"Chemicals" released in headphone with burned cable
Burning or Incineration of Plastic cause carcinogenic chemical products if without suitable catalysts... To pyrolyze plastics such as polyethylene(PE) and polypropylene(PP) of olefin series, the catalysts with high cracking property are
needed.


Dioxin- carcinogenic and antibiotic effect to the environment.
Flyash- may produce respiratory illnesses.
Sulfur dioxide
Nitrogen oxide- green plastics.
Toluene- aromatic compound that is related in the burning of cigarettes.
Carbon monoxide- main product of anerobic/ lack of ventilation combustion.
carbonaceous char, oils and gases.
paraffins, olefins, naphthenes and aromatics


Plastic and Diesel
http://www.chemtec.org/proddetail.php?pr...
http://www.p-fuel.com/index_files/faq.ht...

Thermofuel
http://www.cynarplc.com/thermo-fuel.asp

Mael is right that a  headphone set is made of some plastics (which are mainly made of basic carbon polymers) and the metallic part for the electronic conduction.so even i agree it can not be dangerous for human health to a great extent.