Concentrations of heavy metals and sulphur were measured in soil and oak leaves from localities situated at different distances from an ironwork. The iron concentration in oak leaves, lead concentration in soil and the soil pH decrease with the increasing distance from the emission source. The concentration of monosaccharides in oak leaves changes in the same way but that of macromolecular polysaccharides and tannins increase with a distance. A laboratory test on the two dominant moth species, Cheimatobia brumata, a feeding generalist, and Tortrix viridana, feeding exclusively on oak leaves, shows that the increase of nutritive value of oak leaves makes the time of the development of C. larvae shorter and the weight of pupae greater. Caterpillars of T. viridana survive much better and their pupae are heavier on oak leaves of a lower nutritive value.