Mushrooms And Heavy Metals: What's The Risk?

Mushrooms are known to accumulate heavy metals, which can pose serious health risks to humans. Heavy metals, such as lead, mercury, cadmium, and arsenic, can be absorbed by mushrooms from the soil and accumulated in their bodies. These toxic elements can have harmful effects on various organs and tissues in the human body, and their health effects may manifest after many years of exposure. While mushrooms can be a valuable source of protein for vegetarians, the accumulation of heavy metals in certain species has been a cause for concern. Research has shown that the levels of heavy metals vary depending on the type of mushroom and the environmental factors, with some species containing significantly higher concentrations of these toxic elements. As a result, the consumption of certain mushrooms may pose health risks, especially if the heavy metal content exceeds reference levels.

Mushrooms absorb heavy metals from the soil

Mushrooms can absorb and accumulate heavy metals from the soil. They have a strong capacity to absorb potentially toxic trace elements, including mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), and neodymium (Nd). These metals can be present in the soil due to industrial and transport emissions, agriculture, and runoff from roads and waste storage. The ability of mushrooms to absorb these metals may be due to the horizontal development of their mycelium, which occupies the superficial part of the soil where heavy metals are often present.

The accumulation of heavy metals in mushrooms can vary depending on the species of mushroom, the mineral composition of the soil, and the distance from the source of contamination. For example, a study found that chanterelles (Cantharellus cibarius) had the highest levels of lead and neodymium among the species tested. Another study showed that Boletus edulis had significantly higher concentrations of cadmium compared to Xerocomus badius.

The health risks associated with the consumption of mushrooms containing heavy metals are well-documented. Heavy metals such as cadmium, lead, and mercury have no known essential role in living organisms and are toxic even at low concentrations. Accumulation of these metals in the human body can lead to serious health issues, including organ damage, cancer, and in some cases, amnesia, blindness, and deafness.

Due to the potential health risks, maximum limits for certain heavy metals in mushrooms have been established. For example, European legislation sets maximum Hg contents for cultivated and wild mushrooms, and the maximum cadmium content in mushrooms has been updated by Regulation (EC) No 2023/915. However, it is worth noting that some countries lack proper regulations regarding the presence of heavy metals in edible mushrooms.

The accumulation of heavy metals varies by species

Mushrooms can accumulate heavy metals present in the soil, with their mycelium playing an essential role in this process. The mycelium, which develops mainly horizontally, incorporates metal ions into its cytosol under suitable conditions. This results in mushrooms accumulating higher concentrations of heavy metals than plants. While this characteristic makes mushrooms excellent bioindicators of contaminated areas, it also poses risks to consumers if the heavy metal content exceeds safe levels.

The accumulation of heavy metals in mushrooms is influenced by both environmental and intrinsic factors. Environmental factors include soil pH, metal content, and the amount of organic matter. Intrinsic factors relate to the fungi themselves, such as the type of mushroom, the age of the mycelium, growth phases, and the biochemical structure. Different mushroom species exhibit varying abilities to accumulate heavy metals, as evidenced by studies examining specific species.

For example, a study in Ibadan, Nigeria, analyzed seven wild mushroom species (Cortinarius melliolens, Chlorophyllum brunneum, Pleurotus florida, Volvariella speciosa, Cantharellus cibarius, Entoloma spp., and Coprinus africana) for their copper (Cu), cadmium (Cd), and lead (Pb) contents. The concentrations of these heavy metals varied by the site of collection, with some species showing higher levels of Cu, Pb, and Cd than the safe limits established by organizations like the World Health Organization (WHO).

Another study in Athens, Greece, investigated six wild edible mushroom species (Agaricus bisporus, A. bitorquis, A. gennadii, Coprinus comatus, Psathyrella candolleana, and Volvopluteus gloiocephalus) for their bioaccumulation of heavy metals in an urban environment. This study found relatively high Pb and Ni contents in the mushrooms, while Cu, Zn, Fe, and Mn concentrations varied considerably. The effect of soil texture on metal accumulation was species-dependent, with high correlations observed only for V. gloiocephalus and C. comatus.

Furthermore, a health risk assessment of dried wild-grown mushrooms (Boletus edulis and Xerocomus badius) available for sale revealed varying concentrations of heavy metals. Boletus edulis had significantly higher concentrations of Hg, Cd, Pb, and As compared to Xerocomus badius. The difference in Cd content was particularly notable, with Boletus edulis exhibiting a value almost 170% higher than Xerocomus badius.

These studies demonstrate that the accumulation of heavy metals varies among mushroom species, and certain species may accumulate specific heavy metals to a greater extent than others. The variation can be attributed to the interplay of environmental and intrinsic factors influencing the bioaccumulation process in different mushroom species.

Heavy metals in mushrooms can be toxic to humans

Mushrooms have a strong capacity to absorb and accumulate heavy metals, which can be toxic to humans. Heavy metals, such as lead, mercury, cadmium, and arsenic, can be present in the soil and other substrates in which mushrooms grow. These metals can be absorbed into the mushroom's body and pose a risk to consumers if ingested in high concentrations.

