Cleaning up indoor air quality – VOCs & paint

Indoor air quality is important to our health and wellbeing. Studies have shown that concentrations of volatile organic compounds (VOCs) are consistently higher indoors than outdoors, with some VOC concentrations up to 10 times higher indoors. Some scientists believe that indoor pollutants are 1,000 times more likely to be inhaled as compared to outdoor pollutants because we spend about 90% of our time indoors, our activities put us near sources of indoor air pollutants, and indoor emissions are partially trapped inside buildings.

Household cleaners, scented products, and paints and coatings contribute to indoor air pollution.  Although emissions from paints and coatings are highest during and immediately after application, they release low levels of toxic emissions into the air for years after application.  Some paint-related activities can dramatically increase indoor air concentrations of VOCs.  A basic science lesson:  a paint consists of a resin (or binder), a carrier, and pigments that gives the paint its color.  Once the paint is applied to a surface, the carrier evaporates, leaving behind the solid coating.  The carrier is usually a VOC.

VOCs are chemicals that contain at least one carbon atom and that easily evaporate at ambient temperature.  VOCs are emitted as gases from certain liquids and solids.  In other words, VOCs readily volatilize, or evaporate, out of the solid or liquid into the air we breathe.  You are familiar with VOCs.  The smell of gasoline?  VOCs evaporating.  The scent of a freshly mowed lawn?  VOCs evaporating. In fact, isoprene and monoterpenes are two of the most common VOCs emitted from vegetation. Monoterpenes (VOCs) give us pine, lemon, and many floral scents.

The term “VOC” is often used in a precise regulatory context, and the definition is defined by laws.  From a regulatory perspective, VOCs are usually of concern because they evaporate at room temperature and then react in sunlight to help form ground-level ozone, an integral component of photochemical smog.  These VOCs are referred to as smog precursors.  Smog is that green haze that hangs over many large cities, and that we are working to eliminate.

But you are probably more concerned with VOCs because they have health effects.  VOCs can cause respiratory distress; skin and eye irritation; headaches; nausea; muscle weakness; and even more serious ailments and diseases.  For example, formaldehyde, a VOC often found in the home because of its presence in engineered wood products, including furniture, cabinetry and building materials, is considered a probable carcinogen by the EPA, is listed on California’s Proposition 65 list of chemicals known to the state of California to cause cancer, is genotoxic (damaging to genetic material), and also causes eye, nose and throat irritation.

When it comes to trying to reduce toxic chemical exposures, understanding the regulatory framework is important for any class of products.  For example, if you buy a paint labeled “low VOC”, you are usually buying a paint that has low VOC content based upon the definition of VOC under the federal Clean Air Act.  In this context, VOCs are defined in terms of photochemical reactivity (ability to form ozone), and not toxicity.  In the regulatory context, certain VOCs are exempt from regulation because they are not photochemically reactive (they are not smog pre-cursors).  However, these VOCs may be toxic.  For example, methylene chloride and 1,1,1-trichloroethane are not considered photochemically reactive, so they are exempt.  But they are associated with adverse health effects.

Methylene chloride is irritating to the skin, eyes and respiratory tract and is identified as a probable carcinogen by the EPA. 1,1,1-trichloroethane is not classifiable as to its carcinogencity in humans.  However, animal studies have shown that 1,1,1-TCAcan pass through the placenta.  Babies of pregnant mice exposed to high concentrations ofTCAdeveloped more slowly and demonstrated behavioral problems. So, even if the paint is low-VOC, you may still want to skip it.  Plus, the amount of VOCs is the amount in the base coating.  The colorant added to the paint may have VOCs, so you need to consider the VOC content of the base plus colorant.

How do you find the right paint?  Conventional paints are generally classified into two categories:  latex (or water based) paints (in which the carrier is water), and oil based paints (in which the carrier is an organic solvent).  When you use oil based paints, the carrier, an organic solvent VOC, evaporates after application and pollutes the air.  Latex paints do not use solvents as the primary carrier so VOC emissions are minimized.  So latex paints are usually a better choice over oil based paints to reduce toxic chemical exposures.  However, latex paints may use solvents to emulsify the binder, which are emitted after application, so they may still be problematic.

Paints labeled as “low VOCs” or “zero VOCs” may have fewer toxins present than conventional paints.  However, remember the earlier discussion about regulatory context?  The low or zero VOC paint is designated as such designed for photochemical reactivity (whether or not it is a smog precursor) and/or odor, not the amount of toxins.  The assumption that paints labeled as odor-free or containing low or no VOC’s are free of toxicants is false. While these paints are environmentally friendly, and I am all for reducing smog, they may still have some toxic chemicals present.  Look for the VOC content in grams per liter on the paint label – choose one with the lowest number.  Generally speaking, and keeping in mind that VOC content is regulated for smog formation potential, not health effects, a paint that says “Maximum VOC Content:  45 grams/liter” is preferable to one with a higher number.

Also, there are several specific private certifying companies that consider toxicity as well as simply regulatory VOC content limits. More on these in a separate blog post.

In addition to VOCs, you should look out for other potentially toxic ingredients, such as ammonia, crystalline silica, fungicides, and biocides.  Biocides include copper, arsenic disulfide, phenol, and formaldehyde.  Almost all paints contain toxic preservatives.  The amounts are relatively low, but you may want to consider biocide-free paints.  Also check the pigment used to make the color.  For both the paint and the pigment, ask the manufacturer or supplier for the MSDS (or get it off the web), which should identify the ingredients and have a section on health effects.

Another option is natural based paints and finishes.  These paints are made from natural raw ingredients such as plant oils, plant dyes, clay, chalk, milk casein, and bees’ wax.  Natural paints typically use linseed and soy oils as binders, pine- and balsam-derived terpenes or citrus oils as carriers, minerals and sometimes plant-derived compounds as pigments, and lime and chalk as thickeners.  These paints are preserved by linseed oil or other natural ingredients.  Although natural paints and finishes do not contain petroleum products, they may still emit VOCs from ingredients like citrus based solvents.  Some of these contain essential oils which can cause allergic reactions.  Certain natural oil paints emit odors or compounds, such as those from citrus oil, which chemically sensitive people may find hard to tolerate.  Mineral, lime and milk paints are generally well tolerated and are the least toxic paints available.   But, always check the ingredient list or MSDS.  Not all “natural” materials are safe.  Cadmium may be used as a bright yellow pigment, but cadmium is toxic.

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  1. The Environmental Protection Agency (EPA) advocates three basic strategies to improving indoor air quality. (1) Source Control: “Usually the most effective way to improve indoor air quality…” (2) Improved Ventilation: “Another approach to lowering the concentrations of indoor air pollutants…” and (3) Air cleaners. Check out this blog to learn more about VOCs and how to remove contaminants in the air at:

  2. That’s fascinating about low-VOC paint being designated for ozone not human health reasons, I had no idea. Thanks!

  3. really a great post and valuable information.

  4. Hi! I could have sworn I’ve been to this blog before but after browsing through some of the post I realized it’s new to me. Anyhow, I’m definitely glad I found it and I’ll be bookmarking and checking back often!


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