“…Most often, they concluded that the effects depend on the particle composition (PAH and/or metal content) and also the particle size (e.g., [10,40,50,52,72]). In detail, about a quarter of the authors declared that the PAH content/the organic fraction is responsible for the observed toxic effects (e.g., [9,11,37,88]), and fewer authors correlate the toxic effects with the inorganic water-soluble fraction (e.g., [54,62]), while some authors concluded that both parts attribute to overall toxicity (e.g., [23,71]). In contrast, four authors could not correlate the PAH content to the observed effects [25,42,57,86].…”