Objective: To examine if desert dust enhances allergic symptoms in real-life settings and to investigate its effect modifiers.
Methods: We conducted a cohort study for 3,327 pregnant women during spring and fall in the period spanning October 2011 to May 2013 in three regions in Japan as an adjunct study of the Japan Environment & Children's Study. We timely acquired participants’ daily symptom scores by sending a web-based questionnaire on high desert-dust days and on some randomly selected other days (control days) for each participant.
Results: Pregnant women showed an increased risk of allergic symptom on protocol-defined high desert-dust days (OR 1.24, 95%CI 1.16 – 1.32). The risk elevation was observed from a low level of desert dust in a dose-dependent manner even on control days. The risk-increase according to desert dust levels was observed when the air simultaneously contained pollen from Japanese cedar and cypress among subjects with positive serum IgE antibodies to Japanese cedar pollen, while no clear risk-increase was observed in the absence of pollen in the air.
Conclusions: Ambient desert dust level was associated with increased risk of allergic symptom exacerbation in pollen-sensitized pregnant women when pollen was present in the air. The increase was dose-dependent, and was observed from a very low level. These results support a hypothesis that desert dust exerts adjuvant effects in human.