The reasonable maximum exposure (RME) always use in some case of risk
assessment. The case is defined as the RME or upper bound because it is over
exposure (approximately the 95th percentile). The RME is the worst-case scenario that
evaluates exposures that higher than average, nevertheless the exposures still within a
practical range. The upper confidence at 95th percentile is used to evaluate RME
because the situation involves the uncertainty of concentration value. Exposure time
and exposure frequency are used in term of 95th percentile to calculate the exposure
results in reasonable maximum exposure case, if statistical data are available
(USEPA, 1989 and Siriwong, 2009). The average and upper bound value should be
combined together for estimate the exposure and the results stand for the exact RME
for the case (USEPA, 2002).