Agricultural waste is another great source of water pollution. "Besides depleting the soil, irrigation and other modern agricultural techniques pose additional environmental hazards," Cooper says. (Cooper, Population and the Environment) Agricultural pollution is both a direct and indirect cause of health related issues to humans as well as animals. Agricultural chemicals are used heavily for food productions; excess nitrate in drinking water can reduce the level of oxygen in the blood. This condition is a very real treat to infants and can cause "blue baby disease." In addition, animals' wastes often reach water via the land surface or through surface soil layers. Like other wastes, agricultural runoff, and animal waste can flow through the water and end of in the lakes, rivers and oceans without being treated. This runoff can also affect wildlife and fish, which are a major source of food for humans