. ▁In ▁addition , ▁the ▁comb ust ion ▁of ▁poly vin yl ch lor ide ▁and ▁pl astic ▁wrap ▁made ▁from ▁poly vin yl id ene ▁ch lor ide ▁result ▁in ▁the ▁production ▁of ▁Cl - PA H s , ▁suggesting ▁that ▁comb ust ion ▁of ▁organ ic ▁materials ▁including ▁ch lor ine ▁is ▁a ▁possible ▁source ▁of ▁environmental ▁poll ution . ▁ ▁A ▁specific ▁class ▁of ▁Cl - PA H s , ▁pol ych lor in ated ▁nap h th alen es ▁( PC N s ), ▁are ▁persistent , ▁bio acc um ulative , ▁and ▁to xic ▁cont amin ants ▁that ▁have ▁been ▁reported ▁to ▁occur ▁in ▁a ▁wide ▁variety ▁of ▁environmental ▁and ▁bi ological ▁matrix es . ▁Cl - PA H s ▁with ▁three ▁to ▁five ▁rings ▁have ▁been ▁reported ▁to ▁occur ▁in ▁air ▁from ▁road ▁t unn els , ▁sed iment , ▁snow , ▁and ▁k raft ▁pul p ▁mill s . ▁ ▁Rec ently , ▁the ▁occurrence ▁of ▁partic ulate ▁Cl - PA H s ▁has ▁been ▁investig ated . ▁Results ▁have ▁shown ▁that ▁most ▁partic ulate ▁Cl - PA H ▁concentration ▁detected ▁in ▁urban ▁air ▁t ended ▁to ▁be ▁high ▁in ▁col der ▁seasons ▁and ▁low ▁in ▁war mer ▁seasons . ▁This ▁study ▁also ▁determined ▁through ▁compos itional ▁analysis ▁that ▁relatively ▁low ▁mole cular ▁weight ▁Cl - PA H s ▁domin ated ▁in ▁war mer ▁seasons ▁and ▁high ▁mole cular ▁weight ▁Cl - PA H s ▁domin ated ▁in ▁col der ▁seasons . ▁ ▁To x icity