Pressure treated wood is a staple in outdoor construction, from decks and fences to playgrounds and garden beds. Its resistance to rot, decay, and insect infestation makes it an invaluable material. However, concerns about the chemicals used in the pressure treating process have led many to question its safety. This article aims to provide a comprehensive overview of the potential hazards associated with pressure treated wood, exploring its history, the chemicals involved, safe handling practices, and environmentally friendly alternatives.
Understanding Pressure Treated Wood and its Purpose
Pressure treated wood is lumber that has been chemically treated to resist decay from fungus and attack from insects, primarily termites. This treatment involves forcing preservatives deep into the wood fibers under high pressure, making it significantly more durable than untreated wood, especially in outdoor environments. The lifespan of pressure treated wood can extend for decades, making it a cost-effective choice for many construction projects.
The need for pressure treated wood arose from the limitations of naturally durable wood species. While some woods, like redwood and cedar, possess inherent resistance to decay, they are often more expensive and less readily available than commonly used lumber like pine and fir. Pressure treatment bridges this gap, making readily available wood suitable for applications where rot and insect damage are significant concerns.
The History of Wood Preservatives
The use of wood preservatives dates back centuries, with early methods involving substances like creosote. However, modern pressure treatment methods emerged in the 20th century. The chemicals used have evolved over time due to concerns about their environmental impact and human health.
Initially, chromated copper arsenate (CCA) was the dominant preservative. CCA was highly effective in protecting wood from decay and insects, but it contained arsenic, a known carcinogen. Concerns about arsenic leaching from treated wood led to a voluntary phase-out of CCA for most residential applications in the United States in 2003.
The Shift Away from CCA
The decision to phase out CCA was largely driven by public awareness and scientific studies demonstrating the potential for arsenic to leach from treated wood, especially in contact with soil or water. While the risk from incidental contact was considered low, the potential for long-term exposure, particularly for children playing on CCA-treated structures, raised concerns.
Following the CCA phase-out, alternative preservatives were introduced, including alkaline copper quaternary (ACQ), copper azole (CA), and micronized copper azole (MCA). These preservatives are considered less toxic than CCA and are now widely used in residential and commercial applications.
Current Preservatives in Pressure Treated Wood
Today’s pressure treated wood primarily uses copper-based preservatives. Copper is effective in preventing fungal decay, and it is combined with other chemicals to enhance its effectiveness against insects and to help it penetrate the wood fibers.
Alkaline Copper Quaternary (ACQ): ACQ uses copper and quaternary ammonium compounds. Quaternary ammonium compounds act as co-biocides, enhancing the efficacy of the copper against a broader spectrum of fungi and insects.
Copper Azole (CA): CA combines copper with azole compounds, which are also fungicides. This combination provides broad-spectrum protection against decay and insect attack.
Micronized Copper Azole (MCA): MCA uses finely ground copper particles, which allows for better penetration into the wood and a more even distribution of the preservative. This can lead to improved performance and a more natural-looking finish.
While these preservatives are considered safer than CCA, it is essential to understand their potential hazards and to handle treated wood properly.
Potential Hazards of Current Preservatives
Even with the shift away from arsenic-based preservatives, it’s crucial to acknowledge potential risks. Although the newer preservatives are less toxic, they are still chemicals designed to kill living organisms, and therefore, require careful handling.
Copper, while essential in trace amounts for human health, can be toxic in higher concentrations. Exposure to copper can cause gastrointestinal issues and other health problems. The azole compounds used in CA and MCA are also designed to be biocides, meaning they can be harmful to living organisms.
Safe Handling Practices for Pressure Treated Wood
Proper handling of pressure treated wood is crucial to minimize potential exposure to the chemicals it contains. These practices apply to both the installation and disposal of the wood.
Wear Protective Gear: When working with pressure treated wood, it is essential to wear gloves, a dust mask, and eye protection. Gloves will prevent direct skin contact with the preservatives, while a dust mask will protect against inhaling sawdust. Eye protection will prevent wood particles and preservative dust from entering the eyes.
Work in a Well-Ventilated Area: Cutting, sanding, or machining pressure treated wood should be done outdoors or in a well-ventilated area to minimize inhalation of sawdust.
Avoid Burning Treated Wood: Burning pressure treated wood releases toxic chemicals into the air. It should never be burned in fireplaces, stoves, or open fires.
