The follow articles are from the GreenHomeGuide. http://www.greenhomeguide.com/
Clear finishes protect wood from wear, moisture and aging, but they can degrade the environment—in your home and elsewhere. When selecting a clear finish, we recommend considering the environmental impact of its manufacture and disposal, its effect on indoor air quality, and its durability.
The environmental impact of clear-finish manufacture and disposal ranges from high (for the energy-intensive and polluting manufacture of petroleum-based solvents) to low (for the extraction of natural oil from tung tree nuts). All clear finishes must be disposed of as hazardous waste, so it’s best to buy only the amount you need.
Like paints, clear finishes can contain high levels of volatile organic compounds (VOCs), which contribute to air pollution and can cause health problems. (See About VOCs for more information.) Finishes have a greater effect than paint on your home’s air quality, however, because they must be reapplied more frequently on high-use surfaces like floors, tables and chairs. Toxic and polluting ingredients such as toluene and xylene are common solvents; carcinogens such as arsenic, beryllium, and cadmium can be used as drying agents in linseed oil; and toxic glycol ethers may be used as solvents in many water-based sealers.
All clear finishes are made of a carrier, or solvent, which keeps the finish liquid in the container and evaporates as the finish dries, and a binder, or resin, which protects the surface. Finishes may also contain additives to speed drying or provide fungicidal properties. All these elements contribute to a finish’s environmental impact.
Solvents can be derived from petroleum-based or synthetic materials as well as from materials as simple as linseed oil or water, and can vary within a type of finish: some types of lacquer, for example, use water as a solvent while others use oil. The binder determines a finish’s function, durability and category (lacquer, natural oils, shellac, and so on). Additives may be toxic, though not all are.
Clear finishes vary in their durability and ability to protect wood from heat, water and chemicals. Lacquer, shellac, varnish and water-based sealers coat wood, forming a protective layer on the surface; natural oil sealers penetrate wood, prolonging the wood’s life but leaving the surface susceptible to scuffs and dirt.
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 ten times as high as outdoor concentrations, and can climb up to a thousand times as high as outdoor concentrations when you are applying paint.
While it is important to check VOC content on labels and MSDSes, those sources won’t necessarily tell the whole story. 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.
Beyond VOCs, many paints and coatings are made with 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.
We recommend you maximize ventilation, in addition to selecting the highest quality, lowest toxicity coating that fits pocketbook and project. When buying furniture or flooring ask for finishes to be factory applied. If that’s not possible, install porous materials in your home well after finishes have dried.
See this Q&A with indoor air quality scientist Al Hodgson for tips on reducing chemical exposures from painting. For a list of products picked by green pros, see GreenHomeGuide’s directories of recommended paints, stains, and clear coatings.