"A Chinese-US team has found that PM2.5 plays a key role in suppressing the formation of another type of pollution in built-up areas – “ultrafine particles”. These have a diameter of under 50 nanometres, and an emerging body of work has linked them to health concerns including birth defects"
"Epulopiscium fishelsoni"0.7mm,"Thiomargarita namibiensis"(Science, vol 284, p 493) 0.75mm, "An almost identical sulphur bacterium which, at 0.5 millimetres across, is also visible to the naked eye, was discovered in Mexico in 2002"