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Food chemical safety
Chemical contaminants in foods
Characteristics:
They are not added intentionally added to
food.
Contamination can happen at one or more
stages in food production.
Illness is likely to result if consumers ingest
enough of them.
The above differentiate from other
chemicals in food such as vitamins and
additives.
Examples of chemical contaminants
Pesticides
Herbicides
Fungicides
Veterinary drugs
Pesticides
“eat your fruits and vegetables” is one
of the recommendations for a healthy
diet.
Use of pesticides and chemicals to
protect fruits and vegetables against
insects and pests, and moulds.
Correct and responsible use of
pesticides can enhanced yield and
safety of these produce.
Use of pesticide
Must follow the limits sets by the
Ministry for use on food commodity,
and the safe amount of pesticide
residue that may be present at the
point of sale.
The safe residue level conform with
the international standards set by
Codex Alimentarius Commision.
Potential hazard?
Pesticide residue.
Contamination of surface and ground
water.
Persistent pesticide not degradable
are removed from the registration list.
Acceptable Daily Intake (ADI)
ADI is a measure of toxicity.
Calculated from a known toxicological effect of a chemical
(e.g. pesticide), example: increased serum glutamate
pyruvate aminotransferase (SGPT) in dicator of liver
damage.
The dose of the pesticide below the point at which the
defined toxicological effect occurs in animal studies is
determeined (NO Observable Adverse Effect Level –
NOAEL).
This is the maximum dose that can be consumed without
any adverse effect resulting.
ADI exceeds the level is rare, but cases of lindane in milk
(UK in1996) and chlormequat in pears in 1999.
Maximum Residue Level (MRL)
MRL is not a toxicological parameters but a trading standard
set by national and international authorities (e.g. Codex
Alimentarius) to ensure that residues are controlled in world
food trade.
MRL is the pesticide residue level in particular food following
its production according to Good Agricultural Practices
(GAP) i.e. apply pesticide at the right time and according to
label directions, appropriate withdrawal period (time
necessary between application of pesticide and harvest); the
crop is harvested and residue determined.
If the level of pesticide exceed the MRL, the crop has not
been grown according to GAP and the product not permitted
to be sold, imported or exported.
Exceeded the MRL has no health
implication, but the farmer has
breached the national or international
regulations and is liable for
prosecution.
Exceeding the MRL is more common.
Pesticides must be in harmony with
non target pests and environment.
Those broad-spectrum pesticides
and have long residual effect were
either removed from the market or
restricted usage.
The regulatory body is Pesticide
Board of Malaysia under the
preview of the Ministry.
Pesticides withdrawn or partially banned
by the Pesticide Board of Malaysia
Aldrin
Diledrin
Benomyl
Chlordane
DDT
Heptochlor
Penthachlorophenate
Endosulphan
withdrawn by the parent company
------do-----------do----total ban
total ban
total ban
partial ban – not allowed for paddy
partial ban – not allowed for cocoa and
pepper
Lindane (gamma-BHC) partial ban – allowed for palm oil and
coconut only
(total 17 pesticides)
Pesticides not allowed for use on
vegetables
Some organophosphate pesticides, e.g.
methamidophos and monocrotophos, were
registered for use in vegetables but after
review by the Pesticide Board, they have
been banned based on their residue or
toxicology problems.
All pesticides use in Malaysia must be
registered.
Comply the Pesticide Act 1974 and Food
Act 1985, for the registration, production,
management and application of pesticides.
DDT : organochlorine
(1,1’-(2,2,2-trichloroethylidene)bis(4-chlorobenzene)
Dr. Paul Muller, a Swiss chemist won an Nobel Prize in
Medicine in 1948 for DDT, replacing extremely dangerous
chemicals for pest control (arsenic, lead and mercury).
Effective against mosquitoes causing malaria, kill lice,
improve health in Sri Lanka.
1964 use of DDT was discontinued in Sri Lanka, and
coincide with publication of Carson’s Silent Spring.
Attack on DDT:
(i) cause thin egg shells. (ii) DDT is so stable and could
never be eliminated from the environment. Safe for
human? Cancer? (lipid solubles)
Repeated administration of DDT to animals results in tremor,
incoordination, muscular twitching and weakness.
DDT is excreted in urine.
Organophosphate (OPs)
 Oldest synthetic pesticides.
 Common names: organic phosphates, phosphate
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insecticides, phosphorus esters or phosphoric acid esters.
Genarally speaking they are most toxic to vertebrate
animals.
Mode of action is similar to nerve gas (potent
cholinesterase).
Attack nerve, death as a result of respiratory failure.
e.g. malathion, parathion.
easily metabolized by esterase,low mammalian toxicity.
Residues in food products do not normally result in
exposure sufficient to lead to health problems in humans.
Pyrethroids “green” pesticide from chrysanthemum
(pyrethrum).
Other insecticides
Carbamates similar to Ops, water
solubles, contaminated water.
mode of action; similar to Ops
cholinesterase inhibitors.
Cyclodiene: e.g. aldrin and dieldrin,
stable in soil and relative stable to uv
of sunlight. Use to control soil insects.
