The rate of diffusion is a key factor in toxicant absorption. Once a toxicant is introduced to the body, it must cross cell membranes to reach its site of action. This process often occurs via passive diffusion, where the toxicant travels across a concentration gradient. Factors such as the concentration gradient, the lipid solubility of the toxicant, and the presence of transport proteins can influence the rate of absorption. Lipid-soluble substances tend to diffuse more quickly through cell membranes due to their hydrophobic nature.
