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Food Toxicology
Toxicology is the study of side and toxic effects of xenobiotics in living beings
...

It is connected to Pharmacology, Biochemistry, Chemistry, Genetics and Pathology
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After taking a dose of a substance, it is available to be absorbed, which will then be dissipated
or give place to the formation of active toxic substances (exposure)
...


Accidental
Toxic food (fish, vegetables)
Container (plastic, aluminum, lead)
Biological contamination (mycotoxins)
Chemical contamination (pesticides, growth hormones)
Radiological contamination (additives)

Voluntary
Homicide (biological/chemical war, fraud)

Factors that influence toxic effects
Dose
Quantity of xenobiotics administered by unit of weight
...


Individual
Inter-species differences
Gender
Age

Among the many different types of Toxicology is food toxicology
...


Hazards associated with different foodstuffs
Physical
Foreign materials (glass, metal, plastic, wood, insects, parts of animals)

Radiological
Radioactive materials (uranium mines, nuclear accidents)

Chemical
Vegetable origin - Heavy metals, use of fertilizers with high amounts of nitrogen, subterranean
and superficial water contamination, pesticides
Meat, dairy products, eggs - Dioxins, heavy metals, pesticides, nitrates, pharmaceuticals, additives
Fishery products - Heavy metals, pharmaceuticals, additives

Biological
Meat, dairy products, eggs - Fungi and mycotoxins, parasites, viruses and prions
Vegetable origin - Neurotoxins (Clostridium botulinum), mycotoxins, biogenic amines (histamine)
Fishery products - Fungi and mycotoxins, biotoxins

Foodstuffs alterations
Group of modifications that are done in foodstuffs, destroying partially or totally its essential
characteristics, by compromising its physical and chemistry properties, hygiene status and nutritive quality
...


These alterations are reflected on:
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Organoleptic characteristics
Chemical composition
Physical state
Nutritive value
Hygiene

Favourable conditions for alterations:
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Harvest
Omissions on the manufacturing
Insufficient or incorrect conservation processes
Inadequate packaging materials
Transportation liabilities

Types of alterations
Microbial
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Mould or rotting of parts
Changes in taste, smell or texture

Physical or mechanical
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Impacts or physical/mechanical pressure (cracks on eggshells, cold or dehydration burns
on vegetables)

Chemical


Oxidative staleness/auto-oxidation (peroxides, alcohols, aldehydes, ketones - unpleasant smell)
...


Enzymatic


Insect and/or rodent attacks

Alterations on food due to packaging materials
Food can be altered due to the inefficiency of the container's protection or its interaction with
the foodstuff
...
However, the constant exposure to light may cause the oxidation of very
reactive compounds
...
However, when it's used, it's for dry products,
so there are no interaction hazards
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However, it’s the economic agent that orders its commercialisation
...

The sampling plan is dependant on the type of sample that is analysed
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Food Toxicology Analysis
1
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3
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5
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Designing the sampling plan
2
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A table of random numbers is used to select the samples
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Used in packed foodstuffs, such as food cans
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g
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Systematic
Collecting of increasing quantities in a pre-settled period of time
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Stratified
Used mostly in samplings of liquids in lakes, tanks and reservoirs
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Sequential
Used to verify the compliance to a specification (labels)
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Ad-hoc
Used in specific foodstuffs, such as vegetarian diets
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The collection and conservation of samples must be done with precision and has to obey certain
requirements and norms; only then can it be considered representative of the sample in question
...


