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heavy metal band

Heavy metal band (AarStudio, iStockphoto)
 

STEM in Context

A Taste of Heavy Metal

Nicholas Azad & Let's Talk Science

Summary

Heavy metal is a term for some toxic chemical elements. They can cause problems like bioaccumulation, but are useful in nuclear medicine and medical imaging.

What are heavy metals?

What do bands like Black Sabbath , Metallica and Iron Maiden have in common? If you’re a music lover, you know that these are all famous heavy metal bands. But the term “heavy metal” doesn’t just relate to the Ozzy Osbournes or Alice Coopers of the world. It also refers to an important group of chemical elements. They are important because they can drastically affect the environment and our health.

Most heavy metals are chemical elements with a high atomic number and weight and a specific gravity greater than five. Heavy metals also tend to be highly toxic or poisonous to living things. This is true even at very low concentrations. Due to their high levels of toxicity, the heavy metals that are of greatest concern are arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg). 

Periodic table showing the location of the heavy metals mentioned in this article
Periodic table showing the location of the heavy metals mentioned in this article (© 2019 Let’s Talk Science based on an image from Dmarcus100 [CC BY-SA 4.0] via Wikimedia Commons).

 

Did you know?

In 2019, scientists were shocked to find dangerously high levels of arsenic, lead, and mercury in the blood of a great white shark. They were especially shocked that the shark didn't seem to be affected by them at all!

Do heavy metals deserve their bad reputation? Generally speaking, yes. They are some of the most dangerous contaminants in our environment today. We’ll learn about some problems they can cause. But we’ll also learn about how they can be useful in medicine.

Why are heavy metals harmful?

Heavy metals are harmful because they tend to bioaccumulate. Bioaccumulation happens when toxic substances build up inside an organism at a rate faster than they can be broken down. Over time, the concentration of heavy metals can increase in the bodies of animals higher up on the food chain. Eagles, bears and humans are examples. These animals eat many smaller animals that have heavy metals in their bodies. This results in a bigger buildup of heavy metals in their own bodies.

In the human body, heavy metal poisoning can cause a number of issues. These issues range from skin discolouration, to learning disorders, to kidney disease or even death.

Did you know?

Mad hatter syndrome” is a neurological disorder caused by mercury poisoning. It affects the whole central nervous system. The name comes from hat makers, who had to work with mercury during the hat-making process and often ended up with mercury poisoning.

Body systems impacted by heavy metals
Body systems such as the circulatory, reproductive and nervous systems can be impacted by heavy metals such as iron, zinc, mercury and lead (© 2019 Let’s Talk Science).

 

Are heavy metals always harmful to our health?

Short answer, no. Our bodies need certain heavy metals, like copper (Cu), zinc (Zn), and selenium (Se). These heavy metals help our bodies perform chemical processes or form products, such as hormones. For example, our reproductive systems rely on hormones. Some hormones, like follicle-stimulating hormone (FSH) and luteinizing hormone (LH), have zinc in their structures. Also, iron (Fe) is a heavy metal. We need iron so that hemoglobin in our blood can carry oxygen through the circulatory system to our cells and tissues. 

We get most of the heavy metals we need from our food, water and air. In our diet, these metals are called micronutrients because we only require them in very small and specific amounts. Sometimes, not having enough of these micronutrients can cause health problems. For example, a lack of iron in the body can lead to anemia. A lack of chromium can cause high blood sugar. On the other hand, too much of these heavy metals can lead to toxicity and other serious health problems. For example, iron and copper can accumulate in the liver. If this happens, the liver won’t function properly.  Even small amounts of lead can affect the nervous system and impact mental and physical development. This is especially true for children younger than 3 years old. 

Label from a bottle of vitamins
Label from a bottle of vitamins (Kim Taylor, used with permission).

How are heavy metals used in nuclear medicine?

In nuclear medicine, doctors can use heavy metals to diagnose and treat disease. The drugs used in nuclear medicine are called radiopharmaceuticals

Radiopharmaceuticals are radioactive compounds. They are made up of a radioactive isotope and an organic molecule.

How are heavy metals used to diagnose disease?

Diagnostic radiopharmaceuticals are used to diagnose disease. Hospitals use radionuclides when they perform X-rays. Radionuclides are unstable forms of chemical elements that can release electrons. This makes them radioactive. 

