Percutaneous penetration of esters of the 2,4D family is esterase-dependent both in rats and in humans.

The mean flux of the production of the esterases of the skin is not ratelimiting for percutaneous penetration.

The solubility of the esters is a key factor of the rates of hydrolysis.

The linear decrease of percutaneous penetration as a function of log(k_ow) was the most relevant model.

The QSAR make a good estimation of the ex vivo percutaneous fluxes of the pure esters of 2,4D.