Safety Factor Method:
 
A neurotoxin has a NOEL of .05 gm/day in male rats.  
The EPA Science Advisory Board recommends an 
uncertainty factor of 10.  What is the reference dose 
for humans?
 
 
                    .05 gm/day * 70 kg 
reference dose =    ------------------ = .7 gm/day
                    .5 kg * 10
 
 
Notes: 
 
1. For dose scaling purposes, assume humans weigh 70 kg and the
   male rats weigh .5 kg. 
2. With no other information, we assume no latency and a     
   lifetime of exposure and study (the simplest 
   conditions).
3. Remember that reference dose is a daily dose!
   Doses should always be expressed as a daily dose. 
4. Pay close attention to the units at all times!