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Chemical Exposure: Top 4 Pathways + Prevention Tips

By Adrian Bartha
Last updated: July 15, 2024
Key Takeaways

Understanding the different pathways for chemical exposure will help you prevent incidents and provide more effective treatment to workers who have been exposed to harmful chemicals.

Some chemicals have harmful effects that take place at the surface level. Corrosive substances leave burns and wounds. Irritants cause redness, itchiness, and discomfort.

Toxic chemicals have effects that run deeper, including long-term health conditions.

The acute and chronic health problems that come from chemical exposure result from the hazardous substances entering the body through one of four primary pathways:

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  • Inhalation (breathing it in)
  • Ingestion (swallowing it)
  • Ophthalmic absorption (through the eyes)
  • Dermal absorption (through the skin)

From those access points, the substance can enter the bloodstream and reach the lungs, liver, kidneys, and other internal organs.

In this article, we’ll take a look at these four pathways for exposure and what they mean for preventing or treating chemical incidents.

Why Chemical Exposure Pathways Matter

Understanding exposure pathways is important for identifying the best way to prevent chemical exposure incidents, as well as the first aid procedure to follow if such an incident does happen.

A good respirator, for example, will protect workers from inhalation exposure, but won’t prevent a liquid chemical from being absorbed through the skin. Likewise, disposable clothing paired with a half-mask respirator provides a lot of coverage but won’t be sufficient if the chemical reaches the eyes.

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The same applies to other types of control measures. Ventilation can reduce the risk of inhaling an airborne chemical but won’t keep a worker from getting a chemical on their hands.

The treatment an affected person needs will also differ based on the exposure pathway. A worker whose skin has come into contact with a corrosive substance might need to be quickly escorted to the nearest emergency shower. But that response won’t do anything for someone who has ingested a chemical.

Health Effects of Chemical Exposure

It’s the dose that makes the poison.

That’s the basic concept behind the study of toxicology. In theory, anything can be toxic once you reach a certain level of exposure. And conversely, anything is safe at a sufficiently low concentration.

We’re continually exposed to naturally occurring chemicals in our environment and they do us no apparent harm. The human body produces a little hydrogen sulfide, bananas emit a small amount of radiation – no big deal. The difference when we’re talking about toxic chemicals is that they’re refined into concentrations that can cause serious harm to living beings. Although the risks are very real, they’re used safely every day. It’s just a matter of applying the right controls and applying them diligently.

That starts with a thorough understanding of the hazards present in the work environment.

Exposure isn’t limited to products in drums and bottles. Not every hazardous material comes packaged and labeled with their exact contents and concentrations. Industrial and natural processes can produce chemical byproducts that are hazardous to human health.

To ensure the safety of workers, it’s important to understand the types of exposure, their routes, and their controls.

Chemical Exposure Symptoms: Acute vs. Chronic Effects

Understanding the difference between acute and chronic effects of exposure will also inform the type of controls that are needed, along with the kind of information that needs to be provided to affected workers.

Acute Effects

Acute effects refer to those that arise after a single or short-term exposure. They present themselves soon after exposure and often in fairly obvious ways, like stinging eyes, irritated mucosa, or dizziness.

A worker might notice, for example, the presence of ammonia in their breathing zone by the immediate and painful irritation in their eyes, nose, throat, and lungs.

Chronic Effects

Chronic effects, by contrast, are those that arise from single or repeated exposure but realize themselves over time. The effects are cumulative and symptoms may not present themselves for years or decades.

For some types of exposure, the time lag is so great that the connection isn’t apparent at all. Asbestos, for example, can result in serious lung conditions and cancer, which can become severe years after the exposure to the substance has ceased. Indeed, 3,000 cases of mesothelioma, a cancer caused by asbestos with a lag time of 20 to 60 years post exposure, are diagnosed every year in the United States. That means people exposed to it today would still experience health effects from it decades later.

Chemical Exposure Through Inhalation

Inhalation refers to the introduction of a substance through the breathing pathway.

