Outdoor decks can be perfect for al fresco meals, neighborly get-togethers, and stargazing. However, depending how they’re constructed and cared for, they can also take a toll on the environment and may even pose risks to those using them. If you’ve got a deck in need of refurbishing, or plans to add one to your home this spring or summer, there are steps you can take to make it as healthy as possible for your family and the Earth.

Deck Materials Matter

Decks need to be constructed of materials that can withstand being exposed to weather, insects, and other threats. Cedar and redwood have been popular choices because they’re strong and naturally rot-resistant, but these trees are often logged from endangered forests. Deck builders who want to minimize their harmful impacts on forests have two choices: recycled-plastic lumber and forest-friendly wood.

Plastic lumber is a low-maintenance deck material, because it doesn’t require sealing, staining, painting, waterproofing, or insect-proofing. The most environmentally friendly plastic lumber is made from post-consumer recycled plastic, and buying it can help keep plastic grocery bags, beverage containers, and other items out of landfills.

The Healthy Building Network (HBN) has produced a “Guide to Plastic Lumber” that offers guidelines for plastic-lumber purchases based on environmental, public-health, and recycling considerations. It suggests selecting plastic lumber that has a high percentage of post-consumer recycled content and is made of high-density and low-density polyethylene (HDPE and LDPE), because these are recyclable and made with fewer chemical hazards and impacts than other plastics. HBN recommends avoiding fiberglass-reinforced, polyvinyl chloride (PVC) or polystyrene plastic lumbers because they are associated with more chemical hazards throughout their life cycles.

If you think natural wood is the best option for your deck, look for a forest-friendly source of strong, rot-resistant wood, such as redwood or tropical hardwood. Wood bearing the Forest Stewardship Council (FSC) logo is guaranteed to have come from a forest that’s managed for long-term sustainability. (Such wood may also bear the name of Smartwood or Scientific Certification Systems, which certify wood products meeting FSC standards.) Metafore’s certifiedwood.org Web site has a database you can search for certified-wood retailers in your area. Following pressure from forest advocates, the national chains Home Depot and Lowe’s now carry FSC-certified wood. You can also ask your local lumber supplier if they stock certified wood; if they don’t, let them know you’d like to buy it from them and direct them to the FSC.

Salvaged wood from trees felled during storms can also be a forest-friendly option, although you may have to search to find the quantity and type of wood suitable for a deck.

Some “composite” deck materials made of a blend of wood and recycled plastic are available, and these look more like natural wood than plastic lumber does. The wood used may be reclaimed or scrap wood, reducing its impact on forests. However, HBN recommends avoiding these composites because, being a blend of wood and plastic, they can’t be recycled once their useful lives have ended. Composite supporters counter that because the lumber is made of recycled or reclaimed materials and is long-lasting, it’s still a good environmental choice.

The Arsenic Angle

In 2001, the Environmental Working Group (EWG) and HBN released a report entitled “Poisoned Playgrounds” that drew attention to the problem of pressure-treated wood, which was widely used in playgrounds, decks, and outdoor furniture. To kill insects and prevent rot, this wood was treated with chromium copper arsenate (CCA)—or, in plainer terms, arsenic, a known carcinogen. EWG estimated that a 40-pound child playing daily on CCA-treated wood could be exposed to five times the arsenic allowed under EPA drinking water standards. The group cites studies showing that arsenic sticks to children’s hands when they play on treated wood, and is absorbed through the skin and ingested when they put their hands in their mouths.

EWG and HBN petitioned the US Consumer Product Safety Commission (CPSC) to ban arsenic-treated wood in playground equipment and review its safety for use in other consumer items; at the same time, Clean Water Action coordinated a consumer campaign asking Home Depot and Lowes to stop selling arsenic-treated wood. The CPSC and Environmental Protection Agency (EPA) studied the issue, and in 2002, the EPA announced a voluntary agreement with the wood-treatment industry to cease sales of CCA-treated wood for most residential uses by the end of 2004.

If you have a wooden deck that was built before 2005, you can get a test kit from EWG or HBN to see if it contains arsenic. If it does, the organizations advise replacing it, or at least replacing the parts such as steps and handrails that are heavily used and thus have more potential for exposing users to arsenic. EWG also offers several recommendations for minimizing arsenic exposure from CCA-treated wood, including:

• Seal the wood at least every six months with standard penetrating deck treatments.
• Wash your hands and your children’s hands after every exposure to arsenic-treated wood.
• Keep children and pets away from soil beneath and immediately surrounding an arsenic-treated deck, and don’t store tools or toys underneath it.
• Don’t pressure wash or sand arsenic-treated wood—both will release arsenic-contaminated particles. Use soap and water instead. (If your deck has become too rough, keep children from playing there, because arsenic-treated-wood splinters can be dangerous.)
• Don’t use commercial “deck washing” solutions. These can convert chemicals on the wood to a more toxic form.

If you decide to remove a CCA-treated wood deck, contact your local waste disposal authority and find out how to deal with it properly—it will generates toxic fumes and ash if incinerated, and the CCA can leach from unlined landfills. Also, test the soil near the deck to see if it’s contaminated; EWG has test kits available.

Finishing Safely

If you have a wooden deck—or deck furniture made of wood—you’ll probably want to treat it with a wood finish, such as stain or varnish, for protection against the elements. (Many home-owners do this every year or two.) It’s best to avoid finishes that contain high levels of volatile organic compounds (VOCs), which can cause health problems from dizziness to lung and kidney damage and are infamous for polluting both indoor and outdoor air. The nonprofit Green Seal has published a “Choose Green Report” on wood finishes, which notes that finishes can also contain other problematic substances—including phthlates, fungicides, and the aromatic solvents toluene and xylene—that could harm human health.

Green Seal reports that most US companies are formulating finishes that comply with California’s regulations on VOC content, which set maximums of 350 grams/liter of VOCs in varnish and 250 grams/liter in stains. Their “Choose Green Report” lists several wood finishes that exceed these VOC standards and also do not contain carcinogens, aromatic solvents, phthalates, heavy metals, reproductive toxins, or ozone-depleting chemicals. When shopping for stains, look for ingredient lists free of these substances, and seek out low- or no-VOC finishes, such as those listed in the box below.

Advice on the community-based Web site GreenHomeGuide recommends water-based sealers for their low environmental and health impacts, ease of handling and cleanup, and durability. It suggests avoiding water-based sealers that contain glycol ethers, which are toxic and sometimes used as solvents in these sealers—though if you find them unavoidable, propylene glycol and ethylene glycol are less-toxic types.

The site also features a Clear Coatings Directory reviewed by green-building professionals. Once you’re done sealing or staining your deck or your outdoor furniture, be sure to dispose of leftover sealant or stain responsibly. Store it safely for touch-ups, donate it to a local school or community group that can use it, or call your local waste authority to determine the proper disposal method. Then sit back and enjoy your deck.