years, Kai's Virgin Vapor employed a full-time PhD chemist and operated its own gas chromatography–mass spectrometry (GC-MS) laboratory equipment. We made that investment because we wanted answers, not assumptions.
Kai's Virgin Vapor's GCMS machine bearing a sticker with our original logo. The doodle on the whiteboard is the chemical formula for nicotine!
Whenever we attended industry trade shows, we would return with bags full of e-liquids from other manufacturers. We weren't looking for inspiration—we were looking for data.
Many of these products came from companies that appeared professional and trustworthy. Some advertised rigorous testing programs. Some assured customers that certain compounds were not present.
Yet analytical testing often told a different story.
E-liquid samples being tested in Kai's Virgin Vapor's GCMS machine
In some cases, compounds that manufacturers claimed were absent could still be detected. We even encountered instances where compounds such as diacetyl were detected despite assurances that testing had already been performed and those compounds were not present. In other cases, testing revealed chemical profiles that raised questions about formulation practices, ingredient selection, or quality control.
Those experiences fundamentally changed how we viewed product development.
The most important lesson we learned:
A polished website, attractive packaging, or confident marketing claims do not guarantee that a product has been thoroughly evaluated. The only way to truly understand a product's chemistry is through analytical testing.
Over the years, we tested hundreds of flavors, ingredients, and finished products. The formulations that ultimately became part of the Kai's Virgin Vapor lineup were selected not only for flavor quality, but also informed by years of chemical analysis. Rather than choosing flavors solely on popularity, we evaluated ingredients, reviewed available data, and prioritized formulations that demonstrated favorable chemical profiles during testing.
Kai's Virgin Vapor laboratory, circa 2015. Quality control, formulation development, and analytical testing were central parts of our product development process.
Today, we use independent third-party laboratories rather than conducting testing in-house. Independent testing is both practical and objective, allowing customers to review the same data we review.
While no laboratory report can prove that an inhaled product is risk-free, we believe consumers deserve transparency. Testing is one of the most important tools available for understanding what is—and is not—in a product.
It's important to understand what HPHC testing can—and cannot—tell us.
Testing does not prove that any inhaled product is completely risk-free.
No laboratory report can guarantee zero risk.
What testing can do is help identify, quantify, and compare specific compounds that scientists believe may contribute to health risks.
This is one reason many public health researchers view emissions chemistry as an important part of understanding differences between various nicotine products.
HPHCs are chemicals that regulators and researchers monitor because of their known or suspected health risks.
While the term may sound technical, the concept is simple: these are compounds we generally want to minimize whenever possible.
For many researchers, the question is not simply whether HPHCs exist, but whether specific products reduce exposure to these compounds compared with combustible cigarettes.
Understanding HPHCs can also help consumers better evaluate product quality, laboratory testing, and manufacturer transparency.
As always, we invite you to check out our lab test results for yourself. If you'd like help understanding what you're looking at, you can follow along by reading our guide explaining How to Read a Vape Juice Lab Report.
The more data available, the better equipped consumers are to make informed choices about the products they use.
U.S. Food and Drug Administration (FDA). Harmful and Potentially Harmful Constituents (HPHCs). Available at: https://www.fda.gov/tobacco-products/products-ingredients-components/harmful-and-potentially-harmful-constituents-hphcs
U.S. Food and Drug Administration (FDA). “Harmful and Potentially Harmful Constituents” in Tobacco Products as Used in Section 904(e) of the Federal Food, Drug, and Cosmetic Act. Guidance for Industry and FDA Staff. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/harmful-and-potentially-harmful-constituents-tobacco-products-used-section-904e-federal-food-drug
National Academies of Sciences, Engineering, and Medicine. (2018). Public Health Consequences of E-Cigarettes. Washington, DC: The National Academies Press. doi:10.17226/24952.
Eaton DL, Kwan LY, Stratton K, eds. (2018). Toxicology of E-Cigarette Constituents. In: Public Health Consequences of E-Cigarettes. National Academies Press.
Goniewicz ML, Smith DM, Edwards KC, et al. (2018). Comparison of Nicotine and Toxicant Exposure in Users of Electronic Cigarettes and Combustible Cigarettes. JAMA Network Open, 1(8):e185937.
Cao DJ, Aldy K, Hsu S, et al. (2020). Review of Health Consequences of Electronic Cigarettes and the Outbreak of Electronic Cigarette, or Vaping, Product Use-Associated Lung Injury. Journal of Medical Toxicology, 16(3), 295–310.
Cheng T, Hammad HT, Fisher MT, et al. (2022). Harmful and Potentially Harmful Constituents in Tobacco Products: Analysis and Regulatory Considerations. ACS Omega, 7(29), 25039–25049.
U.S. Food and Drug Administration (FDA). Chemicals in Tobacco Products and Your Health. Available at: https://www.fda.gov/tobacco-products/health-effects-tobacco-use/chemicals-tobacco-products-and-your-health
U.S. Food and Drug Administration (FDA). Reporting Harmful and Potentially Harmful Constituents in Tobacco Products and Tobacco Smoke Under Section 904(a)(3). Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/reporting-harmful-and-potentially-harmful-constituents-tobacco-products-and-tobacco-smoke-under
National Academies of Sciences, Engineering, and Medicine. (2018). Summary Conclusions. Public Health Consequences of E-Cigarettes.
Disclaimer: While HPHC testing can provide valuable information about specific compounds measured under defined laboratory conditions, no laboratory test can demonstrate that an inhaled product is safe or completely risk-free. Consumers should consider HPHC testing as one factor among many when evaluating product quality and transparency.
