Final answer:
Building factories on river banks led to significant environmental pollution, including industrial waste contaminating water supplies, toxic runoff from mines, and poor living conditions for workers, which affected human health and ecosystems.
Step-by-step explanation:
The disadvantages of building factories on river banks included significant environmental impacts such as pollution and health risks. Factories often released untreated industrial waste directly into rivers, which led to the contamination of drinking water sources for downstream communities.
Building factories on river banks led to significant environmental pollution, including industrial waste contaminating water supplies, toxic runoff from mines, and poor living conditions for workers, which affected human health and ecosystems.