Proper Disposal: Pressure treated wood should be disposed of according to local regulations. Many communities have designated disposal sites for treated wood.
Wash Hands Thoroughly: After handling pressure treated wood, wash hands thoroughly with soap and water, especially before eating, drinking, or smoking.
Minimizing Exposure in Existing Structures
If you have existing structures made of CCA-treated wood, such as decks or playgrounds, there are steps you can take to minimize potential exposure.
Apply a Sealer: Applying a penetrating oil-based sealer or stain to the wood can help to reduce the leaching of chemicals. Reapply the sealer every one to two years, as needed.
Wash the Surface Regularly: Regularly washing the surface of the wood with soap and water can help to remove any surface residue of preservatives.
Consider Replacement: If you are concerned about the potential risks of CCA-treated wood, you may consider replacing it with newer pressure treated wood or alternative materials.
Environmentally Friendly Alternatives to Pressure Treated Wood
For those seeking more environmentally friendly options, several alternatives to pressure treated wood are available.
Naturally Durable Wood: Woods like redwood, cedar, and black locust are naturally resistant to decay and insect attack. These woods can be used untreated in many outdoor applications. However, they are often more expensive and may not be as readily available as pressure treated wood.
Wood-Plastic Composites (WPC): WPC is made from a combination of wood fibers and recycled plastic. It is resistant to rot, decay, and insect infestation, and it requires minimal maintenance. WPC is often used for decking, railing, and other outdoor applications.
Bamboo: Bamboo is a rapidly renewable resource that is naturally resistant to decay and insect attack. It is a strong and durable material that can be used in a variety of outdoor applications.
Recycled Plastic Lumber: Recycled plastic lumber is made from recycled plastic materials, such as milk jugs and plastic bags. It is resistant to rot, decay, and insect infestation, and it requires minimal maintenance.
Comparing the Alternatives
Each alternative has its own set of pros and cons, and the best choice will depend on the specific application and budget.
Naturally durable woods offer a natural look and feel, but they can be expensive and may require more maintenance than pressure treated wood. WPC is a low-maintenance option, but it can be more expensive than pressure treated wood and may not have the same natural appearance. Bamboo is a sustainable option, but it may not be suitable for all applications. Recycled plastic lumber is a durable and low-maintenance option, but it can be more expensive than pressure treated wood and may not have the same structural strength.
Conclusion: Weighing the Risks and Benefits
Pressure treated wood offers significant advantages in terms of durability and cost-effectiveness, but it is essential to be aware of the potential hazards associated with the chemicals used in the treatment process. By understanding the history of wood preservatives, the current chemicals used, and safe handling practices, you can minimize potential exposure and make informed decisions about the use of pressure treated wood in your projects.
While newer preservatives are considered less toxic than CCA, they are still chemicals and should be handled with care. Wearing protective gear, working in well-ventilated areas, and properly disposing of treated wood are essential practices.
If you are concerned about the potential risks of pressure treated wood, consider exploring environmentally friendly alternatives such as naturally durable woods, wood-plastic composites, bamboo, or recycled plastic lumber. Ultimately, the decision of whether or not to use pressure treated wood depends on your individual needs, preferences, and risk tolerance. By carefully weighing the risks and benefits, you can make an informed choice that is right for you and your project.
What exactly is pressure-treated wood, and why is it treated?
Pressure-treated wood is lumber that has been impregnated with chemical preservatives to protect it from decay, insects, and fungal attacks. The wood is placed in a large cylinder, and a vacuum is created to remove air. Then, the preservative solution is forced into the wood under high pressure, allowing it to penetrate deep into the wood’s cellular structure. This process greatly extends the lifespan of the wood, making it suitable for outdoor applications where untreated wood would quickly rot or be destroyed by pests.
The primary reason for treating wood is to improve its durability and longevity, particularly when exposed to moisture, soil, or other harsh environmental conditions. Untreated wood is susceptible to rot, decay, and insect infestation, requiring frequent replacement and increasing maintenance costs. Pressure treatment offers a cost-effective solution for extending the service life of wood in decks, fences, landscaping, and other outdoor structures.
What chemicals are commonly used in pressure-treated wood?