The accumulation of heavy metals in mushrooms varies depending on the type of mushroom, the environment, and the growth conditions. Certain species of mushrooms, such as Boletus edulis and Xerocomus badius, have been found to have significantly higher concentrations of heavy metals compared to others. Environmental factors, such as the concentration of metals in the soil, the pH, and the amount of organic matter, also play a role in the bioaccumulation of heavy metals in mushrooms.

The health risks associated with the consumption of mushrooms containing heavy metals have been studied. High levels of heavy metals in mushrooms can lead to serious health problems in humans, including organ damage, cancer, and neurological issues. For example, cadmium, a heavy metal with no known physiological function, has been associated with harmful effects on the kidney, spleen, and liver. Lead, another toxic heavy metal, can cause tissue damage to the brain, kidneys, liver, and bones, and its effects can last for decades.

Regulations have been established to set maximum limits for certain heavy metals in mushrooms. For example, European legislation distinguishes between cultivated and wild mushrooms, setting maximum limits for mercury content. However, the regulations vary across different regions, and some countries lack proper restrictions on certain heavy metals. The health effects of regular consumption of mushrooms containing heavy metals may not be immediately apparent and can manifest after many years. Therefore, routine monitoring of potentially harmful trace elements in food is essential to ensure the safety of mushroom consumers.

Cadmium is a toxic element that inhibits many life processes

Mushrooms can accumulate heavy metals present in the soil, including cadmium. Cadmium is a toxic element that poses severe risks to human health. It is a heavy metal that has been classified as a human carcinogen by the International Agency for Research on Cancer, the Environmental Protection Agency, and the European Chemical Agency. Exposure to cadmium through diet can cause harmful effects on health, particularly the kidney, spleen, and liver, where it accumulates. It can also cause respiratory issues and kidney problems, which can be fatal.

Cadmium is a soft, malleable, bluish-white metal found in zinc ores and, to a lesser extent, in the mineral greenockite. It is produced mainly from zinc byproducts and spent nickel-cadmium batteries. Cadmium has various industrial uses, including in batteries, alloys, coatings, solar cells, plastic stabilizers, and pigments. Worker exposure to cadmium can occur in several industry sectors, particularly manufacturing and construction. Operations associated with cadmium exposure include electroplating, metal machining, welding, painting, and landfill work. Artists who work with cadmium pigments may also be at risk of accidental ingestion.

The daily intake of cadmium through food varies by geographic region. In Europe and the United States, the reported intake is approximately 8 to 30 µg, while in Japan, it can range from 59 to 113 µg. Cadmium can be found in plants, particularly in non-industrial areas, and in higher levels in the liver and kidneys of adult animals. It can also be present in chocolate, with a small study finding that 48% of premium dark chocolate samples had high levels of cadmium due to its presence in the soil where the cocoa was grown.

The accumulation of cadmium in mushrooms can exceed the levels found in crops, fruits, and vegetables. The highest concentrations of cadmium in mushrooms were found in Boletus edulis, with a median concentration of 1.638 mg/kg, which is significantly higher than in other species. The maximum cadmium content in cultivated mushrooms is regulated, with limits established by European legislation to protect consumers from potential health risks.

The health risks of consuming heavy metals in mushrooms

Mushrooms can accumulate heavy metals present in the soil, including mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), and more. These heavy metals are assumed to inflict toxicological damage to human health even at low concentration levels. The health effects of regular consumption of products containing heavy metals may become manifest after many years.

The main factors influencing the bioaccumulation of heavy metals in mushrooms are environmental factors, such as the concentrations of metals in the soil, the pH, the amount of organic matter, and contamination by atmospheric deposition. Mushrooms are able to accumulate higher concentrations of heavy metals than plants because their mycelium develops mainly horizontally, normally occupying the most superficial part of the soil. The mycelium contains the highest concentration of heavy metals.

The health risks associated with consuming heavy metals in mushrooms include the accumulation of toxic elements in organs and tissues, which is conditioned by their rapid absorption and slow excretion from the human body. Pb, for example, has a highly toxic influence, stemming from its action on the immune, nervous, urinary, and cardiovascular systems. Cd has been shown to have harmful effects on the kidney, spleen, and liver, where it accumulates. As is of special concern due to the cancerous effects of some arsenicals.

The risk of dietary intake of heavy metals from mushrooms has been assessed in several studies, with varying results. Some studies have found that the dietary intake of certain mushrooms has certain health risks associated with Cd and As intake, while others have found that the THQ values for mercury in some mushrooms are 0, indicating no risk. The HI value, which assesses the combined risk of multiple heavy metals, indicates that the consumption of a standard portion of dried Boletus edulis may have negative consequences for health, with a value of 76.2%.

Overall, the consumption of mushrooms containing heavy metals may pose health risks, and it is recommended that the content of toxic elements in edible mushrooms be monitored.

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