Selecting green paint

Alex Pennock, Mary Cordaro, Miriam Landman and Willem Maas.

A new coat of paint or stain can make a room feel fresh again, but it often has the opposite effect on the air quality in your home. Paints, stains and other architectural coatings can create volatile organic compound (VOC) emissions, as do many consumer and commercial products, as well as automobiles.

VOCs are carbon compounds that evaporate at room temperature and react in sunlight to help form ground-level ozone, an integral component of photochemical smog. VOCs can cause respiratory, skin and eye irritation; headaches; nausea; muscle weakness; and more serious ailments and diseases, according to the EPA. Formaldehyde, a VOC commonly found in paint, is a probable carcinogen. The EPA has found that indoor concentrations of VOCs are regularly up to 10 times as high as outdoor concentrations, and can climb up to a thousand times as high as outdoor concentrations when you are applying paint.

This overview covers the environmental and health impacts associated with most types of paint on the market. A good coat of paint should last years, so your choice is significant for your home, your health and the environment.

Quick links to materials

• Latex paints
• Natural paints
• Oil paints

VOCs and beyond

When considering the VOC content of any product, keep in mind that EPA and state and local rules are intended to reduce emissions of VOCs that cause smog, not to improve indoor air quality. These rules allow paints labeled “zero-VOC” or “no-VOC” to contain up to five grams of VOCs per liter (g/L) in addition to VOCs that have been exempted from the rules.

The GS-11 paint standard developed by the nonprofit organization Green Seal sets comprehensive environmental requirements for low-VOC, low-toxic paints; the standard was updated (with more stringent requirement) in 2008. To be certified by Green Seal, flat paints cannot contain more than 50 g/L of VOCs, and non-flat paints cannot contain more than 100 g/L of VOCs.

Low- and no-VOC paints may also contain other compounds that affect air quality. While some of these are known and can be avoided, others are not. Manufacturers are not required to disclose all the chemicals used in their products; some ingredients are deemed proprietary information or are used in such small quantities that they do not have to be reported.

Beyond indoor air pollutants, many paints are made with other toxic substances and chemicals that come from nonrenewable resources or are energy-intensive or polluting to produce, so even no-VOC paints and stains can affect the environment. Green Seal’s paint certification standards prohibit numerous non-VOC compounds, including heavy metals, carcinogens and ozone-depleting compounds.

Composition of paint

Paint has three main components: Pigment gives it color; the binder or resin makes the pigment stick when the paint is applied and forms a solid layer of paint; and the carrier or solvent keeps the paint in liquid form and evaporates once the paint is exposed to air. Other additives are sometimes used to thicken paint (such as chalk, which is nontoxic) or give it characteristics such as mold resistance (which requires toxic materials).

Pigment can contribute to a paint’s emissions in a significant way. Much of the latex and oil paint sold in stores comes as white base paint, and colorants (composed of pigments in liquid form, soaps and sometimes solvents) are added to create the desired color at the time of purchase. Pigments add some VOCs to the base paint, so actual VOC emissions will almost always be higher than those quoted on the base paint. The deeper the hue, the more pigment needed, and therefore the more VOCs the colored paint contains. If you must paint in deep, dark shades, consider purchasing paint from a no- or low-VOC line that includes no- or low-VOC pigments.

Toxic substances used in a pigment should be listed on its material safety data sheet (MSDS). Avoid cadmium, chromium, mercury and other heavy metals. Titanium dioxide, which gives white latex and oil paints their base color and accounts for about 25 percent of these paints by weight, is very energy-intensive to produce, so paint containing it creates a certain amount of energy-related pollution before accounting for the binder and carrier.

In the categories below, we differentiate between types of paint based on their binders, since the binders tend to dictate a paint’s characteristics and applications. Both the binder and the carrier, however, can contribute to a paint’s overall environmental and health impact.

Latex paints (acrylic or vinyl acetate binders)

Because they use water as the carrier rather than petroleum-based solvents, latex paints have lower VOC levels than oil-based paints. Although they don’t cover stains as well as their oil-based counterparts, low- and no-VOC latex paints perform well for most household applications, and high-quality latex paint can be as durable as an oil paint. Latex paint actually contains no latex, so it won’t affect people with latex allergies.

Latex paint cleans up easily with water, so you don’t need harsh VOC-emitting solvents to work with it. It can also be “recycled” by combining leftovers; oil paints cannot be recycled in this way.

Using recycled latex paint avoids the manufacturing impact, but recycled paint may not be made of low-VOC paint, so it is best suited to well-ventilated areas like the interior of a garage or shed. Green Seal now has a standard for Recycled-Content Latex Paint (GS-43); paints that are certified under this standard cannot contain more than 250 g/L of VOCs.

We recommend using paints that are free of fungicides and biocides like formaldehyde. Although latex paints are biocide-free to begin with, almost all manufacturers add synthetic biocides, or “can preservative,” to extend shelf life. Manufacturers are not required to list biocides on a paint’s MSDS because they are added in such small amounts, but some paints are labeled biocide- or fungicide-free. If you do not see this on the label and want to avoid biocides, call the manufacturer to determine if biocides are included in the formulation.

