What Is a Toxic Chemical?

You've heard that toxic chemicals are bad for you, but what exactly is a toxic chemical? Here's an explanation of what is meant by the term "toxic chemical" as well as examples of common toxic chemicals you may have in your home or encounter in the environment.

The U.S. Environmental Protection Agency or EPA defines a toxic chemical as any substance which may be harmful to the environment or hazardous to your health if inhaled, ingested or absorbed through the skin.

Many useful household projects contain toxic chemicals. Common examples include:

• drain cleaner
• laundry detergent
• furniture polish
• gasoline
• pesticides
• ammonia
• toilet bowl cleaner
• motor oil
• rubbing alcohol
• bleach
• battery acid

While these chemicals may be useful and even necessary, it is important to remember they should be used and disposed of according to instructions on the packaging.

Many toxic chemicals occur in nature. For example, plants produce toxic chemicals to protect themselves from pests. Animals produce toxins for protection and to capture prey. In other cases, toxic chemicals are simply a by-product of metabolism. Some natural elements and minerals are poisonous. Here are some examples of natural toxic chemicals:

• mercury
• snake venom
• caffeine in coffee, tea, kola and cocoa
• arsenic
• ricin from castor beans
• petroleum
• hydrogen sulfide
• chlorine gas
• smoke

The US Occupational Safety and Health Administration (OSHA) has identified several chemicals it considers highly hazardous and toxic. Some of these are laboratory reagents, while others are used commonly in certain industries and trades. Certain pure elements are included. Here are a few substances on the list (which is extremely long):

• acetaldehyde
• acetone
• acrolein
• bromine
• chlorine
• cyanogen
• isopropyl alcohol
• l-limonene
• hydrogen peroxide >35%

Labeling a chemical as "toxic" or "non-toxic" is misleading because any compound can be toxic, depending on the route of exposure and the dose. For example, even water is toxic if you drink enough of it. Toxicity depends on other factors besides dose and exposure, including species, age, and gender. For example, humans can eat chocolate, yet it's toxic to dogs. In a way, all chemicals are toxic. Similarly, there is a minimum dose for nearly all substances below which toxic effects are not seen, called the toxicity endpoint. A chemical can be both necessary for life and toxic. An example is iron. Humans need low doses of iron to make blood cells and perform other biochemical tasks, yet an overdose of iron is deadly. Oxygen is another example.

Toxins may be categorized into four groups. It's possible for a substance to belong to more than one group.

• Chemical Toxicants - Chemical toxins include both inorganic substances, such as mercury and carbon monoxide, and organic compounds, such as methyl alcohol.
• Biological Toxins - Many organisms secrete toxic compounds. Some sources consider pathogenic organisms to be toxins. A good example of a biological toxin is tetanus.
• Physical Toxicants - These are substances that interfere with biological processes. Examples include asbestos and silica.
• Radiation - Radiation has a toxic effect on many organisms. Examples include gamma radiation and microwaves.