Injuries caused by humidifier disinfectants (HDs) can no longer be grouped under the concept of HD lung injury. Focusing on individual cases, we were able to evaluate the relevance not only of diseases for which epidemiological correlation is recognized but also all diseases and symptoms that the victims complain of.

In-depth interviews and reassessment of 113 HD-exposed patients who had not been acknowledged as victims by the government were conducted, and their medical records were reviewed. Based on these processes, an assessment questionnaire for the injuries related to HDs was completed and the involvement of HDs was assessed either as “strong association,” “association,” or “no association.”

In this study, of the 113 patients included who claimed damages, 78 (69.0%) had HD-related injuries. Among the cases of 22 patients who applied for injury acknowledgment due to upper respiratory inflammation that was not included among the acknowledged diseases, 17 (77.3%) were judged to be HD-related injuries (strong association vs. association: 10 [45.5%] vs. 7 [31.8%]). When the cases of 12 rhinitis patients were reassessed, 9 were HD-related injuries (strong association vs. association: 4 [33.3%] vs. 5 [41.7%]). When the cases of 18 asthma patients unacknowledged as a victim were reassessed, 17 (94.4%) were humidifier-related injuries (strong association vs. association: 12 [66.6%] vs. 5 [27.8%]). Among 4 interstitial lung disease patients unacknowledged as a victim, 2 (50.0%) were HD-related injuries.

HD-related health injuries should be assessed through both individual interviews and detailed chart reviews for more accurate injury acknowledgment. In the future, efforts should go beyond existing methods based on the adherence to acknowledgment criteria to directly listen to the victims.