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Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Water pollution contributes to water shortages by making some water sources unavailable for use. In underdeveloped countries, raw sewage is dumped into the same water that people drink and bathe in. Even in developed countries, water pollution affects human and environmental health. Water pollution includes any contaminant that gets into lakes, streams, and oceans. The most widespread source of water contamination in developing countries is raw sewage. In developed countries, the three main sources of water pollution are described below. Wastewater from cities and towns contains many different contaminants from many different homes, businesses, and industries (Figure 1.1). Contaminants come from: Sewage disposal (some sewage is inadequately treated or untreated). Storm drains. Septic tanks (sewage from homes). Boats that dump sewage. Yard runoff (fertilizer and herbicide waste). Large numbers of sewage spills into San Francisco Bay are forcing cities, water agencies and the public to take a closer look at wastewater and its impacts on the health of the bay. QUEST investigates the causes of the spills and whats being done to prevent them. Click image to the left or use the URL below. URL: Factories and hospitals spew pollutants into the air and waterways (Figure 1.2). Some of the most hazardous industrial pollutants include: Radioactive substances from nuclear power plants and medical and scientific sources. Heavy metals, organic toxins, oils, and solids in industrial waste. Chemicals, such as sulfur, from burning fossil fuels. Oil and other petroleum products from supertanker spills and offshore drilling accidents. Heated water from industrial processes, such as power stations. Runoff from crops, livestock, and poultry farming carries contaminants such as fertilizers, pesticides, and animal waste into nearby waterways (Figure 1.3). Soil and silt also run off farms. Animal wastes may carry harmful diseases, particularly in the developing world. The high density of animals in a factory farm means that runoff from the area is full of pollutants. Fertilizers that run off of lawns and farm fields are extremely harmful to the environment. Nutrients, such as nitrates, in the fertilizer promote algae growth in the water they flow into. With the excess nutrients, lakes, rivers, and bays become clogged with algae and aquatic plants. Eventually these organisms die and decompose. Decomposition uses up all the dissolved oxygen in the water. Without oxygen, large numbers of plants, fish, and bottom-dwelling animals die.
Output:
contaminants such as radioactive substances, toxic chemicals and petroleum come from __________.