What is Heavy Metal Toxicity?
Heavy metals, in terms of health, are natural substances that can build up and cause harm to the environment, living things, and humans. They include substances known as semimetals or metalloids that can also have harmful effects.
We can come into contact with heavy metals by breathing them in, eating them, or through skin contact. Heavy metal pollution can contaminate our air, water, sewage systems, and oceans. Additionally, these metals can build up in plants, crops, seafood, and meat, indirectly affecting humans. Certain jobs increase the risk of exposure to specific heavy metals and their toxic effects.
Some heavy metals are harmful even in very tiny amounts, and are referred to as non-threshold heavy metals. The risk of experiencing toxic effects from heavy metals can be influenced by factors such as age, weight, genes, how you were exposed, how long you were exposed, how much you were exposed to, your health, your nutritional status, and exposure to multiple heavy metals. Some alternative medicines can also result in toxicity.
The symptoms and effects of heavy metal toxicity depend on the type of heavy metal, and can be due to being exposed to large amounts at once, or small amounts over time which can result in toxic build-up. Multiple body systems can be affected. Exposure to multiple heavy metals can cause more damage than exposure to one.
Tests that can detect heavy metal toxicity include tests of urine, blood, skin, nails, and hair. Treatment includes avoiding further contact with the heavy metal, using substances called chelating agents to get rid of the toxic material, as well as supportive treatments and education about the condition.
Preventing or minimizing exposure to heavy metals is crucial, and there are laws in place to help ensure this. Public health measures include monitoring air, water, food, and at-risk people, and controlling the environment, particularly soil, water, and sewage systems, to minimize contamination.
What Causes Heavy Metal Toxicity?
Heavy metals (HMs) are substances found in nature. These substances can be harmful as they build up in the environment and in living things.
Some elements like Arsenic (As) are considered semi-metals or metalloids because they have characteristics of both metals and non-metals, but are labeled as heavy metals because they can have harmful effects similar to metals.
There are certain heavy metals that aren’t needed in the body and can cause harm, such as Arsenic (As), Cadmium (Cd), Lead (Pb), and Mercury (Hg). However, there are also heavy metals which, in very small amounts, are actually essential for the body to carry out various functions, such as Cobalt (Co), Copper (Cu), Chromium (Cr), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Selenium (Se), and Zinc (Zn).
People can come into contact with heavy metals naturally, but also through certain job activities.
The ways in which these heavy metals can harm us and the risk of this happening are outlined in Tables: 1 and 1A.
People can ingest heavy metals, breathe them in, or absorb them through the skin. This can happen through our surroundings, like during mining or agriculture, or consuming food like plants, seafood, or meat which have accumulated heavy metals from polluted soil, rivers, or the ocean. Health problems from exposure to more than one heavy metal can be more severe. Some traditional medicinal concoctions may also contain harmful levels of heavy metals. Children are more prone to be affected than adults. Extreme exposure over a short time can cause acute toxicity, while smaller exposure over a longer period can cause chronic toxicity.
Regarding Mercury (Hg), industrial waste containing Mercury is disposed of into our waters. Microorganisms in the water change this Mercury into another form which fish then ingest. When we eat these fish, we also ingest the Mercury which can lead to heavy metal toxicity.
When renovating old buildings, it’s important to be careful when dealing with old, flaky paint. Sanding can spread lead and other toxins into the air and dust, so it’s better to use a vacuum or suction method instead.
Risk Factors and Frequency for Heavy Metal Toxicity
Heavy metal (HM) toxicity is a global issue. The severity and the types of heavy metals involved vary based on factors such as geographic location, soil content, lifestyle habits, proximity to industries, pollution regulations, access to healthcare, nutritional status, and genetics.
When a heavy metal is released into the environment, it gets absorbed by plans and crops, eaten by livestock and fish, and ultimately enters the human body through the food chain. People can also get exposed to heavy metals, and thus toxicity, due to their work environments, through means like inhaling, swallowing, or skin contact.
According to the World Health Organization (WHO), four out of the top ten pollutants are heavy metals. If groundwater gets contaminated with heavy metals, humans consuming it can suffer from long-term exposure, resulting in chronic heavy metal toxicity. An example of this is the excessive amount of arsenic in the groundwater in Bengal, India, and neighboring Bangladesh, which significantly exceeds the safe limits.
Sadly, there have been multiple instances throughout history where heavy metal toxicity has occurred on a large scale due to careless disposal of toxic industrial waste into the environment. This waste gets released into the air, soil, seas, and water bodies, impacting both wildlife and humans in the process. Some real-life instances include:
- Hunter-Russell syndrome in England, caused by workers inhaling methyl mercury in a seed-packing factory.
- The Minamata disease in Japan, due to industries releasing methyl mercury into rivers and seawater.
- “Itai-Itai (it hurts-it hurts) disease” in Japan, caused by the build-up of Cadmium in bones, leading to pain and fractures.
- Mercury poisoning epidemic in Iraq, where people consumed grains that were sprayed with pesticides containing mercury.
- The infamous case of groundwater contamination with chromium VI in California by a Gas Company that disposed of its waste into the area’s groundwater.
