Little is known about occupational risks for cardiovascular disease. A few specific toxins encountered occupationally are known to affect the heart, most prominently carbon disulfide, nitroglycerin, and carbon monoxide. There is substantial evidence that environmental tobacco smoke, extreme heat, and extreme cold are risk factors for cardiovascular disease, and it is presumed that they are risk factors when they are encountered in the occupational setting. In addition, while the linkages are not yet understood, numerous studies show a relationship between heart disease and depression and exposure to stress at work. Other work-related exposures potentially related to cardiovascular disease include occupational noise exposure, shift work, and physical activity at work.