In this study we examined the potential for environmental levels of ozone (03) to degrade arachidonic acid (AA), a polyunsaturated fatty acid abundantly present in the lung, into products that can produce DNA single strand breaks (ssb) in cultured human lung cells. Human lung fibroblasts were incubated with 60 microM AA that had been previously exposed to and degraded by 0.4 ppm 03 (1 hr.) Incubation of the cells with 03-exposed AA (but not with vehicle alone) for 1 hr at 4 degrees C and 37 degrees C produced 555 and 245 rad-equivalents of DNA ssb, respectively, as determined by the DNA alkaline elution technique. These breaks were completely eliminated when the ozonized AA solution was incubated with catalase prior to cell treatment, indicating that h202 was solely responsible for damaging DNA. Superoxide dismutase bovine serum albumin, or heat-inactivated catalase showed little, if any, inhibitory activity. The H202 content of the ozonized AA (31 +/- 4 microM) could account for only about 40% of the observed breaks. Potentiation of the H202-induced DNA ssb persisted after removal of the carbonyl substances by chromatographic procedures, suggesting that the non-carbonyl component of ozonized AA was the responsible component for inducing augmentation of the observed increases in DNA ssb. Ozonized AA also induced DNA ssb in cultures of the human bronchial epithelial cell line BEAS-2B. Again, these breaks were shown to exceed levels that could be attributed to the presence of H202 alone. These results indicate that products of ozonized AA can interact to potentiate DNA ssb in human lung cells.