Occupational diseases are illnesses that arise mainly because of exposure to hazardous conditions, substances, or processes in the workplace. The etiological agents of occupational diseases can be broadly classified into physical, chemical, biological, mechanical, ergonomic, and psychosocial agents. Their effects depend on the intensity and duration of exposure, individual susceptibility, and the nature of the occupation. Physical agents include excessive noise, vibration, extremes of temperature, radiation, abnormal atmospheric pressure, and inadequate illumination. Prolonged exposure to high noise levels may cause occupational hearing loss, while vibration from machinery can produce hand-arm vibration syndrome and other circulatory or neurological disorders. Heat may cause heat exhaustion and heat stroke, whereas excessive cold can lead to hypothermia and frostbite. Ionizing radiation from X-rays, radioactive materials, and nuclear sources may cause radiation sickness, cancers, and genetic damage. Non-ionizing radiation such as ultraviolet radiation can cause skin and eye disorders. Chemical agents are important causes of occupational morbidity. They include dusts, gases, vapours, fumes, aerosols, solvents, pesticides, heavy metals, and other toxic substances. Silica dust