In the previous review, “Heavy Metals & Cosmetics… Is Beauty Worth it?”, the presence of heavy metals in cosmetics was discussed based on several scientific reviews and studies. And I am sure that “greenarea.info” followers who read the article are now curious to know how heavy metals reach our environment and what their health effects are. The following article sheds light on the sources and health effects of the most abundant and toxic nonessential, heavy metals which are Arsenic (As), Cadmium (Cd), Lead (Pb) and Mercury (Hg), in addition to the light metal Aluminium (Al). Once again it is vital to mention that recent reports issued by the World Health Organization (WHO) and other research institutions ensure that there are no safe levels of exposure to highly toxic metals such as the ones discussed in this article.
The Earth’s crust is the natural habitat of heavy metals; nonetheless both natural and anthropogenic (human) activities contribute to their unhealthy abundance in our environment. Natural events such as volcanic eruptions, weathering, metal corrosion, atmospheric deposition, soil erosion, etc., and human activities including metal-based industries, miners, smelters, founders, and the mismanagement of different kinds of waste, all result in prominent environmental contamination with toxic metals.
Arsenic (As): What does it do to your skin?
Arsenic is the twentieth most abundant element in the Earth’s crust, but several causes have displaced this highly toxic and carcinogenic metal to our air, water and food. According to the WHO the level of Arsenic in drinking water must not exceed 10 μg/l. The sources of Arsenic in our environment include: paints, dyes, soaps, metals, semi-conductors, pesticides, fertilizers, animal feed additives, wood preservatives and Arsenic-based drugs used in human and veterinary medicine. Humans are exposed to Arsenic via the oral, respiratory and dermal routes through contaminated air, water, soil, foods and cosmetics.
Exposure to low levels of As can cause nausea, vomiting, decrease in the synthesis of red and white blood cells, abnormal heart beat, pricking sensation in hands and legs and damage to blood vessels. Chronic exposure to Arsenic (known as Arsenicosis) results in neurological, pulmonary and cardiovascular problems, in addition to cancers of lungs, liver, bladder and skin. Yet, the most commonly reported side effects are the skin manifestations, which are highly specific signs for the diagnosis of Arsenic toxicity, an example is shown in Figure 2: Arsenic Keratosis, Known as “Raindrops on a Dusty Road”.
Cadmium (Cd): How did it reach your cigarettes?
Cadmium is a by-product of Zinc (Zn) production, and is used in rechargeable batteries, alloys, metal coatings, pigments, and plastic stabilizers. Also, several human activities release Cadmium into the environment, such as incineration of municipal waste, synthesis of fertilizers and tobacco smoking. The most alarming properties of Cadmium are its carcinogenicity and ability to accumulate in soils, plants and human bodies (mainly in kidneys). Furthermore, its high rate of soil-to-plant transfer, accounts for its presence in fruits, vegetables, seeds, grains and even tobacco. Foods rich in Cadmium include mushrooms, cocoa powder, shellfish, dried seaweed, mussels and liver. Humans are exposed to Cadmium mostly through ingestion, inhalation and smoking cigarettes.
As per The Agency for Toxic Substances and Disease Registry (ASTDR) ranking, Cadmium is the seventh most toxic heavy metal, and according to the International Agency for Research on Cancer (IARC) Cadmium and its compounds are classified as Group 1 human carcinogens. The lungs are the most common site of carcinogenesis, yet other organs can also be potential sites such as prostate, kidney, liver, stomach and hematopoietic system. Acute ingestion can cause mild to extremely severe symptoms. This metal causes kidney disease, lung damage, osteoporosis, stomach irritation, formation of renal stones and disturbances in Calcium metabolism.
Lead (Pb): Do you want to enhance your IQ?
The sources of Lead in our environment include fossil fuels, house paints, Pb bullets, plumbing pipes, solder, ammunitions, storage batteries, toys, faucets, cosmetics and traditional medicine. Lead released into the air is taken up by plants and fixed to the soils, which can ultimately reach water resources. Thus, human primarily get exposed to this metal through inhalation, ingestion of contaminated food and water, or dermal contact.
In addition to being highly toxic to plants, Lead is extremely noxious to humans. The Environmental Protection Agency (EPA) classified Lead as a human carcinogen. Almost 95% of Lead is stored in skeletal bones. Acute exposure results in loss of appetite, headache, hypertension, abdominal pain, renal dysfunction, arthritis, fatigue, insomnia, hallucinations and vertigo. While long-term exposure causes mental retardation, birth defects, psychosis, autism, allergies, weight loss, hyperactivity, dyslexia, paralysis, brain and kidney damage. Several studies confirmed a correlation between chronic Lead exposure and low IQ levels.
Mercury (Hg): Is it important to limit the number of sushi rolls you eat on a single meal?
Mercury pollution is a result of many sources that release all different forms of mercury into the environment, and these include agriculture, incineration, thermometers, mercury arc lamps, fluorescent lamps, pharmaceuticals, pulp and paper preservatives, chlorine and caustic soda, batteries, dental amalgams, municipal and industrial wastewater discharges. Mercury is present in soil and water resources, where it is taken up by aquatic animals. Therefore, sources of human exposure to Mercury include consumption of contaminated aquatic animals, foods, beverages, and water, or inhalation of Hg vapors. The level of Hg in drinking water is set at 0.001 mg/l by the WHO.
Mercury has a very low excretion rate, and accumulates in the kidneys, liver and nervous system. Human exposure to Mercury results mainly in brain damage, yet it can also affect the nerves, kidneys, muscles and developing fetus. Symptoms of Hg toxicity include tremors, memory problems, changes in vision and hearing, irritability, depression, hair loss fatigue, etc. Acute inhalation of Hg vapors result in bronchitis, asthma, nausea, vomiting, diarrhea, skin rashes, increased heart rate and blood pressure. Also, EPA declared two forms of Mercury (Methyl Mercury and Mercuric Chloride) to be highly carcinogenic.
Aluminium (Al): Will you be able to recognize your family and friends?
Aluminum is the third most abundant element in the Earth’s crust and occurs naturally in the air, water and soil. Yet, various human activities such as processing of Aluminum increased its levels in the environment and resulted in the contamination of food, water, beverages, drugs and even dialysates and phosphate binders used in dialysis. Humans are exposed to Aluminum though the gastrointestinal, respiratory and dermal routes. Although Aluminum is excreted by the kidneys, yet people with kidney diseases cannot efficiently excrete Aluminum and therefore suffer from bone and brain damage due to Aluminum accumulation.
This light metal has adverse outcomes not only on plants and aquatic animals, but also on humans. The most alarming manifestation of Aluminum toxicity is the damage to neurons which is similar to the degenerative lesions associated with Alzheimer’s disease (AD), therefore the WHO hypothesized exposure to Aluminum as a risk factor for the development of AD. Symptoms of Al toxicity include nausea, vomiting, diarrhea, arthritic pain, mouth ulcers, skin ulcers and rashes. Other complications include problems in the lungs, nervous system, remodeling of bone and Iron absorption, in addition to anemia.