Sampling Preparation Techniques
The techniques used in the preparation depend on:
 Physical and chemical properties of the sample
 Physical and chemical properties of the analyte
 Concentration of the analyte
 Technique sensitivity
 Technique specificity

Techniques:
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Size reduction
Drying
Sample attack
o fusion
o dissolution
Sample digestion
o mineralisation
 dry
 wet
o solvent extraction
 continuous
 discontinuous

o
o

 pressurised fluids
 supercritical fluids
 microwave assisted
sample derivatisation
extraction/concentration with adsorbent materials

Classification of toxic agents in foodstuffs according to their
source
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Natural source
Biological contaminants
Chemical contaminants
Additives
Toxic agents formed during processing, preparation and storage of food
Natural carcinogens / nutrient-xenobiotics interactions

Natural source (seafood, fungi, anti-nutritive substances)
These originate from the metabolism of animals plants and microorganisms that we use as food
or are present in it
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Other substances have retarded? Toxicity and it's sometimes difficult to establish a connection
of the toxic agent with the same substance in food
...
The interaction of microorganisms from the gastrointestinal tract with some of the food components may also produce
toxic metabolites (nitrosamines)

Chemical contaminants (inorganic substances - metals and anions; organic
substances)
The inorganic components of water, soil and air can be absorbed naturally and accumulate on
food (Se, Cd, Hg, nitrates) or contaminate it artificially, through agriculture, industry and technology
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Polycyclic aromatic hydrocarbons
Class of chemical compounds that originate from the incomplete combustion of fossil fuels
...
Therefore, they are considered the biggest class of carcinogens and a priority by the
EPA and European Union
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They become accumulated in organisms, sediments and organic matter
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PAH sources (400-1000°C)
Natural


Pyrolytic: incomplete combustion of organic matter (forest fires, use of fossil fuels, incinerations, volcanic eruptions)
 Leakage of petroleum-derived products
 Natural geochemical processes of sedimentary organic matter (decarboxylation, aromatization)
Main sources in food and drinks
 Natural (forest fires, geochemical processes)
 Environmental pollution (traffic, industry)
 Types of processing (grilling, smoking, roasting)
 Package materials

Exposure conditions
Inhalation
 Contaminated air
o factories that produce tar and incinerators
o air with PAH originating from tobacco smoke, wood burning, car exhaust emissions, horticultural product combustion
Ingestion
 Smoked or barbecued products
 PAH-contaminated vegetables
 Contaminated water or milk
 Vegetable oil
o Refining process
o Environmental pollution leads to contamination of the plants, through particle
disposal or absorption
Dermal Absorption

Occurrence in food
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Pyrolysis of lipids above 300C (It’s possible with lower temperatures, but the time of
exposure is higher)
Cooking oils (Extraction of oils and submission of the seeds to high temperatures)
Roasting of coffee and tea
Grilling and smoking food
o Grilling at high temperatures produces PAH on the food’s surface
o PAH are formed during the combustion of the coal used
o The pyrolysis of the food fat originates PAH that scatter on the air and can contaminate food

Analysis of PAH on food
Analytical Method

Sample

Detection Limit

GC-MS

Water
Seafood

1
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8 g/L
1-5 g/kg

LC/GC-MS

Vegetable oil

1 pg per sample

GC-FTIR

Water

0
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06 g/g

HPLC-UV/DAD
HPLC-FD

Malt
Smoked food
Grilled meat
Dietary fat

2
...
1 g/Kg
20-50 ng/g
0
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5 ppb

HPLC

GC
Good repeatability

Higher selectivity, bigger isomer separation Higher efficiency in columns (good for complex mixpower
tures)
Can separate and detect priority HAP
Shorter retention time

Longer retention time

No risk of thermal decomposition at room tem- Possible risk of thermal decomposition at room temperature
perature
Good results in the 0,2 -1000μg/kg range

Main challenges in the analysis of PAH
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Vestigial quantities (ppb or ppt)
Co-extraction of chemically similar impurities
Many of the PAH are present as isomeric compounds, making the separation and identification difficult

Analytical methods used in the extraction and purification
Sample Preparation

Extraction
Elimination of the interferents
Concentration

Chromatographic Separation

Gas chromatography
High pressure liquid chromatography

Determination

Mass spectrometry
Fluorescence detection

Note: Even though the extraction and purification is necessary, it’s not always enough
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They
frequently
have
antigenic
properties
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They can be present in food that is acceptable from an organoleptic point of view
Many of the fungi produce toxins that, when ingested by animals, produce secondary toxic metabolites, which are passed onto milk, meat and eggs and indirectly absorbed by humans
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Fungal action on food
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Alteration of organoleptic characteristics
Decrease of the food value (protein modification, glucids? Percentage,)
Alteration of the technological properties

