Objectives Exposure to fine particles (PM2.5) in urban air has been associated with increased risk of hospitalisation and death from cardiovascular diseases. The endothelium is an important transmitter of signals in the cardiovascular system, and dysfunction of the endothelium is an early marker of increased risk of cardiovascular disease. Workers in metal smelters are occupationally exposed to fine and ultrafine particles in a much higher concentration than from levels in the polluted urban air. Few studies of cardiovascular effects from fine particles have been performed in a working environment. The aim of this study was to examine the association between exposure to different particle size fractions in manganese smelters and endothelial function.

Methods We examined 40 workers in two Norwegian manganese smelters after a working day in the furnace hall, and after at least two consecutive days off work. On the working day, exposure to different particle size fractions was assessed with personal sampling using respirable cyclones and five-stage Sioutas cascade impactors. Endothelial function measured with Endo-PAT2000 (Itamar Medical Ltd.). Associations between the mass of different particle size fractions and endothelial function were assessed using mixed model regression.

Results Reactive hyperemia index (LnRHI) was reduced with increasing levels of particles in the three finest fractions (<0.25 μm, 0.25–0.50 μm, and 0.50–1 μm, respectively), and with total respirable dust. After adjustment for physical activity, the associations were still statistically significant for the two smallest size fractions. Non-significant associations were observed with coarser fractions of particles (1–2.5 μm, and 2.5–10 μm).

Conclusion Exposure to fine particles in the manganese industry is associated with reduced endothelial function.