Historically, chromated copper arsenate (CCA) was the most widely used preservative in pressure-treated wood. However, due to concerns about arsenic leaching into the environment and potential health risks, CCA was phased out for residential use in 2003. Today, the most common preservatives include alkaline copper quaternary (ACQ), copper azole (CA), and micronized copper azole (MCA). These preservatives are generally considered safer alternatives to CCA.
While newer preservatives like ACQ, CA, and MCA are less toxic than CCA, they still contain copper, which can be harmful to aquatic life and may cause skin irritation in some individuals. Therefore, it is important to handle pressure-treated wood with care, wearing gloves and eye protection when cutting or working with it. Always follow the manufacturer’s recommendations for safe handling and disposal.
Is pressure-treated wood safe for vegetable gardens or playgrounds?
For vegetable gardens, it is generally not recommended to use pressure-treated wood that was treated prior to 2003 with CCA. Although current preservatives are safer, some concerns remain about potential leaching of copper and other chemicals into the soil, which could be absorbed by plants. Consider using untreated cedar or naturally rot-resistant wood species, or using plastic or metal barriers to separate the treated wood from the soil.
For playgrounds, pressure-treated wood is typically considered safe, as the chemicals are bound tightly to the wood fibers. However, it’s always advisable to check with the manufacturer’s guidelines and local regulations. Some playgrounds may opt for alternative materials like recycled plastic or naturally rot-resistant wood species to minimize potential exposure, especially for young children who may be more susceptible to the effects of chemicals.
Can pressure-treated wood leach chemicals into the environment?
Yes, pressure-treated wood can leach chemicals into the surrounding environment, although the rate and extent of leaching depend on several factors, including the type of preservative used, the age of the wood, soil conditions, and rainfall. Older CCA-treated wood is known to leach arsenic, while newer preservatives like ACQ, CA, and MCA can leach copper. The amount of leaching is generally low and decreases over time as the preservative becomes more tightly bound to the wood.
To minimize the environmental impact of leaching, several precautions can be taken. Seal the wood with a water-resistant coating to reduce water absorption and leaching. Avoid using pressure-treated wood near bodies of water or sensitive ecosystems. When removing or replacing pressure-treated wood, dispose of it properly at a designated landfill that accepts treated wood waste. Never burn pressure-treated wood, as this releases harmful chemicals into the air.
How should I safely cut and handle pressure-treated wood?
When cutting or handling pressure-treated wood, it is essential to wear personal protective equipment (PPE) to minimize exposure to wood dust and chemicals. This includes wearing gloves, safety glasses, and a dust mask or respirator. Cut the wood outdoors or in a well-ventilated area to avoid inhaling wood dust. After handling pressure-treated wood, wash your hands thoroughly with soap and water.
Avoid eating, drinking, or smoking while working with pressure-treated wood. Collect sawdust and scraps in a container and dispose of them properly according to local regulations. Never burn pressure-treated wood, as this releases toxic chemicals into the air. Use fasteners, such as screws and nails, that are designed for use with pressure-treated wood to prevent corrosion.
What is the proper way to dispose of pressure-treated wood?
The proper disposal of pressure-treated wood is crucial to prevent environmental contamination. Never burn pressure-treated wood, as this releases harmful chemicals into the air. Instead, take the wood to a designated landfill that accepts treated wood waste. Contact your local waste management authority to determine the nearest landfill that accepts treated wood.
Do not use pressure-treated wood as mulch or compost, as this can contaminate the soil. If you have a large quantity of pressure-treated wood to dispose of, consider contacting a professional waste disposal company. They can provide guidance on proper handling and disposal methods. Recycling pressure-treated wood is not widely available, but research is ongoing to develop safe and effective recycling processes.
Can I seal or stain pressure-treated wood?
Yes, you can seal or stain pressure-treated wood, but it’s essential to allow the wood to dry thoroughly before applying any finish. Pressure-treated wood is often saturated with moisture from the treatment process, and sealing or staining it prematurely can trap moisture, leading to mildew or decay. Allow the wood to dry for several weeks or months, depending on the climate and humidity levels.
Use a sealant or stain that is specifically designed for use with pressure-treated wood. These products are formulated to penetrate the wood and provide protection against moisture, UV radiation, and fungal growth. Follow the manufacturer’s instructions for application and drying times. Applying a sealant or stain can help prolong the lifespan of the wood and improve its appearance.