Specific inhalation challenges with chloramines; an updated method

Abstract

Occupational asthma (OA) caused by chlorine has been previously reported. However, we have often been unable to reproduce asthma following specific inhalation challenge (SIC) using chlorine-based agents. This could be due to the actual cause of symptoms being the chloramines produced from the reaction of chlorinated water with a nitrogen source. Initial SICs used nitrogen trichloride but had safety issues. We then reported a positive SIC after adding 5 ml urine to 100 ml of 10,000 ppm chlorine solution generating volatile chloramines. This followed a negative SIC with chlorine in aqueous solution in a nurse with good evidence of occupational asthma. We aimed to further improve this method. Methods: 5 healthcare or swimming pool workers underwent SIC to chloramines created by adding up to 1g of urea powder to 100 ml of 10,000 ppm chlorine solution painted onto cardboard. The chlorine solution alone was used as a control. Results: 3 workers had a positive SIC (a late reaction - Figure 1; an immediate reaction; and a > 10 fold increase in methacholine hyperreactivity). The 2 negative challenges were in a swimming teacher who hadn’t been exposed for 3 years and a healthcare worker who had a number of other possible causes. Conclusion: Chloramines can cause OA in healthcare workers, cleaners and swimming pool workers. It is possible to perform a chloramine SIC in a safe, repeatable and simple way using urea powder mixed with chlorine solution.