In contrast, non-carcinogens are evaluated the effects by using an exposure or
dose called “ Reference dose (RfD)”. RfD is value that specific for an exposure
depended on bioavailability consideration or other parameters to intimate specific
dose-response relationship (USEPA, 2010). Chronic RfD is value for protection in
long term exposure as 7 years of a lifetime, but sub-chronic RfD is used to estimate in
42
short term exposure of chemical agent as 2 weeks to 7 years (USEPA, 1989). Table
2.5 shown dermal Reference dose (RfDd) in unit mg/kg-day and dermal absorption
fraction (ABSd) of elements.