Even different-sized granules of the same chemical can vary in their relative toxicities because of the differences in dissolution rates.
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For example, arsenic trioxide is more toxic in the form of smaller granules than is the same mass of larger granules because the smaller granules dissolve faster. A poison in a liquid form can be absorbed by ingestion or by inhalation or through the skin.
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Poisons that are gases at room temperature e. Because organic liquids are more volatile than inorganic liquids, inhalation of organic vapours is more common. Although vapours are generally absorbed in the lungs, some vapours that are highly soluble in lipids e. Aerosols are solid or liquid particles small enough to remain suspended in air for a few minutes. Fibres and dust are solid aerosols.
Aerosol exposures occur when aerosols are deposited on the skin or inhaled. Aerosol toxicity is usually higher in the lungs than on the skin. An example of a toxic fibre is asbestos, which can cause a rare form of lung cancer mesothelioma. Many liquid poisons can exist as liquid aerosols, although highly volatile liquids, such as benzene, seldom exist as aerosols.
A moderately volatile liquid poison can exist as both an aerosol and as a vapour. Airborne liquid chemicals of low volatility exist only as aerosols. Poisons can be classified according to whether the chemical is metallic versus nonmetallic, organic versus inorganic, or acidic versus alkaline.
Metallic poisons are often eliminated from the body slowly and accumulate to a greater extent than nonmetallic poisons and thus are more likely to cause toxicity during chronic exposure. Organic chemicals are more soluble in lipids and therefore can usually pass through the lipid-rich cell membranes more readily than can inorganic chemicals.
As a result, organic chemicals are generally absorbed more extensively than inorganic chemicals. Classification based on acidity is useful because, while both acids and alkalis are corrosive to the eyes, skin, and intestinal tract, alkalis generally penetrate the tissue more deeply than acids and tend to cause more severe tissue damage. Poisons also may be grouped according to their ability to mimic the structure of certain important molecules in the cell.
Unlike the classifications described above, there is usually no predictive value in classification by target sites or by uses. While levels are generally low, higher concentrations are found in potato sprouts and bitter-tasting peel and green parts, as well as in green tomatoes.
The plants produce the toxins in response to stresses like bruising, UV light, microorganisms and attacks from insect pests and herbivores. To reduce the production of solanines and chaconine it is important to store potatoes in a dark, cool and dry place, and not to eat green or sprouting parts. Wild mushrooms may contain several toxins, such as muscimol and muscarine, which can cause vomiting, diarrhoea, confusion, visual disturbances, salivation, and hallucinations.
Onset of symptoms occurs 6—24 hours or more after ingestion of mushrooms. Fatal poisoning is usually associated with delayed onset of symptoms which are very severe, with toxic effect on the liver, kidney and nervous systems. Cooking or peeling does not inactivate the toxins. It is recommended to avoid any wild mushrooms, unless definitively identified as non-poisonous. Pyrrolizidine Alkaloids PAs are toxins produced by an estimated plant species. The main plant sources are the families Boraginaceae , Asteraceae and Fabaceae. Many of these are weeds that can grow in fields and contaminate food crops.
PAs can cause a variety of adverse health effects; they can be acutely toxic and of main concern is the DNA-damaging potential of certain PAs, potentially leading to cancer. PAs are stable during processing, and have been detected in herbal teas, honey, herbs and spices and other food products, such as cereals and cereal products.
Human exposure is estimated to be low, however. Due to the complexity of the subject and the large number of related compounds, the overall health risk has not been fully evaluated yet. When it comes to natural toxins it is important to note that they can be present in a variety of different crops and foodstuff.
In a usual balanced, healthy diet, the levels of natural toxins are well below the threshold for acute and chronic toxicity. WHO, in collaboration with FAO, is responsible for assessing the risks to humans of natural toxins — through contamination in food — and for recommending adequate protections.
Codex standards are the international reference for national food supplies and for trade in food, so that people everywhere can be confident that the food they buy meets the agreed standards for safety and quality, no matter where it was produced. The outcome of such health risk assessments can either be a maximum tolerable intake exposure level, or other guidance to indicate the level of health concern such as the Margin of Exposure , including advice on risk management measures to prevent and control contamination, and on the analytical methods and monitoring and control activities.
Natural toxins in food 9 May Key facts Some natural toxins can be formed in food as defense mechanisms of plants, through their infestation with toxin-producing mould, or through ingestion by animals of toxin-producing microorganisms. Natural toxins can cause a variety of adverse health effects and pose a serious health threat to both humans and livestock. Some of these toxins are extremely potent. Adverse health effects can be acute poisoning ranging from allergic reactions to severe stomachache and diarrhoea, and even death.
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Respiratory paralysis and heart rhythm abnormalities can lead to death. The treatment is symptomatic and supportive; there is no specific antidote. There is a very low margin of safety between therapeutic and toxic doses of aconitine. For example, a year-old woman with no known heart disease obtained some from an herbalist. She was instructed to make a tea with it to treat her osteoarthritis. About 90 minutes after drinking the tea she developed numbness of her face, arms, and legs. This was rapidly followed by nausea, weakness, and chest pressure. In an ER, she was found to have an abnormal heart rhythm.
After 4 hours of treatment with drugs and electrical shocks to her heart, a normal heart rhythm was restored.
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There are cases of poisoning in which people intentionally swallow A. A year-old man acquired Aconitum napellus plants after reading a book on herbal medicine. He ground up the roots of the plants and filled capsules with the dried material. He then took 1 capsule daily for several months to treat his anxiety.
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In order to increase the effects one evening, he swallowed 3 capsules and went to sleep. Five hours later he awoke with generalized numbness, nausea, diarrhea, dizziness, chest pain, shortness of breath, and defective color vision he was seeing purple. It was believed that early symptoms went unnoticed because he was asleep. In an ER, his heart rate was very slow at 43 beats per minute, and he had an abnormal heart rhythm. Plasma concentrations of aconitine supported poisoning by A.
He spent 48 days in the hospital. Aconitum napellus , monkshood [internet video]. The Poison Garden [accessed Nov 6, ]. Aconite poisoning over 5 years: a case series in Hong Kong and lessons towards herbal safety. Drug Saf ; Successful treatment of monkshood Aconite napel poisoning with magnesium sulfate. Am J Emerg Med ; e Herbal aconite tea and refractory ventricular tachycardia. N Engl J Med ; Severe acute poisoning with homemade Aconitum napellus capsules: toxicokinetic and clinical data.
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