See if you can identify all the things humans do that have a negative effect on the environment. Dumping things in the environment is called pollution, in this case water pollution. Water pollution may come from substances that are insoluble in water, like oil and plastic. Other pollutants (substances that cause pollution) may be soluble, like pesticides, herbicides, fertilizers and soap. Pesticides are chemicals used to kill pests like insects. Herbicides are chemicals used to kill unwanted plants like weeds.
When we pollute water with fertilizer or untreated sewage (waste matter) this causes blue-green algae and bacteria to grow. This is called an algal bloom. These algal blooms affect the water colour, as well as the smell and taste. It may also cause skin rash, hay fever, vomiting, diarrhea, fever and muscle and joint pains.