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Pollution-related lead (Pb) and mercury (Hg) in mor layers of Southern Sweden might have effects on soil biology, although in the literature effect concentrations have been identified at much higher levels. Considerable small-scale spatial variability in heavy metal contents and microbial respiration in mor layers of forest sites was used to calculate correlations that could reveal toxic effects. Negative correlations were always strongest at sites with high loads of Pb or Hg, which was considered to indicate metal toxicity. The high load sites were found in Southwestern Sweden, locally at a motorway and at a chlorine-alkali factory. Other factors of possible influence, such as other pollutants, age of organic material or climatic differences, would affect high and low load sites alike. Negative correlations with respiration were found for Pb at sites with ≥74 μg g−1 of mean Pb content in Of-layer and for Hg at ≥0.25 μg g−1.