Emissions of particulate matter (PM) from vehicle and industrial sources constitute a hazard to human health. Here, we apply biomagnetic monitoring to a) discriminate between potential PM10 sources around a steelworks, and b) examine magnetic source differentiation for a combined, U.K.-based, magnetic dataset (steelworks, roadside, power-generating site). Tree leaves (sampled September 2009, as passive PM receptors) and putative sources were subjected to rapid magnetic characterisation (magnetic remanence measurements). Fuzzy cluster analysis of the combined dataset identified three clusters, showing that particulates emitted from vehicle fleets (e.g. diesel/petrol), and from different industrial processes can be magnetically differentiated. Cluster analysis of the steelworks leaf receptors and potential sources identified seven magnetic groupings. Leaves from one PM ‘hotspot’ showed no affinity with any available source sample, suggesting an as yet untested PM source. These data indicate the value of fast, inexpensive magnetic techniques for particulate source discrimination and indication of ‘missing’ sources.