Radionuclides are either injected, inhaled or swallowed to reach the target tissues. They can be traced through the human body to help detect and diagnose disease. Fortunately, there is no risk of heavy metal poisoning. That’s because the tracers are eliminated from the body by the excretory system within a few hours! 

Some types of imaging technology use very specific heavy metals as tracers to create images. Have you or anyone you know ever had to get an MRI (Magnetic Resonance Imaging)? If so, the heavy metals gadolinium (Gd), iron, and manganese (Mn) may have been used as contrast agents, or dyes. These dyes help produce a sharp image that can help doctors detect tumours or cancer cells.  

MRI images of a brain that has experienced a stroke
MRI images of a brain that has experienced a stroke. The lighter spot on the right image shows where a heavy metal was used as a contrast agent (Source: Hellerhoff [CC BY-SA 3.0] via Wikimedia Commons).

How are heavy metals used to treat disease?

Heavy metals are also used for medical treatments. For example, gold salts were valuable medicines used to treat rheumatoid arthritis until the 1990s. Then, newer medicines, with fewer side effects began to replace them. There are also heavy metals in some highly effective anti-cancer treatments. 

Did you know?

During the 18th, 19th, and 20th centuries, a number of arsenic compounds have been used as medicines, particularly for the treatment of syphilis and psoriasis.

Today, therapeutic radiopharmaceuticals can be used to treat disease. For example, a gamma beam of the isotope cobalt-60 (Co-60) can be directed towards a brain tumour to kill cancer cells.

Sometimes radionuclides are inserted into a part of the body to treat a disease. For example, small amounts of iodine-125 (I-125) can be implanted in the prostate gland to treat early stage prostate cancer.

Scientists are also investigating whether heavy metals could be used as medicinal agents in nanotechnology. In the future, nanoparticles could be used to diagnose and treat cancer by targeting specific cells, cellular structures or even molecules without causing as much damage or as many side effects to other tissues and systems in the body as traditional chemotherapies do.  

Summing up...

Heavy metals can be dangerous. They can bioaccumulate and lead to some serious health concerns for humans and other animals. But heavy metals can also be very useful in medicine. And let’s not forget that we need small amounts of certain heavy metals in our bodies to stay healthy.

So the next time you listen to some heavy metal, remember that it is so much more than just music to your ears!

