Railroad ties, also known as sleepers, are heavy wooden beams used to support train tracks. After decommissioning, these timbers are often resold for residential landscaping projects. Homeowners are attracted to them for their rustic aesthetic, durability, and relatively low cost. Their safety is questioned due to the chemical treatment applied to the wood, which ensures longevity against harsh environmental exposure. Understanding the wood’s preservation process and potential risks is important before incorporating these reclaimed materials.
The Chemical Composition of Treated Ties
The durability of traditional railroad ties comes from treatment with creosote, a heavy-duty wood preservative. Creosote is derived from the high-temperature distillation of coal tar, resulting in a complex mixture of hundreds of chemical compounds. Up to 90% of this substance is composed of Polycyclic Aromatic Hydrocarbons (PAHs).
These PAHs repel insects, fungi, and rot, giving the ties their exceptional lifespan. Specific PAHs, such as benzo(a)pyrene, are categorized as probable human carcinogens by environmental agencies. This chemical makeup, while preserving the wood, necessitates safety precautions when considering residential use.
Assessing Creosote Leaching and Toxicity Risks
The chemical compounds within creosote do not remain permanently bound to the wood fibers; they can migrate into the surrounding environment through a process called leaching. Leaching is a major mechanism by which the PAHs are released from the wood and absorbed into the adjacent soil and water. This chemical migration can lead to the contamination of garden soil, posing a direct threat to the food chain if used in edible plant beds. Studies have shown that some creosote components can bioaccumulate in vegetables and animals.
Applications that involve frequent human or animal contact are considered high-risk. Direct contact with creosote-treated wood can cause severe skin irritation, rashes, and even chemical burns. Additionally, the inhalation of vapors, especially on hot days when the chemicals volatilize, can also pose a risk. High-risk applications include:
- Vegetable gardens and raised beds for food production.
- Children’s play areas.
- Seating or picnic surfaces.
Uses in areas far from food production, water sources, and frequent contact are generally considered lower risk. For instance, creosote-treated wood should not be used where it can come into direct contact with drinking water for people or livestock. Retaining walls or borders for non-edible flower beds located away from play areas represent a less concerning application. However, any structural use requires careful consideration due to the potential for groundwater contamination and the persistence of the chemicals in the environment.
Legal and Regulatory Status of Use
The commercial application of creosote is heavily regulated by the U.S. Environmental Protection Agency (EPA) as a Restricted Use Pesticide (RUP). New creosote products are applied only by certified applicators in specialized facilities. There are no registered residential uses for creosote or creosote-treated wood in a home setting.
The regulatory framework is less clear for reclaimed materials. The EPA states that the reuse of old railroad ties in residential landscaping is not subject to regulation under federal pesticide laws. However, the agency advises against their use in areas involving frequent or prolonged contact with bare skin. The EPA also explicitly warns against using the wood for countertops, cutting boards, or where the preservative may become a component of food or animal feed.
Safer Materials for Landscaping Projects
Given the concerns surrounding creosote leaching and toxicity, several safer alternatives are available for landscaping projects.
Wood Alternatives
Naturally rot-resistant species offer durability without chemical treatment, including redwood, cedar, cypress, and black locust. Modern pressure-treated lumber, using newer treatments like Alkaline Copper Quaternary (ACQ) or Micronized Copper Azole (MCA), is generally safer than older formulations. While suitable for general landscaping and structural supports, these should still be avoided in raised beds for growing food.
Non-Wood Alternatives
Non-wood materials offer completely non-toxic solutions for various uses:
- Stone, brick, and concrete blocks for retaining walls or edging.
- Recycled plastic lumber, a rot-proof alternative for timbers and garden bed construction.