Health & Medical
POLLUTANTS IN LIVESTOCK
PRODUCTS AND ITS IMPACT ON HUMAN HEALTH
What is Pollutant: - Pollutants are the chemicals which
are not normal constituents of food and inadvertently find their way into food
through soil, air, water, animal feed, or technological processing. Numerous
pollutants both natural and synthetic are present in the environment.
Pollutants intoxicate
animal if exposure is excessive. Unless and until it exceeds the maximum level,
it does not cause any significant harm to animal. Naturally occurring toxins or
chemicals deteriorates food quality & ensues in mortality, decreased
availability or usability of food stuffs. It also decreases the wholesomeness
of edible food products. Therefore it
becomes a global and emerging issue now a day.
CLASSIFICATION OF POLLUTANTS: A) Naturally Occurring Pollutants
B) Pollutants caused By Man
C) Arising Secondarily
A) Naturally Occurring Pollutants: -
They are available in environment and get into the foodstuff via food chain.
They can be further divided into two classes-
a)
Minerals
and heavy metals: - Mineral residues from metal as Hg, Pb, Zn, Cu, Co, Fe, Mn
etc. are often coming into the animal body mainly via food. Radioisotopes such
as K-40 may also cause contamination of foodstuff.
Microbiological
Pollutants: - Under this class bacteria like Salmonella, E. coli, M. tuberculosis, Clostridium botulinum, Cl. Perfringens etc. are of great concern. Apart
from that Mycotoxins are there causing great contamination in foodstuff. Mycotoxins
are of two types—Aflatoxins and Ochratoxins. Aflatoxin is produced by Aspergillus flavus and Aspergillus
parasiticus. Four major Aflatoxins are AFB1, AFB2, AFG1
a)
and
AFG2. AFB1 is most potent toxin and carcinogenic also. Ochratoxin is produced
by seven species of Penicillium and six species of Aspergillus. Ochratoxin A is
most prominent, causes liver and kidney damage in birds, mammals and fish.
Substances occurring naturally in food like trypsin inhibitors also may be
considered as pollutants.
B) Pollutants
caused by Man: - Under this class a variety of substance may come like- artificial
dyes and sweetening agents, pesticides, substances formed during production, preparation
or storage of food, Polycyclic aromatic hydrocarbons, Peroxides of unsaturated
fatty acids, Nitrosamines etc. An important group of possibly toxic substances
in our food are pesticides and their residues. Apart from that, this class also includes substances
that are taken in due to environmental influences, such as- toxic heavy metals-
lead, cadmium and mercury and polychlorinated biphenyls (PCBs).
Classification: - This class can be further subdivided into following
sub-classes-
1)
Pesticides
as DDT, BHC, Lindane, Methyl Mercury etc. Pesticides are of different types as
Insecticides (Organochlorine & Organophosphorus Compounds), Herbicides
(Alachlor, Allidochlor), Rodenticides (Sodium fluoacetate), Fumigants
(Napthalene, Ethyl Bromide, Ethyl Dioxide etc) etc.
2)
Compounds of Industrial technology as Perchloroethylene, Benzopyrine
etc.
3)
Medicinal Drugs as Antibiotics, Neuroleptic (Tranquillizers),
Anthelmintics, Anticoccidials, NSAID etc.
4)
Performance Enhancers as Anabolic Steroids.
5)
Synthetic Radioisotopes as I-131, Cs-137 etc.
C) Pollutants Arising Secondarily: - This group includes those
substances which are produced during processing, packaging or storage of foodstuff.
As to furnish an example, during curing of meat we are using Nitrite. But an
excess use of it may produce Nitrosamine, a carcinogenic product after reaction
with secondary amines. Another example is during smoking of meat, Benzopyrine
is formed which is also carcinogenic in nature. Disinfectants like Quaternary
Ammonium compounds may interfere with absorption of certain nutrients. If the
packaging material is not safe and biodegradable then components like Silica,
Antistatic agent (as Na- fluoacetate), plasticizer, lubricants, stabilizer etc
may migrate to the food materials.
Special Emphasis on Pesticide
Pollutants
Pesticides are absorbed
either through skin or GI tract. Due
to its lipophilic nature, it is mainly stored in adipose tissues. Mobilization of adipose tissues during weight loss or
lactation causes these xenobiotics to re-enter into the blood stream resulting
in their harmful effect.
Some chemicals after entering into the animal body transformed into a more
harmful product as Aldrin
is metabolized to Dieldrin inside the body and is apparently independent of the
site of entry to the body. Dieldrin is
stored as such in the body and is recovered unchanged from the animal products
and body tissues. Survey of tropical countries has
shown almost universal presence of DDT and BHC in Milk samples. In India,
the incidence of OC residues (DDT and BHC) in Milk and Milk products in most of
the samples is above maximum residue level (MRL). Hazardous pesticide residues poison twenty-five million people in the
third world annually. Residues of certain pesticides are
known to be a cause of cancer. Pesticide can
cause embryo deformity and mutation as well as sterility in animals. These residues also cause allergic sensitivity, psychiatric
sequel, neurologic alterations, hypertension, cardiovascular diseases etc.
