Causal relationship between indium compound inhalation and effects on the lungs.
BACKGROUND
Recent case reports and epidemiological studies suggest that inhalation of indium dust induces lung damage.


OBJECTIVE
To elucidate the dose-dependent effects of indium on the lungs and to prove a causal relationship more clearly.


METHODS
A baseline observation was conducted on 465 workers currently exposed to indium, 127 workers formerly exposed to indium and 169 workers without indium exposure in 12 factories and 1 research laboratory from 2003 to 2006. Indium in serum (In-S) was determined as an exposure parameter, and its effects on the lungs were examined.


RESULTS
The means of In-S in the current, former and no exposure workers were 8.35, 9.63 and 0.56 ng/ml, respectively. The current and former exposure workers had significantly higher levels of KL-6, and showed significant dose-dependent increases in KL-6, SP-D, and SP-A. Current exposure workers with In-S of 3 ng/ml or above demonstrated a significant increase of KL-6 in both GM and prevalence exceeding the reference value. Approximately a quarter of the former exposure workers had interstitial changes as seen on chest HRCT. In-S of exposed workers who had been working before improvements of the working environment (Group Bef) and those who started working after improvements (Group Aft) were 12.29 and 0.81 ng/ml, respectively. Adjusted odds ratios indicated 87%, 71% and 44% reductions among Group Aft workers who exceeded the reference values of KL-6, SP-D and SP-A, respectively.


CONCLUSIONS
Dose-dependent lung effects due to indium exposure were shown, and a decrease of indium exposure reduced the lung effects. An In-S value of 3 ng/ml may be a cut-off value which could be used to prevent early effects on the lungs.
Nakano
Makiko
M
Department of Preventive Medicine and Public Health, School of Medicine, Keio University, Tokyo 160-8582, Japan.
Omae
Kazuyuki
K
Tanaka
Akiyo
A
Hirata
Miyuki
M
Michikawa
Takehiro
T
Kikuchi
Yuriko
Y
Yoshioka
Noriyuki
N
Nishiwaki
Yuji
Y
Chonan
Tatsuya
T
D000328:Adult; D000395:Air Pollutants, Occupational / Q000633:toxicity*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007204:Indium / Q000097:blood / Q000633:toxicity*; D019570:Inhalation Exposure / Q000009:adverse effects*; D007564:Japan / Q000453:epidemiology; D008171:Lung Diseases / Q000139:chemically induced* / Q000453:epidemiology; D008297:Male; D019370:Observation; D009784:Occupational Diseases / Q000139:chemically induced* / Q000453:epidemiology; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D037662:Pulmonary Surfactant-Associated Protein A / Q000097:blood; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood; D012016:Reference Values
D000395:Air Pollutants, Occupational; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D007204:Indium