Are PG and VG contained in vape harmful to the human body?

The rise of vaping as an alternative to traditional smoking has sparked debates about its safety, particularly concerning the primary ingredients in e-liquids: propylene glycol (PG) and vegetable glycerin (VG). These odorless, colorless liquids serve as carriers for nicotine and flavorings, creating the vapor inhaled by users. While both compounds are widely regarded as safe for consumption in food and pharmaceuticals, their long-term effects when inhaled remain a topic of scientific scrutiny. This article explores the potential risks and safety profiles of PG and VG, separating myths from evidence-based conclusions.

1. What Are PG and VG?

• Propylene Glycol (PG): A synthetic, petroleum-derived liquid, PG is used in food preservation, pharmaceuticals (e.g., inhalers), and cosmetics. It is classified as “Generally Recognized as Safe” (GRAS) by the U.S. Food and Drug Administration (FDA) for ingestion. In vaping, PG provides a “throat hit” similar to cigarettes and carries flavors effectively.
• Vegetable Glycerin (VG): A natural compound derived from plant oils (e.g., coconut, palm), VG is thicker and sweeter than PG. It is also FDA-approved for consumption and commonly found in baked goods, toothpaste, and skincare products. In e-liquids, VG produces dense vapor clouds and mellows the throat hit.

Most e-liquids blend PG and VG in ratios like 50/50 or 70/30, balancing throat sensation and vapor production.

2. Short-Term Effects of Inhaling PG and VG

Studies and user reports highlight mild, reversible effects of vaping PG and VG.

• PG Sensitivity: Some users experience throat irritation, dry mouth, or allergic reactions (e.g., itching, rashes). PG’s hygroscopic nature (attracting water molecules) can dehydrate the respiratory tract.
• VG Sensitivity: High-VG e-liquids may cause phlegm buildup or a “coated” throat due to their thick consistency. These side effects are typically dose-dependent and resolve with reduced use or switching PG/VG ratios.

3. Long-Term Risks: What Does the Science Say?

While PG and VG are safe to ingest, inhalation introduces unique considerations. When overheated (e.g., via “dry puffing” or malfunctioning devices), PG and VG can break down into harmful compounds.

• Formaldehyde: PG may degrade into formaldehyde, a known carcinogen, at temperatures above 230°C (446°F).
• Acrolein: VG can produce acrolein, a respiratory irritant linked to lung damage, when heated above 280°C (536°F).

However, these temperatures exceed typical vaping conditions. A 2018 study in Tobacco Control found that under normal use (e.g., 3.8V devices), formaldehyde levels in vapor are 90–95% lower than in cigarette smoke.

• Lung Health: Often misattributed to PG/VG, this rare condition is caused by inhaling lipid-based additives (e.g., vitamin E acetate in illicit THC cartridges), not PG/VG. Popcorn Lung (Bronchiolitis Obliterans): Diacetyl, a flavoring chemical once used in e-liquids, was linked to this condition. Modern reputable brands avoid diacetyl, and PG/VG themselves are not associated with it.

4. Cardiovascular and Metabolic Effects

A 2021 review in Circulation noted no direct evidence linking PG/VG to cardiovascular disease. However, nicotine—not PG/VG—remains the primary cardiovascular risk factor in vaping.

• PG/VG vs. Cigarette Smoke: Public Health England maintains that vaping is 95% less harmful than smoking, largely because e-liquids lack the 7,000+ chemicals in cigarette smoke, including tar and carbon monoxide. While PG/VG aerosol contains trace toxins, their concentrations are far lower than in combustible tobacco.
• Regulatory and Medical Perspectives: Acknowledges vaping as a less harmful alternative for smokers but emphasizes unknown long-term risks. Requires e-liquid manufacturers to disclose ingredients, including PG/VG ratios.
• Medical Inhalers: PG is safely used in asthma inhalers, though at lower doses and frequencies than vaping.
• Youth Vaping: Concerns focus on nicotine addiction and flavor appeal, not PG/VG toxicity.

5. Who Is Most at Risk?

• Non-Smokers and Adolescents: Inhaling any foreign substance carries risks, particularly for developing lungs.
• Heavy Vapers: High exposure to PG/VG may amplify dehydration or irritation.
• Allergy-Prone Individuals: PG allergies, though rare, warrant caution.

6. Mitigating Potential Harms

• Avoid Dry Puffing: Ensure coils are saturated to prevent overheating.
• Choose Reputable Brands: Avoid products with undisclosed additives.
• Stay Hydrated: Counteract PG/VG’s dehydrating effects with water.
• Monitor Nicotine Intake: Opt for lower nicotine strengths if using high-PG liquids.

PG and VG are not entirely risk-free, but their dangers are often exaggerated or misrepresented. When compared to the proven harms of cigarette smoke, vaping with PG/VG-based e-liquids represents a significantly safer alternative for adult smokers seeking to quit. However, non-smokers, particularly youth, should avoid vaping due to unknown long-term effects and nicotine addiction risks.

Current evidence suggests that PG and VG pose minimal harm under normal vaping conditions, but ongoing research is critical to understanding chronic exposure impacts. For now, informed use—coupled with regulatory oversight—remains the best approach to minimizing risks.

While vaping is not harmless, its risks are dwarfed by those of smoking. PG and VG, while imperfect, are among the least concerning components of e-liquids when used responsibly.