Abstract: In the o ld indu st rial region of L a Louviere inW allon ia (sou thern part of Belgium ) 4 area’s can be dist ingu ished differing in sou rces of em ission s, popu lat ion den sity, and p resence of green zones. The cen t ral“L a Louviere2 Steelwo rk s”area is den sely popu lated and harbou rs b ig steelwo rk; the“Pow er p lan t2L andf ill”sem i2u rban area con tain s and o ld style landf ill, a coke oven and an o ld pow er p lan t fueled w ith coal. Betw een these two o ld in2 du st rial area’s lies themo re ru ral“In term ediate Green”area, w hereas the“Peripheral”area con tain s bo th ru ral and sem i2u rban zones bu t no impo rtan t sou rces of em ission s. Here w e p resen t the resu lt s of b iomon ito ring test s on healthy residen t s of these fou r area’s. Residen t s of the“L a Louvière2Steelwo rk s”(n = 58) and“Pow er p lan t2L andf ill”(n = 41) areas tend to have, compared to residen t s of the“peripheral area”(n = 65) , less p latelet sön l ( respect ively 248±51 & 245±61 vs 267±66) , mo re lymphocytesöLl (1, 915±5223 & 1, 928±5763 vs 1, 754±442) , mo re CD3 lymphocytesöLl (1, 344±4243 & 1, 344±4423 vs 1214±331, mo re CD8 lympho2 cytesöLl (661±2483 3 3 3 & 614±261 vs 545±193) , mo re CD3+ CD56+ lymphocytesöLl (121±104 (57) 3 3 & 125±99 (38) 3 3 3 vs 86±69) , a h igher comp lem en t C3 serum concen t rat ion and a h igher CEA serum concen t ration.