Table 6.

Topics of the sample including the terms “UFP” or “ultra-fine particles” identified through structured topic modelling with topic number k = 11

Topic	n	%	% cum.
Filters and membranes	24	28.57	28.57
Pollutant sources and concentrations	21	25.00	53.57
Preclinical analyses	9	10.71	64.29
Risk communication	8	9.52	73.81
Respiratory diseases	6	7.14	80.95
Air quality management	4	4.76	85.71
Epidemiological analyses	3	3.57	89.29
Energy	3	3.57	92.86
Prediction models	2	2.38	95.24
Pregnancy and birth	2	2.38	97.62
Climate change and adaptions	2	2.38	100.00