Environmental disease is when someone gets sick because the environment is polluted or dangerous. This can include air pollution, water pollution, and exposure to hazardous substances like toxic chemicals and radiation. For example, if a factory near a city is polluting the air, people who live nearby may get sick because they're breathing in the bad air and it can damage their lungs. People could also get sick if they're drinking water that has been contaminated with chemicals or has harmful bacteria in it. Environmental diseases can make people very sick and can even be deadly.