Where are polycyclic aromatic hydrocarbons found?
Polycyclic aromatic hydrocarbon
{'answer_start': array([49]), 'answer_text': array(['coal and in tar deposits'], dtype=object)}
PAHs are uncharged, non-polar molecules found in coal and in tar deposits.  They are also produced by the thermal decomposition of organic matter (for example, in engines and incinerators or when biomass burns in forest fires).