Dermal absorption of N,N-dimethylacetamide in human volunteers.
OBJECTIVE
We investigated the potential for the dermal absorption of N,N-dimethylacetamide (DMAC: CAS No. 127-19-5) vapor, the biological half-life of N-methylacetamide (NMAC) in urine as the biological exposure item of DMAC, and the adjustment method for urinary concentrations.


METHODS
Twelve healthy male volunteers (mean age 25.2 years, range 21-43 years) were exposed to DMAC for 4 h on two occasions at intervals of 96 h or above. Each volunteer sat inside a whole-body-type exposure chamber for the dermal exposure experiment or outside the chamber for the inhalation exposure experiment. The temperature and relative humidity in the chamber were controlled at approximately 26 degrees C and 40% in order to keep the skin (90% naked) of the volunteers dry. DMAC concentrations were 6.1 +/- 1.3 ppm for dermal exposure and 6.1 +/- 1.3 ppm for inhalation exposure. Urine samples were collected from 0 h through 36 h and at 48 h and 72 h after the exposure. Extrapolations from exposure concentrations for 4 h to 10 ppm for 8 h were performed.


RESULTS
Mean dermal absorption was estimated to be 40.4% of the total DMAC uptake. The biological half-lives of urinary NMAC were 9.0 +/- 1.4 h and 5.6 +/- 1.3 h via skin and lung, respectively. Mean NMAC in urine just after 5 consecutive workdays (8 h/day) at 10 ppm DMAC exposure was assumed to be 33.7 mg/g x Cr (18.6-70.0 mg/g x Cr). Creatinine-adjusted NMAC concentration in urine for each volunteer within 12 h after the exposure was more closely correlated with the total excretion amount of NMAC up to 36 h than with urinary-volume-adjusted or specific-gravity-adjusted NMAC concentration in both the dermal and inhalation exposure experiments.


CONCLUSIONS
DMAC vapor was significantly absorbed through the skin. Estimated NMAC values indicate that 20 mg/g x Cr NMAC seems to be appropriate as the biological exposure index.
Nomiyama
T
T
Department of Preventive Medicine and Public Health, School of Medicine, Keio University, Tokyo, Japan. nomiyama@med.keio.ac.jp
Omae
K
K
Ishizuka
C
C
Yamauchi
T
T
Kawasumi
Y
Y
Yamada
K
K
Endoh
H
H
Sakurai
H
H
D000081:Acetamides / Q000493:pharmacokinetics* / Q000652:urine; D000328:Adult; D003451:Cryoprotective Agents / Q000493:pharmacokinetics; D006207:Half-Life; D006801:Humans; D008297:Male; D012016:Reference Values; D012869:Skin Absorption
D000081:Acetamides; D003451:Cryoprotective Agents; C013959:dimethylacetamide