Table 2.

Summary of possible risk factors for NPC

FactorStrength of associationConsistency of associationSubgroup-specific associations
EBVStrongConsistentMore consistent association with types II and III NPC
Salt-preserved fishModerate to strongConsistentStronger association with consumption at weaning
Other preserved foodsModerateFairly consistent
Lack of fresh fruits and vegetablesModerateFairly consistent
Tobacco smokeWeak to moderateFairly consistentStronger association with type I NPC
Other inhalantsWeak to moderateInconsistent
Herbal medicinesWeak to moderateInconsistent
FormaldehydeWeak to moderateInconsistent
Occupational dustsWeak to moderateInconsistentMore consistent association with wood dust exposure
Chronic respiratory tract conditionsModerateFairly consistent
Family history of NPCStrongConsistent
HLA class I genotypesModerate to strongConsistentInconsistent associations with HLA class II genotypes