Ultrafine and Fine Particle Number and Surface Area Concentrations and Daily Cause-Specific Mortality in the Ruhr Area, Germany, 2009-2014.

BACKGROUND: Although epidemiologic studies have shown associations between particle mass and daily mortality, evidence on other particle metrics is weak. OBJECTIVES: We investigated associations of size-specific particle number concentration (PNC) and lung-deposited particle surface area concentration (PSC) with cause-specific daily mortality in contrast to PM10. METHODS: We used time-series data (March 2009-December 2014) on daily natural, cardiovascular, and respiratory mortality (NM, CVM, RM) of three adjacent cities in the Ruhr Area, Germany. Size-specific PNC (electric mobility diameter of 13.3-750 nm), PSC, and PM10 were measured at an urban background monitoring site. In single- and multipollutant Poisson regression models, we estimated percentage change (95% confidence interval) [% (95% CI)] in mortality per interquartile range (IQR) in exposure at single-day (0-7) and aggregated lags (0-1, 2-3, 4-7), accounting for time trend, temperature, humidity, day of week, holidays, period of seasonal population decrease, and influenza. RESULTS: PNC100-750 and PSC were highly correlated and had similar immediate (lag0-1) and delayed (lag4-7) associations with NM and CVM, for example, 1.12% (95% CI: 0.09, 2.33) and 1.56% (95% CI: 0.22, 2.92) higher NM with IQR increases in PNC100-750 at lag0-1 and lag4-7, respectfully, which were slightly stronger then associations with IQR increases in PM10. Positive associations between PNC and NM were strongest for accumulation mode particles (PNC 100-500 nm), and for larger UFPs (PNC 50-100 nm). Associations between NM and PNC<100 changed little after adjustment for O3 or PM10, but were more sensitive to adjustment for NO2. CONCLUSION: Size-specific PNC (50-500 nm) and lung-deposited PSC were associated with natural and cardiovascular mortality in the Ruhr Area. Although associations were similar to those estimated for an IQR increase in PM10, particle number size distributions can be linked to emission sources, and thus may be more informative for potential public health interventions. Moreover, PSC could be used as an alternative metric that integrates particle size distribution as well as deposition efficiency. https://doi.org/10.1289/EHP2054.

Electron microscopy of particles deposited in the lungs of nickel refinery workers.

The size, morphology, and chemical composition of particles deposited in the lungs of two nickel refinery workers were studied by scanning and transmission electron microscopy. The particles were extracted from the lung tissue by low-temperature ashing or by dissolution in tetramethylammonium hydroxide. The suitability of both sample preparation techniques was checked with reference materials. Both approaches lead to Fe-rich artifact particles. Low-temperature ashing leads to oxidation of small (diameter < 2 µm) metallic Ni and Ni sulfide particles, dissolution in tetramethylammonium hydroxide to removal of sulfate surface layers. Silicates and alumosilicates are the most abundant particle groups in the lungs of both subjects. From the various metal-dominated particle groups, Ni-rich particles are most abundant followed by Fe-rich and Ti-rich particles. Ni appears to be present predominantly as an oxide. Pure Ni metal and Ni sulfides were not observed. The presence of soluble Ni phases was not investigated as they will not be preserved during sample preparation. Based on their spherical morphology, it is estimated that a large fraction of Ni-rich particles (50-60 % by number) as well as Fe-rich and Cu-rich particles (27-45 %) originate from high-temperature processes (smelting, welding). This fraction is much lower for silicates (3-5 %), alumosilicates (1-2 %), and Ti-rich particles (9-11 %). The absence of metallic Ni particles most likely results from low exposure to this species. The absence of Ni sulfides may be either ascribed to low exposure or to fast clearance.