There are millions of chemicals on Earth — some found in nature, and others made by people. We use them every day in lots of different ways. But it’s important to know that chemicals can be harmful to both people and the planet if they aren’t handled correctly.

A chemical is a substance that has specific properties or characteristics we can use to identify it. They may interact with other substances and change form. Chemicals can get into our bodies through our skin, things we eat and drink, and the air we breathe — this is called exposure. How harmful chemicals are depends on how we’re exposed, the amount of the chemical we’re exposed to, and the length of time that we’re exposed. In addition, some people, such as children or those with health problems, can be more vulnerable to harmful chemicals.

Some content courtesy of the National Library of Medicine.