This study suggests that humidifier disinfectant inhalation causes an idiopathic type of chILD that is characterized by spontaneous air leak, rapid progression, lack of response to treatment, and high mortality. Further safety studies must be performed on common environmental compounds, particularly those that enter the human body by an unusual route.
BackgroundThe occurrence of numerous cases of interstitial lung disease in children (chILD) every spring in Korea starting in 2006 raised suspicion about a causal relationship with the use of humidifier disinfectants (HDs). The aim of this study was to evaluate the association between HD use and the risk of chILD.MethodsThis retrospective, 1∶3 matched case-control study consisted of 16 cases of chILD that had developed between 2010 and 2011. The three groups of parallel controls (patients with acute lobar pneumonia, asthma, and healthy children) were matched by age, gender, and index date. Indoor/outdoor environmental risk factors, including HD use, were investigated by asking the guardians to complete a questionnaire.ResultsThe median age of the affected children (43.8% male) was 26 months (18.25–36.25). The chILD group did not differ significantly from the control groups with respect to socio-demographic and clinical variables. Indoor and outdoor environmental factors were not associated with a risk of chILD. However, the previous use of HDs (OR; 2.73. 95% CI; 1.41–5.90, P = 0.00) were independently associated with an increased risk.ConclusionsThis study showed that HDs, which are widely used in South Korea in the winter season, independently increased the risk of chILD in spring. Therefore, continuous monitoring and, if needed, changes in policy are essential to prevent and control pediatric diseases caused by toxic chemicals.
The microstructural evolution of the colloidal gel at intermediate volume fraction (15%) under start-up of shear flow has been studied by using the Brownian dynamics simulation method. The structural change was analyzed from three points of view, on cluster length scale, on local length scale and on anisotropy.Correlating the stress change which showed stress overshoot with the structural change on the cluster length scale, a mismatch between the initiation of the structural rupture and the stress maximum was observed. The mismatch was explained through the competition between the structural rupture and the stress bearing network structure. On the local length scale, topology change of the colloidal gel was investigated. As the rupture of the colloidal gel progressed, the multiply connected rigid chains with high bond number changed into singly connected soft chains with low bond number. During the structural evolution, the distinctive structural anisotropy was observed. Associating the structural anisotropy change with direction-dependent cluster behavior, the rupture mechanism of the colloidal gel could be suggested in the sequence of deformation, break up of the percolated network structure, rotation and break up of clusters, and the equilibrium of the three representative motions of small flocs (break up, rotation, and interlocking).
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