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Production of mycotoxins (secondary metabolism)

Most commonly contaminated food
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Oil plant seeds and related food: peanuts (aflatoxins)
Raw vegetable oils: peanuts, olives, coconut (aflatoxins)
Cereals and related food: corn, rice, wheat(aflatoxins, ochratoxins)
Nuts: pistaccio, almonds, walnuts, hazelnuts (aflatoxins)
Fruit: figs (aflatoxins), juices (patuline)
Vegetables (ochratoxins)
Alcoholic beverages (aflatoxins, ochratoxins)
Pepper and spices
Milk and dairy products (aflatoxins)
Meat and related products
Other: potatoes, coffee, etc

Toxicity
Toxicity is related to the molecular structure
The cyclopentanon ring connected to cumarine potenciates the toxic effect of aflatoxin B1,
when compared to the lactone ring in aflatoxin G2
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The compounds are inactive when they don't have the two furane rings in their molecular constitution
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Ochratoxins
Substrates: Corn, wheat, rice, peanuts, coffee beans, barley (beer), smoked meat, dry fish
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It is, however, sensitive to UV light
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Furans are a group of 135 related compounds, most of which are highly toxic
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General Characteristics
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Environmental contaminants (soil, vegetation, water)
Lipophilic, chemically stable and of low volatility
Some of these compounds are highly toxic to lab animals, which means it’s possible
that there are noxious effects for humans as well
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This toxicity is seen in living organisms especially when the substituents are on
the positions 2, 3, 7 and 8
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Sources
Combustion processes originate a high amount of furans and dioxins emissions, especially in
(decreasing order):
 Incineration of municipal waste
 Incineration of medical waste
 Incineration of hazardous wastes
 Incineration of sludge in water treatment plants
 Combustion of products from cellulose industries
 Tire burning
 Biogas combustion
 Cremation
 Regeneration of catalysts on oil refineries
 Smoke from road transport and cigarette smoke
 Fires
 Manufacture of products of mineral origin (glass, bricks, cement, ceramics and rubber)

Ways of exposure
After their emission, dioxins and furans can be transported over long distances, through air
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However, the majority becomes attached to the soil and sediments
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ADME
Depends on relative lipophilicity, smaller/bigger capacity of connection to CYP P4501A2 in the
liver, metabolism velocity (endogenous factors)
Absorption (GIT, intestines):
50-90% for dioxins with 4, 5 or 6 atoms of chlorine
Lesser extension to dioxins with 7 and 8 atoms of chlorine
Metabolism:
Hydroxylation
Elimination:
Females can eliminate through biotransformation or excrete the non biotransformed product
through the placenta to the fetus and/or through breast milk
The average half-life time of TCDD (2,3,7,8-Tetrachlorodibenzo-p-dioxin) on humans is 7
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Toxic effects
TCDD has noxious effects to wildlife in general and humans in particular
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Besides that, dioxins can also cause more effects on four
different levels:
 Immune system
 Nervous system
 Reproductive system
 Endocrine system
 Higher incidence of different types of cancer
Risk groups:
 Fetuses and newborns
 Children breastfed with milk that has high dioxin levels (10-35 pg/g of milk fat in industrialized countries)
 Groups of individuals with particular food habits
 Workers and population in zones that contain dioxins and furans sources

Polychlorinated biphenyls
PCBs constitute a family of 209 compounds, in which their structure consists of connected benzene rings (variable number)
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Unlike dioxins, PCBs are produced intentionally, due to their physico-chemical properties that
give them many different applications
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Heavy Metals
Natural occurrence of lead
Lead is present in pretty much any living being, including humans
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Rarely occurs in its metallic form (Pb2+ or Pb3+)
Occurs in higher quantities in galena, as lead sulphide (PbS2)
Classic Period
Despite the simplicity of the extraction and transformation processes, the industrial exploration of lead was initiated with Greeks and Romans, intensively:
 in the construction of buildings, plumbing and ships
 in the manufacture of kitchen utensils (cups, plates)
 as preservative and sweetener for wines
Middle Ages
Slowdown in the exploration of lead
Use of silver for coin minting
Coating of ceilings (France and England)
Modern Society
Used in many alloys and organic and inorganic compounds:
40% of lead is used in its metallic form, in alloys with other metals and chemical compounds
Inorganic compounds: lead oxides (PbO, PbO2, Pb3O4, and Pb2O3) and lead salts (carbonate, sulfate, chromate, and arsenate)
Organic compounds: lead tetraethyl, tetramethyl, acetate, salicylate and stearate

