this suggests that nearly all arsenic that is deposited in the lung is excreted in the urine. We can thus infer that paint factory workers may be exposed to as high as 20 times more arsenic than the general population. The time course of excretion in humans exposed by inhalation has not been thoroughly investigated, but urinary arsenic levels in workers in a smelter rose within hours after they came to work on Monday and then fell over the weekend [43].