This summary was written in this academic year. It contains all lecture notes and e-module information from this course. It includes a list of definitions necessary for the exam. The case study is included, but it is not necessary for the exam.
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- Notes from all le...
Food Toxicology (TOX30306)
This summary contains all lecture notes and e-module information from this course. It includes a list
of definitions necessary for the exam. The case study is included, but is NOT necessary for the exam.
Lecture 1: course introduction
Toxicology = field of science studying and predicting the harmful effects that chemicals, substances or
situations, can have on people, animals and the environment. Everything is toxic if you increase the
dose/exposure, so there are no toxic compounds. The dose will determine the degree of effect it
produces (=dose-response relationship1).
• NOAEL = no observed adverse effect level.
• LOAEL = lowest observed adverse effect level.
• EDXX = the dose at which X% of the population exhibit a response.
• ED50 = median effective dose.
• LD50 = median lethal dose.
• Therapeutic index = ratio between ED50 and LD50.
Aims of modern & food toxicology
• Define toxicity, mechanism of action and structure activity relationships for chemicals to
which humans are exposed via food.
• Evaluate health and environmental factors and risks.
• Advise regulatory authorities, industry and consumers.
History of food toxicology
1. Hunters and gatherers had knowledge on acute toxic properties of plants, mushrooms and
some minerals.
2. 5000-3000 B.C. cooking allowed cultivation of new plants containing toxins; storage and
transport introduced new toxic compound such as moulds (mycotoxins).
3. The increased distance between food sources and consumer called for new preservation
methods, e.g. canning; food additives added to preserve/colour/flavour → legal steps
(regulations and control) to guarantee safety.
Avoidable chemicals = ADI
Avoidable chemicals = purposely added chemicals to food products.
Additives
Additives = substances added to food to perform certain technological functions (colour, sweeten,
preserve).
• Have no proven track record of safety and must be approved before they can be used.
• Receives E-number in EU when approved based on safety/no safety concern.
Flavourings
Flavourings = substances added to flavour food.
• Excludes sweeteners (these are E-numbers).
• Not considered food additives.
• Must be approved before they can be used.
• Regulation EU 872/2012: EU list of flavouring substances which can be used in food.
Food supplements
The Regulation of supplements varies per country. In some countries and EFSA, supplements are
considered to be foods. In other countries, supplements are considered to be drugs/natural health
products. Natural does NOT mean safe.
1
Video about dose-response relationships: https://youtu.be/JdY2P55JiSI?si=vltIozqqh37CZvek
Veterinary drugs
There is an increased number of animals → more disease → increased use of veterinary drugs.
Pesticides
Pesticides protect food and non-food crops against unwanted effects caused by:
• Insects (insecticide)
• Fungi (fungicides)
• Weeds (herbicides)
• Other biological causes
May end up in food chain.
Unavoidable chemicals = TDI
Unavoidable chemicals = chemicals that accidentally end up in the food chain.
Persistent Organic Polutants (POPs)
POPs are very persistent: slow breakdown in the environment and human body → accumulation in
the food chain. Includes:
• Organochlorine pesticides (DDT)
• Polychlorinated biphenyls (PCBs)
• Dioxins (TCDD)
• Brominated flame retardants (PBDEs)
• Perfluoroalkylated substances (PFAS)
Heavy metals
Heavy metals are unavoidable chemicals that may raise concern due to higher exposure levels,
including: Mercury (Hg), Lead (Pb), Cadmium (Cd) and Arsenic (As).
Learning objectives
• Know relevant terms and methods in food toxicology.
• Distinguish sources and types of foodborne toxicants and modes of action underlying adverse
effects.
• Design and execute comprehensive toxicological experiments and critically analyse results.
• Understand basic principles of risk assessment of chemicals in food.
• Evaluate human risks of a food ingredient or contaminant.
Lab practical
Perform in vitro experiments to assess the toxicity of a selected food ingredient or contaminant.
1. Make a range of concentrations (i.e. doses) of your test chemical in dimethylsulfoxide
(DMSO) which you will use to dose the in vitro assays performed in this course.
2. Perform a cytotoxicity assay to assess the cytotoxic potential of your chemical.
3. Perform a substrate depletion assay to assess the rate at which your chemical is metabolised
and understand its accumulation potential in the body.
4. Perform the micro-Ames test to determine whether your chemical is genotoxic.
5. Perform a reporter gene assay and analyse results from this reporter gene assay to get more
insight into your chemical's mechanism of toxicity.
