Henry's law constant of N,N-dichloromethylamine: application to the contamination of the atmosphere of indoor swimming pools.

The volatility of N,N-dichloromethylamine (DCMA), a disinfection by-product formed during chlorination of swimming pool water, has been investigated in the present work. The Henry's law constants for DCMA were experimentally determined at five temperatures (5, 15, 25, 35 and 45 degrees C) using the single equilibrium technique. The volumic ratio between the gas and the water phases in the headspace vessels ranged from 1 to 60 and the initial concentration of DCMA in the aqueous solutions was approximately 2mM. The values obtained for the dimensionless Henry's law constant varied from 0.047 at 5 degrees C to 0.312 at 45 degrees C. The temperature dependence of the Henry's law constants followed the van't Hoff equation. Trace levels of DCMA (16-70 microg m(-3)) were detected in the atmosphere of an indoor swimming pool whereas the concentrations of DCMA in water pools were in the range 8.8-15 microg L(-1).