DETERMINATION OF HUMAN EQUIVALENT DOSES

Common sense: The same amount of a substance has a larger effect on a small animal than on a large animal.

Plausible assumptions:

1. The effect of the dose is proportional to blood volume, hence to body weight.

2. The effect of the dose is proportional to surface area of absorption regions, hence proportional to volume^2/3, hence to weight^2/3.

Empirical evidence: Maybe weight^3/4 is better.

• Many energy-related quantities scale this way, and metabolism is an energy-related process.
• Data on toxic effects of substances
• But does this apply to carcinogenesis?

Old EPA default assumption: 2/3 power