Types of exposure
Professional
Extraction of galena in mines (exposure to dust containing lead; risk of ingestion)
Smelting of lead (exposure to fine dust and smoke containing lead; risk of inhalation)
Arc welding (high risk of inhalation containing lead and lead oxides)
Demolition of structures and buildings painted with paints that contain lead (risk of ingestion)
Preparation and application of lead arsenate based insecticides (risk of inhalation and ingestion)

Environmental
Breathable particles and lead bromate and chloride emitted by exhaust tubes
Ingestion of particles and inhalation of dust containing lead from the scraping of paints
Ingestion of water from corroded plumbing made of lead
Ingestion of food and drinks contaminated by lead (fruit and wine from gardens and vineyards
treated with lead arsenate)

Toxicokinetics in humans
Entry ways - Respiratory, gastrointestinal and cutaneous
Lead is sent to the vicinity of blood vessels regardless of the entry way
...
The biggest part of
the vapours and fine particles in the lungs pass through to the blood stream
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30-50% of the inhaled lead is absorbed
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Bile and stomach acids promote the intestinal absorption
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5-10% of the ingested lead is absorbed through blood in adults, whereas this percentage can reach 50% on children through digestive absorption
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Entry through this way
is only possible to organic compounds of lead and thallium
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In equilibrium conditions, plasmatic lead is connected to plasmatic proteins
...
5-2% of total lead in the blood) has a great toxicological importance, since it can be transferred to organs and more sensitive tissues
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Until 1993, it was believed that hemoglobin was the main transporter of red cell lead
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Accumulation of lead: bones
Lead mimics calcium in the organism, determining its high bone fixation capacity
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This fixation is a protection mechanism against the action of lead on other organs and tissues
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Elimination
 Urine, feces, hair, nails and sweat
 Liver and kidneys have higher concentrations of lead than other organs, due to their
role in eliminating this metal
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6mg
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Nitrates and nitrites
Naturally distributed, part of the global biogeochemical cycle of nitrogen
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All the natural chemical elements have a dynamic movement in the ecosystems, transitioning constantly between the physical environment and the
organisms
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Exposure
Endogenous way
Nitrates and nitrites are metabolites of nitric oxide, a free radical that plays a relevante role in
physiological functions such as:
 Vasodilation and neurotransmission
 Rejection of transplants and diabetes
 Cytotoxic agent used by macrophages against pathogenic bacteria and carcinogenic
cells
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Nitrates can be converted into nitrites with saliva or in the GIT
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Ex
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(blue-baby syndrome)

Toxic effects
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Anxiety
Tachycardia

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Increase of the respiratory rate and trouble breathing
Vomit, salivation and tearing
Cyanosis

Chronic doses:
 Depression
 Weakness
 Physical debilitation
 Cancer (due to nitrites and N-nitrosamines)

Pesticides
Chemical or biological substances or mixtures that are designed to prevent, destroy, repel or
mitigate a plague
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Requirements for pesticide registration (according to FIFRA - Federal Insecticide, Fungicide and Rodenticide Act)
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Physico-chemical characteristics of the product
Environmental impact

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Toxicological studies
Biotransformation/degradation
Occupational exposure
Product behaviour and efficiency
Establishment of tolerance levels for pesticide residues in agricultural products

Why is it important to control pesticide residues in food?
Illegal use of pesticides that are no longer in the market
Abusing the application speed to hasten the harvests
Presence of the pesticide in concentrations above the recommended (due to excessive use)



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