The following points highlight the three main classification of toxicants present in food. The classification are: 1. Naturally Occurring Toxicants 2. Toxicants from Microorganisms 3. Toxic Chemicals, Pesticides and Insecticides.
1. Naturally Occurring Toxicants:
i. Lathyrism:
a. This is a crippling disease accompanied by paralysis of the leg muscles occurring mostly in adults who consume large quantities of the seeds of L-sativus or other lathyrus species for a long period.
b. The disease is found to occur in Bihar, Uttar Pradesh and Madhya Pradesh as well as Spain, Algeria, France and Italy.
Symptoms:
a. First of all weakness in the lower limbs with spasticity of leg muscles. As a result, the movement of the ankle and knee joints are restricted and painful.
b. Flexion of the knee is prominent in the second stage and there is inversion of foot with a tendency to walk on toes.
c. In the third stage, the above symptoms become more prominent and the individual can walk only with the help of sticks.
d. In the fourth stage, the knee becomes completely flexed and walking becomes quite impossible. The thigh and leg muscles become atrophy.
ii. Ackee Fruit Poisoning:
1. The ackee fruit is cultivated in Nigeria. This fruit is consumed after boiling for 15 to 20 minutes.
b. The poisonous properties of the fruit are due to unusual amino acid, hypoglycin A, hypoglycin B. Both hypoglycin A and B have strong hypoglycemic action resulting in coma and death.
c. The signs and symptoms of this fruit poisoning in young children are found that the children sometimes vomit and they show drowsiness, convulsions or coma. These symptoms are due to severe hypoglycemia. They are treated by intravenous glucose for recovery.
iii. Goitrogens:
a. Many food stuffs contain organic compounds which have goitrogenic properties.
b. The active goitrogenic principle present in brassicae family in 1, 5-vinyl-2-thio- oxazolidone which is present in cabbage and turnip.
c. Certain oilseeds namely rapeseed, mustard etc. contain thioglycosides which act as goitrogens.
d. The red skin of groundnut contains phenolic glycosides which possess goitrogenic properties.
iv. Pressure Amines:
1. A number of amines namely histamine, tyramine, serotonin and norepinephrine found in some foods have profound physiological activity. Most of them are inactivated by mono-amino oxidase in the intestinal tract. The poisoning effect of pressure amines due to consumption of aged cheese has been reported in patients receiving mono-amino oxidase inhibiting drugs.
2. In Africa, the serotonin intake from plantains as a staple food may reach 100 to 200 mg per day. The endo-myocardial fibrosis may occur as a result of large amount of serotonin.
3. The pressure amine foods are mainly plantains (green and ripe), juices of pineapple and tomato, banana, lemon etc.
v. Argemone Seed Oil Poisoning:
a. During the harvest of rapeseed, argemone seeds are mixed up with rapeseed which grow as weeds. The rapeseed oil obtained from a mixture of rapeseed and argemone seed causes epidemic dropsy in man.
b. The toxic substance in argemone seed is sanguinarine.
2. Toxicants from Microorganisms:
a. The harmful microorganisms contaminate the raw foods such as meat, fish, milk, etc. purchased from the market.
b. These microorganisms are destroyed during cooking or processing but some of the microorganisms survive due to insufficient heat.
c. Pathogenic fungus infects food-grains and oilseeds when stored in humid atmosphere causing serious illness.
The pathogenic microorganisms responsible for contaminating foods are:
Salmonella:
This group frequently causes food poisoning developing the symptoms like vomiting, diarrhoea, rise in body temperature. Infection is transmitted mainly to the processed animal foods.
Staphylococci:
The contaminated food is poisoned owing to the presence of exotoxin produced by this organism. Precooked animal foods cause poisoning developing the symptoms such as vomiting, diarrhoea, and abdominal pain.
Streptococci:
This group is the agent for sore throat producing the symptoms like vomiting, diarrhoea, and abdominal pain.
Shigella:
Bacillary dysentery is caused by this group. Loose motions with mucus and blood and abdominal pain are the main symptoms. Flies are the carriers for the bacteria from infected material to food when cooked foods are kept exposed. The consumption of raw milk to which unclean water is added also causes the disease.
Fungal Contamination:
Fungi, e.g., Aspergillus flavus, Penicillium islandicum, Fusariums, Claviceps purpurea (ergot) produce a good number of toxic compounds (myco-toxins).
Aspergillus flavus:
This fungus has been found to be grown in cotton seed, cereals, moist groundnut, and soya bean. It produces a toxic substance named as aflatoxins which can develop cancer and cirrhosis of the liver in experimental animals. The aflatoxin poisoning has recently been occurred in Rajasthan and Gujarat owing to consumption of maize highly contaminated with Aspergillus flavus.
Penicillium islandicum:
The yellow discolouration in rice has been reported in Japan by the contamination of rice by Penicillium islandieum during storage and develops toxic symptoms in man.
Claviceps purpurea (Ergot):
This parasitic fungus infects food grains such as rye and pear millet during cultivation. The disease ‘Ergotism’ occurs as a result of the consumption of the contaminated grain. The symptoms of this disease are nausea, vomiting, diarrhea, giddiness, severe burning sensation in the extremities, painful cramps in limbs, gangrene in the fingers and toes, depression, weakness and convulsions.
The fungus produces the toxic alkaloids causing the disease.
Fusarium and eladosporium:
The millet is infected by this fungus when left un-harvested in the field during winter. The toxic compound formed by this fungus causes local inflammatory response, acute gastro-enteritis, nausea, and vomiting within 1 to 3 days after the consumption of the infected grain.
The progressive pathological changes in the bone-marrow due to the toxin leads to leukopenia, agranulocytosis and anemia. There is also petechial hemorrhages followed by the development of necrotic ulcers of the skin. In less advanced cases, the recovery of the disease takes place, in case, the patient is put on a good diet with proper treatment.
Parasitic Infection:
The contaminated foods transmit some parasitic diseases, e.g., amoebiasis, ascariasis and hookworm, when raw vegetables grown on sewage are consumed.
3. Toxic Chemicals, Pesticides and Insecticides:
Lead, mercury, arsenic, antimony, D.D.T., and B.H.C., etc. can contaminate foods due to the following reasons:
i. The toxic chemicals such as barium carbonate, arsenic oxides, lead arsenate, etc. used as rat poisoning are accidentally mixed with food.
ii. Accidental contamination of food with pesticides and insecticides.
iii. Some toxic chemicals or minerals are also present in certain marine foods.
4iv. The presence of large amounts of certain food additives.
Toxic Metals:
The toxic element lead causes toxic symptoms after contamination with food, the pathological changes in the kidneys, liver, and arteries are brought about by lead. The common signs of lead poisoning are nausea, abdominal pain, anemia, muscular paralysis, and brain damage.
The toxic effects of methyl mercury are neurological. When the brain is affected, the subject becomes blind, deaf, and paralysis of the various muscles makes him cripple. Cadmium, arsenic, antimony, cobalt, etc. are toxic in small doses.
Pesticides:
The organic pesticides are D.D.T., B.H.C., and malathion, etc. and these are the toxic compounds. The presence of large amounts of pesticides causes toxic effects.
Additives:
In U.S.A. and other western countries, the additives such as diethyl stilbesterol and antibiotics are added to animal and poultry feeds. These are present in the meat of animals fed on feeds containing these chemicals. Stilbesterol can cause leukemia and cancer even in small doses. Antibiotics can cause drug resistance and hardening of arteries.