Starting Points

Connecting and Relating
  • Have you ever looked closely at the ingredients in a multivitamin? What heavy metals can you identify in the ingredients? 
  • Have you ever been given a tracer for an x-ray or other form of medical image? If so, do you know what it was? How was it administered (given) to you? 
Connecting and Relating
  • Have you ever looked closely at the ingredients in a multivitamin? What heavy metals can you identify in the ingredients? 
  • Have you ever been given a tracer for an x-ray or other form of medical image? If so, do you know what it was? How was it administered (given) to you? 
Relating Science and Technology to Society and the Environment
  • In what ways have the use of heavy metal tracers impacted the diagnosis and treatment of disease? 
  • The growth of nuclear medicine has resulted in an expansion of careers. What careers are now available in the field of nuclear medicine? (Note: This question will require some additional research) Check out Let’s Talk Science Careers.
Relating Science and Technology to Society and the Environment
  • In what ways have the use of heavy metal tracers impacted the diagnosis and treatment of disease? 
  • The growth of nuclear medicine has resulted in an expansion of careers. What careers are now available in the field of nuclear medicine? (Note: This question will require some additional research) Check out Let’s Talk Science Careers.
Exploring Concepts
  • How can heavy metals be dangerous to human or animal health? In what ways are heavy metals useful to human and animal health? 
  • What is a micronutrient? Why is it important to read and follow dosage recommendations on vitamin preparations before you take them? 
  • Define nuclear medicine. 
  • In medical imaging, what are some of the ways in which heavy metals are used? 
Exploring Concepts
  • How can heavy metals be dangerous to human or animal health? In what ways are heavy metals useful to human and animal health? 
  • What is a micronutrient? Why is it important to read and follow dosage recommendations on vitamin preparations before you take them? 
  • Define nuclear medicine. 
  • In medical imaging, what are some of the ways in which heavy metals are used? 
Media Literacy
  • What news stories have you heard that reference heavy metals? Does the story talk about a problem or an innovation with respect to heavy metals?
  • Are you familiar the character of the Mad Hatter in Lewis Carroll's book Alice in Wonderland? Where do people think Carroll gained his inspiration for this character? What symptoms of mercury poisoning does this character display? 
Media Literacy
  • What news stories have you heard that reference heavy metals? Does the story talk about a problem or an innovation with respect to heavy metals?
  • Are you familiar the character of the Mad Hatter in Lewis Carroll's book Alice in Wonderland? Where do people think Carroll gained his inspiration for this character? What symptoms of mercury poisoning does this character display? 
Teaching Suggestions
  • This article supports teaching and learning in Chemistry and Health & Human Body related to chemical elements, bioaccumulation, human body systems, nuclear medicine and medical imaging. Concepts introduced include heavy metals, toxic, poisonous, contaminants, bioaccumulation, hemoglobin, circulatory system, nervous system, reproductive system, micronutrients, deficiency, nuclear medicine, radionuclides, isotopes, diagnostic radiopharmaceuticals, magnetic resonance imaging, anti-cancer, therapeutic radiopharmaceuticals and nanotechnology. 
  • After reading this article, teachers could have students conduct a Concept Definition Web learning strategy to consolidate their understanding of a key concept, such as heavy metals, bioaccumulation or radionuclides. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To further consolidate learning from the article, students could organize and compare the positive and negative impacts of heavy metals on human health by conducting a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in  [Google doc] and [PDF] formats. 
  • Students could also go further by exploring the different types of medical imagery technology available, what each type is used for, and how heavy metals are involved in obtaining or the creating images in each case. Results of this research could be summarized in a graphic organizer or infographic. 
Teaching Suggestions
  • This article supports teaching and learning in Chemistry and Health & Human Body related to chemical elements, bioaccumulation, human body systems, nuclear medicine and medical imaging. Concepts introduced include heavy metals, toxic, poisonous, contaminants, bioaccumulation, hemoglobin, circulatory system, nervous system, reproductive system, micronutrients, deficiency, nuclear medicine, radionuclides, isotopes, diagnostic radiopharmaceuticals, magnetic resonance imaging, anti-cancer, therapeutic radiopharmaceuticals and nanotechnology. 
  • After reading this article, teachers could have students conduct a Concept Definition Web learning strategy to consolidate their understanding of a key concept, such as heavy metals, bioaccumulation or radionuclides. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • To further consolidate learning from the article, students could organize and compare the positive and negative impacts of heavy metals on human health by conducting a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in  [Google doc] and [PDF] formats. 
  • Students could also go further by exploring the different types of medical imagery technology available, what each type is used for, and how heavy metals are involved in obtaining or the creating images in each case. Results of this research could be summarized in a graphic organizer or infographic. 

Learn more

Bioaccumulation and Biomagnification: Increasingly Concentrated Problems! (2017)

This article by Alisa Vinzant for the Catalina Island Marine Institute outlines the concepts and effects of bioaccumulation and biomagnification in the environment, and the impacts that it has on nature. The article contains a short video (0:26 min.) on the topic .

Metals as Contaminants in Foods

An article from the European Food Safety Authority that discusses heavy metal contamination in food and the effects it can have on people. The article includes a video (3:26) that gives additional information.

What to Expect from an MRI with Contrast (2018)

This video (2:10 min.) from the Center for Diagnostic Imaging tells us what you can expect when you have an MRI Scan, and how contrast dye is used to create the images from the scan.

References

Cronan, K. M., MD (Ed.). (2019, March). Lead poisoning. KidsHealth.

Lenntech. (n.d.). Arsenic - As.

Mae, J. R., Dr. (2018, April 15). Mad hatter disease. HealthGuidance.

Mayo Clinic. (2016, December 6). Lead poisoning.

Mendability. (n.d.). Our brain and metals.

National Institute of Biomedical Imaging and Bioengineering. (2016, July). Nuclear medicine.

Put, P. V. (n.d.). Radiopharmaceuticals. What is Nuclear Medicine.

Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2014). Heavy metals toxicity and the environment. Molecular, Clinical and Environmental Toxicology, 101, 133-164. DOI: 10.1007/978-3-7643-8340-4_6

World Nuclear Association. (2019, February). Radioisotopes in medicine.