Chloronaphthalenes

Chloronaphthalenes are a group of synthetic organic compounds derived from naphthalene by the substitution of hydrogen atoms with chlorine atoms. They are also known as polychlorinated naphthalenes (PCNs). The number of chlorine atoms and their position on the naphthalene rings can vary, resulting in 75 different possible isomers. Commercially, they were produced as mixtures of these isomers, with varying physical properties depending on the degree of chlorination.

PCNs were manufactured from the late 19th century until the late 20th century. They found widespread use as dielectric fluids in electrical capacitors and transformers, as well as in wood impregnation, cable insulation, metal coatings, and as additives in lubricants and paints. Their desirable properties included high chemical and thermal stability, low flammability, and excellent electrical insulating characteristics.

However, like other persistent organic pollutants (POPs), chloronaphthalenes are environmentally persistent, bioaccumulative, and toxic. Their production and use have been significantly reduced or banned in many countries due to these concerns. Environmental contamination can occur through industrial discharge, improper disposal of products containing PCNs, and emissions from incineration. They can pose risks to both human health and ecosystems, with potential effects on the liver, thyroid, and immune system, as well as developmental and reproductive issues.