News from CRIS: Everyday Toxicology - Exposure

June 10, 2024

What is exposure?

Exposure is the way we physically come in contact with an ingredient or contaminant. We are exposed to many different ingredients and elements daily, most of which do not cause us harm.

We are primarily exposed to ingredients through food, beverages, medications, topical products, inhalants, and personal care items we use regularly. This exposure allows our body to come into contact with essential chemicals such as nutrients, including vitamins, minerals, proteins, fats, and more.

What are exposure routes?

Exposure routes are the pathways that allow ingredients to enter our bodies.

Primary exposure pathways include:

  • Inhalation: Breathing in airborne substances, such as gases and dust.

  • Ingestion: Consuming substances through eating or drinking, including food, water, or medications.

  • Dermal (Skin) Contact: Absorbing substances through the skin, such as from cosmetic products.

  • Mucosal Contact: Absorption through mucous membranes, include

    • Oral: Through the lining of the mouth.

    • Nasal: Through the nasal passages.

    • Ocular: Through the eyes.

    • Vaginal: Through the vaginal lining.

    • Rectal: Through the rectal mucosa.

  • Injection: Direct introduction into the body through needles, medical procedures, or accidental punctures.

What happens when our body is exposed to a chemical ingredient?

Our body is a complex system capable of managing and operating numerous processes simultaneously and efficiently. When exposed to an ingredient, our bodily systems immediately begin to absorb, distribute, metabolize, and eliminate the substance.

  • Absorption is the process by which substances enter the body's internal environment from the exposure site. This process involves the movement of chemicals, nutrients, or other compounds from the surface of the skin, lungs, gastrointestinal tract, or mucous membranes into the bloodstream or tissues.

  • Distribution occurs once the absorbed chemical is transported via the bloodstream to various organs and tissues in the body.

  • Metabolism and Elimination are the processes our organs undertake to break down or make compounds more water soluble to enhance their excretion. Key organs involved include

    • Liver: The liver primarily processes nutrients to be used throughout the body and modifies toxicants, often making them more water-soluble so they can be more easily eliminated from the body by the kidney.

    • Kidneys: The kidneys mainly filter blood to help remove compounds and byproducts from the body via urine.

    • Colon: The colon eliminates byproducts from the body via bowel movements.

    • Lungs: The lungs eliminate airborne byproducts and gases via breathing.

Why does the exposure route matter?

The exposure route can determine whether an ingredient is safe or harmful. Many compounds may be harmless when encountered through one route but can cause severe adverse health effects when exposed through another.

Let's look at vitamin E acetate.

Vitamin E acetate is a Generally Recognized as Safe (GRAS) ingredient, meaning it's safe for typical human consumption because our digestive system can safely process it. It is also considered safe for dermal use and is found in lotions, soaps, and more because our skin processes it without adverse effects.

However, the safety of vitamin E acetate does not transfer to inhalation. Manufacturers added it to vaping liquids, and it led to severe, adverse health outcomes, including the need for organ transplants and death.

As you can see, the exposure route for vitamin E acetate dramatically changes the health outcome.

What happens when our body is exposed to a potentially harmful chemical ingredient or contaminant?

First and foremost, it's essential to recognize that everything on the planet—be it you, me, rocks, or bananas—is composed of chemicals. What's key is identifying the specific compound in question, understanding its safe dosage, and determining whether our exposure route, amount, and duration (dose-rate) is within safe limits or potentially harmful.

Our bodies respond in many ways depending on the contaminant, toxicant, or chemical ingredient to which to our system is exposed. The response will vary greatly depending on the exposure route, dose, and dose-rate.

Let's take a deeper look.

Ingestion–eating food—is how our body gets the nutrients we need to live. Food can contain beneficial chemical nutrients while also containing some contaminants that may cause harm if we're exposed to too much of the contaminant.

For example, if we eat seafood, our body will absorb iodine from the seafood. The iodine will enter the bloodstream and travel to the thyroid, then the thyroid will use it to synthesize hormones. Without iodine, our thyroid will not function properly.

However, if the seafood contains a contaminant such as mercury, our liver and kidneys will filter out the mercury–to a point–without harm. We only need to worry about harm from too much mercury if we consume more than the recommended amount of seafood in a week (dose-rate) because in that rare situation our body may not keep up with the elimination process, and we can have adverse health outcomes over time.

We safely eat seafood and enjoy its health benefits without harm because our body can process the nutrients and eliminate the contaminants when consumed in moderation.

Personal care products function similarly.

People can safely use products that are exposed to mucus membranes, such as tampons, without adverse health effects from chemical ingredients because our body isn't exposed to levels of chemical ingredients (dose) over a long time (dose-rate) that can cause harm. Our body may absorb, process, and eliminate some of the ingredients, but not at levels known to be harmful.

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To continue reading the entire blog post, visit: https://www.canr.msu.edu/news/everyday-toxicology-exposure2.