Soon, sewage systems were built to manage wastewater. After sewers were put in, there was a noticeable decrease in the amount of disease that was affecting people so badly. Adding sewers to the cities had a positive impact on the living conditions of the people, but unfortunately, that didn't last for very long. During the early 1900s, pollution from factories was becoming a problem. The water and air pollution began to rapidly increase because of chemical wastes such as sulfuric acid and also other types of pollutants. By the 1900s, water and air pollution just kept getting worse. Because of the severe pollution, many fires were caused. The Cuyahoga River in Cleveland, Ohio burst into flames several times because it was so polluted. This and other events were serious enough problems that the Clean Water Act was started in 1972. This has helped take care of some of the water pollution in the US, but experts are still concerned today that there are still many risks to people who could be exposed to the pollutants in the water.
Water pollution has a negative effect on plants and animals as well as people. Pollution now is a lot worse than it was in the 1800s when fertilizers and other toxic chemicals that humans use nowadays weren't around to contaminate the environment. Human activities have lately been contaminating ecosystems around the world. Although fertilizers have improved crop production all around the world and aren't directly toxic, they can alter the nutrient system in the water that organisms live in. Thousands of beneficial insects, fish, and other organisms can be killed by the chemicals that wash into streams, groundwater, and waterways when it rains. When excessive amounts of nutrients get into water, an algal bloom occurs. The pesticides or fertilizer can stimulate the growth of too much phytoplankton and algae. Harmful algal blooms of species that produce deadly toxins are sometimes called "red tides" or "brown tides" because of their appearance in the water.
