Characteristics of the Chiba environmental challenge chamber.

Background: An environmental challenge chamber (ECC), which we refer to as the a-chamber, was built at Chiba University in 2008. The aim of this study was to validate the functionality of the ECC. Methods: The stability of the pollen distribution and concentration in the ECC and symptoms of patients with Japanese cedar pollinosis induced by cedar pollen exposure were examined. Carryover effects of symptoms induced by different exposure protocols and correlations between symptoms induced in the ECC and those in the natural cedar pollen season were also determined. All the studies using the a-chamber were conducted out of the cedar pollen season. Results: The severity of symptoms in the chamber reached a peak about 2 hours after the start of pollen exposure and plateaued thereafter. After subjects left the chamber, the symptoms persisted for several days. There was no significant difference between the severity of symptoms at exposure levels of 8000 and 12000 grains/m(3). The symptoms were significantly increased by exposure for 3 consecutive days; however, there were no carryover effects in a study performed with a two-week interval. The total nasal symptom score (TNSS) in the natural pollen season showed a weak correlation with the mean TNSS on the day of exposure and the following 3 days. Symptoms in the ECC also had weak correlations with those in the early natural pollen season. Conclusions: The ECC under well-controlled conditions is suitable for clinical studies and might accelerate development of treatment for seasonal allergic rhinitis. A complete evaluation requires inclusion of the persistent reaction after subjects leave the ECC.