THMs were monitored at twenty locations in these twin cities using solid
phase micro extraction-gas chromatography(SPME-GC).Total concentration of THMs was ranged
between21and373 mg/L, whereas both cities had an average total THMs concentration of 142and
260 mg/L,respectively.Chloroform was found as one the major contributortotheTHMsconcentration
(485%). TheoccurrenceofTHMsfollowedthegivenorder:chloroform,bromodichloromethane4dibromochloromethane4bromoform.LifetimecancerriskassessmentofTHMswascarriedoutusing
predictionmodelsviadifferentexposureroutes(ingestion,inhalationanddermal).Anaveragelifetime
cancerriskwasfoundtobe0.74104 and 1.24104 forRawalpindiandIslamabad,respectively.
The numberofexpectedcancercasesperyearcouldreachtwocasesforeachcity.Hazardindexvalues
were foundbelowunityforboththecitiesimplyingthattherewouldbenoconsiderablenon-cancer
risk. Oralingestionwasfoundtobeoneofthemainroutesofexposureforbothtypesofriskwhichwas
followedbyinhalationanddermalroutes.