Used primarily as a biocide and preservative, especially in wood treatment to protect against fungal decay, termites, and other pests. Commonly applied in utility poles, railroad ties, and marine pilings due to its strong resistance to environmental degradation. Also found in some industrial systems to control microbial growth in cooling towers and fuel oils. Its use has declined in many countries due to environmental persistence, toxicity, and bioaccumulation concerns, leading to strict regulations or bans in consumer and residential applications.