Epidemiological studies have shown a clear link between exposure to heavy metals and the development of chronic diseases. These include diabetes, kidney disease, neurological disorders, skin diseases, respiratory diseases, cardiovascular diseases, and even cancer.
Signs and Symptoms of Heavy Metal Toxicity
Heavy metal toxicity is a condition that is often not diagnosed due to the lack of clear symptoms. This happens when your body absorbs high levels of heavy metals like lead and mercury, either through the environment, certain jobs, or some medicines. Recognizing the potential sources of heavy metals is key to identifying the condition. Suspected sources can include alternative medicine with heavy metal components, older homes with lead-based paint or pipe systems, and areas with industrial contamination. Furthermore, exposure during pregnancy can impact a newborn’s health and development. Children may also be at higher risk, displaying symptoms such as lack of focus, loss of appetite, abdominal pain, anemia, and developmental delays.
While accidental ingestion is the most common cause, in some cases, the exposure might be intentional and suicidal, requiring mental health support. If a person is exposed to more than one heavy metal, the symptoms might be more severe. Acute and immediate exposure often results in clear symptoms while long-term chronic exposure can cause more subtle signs. These signs can vary depending on which organ system the heavy metal affects.
Certain heavy metals can cause specific symptoms; for instance, lead toxicity might cause a blue line to appear on the gums, mercury toxicity may result in identifiable lines on the nails, and chromium toxicity can cause skin ulcers that look as if they’ve been cut cleanly and have raised, thickened edges. Please refer to the referenced tables for a more detailed list of symptoms associated with each heavy metal.
Testing for Heavy Metal Toxicity
If your doctor suspects heavy metal toxicity, several tests can help confirm this. These tests might examine your blood, urine, hair, nails, or tissue samples. To ensure accurate readings, you should avoid eating seafood for at least two days before the tests. If you’ve recently had a medical procedure using iodine contrast (a special dye used in some medical imaging tests) or a type of metal called gadolinium, you’ll need to wait at least four days instead.
For people who work in industries with heavy metal exposure, regular blood and urine tests are important. These tests are usually done at the end of the workweek to reflect the actual levels of exposure. Special containers, which are free of metal for blood or specially washed for urine samples, are used to ensure the most accurate readings.
It’s important to know that the amount of heavy metals you see in your blood or urine represents recent exposure. These tests might not accurately show long-term exposure. So, even if your heavy metal levels are just a little higher than normal, you might still have significant symptoms. In some cases, a test called a chelation challenge might be necessary. This test involves giving a medication that binds with the heavy metals, so they can be measured more easily in tests.
Other tests can also be helpful, such as blood tests to look for anemia or tests to look at liver and kidney function. Changes in certain blood chemicals or proteins can suggest damage related to heavy metal exposure. For instance, changes in phosphate or calcium levels, proteins in the urine, or vitamins related to bone health can suggest bone disease from exposure to a heavy metal called cadmium.
X-ray images of your abdomen or chest may show the presence of heavy metals or signs of damage from inhaling these substances. These images might also help your doctor rule out other conditions that can cause similar symptoms, such as infections or cancer.
There are also specific tests to look for exposure to certain types of heavy metals. For example, the beryllium lymphocyte proliferation test can detect past exposure to beryllium, a metal that can cause lung disease. Similarly, a Chronic Arsenic Intoxication Diagnostic Score can help gauge the risk of long-term toxicity from arsenic exposure.
Finally, advances in technology are helping to detect heavy metal pollution in water supplies faster and more accurately. The study of how different genes respond to heavy metals may also help us understand how these substances can cause cancer.
Treatment Options for Heavy Metal Toxicity
If a patient is exposed to harmful metals, the first step in treatment involves removing them from the source of exposure. The body can then be helped in eliminating the harmful metals through methods like stomach washing, activated charcoal treatment, and skin decontamination. Medical professionals also offer supportive care like intravenous fluids, oxygen, and assistance for breathing and blood circulation if necessary. In severe cases, treatments like hemodialysis, plasma exchange, or extracorporeal membrane oxygenation (ECMO: a treatment that uses a pump to circulate blood through an artificial lung back into the bloodstream) may be required.
Specifically, to remove the harmful metals, doctors administer substances called chelating agents. These substances bind to each specific metal to form a ring-like structure known as a “chelate”. This procedure can be more effective when combined with antioxidants. However, the perfect chelating agent does not exist. A chelating agent should ideally be highly soluble, able to permeate cells, capable of binding most toxic metals to form non-toxic compounds, effective when taken orally or injected into the body, and quickly eliminated from the body. Since no such ideal exists, researchers are exploring the use of plant products as potential chelating agents. These agents, also known as phytochelatins, could potentially offer a cheaper and safer alternative for economically challenged nations where harmful metal exposure is a significant problem.