Mode of action is neurotoxicity.
Herbicides
Weed killers.
Trace residues present in final food products.
Chlorophenoxy acid esters: 2,4-D and 2,4,5-T
No apparent adverse effects on human and
animals.
The 2,4,5-T used in Agent Orange contains
excessive amounts of tetrachrodioxin, suspected
toxic impurity.
Bipyridyliums: paraquat and diquat.
On contact plant tissues are quickly damaged.
Cases of accidental or suicidal fatalities from
paraquat poisoning.
Fungicides
Chemicals used to kill or stop the
development of fungi.
To treat plants, roots,seeds
Industrial and environmental
contaminants
Most do not pose threats to human, but some
certain incidences have indicated that they can be
a potential hazard.
Halogenated hydrocarbons: polychlorinated
Biphenyls (PCBs) or trade name Aroclor ® first
synthesise in1881.
Uses: insulating fluids in electrical industries, food
packaging made from recycled paper, paints,
lubricants, insulating tapes, fireproofing materials,
and ink.
Considerable resistant to acids, bases, high
temperature, electrical current and is
nonflammable.
Safety: no significant health threats to human.
Dioxin
TCDD (tetrachlorodibenzo-p-dioxin) are among most
potent toxicants known, chemically very stable and binds
strongly to to solids or particulate matter in soil, is lipophilic
but sparingly soluble in water or organic liquids.
LD50 for TCDD in guinea pig is under 1 mg/kg; hamster is
more than 10g/kg.
Toxicity affect the kidney and skin, promoter of
carcinogenesis and is a carcinogen. Liver tumors, tumors
of the mouth, nose and lung have been found.
Three times more potent than aflatoxin B1.
In rhesus monkeys, TCDD is fetotoxic, resulting in higher
levels of abortion and death in pregnant females.
Human exposure: no fatalities, toxic effects include
fatigue, affect peripheral nervous system and liver toxicity.
Heavy metals
Mercury: exists in many forms.
metallic mercury, inorganic mercury compounds or
salts, organic mercury compounds.
Nervous system is very sensitive to all forms of
mercury. Exposure to high levels of metallic,
inorganic or organic mercury can permanently
damage the brain, kidneys and developing fetus.
Mercury chloride and methyl mercury are possible
human carcinogens.
Children are more sensitive to
Children are more sensitive to mercury than are
adults, can be passed through breast milk.
Mercury level in water
FDA maximum permissible level of
1ppm methyl mercury in seafoods.
EPA mercury in drinking water 2 ppm.
Lead
Previously, this heavy metal was found in a variety
of consumer products (lead-based paints,
antiknock petrol, lead-glazed glasses, lead water
pipes, lead glazes, lead solders).
Lead poisoning is normally due to occupational
situations.
Children are most affected, lead absorption in
children is about 40%, adult 10%, highest in the
bone.
Anemia, neurological disorders in developing
children brains, can pass from placenta to fetus.
Elimination or minimize exposures.
Cadmium
Cadmium in food is as inorganic cadmiun salts.
Organic cadmium is unstable.
In Japan, chronic cadmium intoxication over 12-yr
period occurred in some population that consumed
rice contaminated with cadmium because of
pollution. Painful disease called itai itai meaning
“ouch ouch” bone disease, with symptoms of
skeletal deformation and multiple fractures.
Cadmium stays in the liver and kidneys.
Breathing air with very high levels of cadmium can
severely damage the lungs and cause death.
Arsenic
Found as inorganic and organic compounds. In foods,
drinking water, wine and other sources.
Used widely in manufacture of glass to remove green colour
cause by impurities.
Previously arsenic is used to treat syphilis until penicillin and
other sulfa drugs were developed.
Arsenic is abundant in seafoods, but in an organic form, not
toxic, rapidly absorbed and excreted in the urine and bile.
Classical syndromes of chronic arsenic exposure include
hyperkeratosis, corns and warts on the feet and hands.
May be indirect carcinogen.
10 to 50 ppb may be necessary to maintain homeostasis of
the body, used successfully to treat acute promyelocytic
leukemia (APL).
Standard in drinking water is 10ppb.
