Have you ever wondered about the impact of metals? Metals are everywhere, from the products we use daily to the materials in our workplaces. Today, we will explore the critical issue of metal toxicity and how it can affect our health.
This post will delve into the different types of toxic metals, how they can enter your body, and the potential health risks they pose. We’ll also cover practical tips for minimizing exposure to these harmful substances. By the end, you’ll be equipped with the knowledge to protect yourself and maintain a healthier lifestyle.
What You’ll Learn
- Types of Toxic Metals: Understand the toxic metals and their sources in our environment.
- Health Risks of Metal Exposure: Learn about the potential health effects of exposure to toxic metals and how they can impact your well-being.
- Minimizing Metal Exposure: Discover practical strategies to reduce exposure to harmful metals.
Introduction
Metals affect systems and organs within the human body in different ways. Let’s describe metals’ chemical structure and properties to understand how this happens. Metallic elements and metallic compounds (alloys) are strong, lustrous, and malleable. They are also able to conduct electricity. This makes them highly versatile in many applications, such as:
- Copper is drawn out into threads and used in electrical wire.
- Aluminum is used as a reflector of heat.
- Steel pressed into the shape of motor vehicle panels.
- Platinum and gold for jewelry.
The Chemistry of Metals and its Importance to the Human Body
Most elements in the periodic table are metals, found in groups I to VI and the transition block. Most metallic elements have very few electrons in their outer shell. This means that metals bond as the positive ions from each atom repel one another but are attracted to the negative ions (electrons).
Metals are needed for normal functioning and homeostasis in our bodies. However, the levels of essential metals must be kept within a concentration range. With typical absorption, essential metals are taken up from the gut, and heavy metals may also affect the diversity of gut microbiota (Assefa & Köhler, 2020). They bind with a carrier protein, transport (or store) protein, and move throughout the body. However, non-essential meals use this path, taking advantage of the exact mechanism. Therefore, the degree of update of non-essential metals is influenced by the concentration of other metals in the gut (Kim et al., 2019).
Essential metals have several functions in the body. Mostly, they are bound to enzymes (as metalloenzymes) for the enzyme to become activated. Their use includes assisting in the carriage of oxygen (iron in hemoglobin), as cellular messengers (calcium acts as a trigger mechanism for the nerves’ post-synaptic transmission and muscle contraction), in the structural components of proteins as nucleophiles. Common metals found in enzymes include sodium, potassium, calcium, magnesium, manganese, zinc, iron, cobalt, nickel, molybdenum, and tungsten.
Another essential part of metal toxicology is metals’ ability to interact with other metals. This can result in a synergistic or antagonistic relationship. For instance, exposure to cadmium can cause the displacement of zinc in some metalloenzymes. Lead can cause calcium displacement, leading to lead storage in bone and inhibition of postsynaptic transmission.
Examples of Industrial Exposure to Metals
Metals and their compounds can exist in various forms (dust, fume, mist, vapor, or gas). In an industrial setting, however, most occupational exposure occurs from particulates or aerosols because most metals and their salts are solids. The exception is mercury and some metal hydrides, such as arsine and stibine, which exist in the gaseous state or have a high enough vapor pressure at room temperature to exist as vapor.
Some specific examples of exposure to metals include;
- Lead oxide fume when removing impurities from gold
- Mercury vapor, where a manometer has blown or broken
- Zinc oxide fume from the production of metallic zinc after roasting zinc sulfide ore, which is then reduced using carbon monoxide
- Tungsten carbide and cobalt dust from machine grinding of hard metal tools.
In some cases, elements are not strictly metallic. These substances are known as metalloids. The metalloids include boron, silicon, germanium, arsenic, antimony, tellurium, and polonium,
Metalloids have properties similar to those of both metals and nonmetals. For instance, they conduct electricity poorly under certain conditions and are called semiconductors. Because of this characteristic, semiconductors are used in electronics and computers.
Acute and Chronic Exposure
Metals may show their effects through acute or chronic exposure. Acute effects result from inhaling air or ingesting liquids containing metals in very high concentrations. Some metals, such as mercury and thallium, may be absorbed through the skin. Inhaling high concentrations of metals is irritating and may cause severe damage to the respiratory tract. Many metals are also sensitizers. Exposure to nickel, for instance, may lead to a rash called nickel itch. Other metals (e.g., chromium) can cause skin and mucous membrane corrosion.
Chronic exposure to metals has also been well documented, for instance:
- Lead exposure from operations reclaiming lead-acid accumulator batteries
- Felting involving the use of inorganic mercury compounds, which caused several central nervous system symptoms, including a pronounced tremor
- Manganese exposure from welding hard metals, such as dragline buckets from coalmines
- Inorganic arsenic, an impurity of lead and copper ores, is given off during smelting.
Since most exposure to metals occurs through inhalation of particulate (dust or metal), most workplace monitoring requires dust sampling. However, where the metal becomes airborne as an aerosol (such as in an electroplating process where chromium and nickel are the metals), these aerosols are monitored similarly to particular clouds containing metals.
Summary
Many metals are essential to maintaining the body’s homeostasis. However, some can put workers’ health at risk, causing adverse health effects and polluting the environment.
The major route of entry of most metals and metalloids is through inhalation of the dust or fume. Exposure via ingestion or through the skin occurs less frequently.
Some examples of occupationally significant metals include aluminum, antimony, beryllium, boron, cadmium, chromium, cobalt, copper, lead, manganese, mercury, nickel, tin, vanadium, and zinc.
Helpful Resources
- Fundamentals of Industrial Hygiene, by Jill Niland and Lucy Elam
- Industrial Hygiene Monitoring Blog Post, by Megan Tranter
- Occupational Exposure Limits Blog Post, by Megan Tranter
Bibliography
Assefa, S., & Köhler, G. (2020). Intestinal microbiome and metal toxicity. Current Opinion in Toxicology, 19(February), 21-27. https://www.sciencedirect.com/science/article/abs/pii/S2468202019300671
Kim, J.-J., Kim, Y.-S., & Kumar, V. (2019). Heavy metal toxicity: An update of chelating therapeutic strategies. Journal of Trace Elements in Medicine and Biology, 54, 226-231. https://www.sciencedirect.com/science/article/abs/pii/S0946672X1830748X
