Essential oils are popular for their pleasant scents, leading many to question their chemical nature and whether they are Volatile Organic Compounds (VOCs). The answer lies in the chemical definitions of both. Understanding this relationship is important for evaluating how these products affect the air within our homes.
Defining Volatile Organic Compounds
The term “Volatile Organic Compound” is a broad chemical classification, not a judgment of a substance’s toxicity. “Volatile” describes a chemical that easily evaporates or turns into a gas at room temperature, which is why you can smell them. The “organic” part of the name signifies that the chemical’s structure is based on carbon.
A “compound” is a substance formed from two or more different chemical elements. Many common household items are sources of VOCs, such as paints, cleaning supplies, air fresheners, and new furniture. These products release gases into the air, a process often called off-gassing.
This volatile nature allows them to become airborne and spread throughout an indoor environment. While some VOCs, like benzene and formaldehyde, are known to be harmful, the classification itself is neutral. The category is extensive, encompassing thousands of different chemicals that share this property.
The Chemical Nature of Essential Oils
Essential oils are a source of naturally occurring VOCs. These oils are complex mixtures of chemical constituents extracted from plants, with each oil containing dozens or even hundreds of components. These components create the oil’s unique scent and are almost entirely made of compounds that are both “organic” and “volatile.”
The primary chemical constituents of essential oils are terpenes and terpenoids, which are carbon-based molecules. These compounds, such as limonene in citrus oils, pinene in pine oils, and linalool in lavender, are responsible for the characteristic aromas. Because these compounds evaporate easily to release their scent, they fit the definition of “volatile.”
Therefore, when you diffuse lavender oil, you release VOCs like linalool into the air, and the scent of lemon is due to the volatilization of limonene. The properties that make essential oils useful for aromatherapy are what place them into the chemical category of VOCs.
How Essential Oils Affect Indoor Air
When essential oils are used in diffusers or sprays, their VOCs are released into the indoor atmosphere. These devices aerosolize the oil, breaking it down into tiny droplets that hang in the air and then evaporate, increasing the concentration of these plant-based VOCs. This process is how their aroma spreads through a room.
A significant consequence of releasing these compounds indoors is their potential to react with other substances. Indoor environments contain oxidants, with ozone being a common one, often introduced from the outdoors. When certain essential oil VOCs, particularly terpenes like limonene, interact with ozone, they can undergo chemical reactions.
These reactions can lead to the formation of different airborne pollutants, such as secondary organic aerosols (SOAs). SOAs are new, ultrafine particles formed in the air as a result of these chemical transformations. This production demonstrates how natural compounds can alter indoor air chemistry.
Health Implications and Safe Practices
The health profile of VOCs from essential oils differs from industrial VOCs like benzene. While not acutely toxic, high concentrations can lead to health issues for some individuals. Common effects include respiratory irritation, headaches, and allergy-like symptoms, particularly for those with asthma or chemical sensitivities.
The particles generated from the reaction between essential oil VOCs and ozone can also pose a risk. These ultrafine particles can penetrate deep into the lungs, which may cause irritation or other respiratory problems. The risk is related to the concentration and duration of exposure.
To use essential oils safely, practice moderation. Avoid diffusing them constantly, especially in small, unventilated spaces. Ensuring good ventilation by opening windows helps disperse the VOCs and prevents them from accumulating. Be mindful of others in the household, like infants, children, and pets, who may be more sensitive.