Pesticides as such are immunosuppressive
as they alter the structural integrity of immune system. PCDDs, PCDFs, and PCBs are found in tissues of human, fish,
chicken, lamb, goat, predatory bird, and Ganges River
dolphin. Concentrations of PCDDs/DFs are found
in the following order: chicken < goat/lamb < fish < river dolphin
< predatory bird. Processing lowers the amounts of
PCDD/Fs present in the food. It is due to loss
of water and elimination of PCDD/Fs with released fat. Dietary intake of PCDD/Fs can
therefore be reduced by removal of fat from meat before cooking and discarding
any fat released from foods during the cooking process. beta-HCH showed the highest residue rate of isomers, except
for pork and poultry samples. But residues of PCB and Organochlorine pesticides
in processed meat products tended to be lower than those of the corresponding
meat samples.
Special Emphasis on Drug Residues
The public health
significance of drug residues in milk and meat products is an area of much
debate. Most adverse
reactions to drug residues in foods are caused by allergic responses. Example:
- Sensitization in beef to Amino glycosides. Some emerging issues related with drug residues are resistant bacteria are present in
meat commodities due to the use of sub therapeutic antibiotics. The appearance of resistance among pathogenic organisms, such
as Salmonella DT-104 and Campylobactor is of more concern.
üAntibiotics: -
Antibiotics as Sulfonamides, β-lactum antibiotics, Chloramphenicol,
Tetracycline, Macrolide antibiotics etc. are frequently given to food animals
to prevent disease and increase feed efficiency. Aminoglycosides are generally excreted through kidney,
and the drugs tend to concentrate on that organ. Nitroimidazoles and Nitrofurans may be carcinogenic,
and therefore not approved for food animals in USA.
üHormones and Growth Agents: - The use of hormones for increasing the weight gain of food
animals is a controversial global issue. Naturally occurring sex hormones as estradiol, progesterone
and testosterone are given to increase feed efficiency and to have a more
favorable muscle/fat ratio. Synthetic compounds as melengestrol acetate, trenbolone acetate and
diethylstilbestrol (DES) mimic the natural hormones. Because of the concern of human
health, the use of DES is universally banned in 1978. In 1988, the European Community also
banned the use of any anabolic steroids in food producing animals. In USA, some of these compounds are
approved, providing the manufacturer adheres to proper treatment and withdrawal
requirements.
üOther Animal Drugs: - Tranquilizers and Anti-inflammatory drugs are of concern because they
are often given to animals shortly before slaughter. Hence high levels of residues may
persist in edible tissues. The use of Carazolol (β-Blocker), Azaperon, Promazines in food animals is
not allowed. Residues of
Phenylbutazone induce tumors and may cause aplastic anemia and
gastro-intestinal bleeding in susceptible people. Clenbuterol, the β-agonist given to animals illegally
to increase their muscle mass, has been reported to cause human illness as
headache, tremors, nausea etc.
Special Emphasis on Heavy Metals
üLead (Pb): - Residues
of Pb are detected in muscle, bone, kidney, liver & other organs of food
animals.
Kidney & Bone show
higher Pb content than muscle. Safe permissible limit of Pb in meat & meat products is 1 mg/kg
(FAO/WHO- 1992). A
weekly uptake of 3-4 mg Pb is accepted as toxicologically harmless.
üMercury (Hg): - No Hg toxicity has been seen at levels up to 15 ppm whereas WHO
recommendation is 5 ppm. Metallic
Hg is relatively non-toxic & is not significantly absorbed. Liver, kidney of food animals &
red meat is most prone to Hg accumulation. Methyl Hg has teratogenic effect. Provisional Tolerable Weekly Intake
(PTWI) of M-Hg is lowered from 3.3μg/kg body weight. to 1.6 μg/kg body weight
by FAO/WHO/JECFA in 2003.
üCadmium (Cd): -
No accumulation of Cd is observed in bone & brain. However, a slight increase of Cd
level is observed in chicken muscle after six months of exposure. Liver and kidney show a dose and
time-related increase in Cd values. No accumulation of Cd has been recorded in
eggs or bones in poultry. The
kidney Cd levels are several folds higher than those of liver. A dramatic rise in Cd levels in renal
cortex than medulla is observed in animals exposed to supplemental Cd. Cd-binding protein may explain
accumulation and persistence of Cd-residues in these organs. The concentrations of renal
Cd-binding protein increased at a rate greater than those in liver.
Regulations to Control of Pollutants: -
ü PFA Act, 1954
ü Export Act, 1963
ü Export of Meat & Meat product
Rules, 1998
ü Drug & Cosmetic Act, 1940
ü Animal feed confirm requirement as
per std. laid down by BIS Act, 1988
Conclusion: - Pollutants are not harmful unless they cross the Max. Residue
Limit (MRL). Addition of flavoring agents & additives in food products
should be minimized. Use of harmful pesticides & drugs should be
restricted. Fixation of tolerance levels for defined residues to be set
according to their toxicological evaluation. Condemnation of organs of food
animals is obligatory in which these chemicals accumulate.
