Volatile Organic Compounds (VOCs) are carbon-containing chemicals that easily evaporate at room temperature, releasing gases from solids or liquids into the air. These compounds are a significant component of indoor air pollution, often found at concentrations up to ten times higher inside a home than outside. The health risk depends on the specific chemical, its concentration, and the duration of exposure, making the determination of a singular “safe” standard challenging.
Understanding Regulatory Thresholds for VOCs
The question of a safe level for VOCs does not have a simple answer because a single exposure limit cannot apply to the thousands of different chemicals involved. Since measuring every individual VOC is impractical, air quality monitoring often relies on the metric of Total Volatile Organic Compounds (TVOC). TVOC represents the combined concentration of multiple VOCs simultaneously present in the air, typically measured in micrograms per cubic meter (\(\mu\)g/m³).
Concentrations of TVOC below 300 \(\mu\)g/m³ are generally considered a low-concern level, suggesting good air quality that is unlikely to cause immediate health effects. Levels ranging from 300 to 500 \(\mu\)g/m³ are often classified as acceptable, though they may trigger mild symptoms in sensitive individuals. As the concentration rises above 500 \(\mu\)g/m³, the level of concern becomes considerable, indicating a need for investigation and mitigation. These thresholds are advisory guidelines for non-industrial settings and are not legally mandated standards for residential homes.
Acute exposure involves high concentrations of VOCs over a short period, leading to immediate symptoms like headaches, dizziness, nausea, and eye or respiratory tract irritation. Chronic exposure involves breathing lower levels of VOCs over many years, which is the main concern in residential settings. Long-term exposure carries the risk of more serious health consequences, including damage to the liver, kidneys, and central nervous system.
For certain individual VOCs, such as formaldehyde and benzene, specific and stricter guidelines exist due to their known toxicity. Benzene, for example, is a known human carcinogen for which no completely safe exposure level can be recommended. Formaldehyde, released from pressed wood products, has separate, lower exposure limits due to its irritant properties and classification as a probable human carcinogen. Measuring TVOC provides a general picture of air quality, but it does not account for the varying toxicity of the specific chemicals within that total.
Pinpointing Primary Indoor Sources of VOCs
The high concentration of VOCs indoors is primarily due to the constant off-gassing from common household products and building materials. Off-gassing is the process where chemicals slowly evaporate from a solid or liquid into the surrounding air. The familiar “new car” or “new paint” smell is a direct indicator of these compounds being released into the environment.
Building materials are a major source, including many paints, varnishes, sealants, and adhesives used in construction and remodeling. Composite wood products, such as particleboard and plywood, often contain formaldehyde-based resins that release VOCs into the home environment. New furnishings, including carpets, vinyl flooring, and upholstered furniture, also contribute significantly as glues, dyes, and finishes evaporate.
Cleaning and personal hygiene products introduce common sources of short-term, high-concentration VOCs. Solvents in cleaning supplies release VOCs during and immediately after use. Other sources that contribute to the overall TVOC load include:
- Aerosol sprays, air fresheners, and disinfectants.
- Cosmetics, perfumes, and nail polish.
- Stored fuels, hobby supplies, and certain activities like smoking or burning wood.
Strategies for Reducing VOC Exposure
Controlling the sources of VOCs is the most effective approach to improving indoor air quality. Homeowners should prioritize choosing products labeled as “low-VOC” or “zero-VOC” for paints, adhesives, and sealants during any renovation or decorating project. Air out new furnishings, such as new carpets or furniture, in a well-ventilated space before bringing them fully into the living area.
Ventilation works to dilute and remove airborne VOCs from the indoor environment. Increasing the flow of fresh outdoor air by opening windows and doors, when weather permits, is a simple and immediate method to lower concentrations. Using local exhaust fans in kitchens and bathrooms is also an effective way to remove airborne contaminants directly from the room where they are generated.
Air filtration requires the correct type of filter to be effective against gases. Standard HEPA filters capture solid particles like dust and pollen, but they are ineffective against VOC gas molecules. For gaseous contaminants, an air purifier must contain an activated carbon filter, which uses adsorption to chemically trap the VOC molecules onto the surface of the carbon material.