Symptoms

Inhaling chemicals can be locally hazardous, causing irritation or inflammation of the pleura, alveoli, bronchi, or other parts of the respiratory tract. It can also have systemic effects, since the respiratory system is built for gas exchange and is a prime route of entry for any airborne toxic substance.

In addition to exposure, it’s important to discuss the substances that are harmful because they simply displace oxygen (e.g., nitrogen, CO2). In those cases, it isn’t exposure to the substance that has ill effects, it’s the fact that it creates an oxygen deficient atmosphere. This can occur through industrial processes such as inerting a vessel or by natural processes which consume oxygen (decomposition, oxidation).

One of the most well-known harmful inhaled substance is asbestos. Asbestos fibers in the air make their way into the lungs and linger there for years, resulting in the formation of scar tissue that is prone to turning cancerous. Even a single fiber is theoretically enough to kill a person in the long term, which is why most jurisdictions hold that there is no safe dose for asbestos.

Treatment

If a worker has inhaled harmful chemicals:

  • Prevent further exposure by removing them from the area and bringing them outdoors or to a space with uncontaminated air
  • Call paramedics or bring them to the emergency room for medical attention
  • Perform artificial respiration (mouth-to-mouth resuscitation) if they have stopped breathing

Prevention

Inhalation exposure is the trickiest to control, since gases, vapors, fumes, and small particulate matter will disperse into the air and diffuse throughout the local atmosphere.

Since these substances can quickly and thoroughly fill the space, it’s important to protect the breathing zone.

When inhalation hazards are present, workers will need to wear respirators to filter harmful substances from the air. In cases where filtration would be insufficient or too much oxygen has been displaced, workers will require a respirator that supplies them with clean, breathable air (a supplied air respirator or an SCBA).

Chemical Exposure Through Ingestion

Ingestion exposure refers to any substance introduced to the body through swallowing.

At first blush, it might be hard to imagine a scenario in which someone would swallow an industrial chemical, but it’s best to think of these substances as stowaways. While it’s highly unlikely that someone would take a sip from a chemical container, those chemicals can get on surfaces or people’s hands where they can, in turn, contaminate food or beverage containers.

Directly ingesting a chemical isn’t entirely out of the realm of possibility, either. It could happen when chemicals are kept in improperly labelled containers. Methyl Hydrate looks just like water, and I used to work in a shop where people would decant it into water bottles for easy use, which is an ingestion incident just waiting to happen.

Symptoms

The severity of the symptoms will depend less on how much of the chemical has been swallowed and more on how much has been absorbed into the system.

This is reflected in the four types of doses involved in a chemical ingestion incident:

  • Potential Dose: The amount of the chemical that makes it into the mouth
  • Applied Dose: The amount available to be introduced into the body at the absorption barrier within the gastrointestinal tract
  • Internal Dose: The amount that is able to traverse that barrier
  • Biologically Effective Dose: The amount that interacts with the target organ

There needs to be a relatively high dose at the starting point for the chemical to have an effect, since the amount absorbed is reduced through each of these stages.

Treatment

When someone has ingested a chemical substance, it’s typically assumed that the best course of action is to induce vomiting. After all, expelling the substance from the body means that less of it can be absorbed, thereby reducing the effective dose. However, this is only advisable for certain chemicals and should not be done unless it is explicitly mentioned in the Safety Data Sheet (SDS).

In most cases, administering activated charcoal can reduce the absorption of the ingested chemical.

Prevention

The best way to prevent ingestion is by implementing administrative controls to prevent contaminating food or water bottles. These can include:

  • Barring food and drinks from work areas where chemicals are used
  • Requiring workers to wash their hands thoroughly before leaving the work area
  • Training workers on how to safely remove disposable gloves

Chemical Exposure to the Eyes

The human eye is a delicate and intricate system. Damage to any part of it can devastate its function, resulting in partial loss of vision, permanent blindness, or the loss of the eye altogether.

Most chemical exposures to the eye will cause irritation of the cornea (the clear, external surface of the eye) and the conjunctiva (the interior surface of the eyelid).

Symptoms

Chemical exposure to the eyes broadly fall into three categories:

  • Alkali burns
  • Acid burns
  • Irritants

Alkali burns are the most dangerous. Chemicals with a high pH (such as potassium hydroxide or ammonia) can penetrate the eye surface readily and cause damage to both the cornea and deeper eye structures such as the lens.

