Air particle contamination in Beijing (DFG)

Short-term health effects of fine and ultra-fine particle exposure in Beijing, China

Knowledge gap: There still exist just few knowledge of the effect of ultra-fine and submicron particles effect on human health. The number of the studies, which focus on the connection between health effect and the air contamination in relation to the particles in differentiated size fractions is once more smaller.

Aim of the study: The identification of the effect of a wide size range on 3 - 10.000 airborne particles and other air pollutants on the respiratory health in Beijing, China.

Data: The assessment based on time series of the concentrations of airborne particles, NO₂ and other air pollutants. Additionally, meteorological data including the air masses origin (back trajectories) were available. Hospital emergency admissions (altogether 15, 981 cases for 15 months) and deaths (altogether 3,016) were evaluated, case-specific for different respiratory diseases.

Results:
A) MORBIDITY: Multiple-exposure models demonstrate harmful effects of elevated number concentrations of small particles to respiratory health. These effects were even significant after control for mass concentrations of particulate matter (PM10, PM2.5) for all controls and for NO₂ controlling for particles in the size-fraction 100 - 300 nm . The harmful effect occurs with a time lag of circa 2 - 3 days after the increase in concentration. Numbers of hospital emergency admissions due to respiratory diseases are increasing by 8% if concentration increases by 5,200 particles/cm³ (IQR- interquartile range of particle number concentrations).
B) MORTALITY: The respiratory mortality raised one day after increasing the total particle number concentration, were significantly increased (IQR ca. 5%) on day 2 up to day 4 and reached again the initial value on day 6. The particle fractions 50 - 100 nm, ultra-fine particles and the total number concentration were most strongly associated with the mortality increase. For these particle metrics, the effects are occurring with a time delay, while they could be shown on the same day for 300 - 1,000 nm particles. It is not possible to determine the chemical composition of airborne particles with daily time resolution. Therefore, air mass origins were used by means of back trajectories. It could be shown that for the same particle concentration the highest adverse impact was associated with stagnant air-masses and air masses from the heavily industrialized southern part of Beijing.

Conclusions: Currently, worldwide mass concentrations of particles (PM10 or PM2.5) were measured mandatory. To improve public health protection, it is essential to complete these data by monitoring of particle number concentrations. The health of the inhabitants of Beijing would benefit from an improvement of the air quality with regard to the concentrations of NO2, particle mass and particle numbers, especially if pollutant emissions in the capital itself and in the adjacent southern areas could be reduced.