One hundred percent acrylic paint is more water-resistant than vinyl acetate paint and is good for kitchen, bath and exterior applications. Vinyl acetate paint is adequate for most indoor applications and is less expensive. Look for solids content of over 30 percent to hide stains, cover in fewer coats, and cover more surface area per gallon. This information should appear on the paint’s label or technical data sheet (TDS).

Almost every major brand of latex paint now has a low-VOC or zero-VOC product line; many of these products are also low-odor. See the list of low-VOC and zero-VOC paints that have been certified by Green Seal (which include regular as well as recycled paints). For a longer list of recycled paint manufacturers, see the Product Stewardship Institute’s list. 

Natural paints (natural oil or casein binders)

“Natural” paints are made mostly of renewable or abundant, naturally occurring materials such as citrus oil, lime, clay, linseed oil, casein and chalk. These paints can create a vibrant, nicely textured, “old world” or “wash” look (particularly lime plaster paints) or a look similar to traditional even-toned paints. Because natural paints do not contain petroleum products, they emit few if any of the VOCs the EPA regulates for smog, though they may contain significant amounts of other VOCs from ingredients like citrus-based solvents.

Overall, natural paints are healthier and more environmentally sound than latex or oil paints. 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 (like chrome oxide for green) and lime and chalk as thickeners. These paints are preserved by linseed oil or other natural ingredients. The manufacturing process for most natural paints is cleaner than for other paint types, with some manufacturers claiming that they produce no hazardous waste.

Certain natural oil paints, however, 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. Not all natural materials are safe: for example, cadmium, used as a bright yellow pigment, is toxic. Check the MSDS and ingredient lists when considering natural paints. 

Milk-based paint—made from powdered casein, a milk protein—is the simplest, least toxic and least environmentally damaging paint. It contains no VOCs, lead, formaldehyde, oils or biocides. You can buy milk-based paint premixed or mix it yourself, which saves shipping costs and transport-related pollution. (Note that a premixed, wet-in-the-can milk paint must contain a can preservative to extend shelf life.)

Because each milk paint batch you mix will be a slightly different color, and the mix’s shelf life is short, touching up the paint a month later requires a new batch, which may not be a perfect color match to the original. After application, heavy moisture can damage milk-based paint and lead to mold growth, so it is unsuitable for the kitchen or bathroom; it is best on raw, clean wood, where it gives a soft, old-world look. If you apply a layer of sealer on top of milk-based paint, make sure it is a low-VOC, water-based sealer; otherwise you will negate many of the paint’s health and environmental benefits. For lists of low-VOC sealers (and other coatings and finishes), see the Green Seal and Greenguard listings.

Natural paints do have some disadvantages. They can cost 20 to 80 percent more than latex or oil paints, many paint stores don’t sell them and they may meet resistance from painters used to conventional paints. In addition, natural paints take two days or more to dry rather than the one day latex paints take, and they are not always compatible with existing synthetic latex paint surfaces, so more extensive prepping and priming may be necessary. In some cases, natural paint manufacturers use synthetic (and not always nontoxic) additives for better compatibility with existing surfaces.

Oil paints (petrochemical/synthetic binders)

Oil paints, also known as alkyd or enamel paints, use binders derived from petrochemicals. Oil paints’ high durability, scrubability and water resistance make them well suited to high-abuse areas like kitchens, bathrooms and hallways, and to exterior applications. They also give the highest gloss finish of all paints.

The manufacture of binders for oil paints is more environmentally harmful than that of latex paints. And because of their petroleum-based binders and carriers, oil paints typically emit more VOCs than other paint types. Oil paints contain more compounds with known health effects, such as formaldehyde, toluene, xylene and benzene, and take longer to dry, allowing higher concentrations of VOCs to be emitted for longer periods of time.

On the plus side, oil paints typically require fewer coats, which could reduce the total amount of VOCs emitted during the painting process and the lifetime of the painted surface. Oil paints also contain naturally occurring preservatives, so they are inherently toxic to mold and mildew and require fewer additional biocides than latex paints.

Oil paints are widely available, and some are less expensive than latex paints, but latex paints account for over 70 percent of household paint sales—with good reason. Disposing of oil paints is difficult because they cannot be recycled as latex paints can, but must be “downcycled” into other petroleum-based products or incinerated for energy after they are brought to disposal sites. Cleaning up oil paints typically calls for the use of solvents that release VOCs (though vegetable oil can be used as an alternative to toxic cleaning solvents). Beyond durability (paint longevity) concerns, at no stage in oil paints’ life cycle, from petroleum extraction to paint disposal, are they cleaner or greener than latex or natural alternatives. For indoor applications, they should be used only where necessary.

When buying oil paints, look for the lowest-VOC product that will do the job. The EPA requires VOC content of less than 380 g/L, but check a paint’s MSDS for lower levels; some oil-based paints now contain less than 100 g/L of VOCs. Mercury-free oil paints are also available; this heavy metal and other toxins should be disclosed on the MSDS.

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