Firefighters are potentially at increased risk for cancer and non-malignant respiratory disease due to their toxic exposures on the job. Growth factors and oncogene proteins are thought to play a role in the development of various malignancies and pulmonary fibrotic diseases. Therefore, a cohort of firefighters and matched controls have been screened for the presence of nine different growth factors and oncoproteins using an immunoblotting assay. Fourteen of the firefighters were found to be positive for β-transforming growth factor (β-TGF) related proteins compared to no positives in the controls (P=0.0017). These results suggest that β-TGF may be a possible biomarker for monitoring firefighters and other exposed workers for the potential development of cancer or non-malignant respiratory disease.