In treating lead toxicity, a substance called DMSA has been found to be more effective than certain mixtures that were used in the past. In cases of Cd toxicity, a combination of two substances, deferiasirox, and deferiprone, has proven highly effective. In As toxicity, the benefits of chelation therapy outweigh the side-effects and help in preventing acute kidney failure. For this case, either DMPS or DMSA are usually used. Both substances are more soluble in water than past treatments and can be taken orally. In toxcity caused by Ni, Sodium diethyldithiocarbamate has been found useful and superior to past used treatments.
For Hg toxicity, DMSA is very effective, while the use of another substance known as BAL is discouraged as it increases the levels of certain forms of mercury in the brain. It’s also worth noting that Selenium and Vitamin E can support the treatment of Hg toxicity.
In the case of Zn toxicity experienced outside of the cell, doctors use CaEDTA as a chelating agent. However, since it cannot cross the blood-brain barrier, other chelators that can enter cells and have an affinity for zinc have been developed.
What else can Heavy Metal Toxicity be?
The nervous system can be affected in ways that might look like dementia, depression, degenerative disease, or nerve damage outside the brain and spinal cord. The kidneys might be impacted in ways that seem like they’re dealing with certain types of kidney diseases. In addition, more general symptoms like being tired all the time, not feeling hungry, losing weight, and anemia might be mistaken for long-term infections or cancer.
Physical examination findings might not always be obvious and will need careful investigation. For instance:
- Ulcers on the skin caused by Chromium VI might be mistaken for long-lasting ulcers caused by poor blood flow or infections.
- Nickel and Chromium VI, as well as Cadmium, can cause holes in the nasal partition (the wall dividing the two nostrils), which might be confused with a variety of causes, like infections, injury, and problems with connective tissue.
- Severe arsenic poisoning may look like ciguatera poisoning, which is food poisoning from eating certain contaminated tropical and subtropical fish.
- Long-term mercury poisoning might look like pheochromocytoma, which is a rare tumor of the adrenal glands that can cause high blood pressure.
- Lead poisoning can be mistaken for porphyria, a group of rare genetic disorders that affect the nervous system or skin. It might also be mistaken for ADHD (Attention Deficit Hyperactivity Disorder) in children.
What to expect with Heavy Metal Toxicity
The focus should be on preventing exposure to heavy metals (HMs). However, in certain situations where full prevention is not possible (such as industrial exposures), the focus should shift to minimizing contamination. Workers who are at risk of exposure to these metals should take the proper preventative measures. It’s important that their management support them in this, providing the necessary resources and protections. Health authorities should oversee and enforce these preventative measures.
Early detection and minimal exposure usually lead to a good outcome. However, a delayed diagnosis or serious toxic exposure can lead to a worse outcome. Specialized healthcare centers equipped with the necessary testing and treatment facilities may provide better care for severe and complex cases.
The prognosis for the community based on heavy metal toxicity can depend on various factors. These include:
1) Ensuring factories properly dispose of waste materials.
2) Regularly checking soil and groundwater for excessive amounts of heavy metals. If found, measures to remove them can involve methods like:
* Digging them up and getting rid of them.
* Modifying the soil in place.
* Growing certain types of plants that can absorb heavy metals from the soil, a process known as phytoremediation.
* Treating the soil using a method known as asymmetrical alternating current electrochemistry.
* Using nanotechnology to remove toxic heavy metals from the soil and water.
* Implementing new methods to rapidly and effectively remove heavy metals from wastewater. This can offer solutions to widespread polluted waterways, including seawater.
3) Regularly checking seawater for contamination to prevent heavy metals from entering fishing areas, and inspecting seafood for any contamination.
There are three official agencies involved in regulating heavy metals:
* The Food and Drug Administration (FDA), which decides the acceptable levels of heavy metals in food.
* The Centers for Disease Control (CDC), which oversees testing for lead in children who are at risk.
* The Environmental Protection Agency (EPA), which researches the effects of exposure to heavy metals, regulates industrial emissions, and sets the maximum contaminant levels for heavy metals.
Possible Complications When Diagnosed with Heavy Metal Toxicity
Treatment for heavy metal toxicity often involves using substances called chelating agents. However, these agents aren’t free from side effects.
Some chelating agents can cause metal ions to move to other organs, like the brain, which can increase harm to the nervous system. Other chelating agents can bind to essential trace elements in our body and create a deficiency. Also, some can lead to hepatotoxicity, which is a medical term for damage to the liver.
Types of side effects:
- Movement of metal ions to the brain, leading to nervous system damage
- Creation of a deficiency by binding with essential elements in our body
- Liver damage
Preventing Heavy Metal Toxicity
Patients and their families should be cautious of the amount of heavy metals (HMs) that are found in many things like everyday foods, health foods, and over-the-counter medicines. This is especially important when taking care of young children, and if the family lives in an older house.
People who work in industries and other jobs where they may be exposed to heavy metals need to have regular health screenings to check for potential harm from these substances. All workers should work together with health officials and follow safety guidelines to reduce their risk of being exposed to heavy metals. It’s important to keep learning about safety controls to keep their health protected.
Businesses, particularly those in manufacturing, need to know that they have a responsibility to the community to properly get rid of waste materials. It’s important for them to work closely with health departments and city officials to ensure they are following all the rules and regulations for safe waste disposal.