Contaminants of Industrial and
Environmental Origin
CHEMICAL
Polychlorinated
biphenyls
SOURCE
Electrical appliances
ASSOCIATED FOOD
Fish, animal fat
Dioxin
Impurity
Fish, milk, beef fat
Mercury
Chlor-alkali
Fish
Lead
Vehicle emission,
smelting, paint,
glazes, solder
Vegetables, canned
food, canned dish,
acidic food
Cadmium
Sludge, smelting
Radionuclides
Accidental release
Grains, vegetables,
meat, molluscs
Fish, mushrooms
Contaminants of Biological Origin
(Inherent Plant Food Toxicants)
CHEMICAL
Oxalates
Glycoalkaloids
Cynide
Phytohaemagglutinin
Various carcinogens
ASSOCIATED FOOD
Tea
White potato (solanine)
Cassava, Lima beans
Red kidney beans and
other beans
Herbs, spices
Contaminants of Biological Origin
Mycotoxins
CHEMICAL
SOURCE
ASSOCIATED FOOD
Aflatoxin
Aspergillus flavus and
A. parasiticus
Corn, peanuts, copra,
milk
Trichothecenes
Mainly Fusarium spp
Ochratoxin A
A. ochraceous
Cereals and other
foods
Wheat, corn, barley
Ergot alkaloids
Claviceps purpurea
Barley, wheat
Patulin
Penicillium claviforms
Apples and other fruits
Zearalenone
Fusarium spp
Cereals, oils, starch
Minimum Water Activity for Growth
of Toxigenic Moulds
Mould
Aspergillus flavus
Aspergillus ochraceus
Penicillium griseofulvum
Minimum Aw
0.81
0.78
0.83
Target Organs of Some
Mycotoxins
Mycotoxin
Target
Aflatoxin
Ochratoxin
Trichothecenes
Ergot alkaloids
Liver
Kidney
Mucosa
Peripheral vascular
system
Uro-genital tract
Zearalenone
Regulatory Limits for Mycotoxins in
Foods
Mycotoxin
Aflatoxins B and G
Aflatoxin M1
Ochratoxin A
Deoxynivalenol
Patulin
Zearalenone
Limit (ppb) Commodities
0 - 50
10 – 1000
0 – 0.5
1 – 300
All foods
Animal feeds
Milk, dairy
Rice, corn, barley,
beans, pork kidney
1000 – 4000 Wheat
Apple juice
20 – 50
30 - 1000 All foods
Regulatory Limits for Aflatoxins in
Some Asian Countries
Country
China
Hong Kong
India
Japan
Malaysia
Philippines
Singapore
Sri Lanka
Thailand
Limit (ppb)
50
20
15
30
10
10
20
Absence
30
20
Commodity
Peanuts
Peanuts
Other foods
All
All
All
All
All
Peanuts
All
Other Toxicants of Biological Origin
Chemical
Source
Associated Food
Ciguatera
Dinoflagellates Tropical fish
Shellfish toxins:
Dinoflagellates Shellfish
Paralytic, neurotoxic,
diarrheic and amnesic
Pyrrolizidine alkaloids
Various toxic
plants
Cereals, honey
Histamine
Spoilage
bacteria
Fish, cheese
Contaminants Produced During
Processing
Polynuclear aromatic hydrocarbons
Heterocyclic amines, nitropyrenes
Nitrosamines
Oxidized fats
Ethyl carbamate (urethane)
Improperly Used Agrochemicals
Pesticides:
Organochlorine insecticides
Organophosphorus insecticide
Carbamate insecticides
Other pesticides
Animal Drugs:
Antimicrobials
Growth promotants
Anthelminthics
Therapeutics
Fumingants
Fertilizers
Nematocides
Fungicides
Herbicides
Molluscicides
Plant growth regulators
Rodenticides
Biotechnology
Direct Food Additives
(Improperly Used Additives)
Anti-caking agents
Antimicrobial agents
Antioxidants
Colours
Curing and pickling agents
Emulsifiers
Enzymes
Firming agents
Flavour enhancers
Flavourong agents
Humectants
Leavening agents
Release agents
Non-nutritive sweeteners
Nutrient supplements
Nutritive sweeteners
Oxidizing and reducing agents
pH control agents
Propellants and gases
Sequestrants
Solvents and vehicles
Stabilizers and thickners
Surface-active agents
texturizers
Indirect Food Additives
(improperly used)
Processing Aids
Ion-exchange resins, filter aids
Enzyme preparation
Microorganisms
Solvents, lubricants, release agents
Specific function additives
Food Contact materials
Utensils
Working surfaces
Equipment
Packing materials
Metals, plastics, paper, wood, etc.
Cleaning Agents
Detergents
Sanitizers
Adultrants
Borax
Boric acid
Formaldehyde
Unapproved colouring agents.
Monitoring Points for Chemical
Hazards
Point source
Environmental compartments
Primary production
Import/export
Production and processing
Consumer level
Biomonitoring
Criteria for Establishing Priorities
Severity of potential effects on health
Levels in individual foods and the diet
Size and susceptibility of the exposed
population
Significance in domestic and
international trade
Nature and cost of management
options
Chemical Hazards in the Home
Contaminated food and water
Metal cookware contaminated with
heavy metals
Ceramic serving dishes with toxic
glazes
Leaded crystal used with acid foods
Miscellaneous home-use chemicals
Exposure
Chemical Hazards in Food
Areas
of
Concern
Toxicity
Potential Physical Hazards
 Glass
 Slime
or scum
 Metal
 Bone
 Plastic
 Stones
and rocks
 Capsules or crystals
 Pits or shell
 Wood
 Paper
Distribution of Complaints of
Foreign Objects in Foods
Soft drinks
Infant foods
Bakery
Chocolate and cocoa products
Fruits
Cereals
Vegetables
Fish
Others
19%
16%
14%
7%
7%
5%
4%
3%
25%
Possible Control Measures
 Visual
inspection
 Filters or sieves
 Magnets
 Separation by density
 Personnel precautions
Assignment: search for literature for
reports on interaction of selenium and
heavy metals.