A cluster of lung injury cases associated with home humidifier use: an epidemiological investigation.
BACKGROUND
In April 2011 a tertiary hospital in Seoul, Korea reported several cases of severe respiratory distress of unknown origin in young adults.


METHODS
To find the route of transmission, causative agent and patient risk factors of the outbreak, an investigation of the epidemic was initiated. Clinicopathological conferences led to the suspicion that the cases related to an inhalation injury. An age- and sex-matched case-control study was therefore performed to examine the inhalation exposure of the patients to various agents.


RESULTS
Of the 28 confirmed cases, 18 agreed to participate. A total of 121 age- and sex-matched controls with pulmonary, allergic or obstetric disease were selected. All patients and controls completed questionnaires with questions about exposure to various inhalants. The crude ORs for patient exposure to indoor mould, humidifier use, humidifier detergent use and insecticide use were 4.4 (95% CI 1.5 to 13.1), 13.7 (95% CI 1.8 to 106.3), 47.3 (95% CI 6.1 to 369.7) and 3.9 (95% CI 1.3 to 11.7), respectively. However, when considered concurrently, indoor mould and insecticide use lost statistical significance. Moreover, humidifier use was ruled out as the cause because of a lack of biological plausibility and the weak strength of the association. This suggested that humidifier disinfectant was the cause of the outbreak. This information led the Korean government to order the removal of humidifier detergents from the market. In the years following the ban, no additional cases were detected.


CONCLUSIONS
Epidemiological evidence strongly suggests that the lung injury outbreak was caused by humidifier detergent use at home.
Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Hwa Jung
HJ
Kim
Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea Department of Preventive Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Moo-Song
MS
Lee
Department of Pulmonary Medicine and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Sang-Bum
SB
Hong
Department of Pulmonary Medicine and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Jin Won
JW
Huh
Department of Radiology, Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Kyung-Hyun
KH
Do
Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Se Jin
SJ
Jang
Department of Pulmonary Medicine and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Chae-Man
CM
Lim
Department of Radiology, Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Eun Jin
EJ
Chae
Department of Nursing, Hanyang University, Seoul, Korea.
Hanyi
H
Lee
Department of Nursing, Asan Medical Center, Seoul, Korea.
Miran
M
Jung
Division of Vaccine-preventable Diseases Control and National Immunization Program, Korea Centers for Disease Control and Prevention, Osong, Korea.
Young-Joon
YJ
Park
Division of Epidemic Intelligence Service, Korea Centers for Disease Control and Prevention, Osong, Korea.
Ji-Hyuk
JH
Park
Division of Epidemic Intelligence Service, Korea Centers for Disease Control and Prevention, Osong, Korea.
Geun-Yong
GY
Kwon
Division of Epidemic Intelligence Service, Korea Centers for Disease Control and Prevention, Osong, Korea.
Jin
J
Gwack
Division of Epidemic Intelligence Service, Korea Centers for Disease Control and Prevention, Osong, Korea.
Seung-Ki
SK
Youn
Center for Infectious Disease Control, Korea Centers for Disease Control and Prevention, Osong, Korea.
Jun-Wook
JW
Kwon
Bureau of Public Health Policy, Ministry of Health and Welfare, Seoul, Korea.
Byung-Guk
BG
Yang
Korea Centers for Disease Control and Prevention, Osong, Korea.
Byung-Yool
BY
Jun
Department of Occupational and Environmental Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
Yangho
Y
Kim
Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, Suwon, Korea.
Hae-Kwan
HK
Cheong
Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea.
Byung Chul
BC
Chun
Department of Preventive Medicine and Medical Research Institute, College of Medicine, Chungbuk National University, Cheongju, Korea.
Heon
H
Kim
Inhalation Toxicology Center, Korea Institute of Toxicology, Jeongeup, Korea.
Kyuhong
K
Lee
Department of Pulmonary Medicine and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
Younsuck
Y
Koh
D000328:Adult; D016902:Air Pollution, Indoor / Q000009:adverse effects*; D016022:Case-Control Studies; D004196:Disease Outbreaks; D004202:Disinfectants / Q000633:toxicity*; D005260:Female; D006801:Humans; D006813:Humidity; D019570:Inhalation Exposure / Q000009:adverse effects*; D055370:Lung Injury / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D011795:Surveys and Questionnaires
D004202:Disinfectants
Not Applicable