Why are some wood preservatives categorized as "restricted use"?

Wood preservatives are categorized as "restricted use" primarily due to the potential health risks and environmental hazards they pose. These substances may contain chemicals that can be toxic to humans or wildlife, or they may have a negative impact on the environment if not used properly. Because of these risks, their application is often limited to trained professionals who know how to handle them safely and are aware of the regulatory requirements governing their use. This classification is meant to ensure that protective measures are taken to minimize exposure and environmental contamination, reflecting a commitment to safety and sustainability in wood treatment practices.

In contrast, other factors such as effectiveness, cost, and market popularity do not necessarily dictate whether a preservative is restricted. Both effectiveness and cost can vary widely across formulations, and a product being popular in the market does not inherently mean it is safe for unrestricted use. Thus, the primary reason for the restricted use categorization focuses on the safety and environmental implications associated with these preservatives.