Contaminants are substances that make something impure or unclean, often posing risks to health and the environment. They can be found in air, water, soil, and food, and can originate from various sources, including industrial processes, agricultural activities, and household products. Common examples include heavy metals, pesticides, and bacteria. The presence of contaminants can lead to serious health issues, such as respiratory problems or foodborne illnesses. Regulatory agencies, like the Environmental Protection Agency (EPA), monitor and set limits on contaminants to protect public health and the environment. Reducing exposure to these harmful substances is essential for maintaining a safe and healthy ecosystem.