Like any product that is widely used and sold, overexposure can cause significant health problems. Many of us occasionally come into contact with diesel fuel and its emissions when we use heavy power equipment or when we follow a large truck up a hill. However, workers in industries such as the railroad, construction and trucking often breathe in large amounts of diesel exhaust every day on the job. Studies show that occupational exposure to diesel fumes is the leading cause of toxic exposure. Diesel fumes contain carbon monoxide and certain carcinogens, which can cause cancer. Respirators can help slow negative effects of inhalation when properly used.