Pollution in cities during the late 1800's was caused in part of horses, coal and inadequate sewer systems

That's true. In the 1800s, burning coal was the main method of heating homes, water and cooking food. Burning coal gave off a lot of pollution, including gases like sulfur dioxide and carbon dioxide. In Britain, manufactured gas also started at this time, and the waste was dumped in rivers and sewers which then became polluted.