Substances with a neutral pH (capsaicin, detergent) can cause irritation, pain, and lasting discomfort to the eye without causing a burn.

Treatment

In most cases, the first response to any foreign body or substance in the eye is to irrigate it with sterile, tepid water for at least 15 minutes. Then, seek medical attention.

A quick response is critical for limiting damage to the eye. Any affected worker should be taken immediately to the nearest eyewash station or emergency shower.

Prevention

Protecting the eye from liquid chemical splashes can usually be achieved with safety glasses.

For vapors, fumes, and other chemicals in gas form, safety goggles that form a tight seal around the eyes will be needed instead.

Chemical Exposure Through the Skin

The skin is a robust barrier against many substances – but not all of them.

There are two main types of skin exposure, and it’s worth understanding the differences between them.

  • Exposure to the Skin: Chemical exposure that affects the surface of the skin (causing, for instance, dermatitis, or burns)
  • Exposure Through the Skin: A chemical absorbed into the skin and passing into the bloodstream, which can cause systemic effects

Symptoms

Dermal absorption means that some chemicals can cause harm without being conspicuous. Benzene, for instance, will “de-fat” the skin and cause it to dry out, which often presents as dermatitis. It’s irritating, but many workers would simply put up with the slight discomfort and tough it out. Meanwhile, it is being absorbed through the skin, where it can cause a range of serious problems like anemia, immune system depression, and cancer.

Treatment

Wash the chemical off the skin as soon as possible.

If it covers a large area of the body or is in a spot that is difficult to wash off easily, use the emergency shower if there is one in the facility.

If there is a possibility of dermal absorption (as opposed to a surface-level effect), bring the affected worker to the emergency room so they can be assessed and treated by a medical professional.

Prevention

Covering the skin is the simplest way to prevent dermal exposure.

In many cases, this will simply mean providing workers with chemical-resistant gloves. However, some jobs will also require gowns or coveralls for more extensive protection.

Knowing the nature of the hazard is critical, because simply covering the skin isn’t always enough. Nitrile gloves, for example, are great for working with oil and grease but can be penetrated by acetone. Latex gloves can protect against acetone, but aren’t effective for handling ethyl ether (nitrile is a better option).

When gloves fail, exposure happens. So, always make sure the right PPE is available.

Preventing Chemical Exposure

Safety Data Sheets provide a wealth of information that is critical for chemical safety. Section 6 details safe handling and storage, while Section 7 covers accidental release of the substance. That information should be made available to all affected workers, along with training to ensure that they understand and can apply it when needed.

Follow the hierarchy of hazard controls when dealing with chemicals. Attempt to implement the most effective control measures (Elimination) before moving on to progressively less effective solutions (Substitution, Engineering Controls, Administrative Controls, and finally PPE). If none of these individual methods completely eliminates the risk, consider a combination of controls.

To know exactly what you’re dealing with and how to best protect workers, you will need a thorough risk assessment. In the case of chemical exposure, this is largely handled by industrial hygienists.

Finally, supervision and monitoring can ensure that the chemical safety plan is effective and being followed correctly. Audits and investigations can help identify areas of improvement to reduce the risk of exposure even further.

Conclusion

Hazardous chemicals can not only harm workers, but harm them in a number of different ways. Understanding the different pathways for chemical exposure is the first step to ensuring that your organization’s safety plan provides adequate protection from chemical hazards.

Ready to learn more? Check out our free webinar on Confined Space Gas Detection for Construction Workers and Contractors!

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Written by Adrian Bartha | Chief Executive Officer

Adrian Bartha
Adrian Bartha is the CEO of eCompliance, which he joined in 2012 after experiencing first-hand how a workplace incident affected a power and utilities company which he led as a member of the Board of Directors. Previously, Adrian was an investment professional for a $5 billion dollar private equity firm investing in energy, construction, and transportation infrastructure companies across North America. When Adrian is out of the office, he can be found riding his futuristic motorcycle and wearing his RoboCop helmet.

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