• Interstitial Fibrosis
• Clinical Epidemiology

Over the last two decades several publications have reported outbreaks of interstitial lung disease caused by inhalational exposure to a chemical, usually at work, but occasionally in a domestic situation. These outbreaks frequently follow a change in formulation, which may be minor,1 of a chemical already being used in the workplace, or a change in process leading to its aerosolisation.

In 2006, paediatricians in South Korea became aware of a severe, rapid-onset interstitial pneumonitis in young children and infants; the disease responded very poorly to treatment, and mortality rates were close to 50%.2 Its seasonal presentation, with most cases presenting in the spring, raised the possibility of an infective aetiology; hypersensitivity pneumonitis was also considered. The failure to find any microbiological evidence for the former, and the distinct clinical and pathological features that distinguished it from the latter led to the consideration of other hypotheses. As a result, the Korean Centre for Disease Control set up a series of case-control studies designed to examine a wide variety of alternative environmental explanations. In early 2013, the findings of a small (n=16) study of affected children were published3; intriguingly, they indicated that all the cases, but just a third of the matched controls, had exposure to disinfectant used in domestic humidifiers, producing an OR of 2.73.

The epidemic …