Chemicals
• Benzo(a)pyrene = one of a number of polycyclic aromatic hydrocarbons formed during the
pyrolysis of fat (300-600°C) when smoking or grilling food.
• Bisphenol A = chemical used to manufacture plastics and can leach from packaging into food.
• Benzyl butyl phthalate = one of a number of phthalates plasticizers leaching into foods
through packaging.
• Quercetin = a flavonoid found in many plant products, such as apples and red onions, and
taken as a food supplement.
• Genistein = an isoflavone found in various plants including soybeans and taken as a
supplement.
Lecture aim
• Explain how chemical risk assessments differ for genotoxic and non-genotoxic chemicals.
Basic principles of risk assessment
For the basic principle of risk assessment, the dose-response relationship and exposure should be
known.
• Hazard = potential danger of chemical or process.
• Risk = probability that adverse effect will occur → risk = hazard + exposure.
Risk assessment = the systematic scientific evaluation of potential adverse health effects resulting
from (human) hazardous agents or situations.
Four steps of risk assessment
1. Hazard identification → what type of toxicity to expect.
2. Hazard characterisation (dose-response) → at what dose do these effects occur.
3. Exposure assessment → at what dose can we expect to be exposed.
4. Risk characterisation → compare expected effects and exposure.
a. Risk management
b. Risk communication
Hazard identification
Within food toxicology, the focus is on chemical hazards. The aim is define the source of potential
harm and intrinsic properties of the agent.
Hazard characterisation
Exposure assessment
Exposure assessment = the process of estimating or measuring the magnitude, frequency and
duration of exposure to an agent, along with the number and characteristics of the population
exposed. Ideally, it describes the sources, transport, routes, and the uncertainties in the assessment.
• Assess applied dose.
• Consider exposure continuum and associated modelling and measurement tools to define
applied dose.
Risk characterisation
Risk characterisation = the probability of an adverse outcome based upon the exposure and potency
of (a) hazardous agent(s).
Risk management
Risk management = the process of identifying,
evaluating, selecting and implementing scientifically
sound, cost-effective, integrated actions to reduce risk
to human health and ecosystems while taking into
account social, cultural, ethical, economical, political
and legal considerations.
Regulatory agencies
There are several EU bodies that deal with risk assessment of chemicals:
• European Medicines Agency
• European Food Safety Authority
• European Chemicals Agency
Risk assessment of non-genotoxic chemicals
The first step of risk assessment within toxicology is to discriminate between two types of chemicals:
1. Non-genotoxic chemicals → defined threshold (=safe level of exposure).
2. Genotoxic chemicals (=chemicals causing DNA damage).
The type of risk assessment is dependent on the type of chemical.
Dose-response relationships
• ED50 → for comparing chemical potency.
• LOAEL → lowest tested dose at which adverse effect was observed.
• NOAEL → highest tested dose at which no adverse effect was observed.
A toxicity testing scheme is used to identify and characterise hazards:
From all these toxicity tests, many dose-response curves are made. Next, the dose-response
relationship is defined for the target organ (=the organ toward which the effects of a chemical are
primarily directed) → i.e. most sensitive organ (=where the effect occurs).
Reference dose (RfD) setting
Establish causality that the chemical has in fact induced the observed effects.
• Establish NOAEL, LOAEL (to ID point of departure, POD).
• Determine rate at which injury builds up: slope of dose response curve.
• Apply uncertainty factors.
Uncertainty factor (UF) = uncertainty/safety factors used to extrapolate from a group of test animals
to an average human and from average humans to potentially sensitive sub-populations.
Toxicodynamics = what the chemical does to the body.
Toxicokinetics = what the body does to the chemical.
• Absorption, Distribution, Metabolism and Excretion.
ADI and TDI
Reference doses determined by a.o. EFSA to indicate doses of chemical which we can safely be
exposed to daily.
• ADI (Acceptable Daily Intake) = an estimate of the amount of a food additive (expressed per
kilograms of body weight) that can be ingested daily over a lifetime without appreciable
health risks (voluntary exposure) e.g. cyclamate (sweetener).
The ADI is derived from the No Observed Adverse Effect Level (NOAEL) or No Observed Effect Level
(NOEL) of a compound as determined in an animal study. To compensate for uncertainties in
extrapolating animal data to potential human effects and variation within the human species (e.g.
differences in sensitivity and exposure) uncertainty factors are applied. The ADI for an additive is
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