Occasional overexposure and sunburn are probably greater risk factors for melanoma than long-term moderate exposure. Environmental factors may affect aging, for example, overexposure to ultraviolet radiation accelerates skin aging. The exposure time is managed so that the skin does not suffer overexposure. Severe overexposure may cause weakness, drowsiness, and unconsciousness. They can be sunburned and display a yellowing chlorotic reaction to overexposure to sunlight. Fluorosis leads to mottled enamel and occurs from overexposure to fluoride. Zinc toxicity is a medical condition involving an overdose on, or toxic overexposure to, zinc. Chronic overexposure can have adverse effects on the thyroid. Camera overexposure was also occasionally used to avoid continuity errors. Vitamin D deficiencies and UVR overexposure are concerns for many. Film can often have areas of extreme overexposure but still record detail in those areas. Overexposure to mercury, mercurialism, was seen as an occupational disease to the ancient Romans. Engineering noise controls can be used to reduce noise propagation and protect individuals from overexposure. Occasionally, a pen name is employed to avoid overexposure. Bright areas due to overexposure are sometimes called blown-out highlights.