The causes of toxins can vary widely, as they can be derived from both natural and human-made sources. Natural sources include certain plants, animals, and microorganisms that produce toxins as a defense mechanism. Human-made sources of toxins include industrial processes, pollution, chemical spills, and the use of pesticides and herbicides.

Mold exposure is primarily caused by the presence of moisture and dampness in indoor environments, providing an ideal breeding ground for mold growth. Water leaks, high humidity, inadequate ventilation, and poor building maintenance contribute to the growth and spread of mold. Mold can also be found outdoors in areas with high humidity or damp conditions.

Heavy metals can enter the environment through natural processes such as weathering and erosion of rocks and soil, as well as human activities and work environments. Industrial processes, mining, improper waste disposal, and the burning of fossil fuels can release heavy metals into the air, water, and soil. Once released, these metals can accumulate in the food chain and be ingested by humans through contaminated water, food, or air.