Studies on phenoxy acid herbicides. II. Oral and dermal uptake and elimination in urine of MCPA in humans.

Five healthy volunteers were given 15 micrograms MCPA per kg body weight. The highest concentration in plasma, 0.15 micrograms/ml, was found after 1 h. In urine the excretion during the first 6 h was 0.46 microgram/min and 40% of given dose was excreted during the first 24 h. About 1 g of MCPA emulsion was applied on the skin of the thigh and was washed away after 2 h. Plasma level slowly increased with maximum, 0.12 micrograms/ml, after 24 h. In urine a slow excretion continued for up to 5 days later with maximum 24-48 h after application. In agricultural field exposure urinary MCPA should be estimated immediately after stop of exposure as well as 24 h after exposure. Levels under 0.5 micrograms/ml of MCPA in urine might be used as a practical biological level for good work practice. In spot samples the concentration of urine must be considered.