Heavy metals such as arsenic, lead, zinc, tin… if present in food at excessive levels, can harm consumers. The immediate symptoms can manifest as acute or chronic poisoning.
For consumers:
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| Heavy metals such as arsenic, lead, zinc, tin… if present in food at excessive levels, can harm consumers. (Photo: willowspringscabins) |
Acute toxicity, for instance, arsenic in high doses can cause fatal poisoning immediately.
Chronic or cumulative toxicity, for example, even with small daily doses over time, can lead to lead poisoning, which is very difficult to treat.
For food:
It can spoil food; for instance, even a trace of copper can trigger oxidation processes and cause fats and oils to oxidize…
It can reduce the nutritional value of food; for example, even a trace of heavy metals can promote the degradation of Vitamin C, Vitamin B1…
Below are some common heavy metals found in food, along with their toxic properties.
ARSENIC (As)
Arsenic is not considered an essential mineral. Inorganic compounds of arsenic are highly toxic at elevated levels. Arsenic poisoning is primarily acute: with a dose of 0.06g As203, poisoning occurs, and with 0.15g/person, it can be fatal. Acute poisoning occurs from consuming food contaminated with arsenic…
In humans, poisoning often occurs due to the accumulation of arsenic in the body, resulting from occupational exposure, or from food and beverages contaminated with arsenic during industrial processing. Therefore, each type of food has a maximum allowable level of arsenic, for example:
– Fruits can contain a maximum of 1.4ppm As.
– Tin used for food packaging can contain a maximum of 0.001ppm As, and aluminum under 0.0016ppm As.
The maximum acceptable daily dose of arsenic (As) for humans is 0.05mg/kg body weight.
Acute poisoning symptoms resemble cholera, appearing rapidly, sometimes immediately after consuming arsenic. Victims may experience vomiting, abdominal pain, diarrhea, intense thirst, weak pulse, pallor, then cyanosis, urinary retention, and death within 24 hours.
Chronic poisoning occurs due to the long-term accumulation of small doses of arsenic, with symptoms including: gray complexion, hair loss, gastritis and enteritis, eye pain, ear pain, disturbed sensation of movement, diminishing arsenic levels in urine, weight loss, exhaustion, and death after months or years.
LEAD (Pb)
Lead is an unnecessary component of the diet. The average lead intake from food and beverages is 0.0033 to 0.005 mg/kg body weight. This means that an adult consumes about 0.25 to 0.35mg of lead daily. With this intake, lead levels accumulate with age, but so far there is no evidence that this accumulation can cause poisoning in healthy individuals.
The maximum acceptable daily intake of lead (Pb) from food is temporarily set at 0.005mg/kg body weight.
Acute lead poisoning is rare. Chronic poisoning occurs due to consuming food with a continuous, albeit low, lead content. If the body absorbs more than 1 mg of lead daily over several years, specific symptoms may appear: foul breath, swollen gums with dark edges, jaundice, severe abdominal pain, constipation, joint pain, upper limb paralysis (deformed hands), weak pulse, reduced urine output, and the presence of porphyrin in urine, with women being more prone to miscarriage.
MERCURY (Hg)
Mercury has no essential function in human metabolism and is usually found in very low levels in fruits and vegetables. If food contains mercury, it can be very harmful to human health. Therefore, it is crucial to ensure that fruits and vegetables are free from any mercury contamination, even at very low levels.
COPPER (Cu)
Copper is an essential component for the body, with daily intake from food ranging from 0.033 to 0.05 mg/kg body weight. At this level, there is no observed accumulation of Cu in the bodies of healthy individuals.
At a certain concentration, even traces of copper can affect the taste and nutritional value of food; for example, it can stimulate the self-oxidation of fats, leading to quick spoilage and accelerated degradation of vitamins…
The acceptable daily intake of copper for humans is 0.5 mg/kg body weight. This level is not a concern as long as the concentrations of molybdenum and zinc in food do not exceed normal limits, as these substances affect copper metabolism in the human body. Copper does not cause toxicity through accumulation, but if a large amount of copper salts is ingested, it can lead to acute poisoning. Symptoms manifest immediately as severe vomiting, which expels most of the ingested copper. This is why fatal cases of copper poisoning are rare. The vomit has a distinctive green color due to copper, and after vomiting, saliva continues to flow, leaving a lingering copper taste in the mouth for an extended period.
ZINC (Zn)
Zinc is a natural component of food and is essential for human life. A typical diet provides daily intakes of 0.17 to 0.25 mg Zn/kg body weight.
Generally, all types of animals tolerate zinc, a metal that is less toxic at low levels and when the diet is high in copper and iron and interacts with other factors.
Due to the established safe limits between normal dietary zinc concentrations and the amounts that can cause toxicity due to accumulation, the regulated zinc content in food (from 5 to 10 ppm) does not adversely affect consumer health. Zinc poisoning is also acute, resulting from accidentally ingesting large quantities of zinc (5-10g ZnSO4 or 3-5g ZnCl2), which can be fatal with symptoms like a persistent and unpleasant metallic taste in the mouth, vomiting, diarrhea, cold sweat, weak pulse, and death occurring within 10 to 48 seconds.
TIN (Sn)
Tin is a normal component of the diet, having no physiological function, but it has very low toxicity. The allowable tin content in food is typically regulated between 100 to 200mg/kg of product. Generally, food containing less than 100 mg has an unpleasant metallic taste, thus failing to meet sensory quality standards.
