Dust is a particulate contaminant suspended in the atmosphere. Like carbon dioxide it limits the amount of energy arriving and leaving the surface of the planet, with consequent changes in weather patterns. Industrial, transport and domestic equipment all release particles of dust into the atmosphere. Such man-made contaminants include: carbon and metal flakes, nuclear bomb debris, pesticides and other agricultural chemicals, and lead from combustion engines. The exposure of man to dusts can lead to a wide variety of respiratory diseases, including pulmonary fibrosis, obstructive lung disease, allergy and lung cancer.