Final answer:
Hazardous wastes, toxic waste, deforestation, mining operations, and pollution from heavy metals can harm the environment if not managed properly.
Step-by-step explanation:
Some materials that can harm the environment if not managed properly include hazardous wastes, toxic waste, deforestation for agriculture and the timber industry, mining operations, and pollution from heavy metals. These materials can cause pollution to air, water, and soil, leading to the destruction of ecosystems and loss of habitats. Careless human actions, such as improper disposal of garbage and electronic waste, can also contribute to environmental degradation.