Metals are some of the most abundant elements found in the universe, and they are essential to life. In the periodic table of elements, metals are categorized based on density and atomic weight. Among the 35 naturally occurring metals, 23 are defined as “heavy metals,” thanks to their high density and atomic weights.
We’re exposed to these elements every day: in our water supply, food chain, polluted air, and industrial waste. We all have trace levels of heavy metals in our bodies, but some of us have higher levels due to diet and lifestyle factors. While some are necessary for life and are harmless at low levels, exposure to large amounts of heavy metals can lead to serious neurological, cardiovascular, and immunological issues.
The production of metals has increased dramatically since the start of the industrial revolution. Mining, refining, and production of metals has seen a tenfold increase in the past century. Today, industrialization and the mass production of hardware, vehicles, and industrial equipment has led to contamination of soil, groundwater, and surface water.
Evidence suggests elevated levels of heavy metals may be linked to a range of acute and chronic conditions such as attention deficit hyperactivity disorder (ADHD), Parkinson’s disease, Alzheimer’s disease, multiple sclerosis (MS), depression, anxiety, schizophrenia, blood disorders, and cancer.
Today, we'll dive into the history of heavy metals, including how they became so prevalent in our environment, the negative health effects associated with high levels, and what you can do about your exposure.
What Are Heavy Metals and Why Should I Care?
First, let’s look at what heavy metals are.
Heavy metals are high-density metals
Heavy metals are dense metals with high atomic weights. They can be divided into essential metals (e.g., copper), which are required for various physiological and biochemical functions, and nonessential metals (e.g., mercury), which have no biological role. Our bodies need just trace amounts of essential metals, and even they can be toxic in excess. Heavy metals are not biodegradable, meaning these elements can accumulate in the environment and in our bodies, and can lead to a variety of health problems. (Source)
Heavy metals can oxidize and create free radicals
On a molecular level, heavy metals bind to vital cellular components like proteins, enzymes, and nucleic acids and can interfere with their function. Metal ions have been found to interact with cell components such as DNA and nuclear proteins, causing DNA damage. When heavy metals oxidize, our bodies generate free radicals, which promotes oxidative stress and damage to surrounding tissue in the process. (Source)
Heavy metals magnify as they move up the food chain
Toxic metals have been around for millennia, but human activity has accelerated their release into the environment, leading to an accumulation in our food chain. They are now found in pesticides, fertilizers, and animal feed containing industrial byproducts. Additionally, contaminated fish and other seafood represent yet another source of heavy metal exposure, as pollutants enter the lowest levels of the food chain and are retained and passed along from one level to the next. This increase in concentration of substances over time and in bigger living organisms is called biomagnification, which explains why fish at the top of the ocean food chain, such as tuna, often contain significant quantities of mercury. (Source)
Heavy metals can accumulate in organs, causing damage
An excess of heavy metals can affect the function of the central nervous system and may contribute to neurological disorders and damage to the lungs, liver, kidneys and other vital organs. Toxic heavy metals can also have a detrimental effect on our immune system, leaving us vulnerable to a variety of illnesses. Long-term accumulation of heavy metals in the body may accelerate the progression of physical, muscular and neurological degenerative processes seen in diseases such as Parkinson’s. (Source, Source, Source)
Heavy metals can be difficult to avoid
Although multiple heavy metals exist in the earth’s crust, mercury, cadmium, arsenic, and lead are the most common contaminants in our air, water, soil, and food. Chances are you're exposed to low-to-moderate levels of several of these toxins daily, depending on your lifestyle. People who are chronically exposed to high levels of heavy metals from occupational exposure, such as mining or manufacturing, will accumulate higher levels of these elements. Other unexpected sources of heavy metals include medicines, food containers with improper coating, industrial exposure, and lead based paints. Many heavy metals are not easily eliminated from the body, including mercury, and can accumulate in the organs, primarily the kidneys, brain, and liver. (Source, Source)
What Does the Research Show About Heavy Metals?
Heavy metals are linked to chronic disease
A growing body of evidence suggests that exposure to heavy metals can contribute to the development of chronic conditions such as asthma. The severity of adverse health effects depends on the type of heavy metal, its chemical form, and the amount and duration of exposure. In one study, higher levels of lead were associated with a greater likelihood of developing asthma in children 2 to15 years old. (Source)
Heavy metals can impair mitochondrial function
Mitochondria are the powerhouses of the cell. Heavy metals can induce mitochondria dysfunction — altering protein synthesis, impairing mitochondrial structure, and reducing production of ATP (our key source of cellular energy!). (Source)
One specific compound may be especially damaging to the brain
In a recent review, studies looking at memory found significant deficits in individuals exposed to inorganic mercury. Animal and lab studies suggest that exposure to this type of mercury, which is formed when elemental mercury combines with other elements, may cause nerve cell damage and promote the production of the plaques found in the brains of Alzheimer’s patients. Researchers have also found that patients with the ApoE 4 gene, aka the “Alzheimer’s gene,” may have more trouble eliminating mercury from their brains, contributing to its toxic effects on this organ. (Source, Source)
Children are at greatest risk from lead poisoning
Exposure to lead interferes with the development of the nervous system, so it’s particularly toxic to children and can cause potentially permanent neural and cognitive impairments. Fortunately, since the institution in the 1970s of preventive measures such as banning lead in paint, the number of children in the US with lead levels known to be harmful have fallen significantly. However, it’s since been determined that even low-level, seemingly asymptomatic lead exposure can cause irreversible harm, and in 2012 the CDC lowered the blood lead level requiring investigation and management. (Source)