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 withdrawn by the parent companyDiledrin ------do-----Benomyl -------do-----Chlordane total banDDT total banHeptochlor total banPenthachlorophenate partial ban – not allowed for paddyEndosulphan partial ban – not allowed for cocoa

and pepperLindane (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

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-TNo 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.

DioxinTCDD (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 toChildren 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

Dioxin

Mercury

Lead

Cadmium

Radionuclides

SOURCE

Electrical appliances

Impurity

Chlor-alkali

Vehicle emission, smelting, paint, glazes, solder

Sludge, smelting

Accidental release

ASSOCIATED FOOD

Fish, animal fat

Fish, milk, beef fat

Fish

Vegetables, canned food, canned dish, acidic food

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 OriginMycotoxins

CHEMICAL

Aflatoxin

Trichothecenes

Ochratoxin A

Ergot alkaloids

Patulin

Zearalenone

SOURCE

Aspergillus flavus and A. parasiticus

Mainly Fusarium spp

A. ochraceous

Claviceps purpurea

Penicillium claviforms

Fusarium spp

ASSOCIATED FOOD

Corn, peanuts, copra, milk

Cereals and other foods

Wheat, corn, barley

Barley, wheat

Apples and other fruits

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

Aflatoxin

Ochratoxin

Trichothecenes

Ergot alkaloids

Zearalenone

Target

Liver

Kidney

Mucosa

Peripheral vascular system

Uro-genital tract

Regulatory Limits for Mycotoxins in Foods

Mycotoxin

Aflatoxins B and G

Aflatoxin M1

Ochratoxin A

Deoxynivalenol

Patulin

Zearalenone

Limit (ppb)

0 - 50

10 – 1000

0 – 0.5

1 – 300

1000 – 4000

20 – 50

30 - 1000

Commodities

All foods

Animal feeds

Milk, dairy

Rice, corn, barley, beans, pork kidney

Wheat

Apple juice

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

ChemicalCiguatera

Shellfish toxins:

Paralytic, neurotoxic, diarrheic and amnesic

Pyrrolizidine alkaloids

Histamine

SourceDinoflagellates

Dinoflagellates

Various toxic plants

Spoilage bacteria

Associated FoodTropical fish

Shellfish

Cereals, honey

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 Fungicides Plant growth regulatorsFertilizers Herbicides RodenticidesNematocides Molluscicides 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 AidsIon-exchange resins, filter aidsEnzyme preparationMicroorganismsSolvents, lubricants, release agentsSpecific function additives

Food Contact materialsUtensilsWorking surfacesEquipment

Packing materialsMetals, plastics, paper, wood, etc.

Cleaning AgentsDetergentsSanitizers

Adultrants

Borax

Boric acid

Formaldehyde

Unapproved colouring agents.

Monitoring Points for Chemical Hazards

Point sourceEnvironmental compartmentsPrimary productionImport/exportProduction and processingConsumer levelBiomonitoring

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

Chemical Hazards in Food

Toxicity

Exp

osur

e Areas

of

Concern

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 19%

Infant foods 16%

Bakery 14%

Chocolate and cocoa products 7%

Fruits 7%

Cereals 5%

Vegetables 4%

Fish 3%

Others 25%

Possible Control Measures

Visual inspectionFilters or sievesMagnetsSeparation by densityPersonnel precautions

Assignment: search for literature for reports on interaction of selenium and heavy metals.