This study evaluated the hazard caused by $NO_{2}$, an oxidant generated in the process of welding. We compared hematological and biochemical parameters in workers who chronically inhale $NO_{2}$ and office workers not exposed to $NO_{2}$. $NO_{2}$ exposure affected the hematological and biochemical parameters. Increasing $NO_{2}$ concentrationincreased the number of leukocytes, while decreasing the number of erythrocytes. Blood urea nitrogen, creatinine, uric acid, and lactate dehydrogenase were increased, while total protein and triglycerides were decreased. The mean concentration of $NO_{x}(NO_{2}^{-}/NO_{3}^{-})$ in the serum of welders and the control group was $35.97{pm}2.85;and;55.40{pm}5.81;{mu}mol/L,$ respectively. The difference was significant (p < 0.05), although $NO_{2}^{-}$ was not detected in the serum.
