In contrast, when air mixed with 0.5 milligrams per cubicmeter of formaldehyde was passed through the chamber, they observed a 7.4 per cent increase in cilia beating frequency relative to the baseline value.
Further increasing the formaldehyde concentration to 1 milligram per cubicmeter led to a dramatic increase — up to 136.4 per cent — in cilia beating frequency relative to the baseline value.