Is there a way to estimate the acceptable surface limit from the ADE?

Exact determination of an acceptable surface limit is a difficult problem. This is due to the following issues:

• Compound specific data on skin absorption does not exist;
• The actual amount of compound absorbed depends upon the location on the body and condition of the skin;
• metabolic pathways are different than inhalation; and
• Environmental factors, such as temperature and humidity, impact the amount of compound actually absorbed.

Unless there is compound-specific data to indicate otherwise, a good way to estimate the ASL from the ADE (or acceptable daily intake (ADI)) is as follows:

• Assume that the actual surface area in contact with a potentially contaminated surface is 100 cm^2. This is approximately the surface area of one hand.
• Dermal absorption is assumed to be 10%. This is based on historical information from steroid compounds, which have significant skin absorption properties.
• Therefore; take the ADE value and divide by 0.1 and use the units 100 cm^2 in the denominator.

For example Compound A has an ADE of 20 ug/day; to determine the ASL take 20/0.1 to obtain 200 ug and then use the units 100 cm^2 in the denominator. The ASL would then be 200 ug/100 cm^2.