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The partitioning of organic soil pollutants into soil organisms is driven by their chemical activity, which normally does not exceed that of the pure pollutant. Passive dosing with the silicone poly(dimethylsiloxane) (PDMS) was used to initiate and maintain the maximum chemical activity of 10 polycyclic aromatic hydrocarbons (PAHs) in toxicity tests with the springtail Folsomia candida. The test animals could move freely on the PDMS saturated with PAHs, resulting in direct contact and exposure to saturated air. After 7 days, springtail lethality correlated neither with the octanol−water partition coefficients of the PAHs nor with their molecular size, but with their melting point. All low-melting PAHs (T_M ≤ 110 °C) caused 100% lethality, whereas all high-melting PAHs (T_M ≥ 180 °C) caused no significant lethality. The lethality was successfully fitted to one chemical activity response curve for all PAHs tested, with effective …