Final answer:
Unforeseen damage caused by man-made substances is illustrated by the pollution in the Gulf of Mexico, the presence of Oscillatoria rubescens in Lake Washington, and the condition of the ozone layer.
Step-by-step explanation:
The fact that useful man-made substances can cause unforeseen damage is illustrated by the pollution of the Gulf of Mexico from farm chemicals, the detection of Oscillatoria rubescens in Lake Washington, and the condition of the atmosphere's protective ozone layer. These examples show how human activities can lead to unintended negative consequences on the environment. For instance, the pollution from farm chemicals in the Gulf of Mexico has caused a dead zone where low oxygen levels have killed all ocean life, highlighting the unforeseen damage caused by man-made substances.