Polychlorinated naphthalene

Polychlorated naphtalenes, or PCN are the products that are made when naphtalene is treated with chlorine. In many respects, these substances are similar to Polychlorinated biphenyls, or PCBs.
Uses.
PCNs are used as insicticides and as fungicides. Wood is often treated with PCNs to make it more resistant. Sometimes, they are used to produce water-resistant dyes and colors. Sometimes, they replaces PCBs in the form of artificial resins. 
Hazards.
Like PCBs, they are very poisonous. They cause chloracne when they have direct contact with the skin. There are other symptoms, such as being irritable, losing weight, and certain liver dysfunctions. Because, like PCBs, they take a long time to decay, they were classified as persistent organic pollutant in 2015.