Human exposure to polyhexamethylene guanidine phosphate from humidifiers in residential settings: Cause of serious lung disease.

Exposure to the humidifier disinfectant, polyhexamethylene guanidine phosphate (PHMG), in mists generated from ultrasonic humidifiers was studied in a simulation chamber and apartment rooms. PHMG is suspected as a causative agent of lung disease in Korea residences. In the simulation-chamber study, the amount of disinfectant discharged from three different ultrasonic humidifiers was measured. Mists generated at 1, 2, and 4 times the recommended amount of disinfectant were sampled with an impinger, and the effect of relative humidity (RH) on airborne disinfectant concentration was studied by changing RH from 60%-70% to 90%-100%. In addition, particle size distribution (PSD) in mists was measured by scanning mobility particle sizer (SMPS), aerodynamic particle sizer (APS), and Mastersizer. In the apartment study, mists generated from ultrasonic humidifiers were sampled for 6 h in small and large rooms during fall ( n = 10) and winter ( n = 15). In the simulation study, the humidifiers discharged 205 ± 24.6 ml/h of mist at maximum capacity. Concentrations of airborne disinfectant increased with increasing concentration of disinfectant. RH affected airborne disinfectant concentration in the chamber, with increasing concentration with increasing RH. Below RH 70%, no airborne PHMG was detected. PHMG-containing mists generated from ultrasonic humidifier showed various sizes ranging from 149-157 nm to 690-740 nm to larger than 5.4 µm by SMPS, APS, and Mastersizer, respectively. Surface area mean diameter measured by Mastersizer ranged from 5.39 µm to 5.72 µm. In the apartment study conducted during the fall, the geometric mean (GM) and geometric standard deviation (GSD) and arithmetic mean (AM) and standard deviation (SD) of airborne PHMG concentration were 3.22 + 5.13 µg/m and 8.26 ± 12.18 µg/m, respectively. In the winter, GM + GSD and AM ± SD of airborne PHMG concentration were 0.21 + 2.11 µg/m and 0.35 ± 0.62 µg/m, respectively. RH and temperature in the apartment rooms for fall and winter were 22.5 ± 1.7°C, 74.5 ± 15.6% and 22.0 ± 2°C, 51.1 ± 12.9%, respectively. Different RHs in the fall and winter resulted in very different airborne concentrations of disinfectant in the apartment rooms. Exposure levels and PSD of mists generated from ultrasonic humidifiers in apartments are not sufficient to conclude that PHMG causes lung disease in Korean residences.