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Ultrafine particles: insidious invaders

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Children living on a main road have ultrafine particles in their lower lungs. Evidence from a study led by Grigg in Leicester, UK, is also the first indicator that these children inhale more ultrafine particles.

Until now it was unclear whether PM10—carbon based particles <10 μm diameter associated with lung disease and a major pollutant in traffic emissions—or smaller constituents—coarse (<10->2.5 μm), fine (<2.5-.0.1 μm), and ultrafine (<0.1 μm) particles— could penetrate deep into the lungs. Bunn et al used electron microscopy to look at alveolar macrophages, which ingest inhaled material, for intracellular particles. These came from bronchoalveolar lavage fluid obtained opportunistically from 22 healthy children aged 3 months to 16 years before an elective operation. For each child Bunn et al determined the proportion of alveolar macrophages containing particles by examining a single section from 100 macrophages and the particle size in each macrophage by measuring against known standards.

Alveolar macrophages from all children contained ultrafine particles only. The proportion with particles (range 1–16%, median 5%) was not affected by the child's age but was significantly higher in all seven children living on a main road than the 15 living in a residential road (10% versus 3%, 95% confidence interval for median difference 1.0 to 7.9, p<0.005).

This is the first evidence to link traffic pollution directly with inhaling ultrafine particles, and it ties in with evidence from population studies that being close to traffic increaces children's respiratory disease.


Ultrafine particles within a phagosome of an alveolar macrophage from a child aged 3 months. Bar=1000 nm.

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