Carbon monoxide, or “CO,” is an odorless, colorless gas that can kill you. CO is found in fumes produced any time you burn fuel in cars or trucks, small engines, stoves, lanterns, grills, fireplaces, gas ranges, or furnaces. CO can build up indoors and poison people and animals who breathe it. The most common symptoms of CO poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion. CO symptoms are often described as “flu-like.” If you breathe in a lot of CO it can make you pass out or kill you. People who are sleeping or drunk can die from CO poisoning before they have symptoms.

Pesticides are poisons and, unfortunately, they can harm more than just the “pests” at which they are targeted. They are toxic, and exposure to pesticides can cause a number of health effects. They are linked to a range of serious illnesses and diseases from respiratory problems to cancer.

In biochemistry, a poison is defined as any substance—whether natural or synthetic—that can damage living tissue and cause harmful or even fatal effects in the human body. The way a poison enters the body is just as important as the substance itself. A chemical may be dangerous when swallowed, inhaled, absorbed through the skin, or injected directly into the bloodstream. Each route of exposure changes how quickly and severely the body is affected.