Figure 1From: Comparison of cellular toxicity caused by ambient ultrafine particles and engineered metal oxide nanoparticles Mass concentration of ambient size-resolved particles collected at SDK site in winter in 2009. The sampling campaign was carried out from November 23 to December 5, 2009. The value of mass concentration of the size-resolved particles was expressed as means ± standard deviations (SDs; n = 5). The error bars indicate standard deviation.Back to article page