Respiratory effects are associated with the number of ultrafine particles.

TLDR

The study monitored daily peak expiratory flow and symptoms in 27 nonsmoking asthmatics while measuring ambient particle size distribution (0.01–2.5 µm) with an aerosol spectrometer during winter 1991–1992, enabling comparison of ultrafine and fine particle fractions. Ultrafine particles (≤0.1 µm) comprised 73 % of particle number but only 18 % of mass, and their daily mean number was more strongly linked to reduced PEF, increased cough, and malaise than fine‑particle mass or PM10, indicating that particle size distribution clarifies the health‑impacting aerosol components.

Abstract

The association between fine and ultrafine particles and respiratory health was studied in adults with a history of asthma in Erfurt, Eastern Germany. Twenty-seven nonsmoking asthmatics recorded their peak expiratory flow (PEF) and respiratory symptoms daily. The size distribution of ambient particles in the range of 0.01 to 2.5 microm was determined with an aerosol spectrometer during the winter season 1991-1992. Most of the particles (73%) were in the ultrafine fraction (smaller than 0.1 microm in diameter), whereas most of the mass (82%) was attributable to particles in the size range of 0.1 to 0.5 microm. Because these two fractions did not have similar time courses (correlation coefficient r = 0.51), a comparison of their health effects was possible. Both fractions were associated with a decrease of PEF and an increase in cough and feeling ill during the day. Health effects of the 5-d mean of the number of ultrafine particles were larger than those of the mass of the fine particles. In addition, the effects of the number of the ultrafine particles on PEF were stronger than those of particulate matter smaller than 10 microm (PM10). Therefore, the present study suggests that the size distribution of ambient particles helps to elucidate the properties of ambient aerosols responsible for health effects.