concepte in toxicologietoxicologia produselor alimentare ramona suharoschi 10.10.2011

concepte in toxicologietoxicologia produselor alimentare

ramona suharoschi10.10.2011

obiectivele cursului

• Definitia toxicologiei si a toxicitatii. • Discutie diferite tipuri de raspunsuri toxice. • Explicatie clasificarea toxicelor. • Descrierea fazelor toxicozelor. • Explicatie cum expunerea concomitenta influenteaza

toxicitatea. • Introducerea testelor de toxicitate.

toxicologia

• Stiinta ce studiaza efectele adverse ale substantelor chimice asupra sistemelor vii. o Clasificare

Toxicologie descriptiva (Cum? ) Toxicologie mecanistica (De ce?) Toxicologie analitica (Cat?)

definitia toxicitatii

• Toxicitatea: Gradul cu care o substanta poate avea efecte daunatoare asupra oamenilor sau animalelor. o Toxicitatea poate fi acuta, subcronica, sau cronica.

toxicitate acuta

• Implica efectele daunatoare intr-un organism la o expunere unica sau o expunere pe termen-scurt.

The Death of Socrates, 1787 Jacques-Louis David(Metropolitan Museum of Art, New York)

toxicitate subcronica

• Capacitatea unei substante toxice de a produce efecte la o expunere > de 1 an dar < decat expunerea pe toata durata vietii organismului.

toxicitate cronica

• Capacitatea unei substante sau amestec de a determina efecte daunatoare la o expunere indelungata, de obicei ca urmare a unei expuneri repetate sau continue, uneori pe toata durata de viata a organismului.

arii de specialitate in toxicologie • Tinta Organ/Sistem

o Neurotoxicologie, Toxicologie Genetica (genotoxicologie), Toxicologie Reproductiva, Imunotoxicologie, Toxicologie endocrina.

• Tinta Specie/Sisteme o Toxicologie Acvatica, Toxicologia Mediului

(ecotoxicologie), Toxicologia vietii salbatice, Toxicologie veterinara.

• Raspuns specifico Teratogeneza, Carcinogeneza, Mutageneza

toxicologie aplicata

• Toxicologia muncii. • Toxicologie clinica.

o Toxicele induc boli si antidot • Toxicologie criminalistica

o Determinarea cauzelor mortii. • Toxicologie Legislativa

o Evaluarea Riscului prin teste descriptive • Toxicologia dezvoltarii

o Noi substante chimice si utilizari

clasificarea toxicelor • Organ tinta.

o Hepatotoxine, neurotoxine. • Utilizari.

o Pesticide, solventi. • Sursa.

o Natural, sintetic. • Efect special.

o Carcinogen, mutagen, disruptor endocrin

clasificarea toxicelor, 2

• Stare fizicao Gaz, solid.

• Toxicitateo Extrema, redusa.

• Compozitie chimicao Metale grele, organofosfati.

• Mecanism de actiuneo Anticholinergic, inhibitor, necuplat/nelegat

tipuri de raspuns toxic

• Localo Efecte la locul de actiuneo TGI, plamani

• Sistemico Efect la distanta de locul de

expunereo SNC, rinichi, plamani.

• Unele ambele.

• Imediateo Minute cateva ore de la o

expunere unica. • Intarziat

o Zile ani de la expunere. • Unele ambele

tipuri de raspuns toxic, 2

• Reversibil vs. Ireversibil o Determinat in mare de

Tesutul implicat, durata expunerii si magnitudinea insultei toxice.

Reversibil – tesut regenerat rapid. Ficat, mucoasa intestinala, celule sanguine. Ireversibil Afectarea SNC, carcinogeneza, mutageneza, teratogeneza

biodisponibilitatea

• Coeficient de partitie Octanol-Apa, Kow • Putem folosi un termen empiric pentru evaluarea

potentialului transportului transmembranar. Kow = 102 - 103 absorbtie buna chimica(Log Kow = 2 - 3). OK solubilitate in lipide (liposolubile) si OK solubilitate in

apa (hidrosolubile). Kow = [T]octanol / [T]apa

trei etape ale toxicologiei • Faza de expunere.

o Faza toxokinetica (TK). Absorptia. Distributia. Metabolismul. Excretia

• Faza toxodinamica (TD)o (TD/TK)

faza de expunere

• Biodisponibilitate o Fractiunea dintr-o doza disponibila pentru absorbtie.

• Factori principali o Timpul si frecventa expunerii, e.g. acuta, subcronicao Ruta de adminsitrare.

Animale: oral, pulmonar, cutanat, injectabil. Plante: radacini, frunze

faza de expunere, 2

• Factori legati de gazda. • Metabolismul Pre-

absorptiei

• Doza. o Forma fizica si chimica a

toxicelor.• Dimesniunea / marimea

particulelor, solubilitatea

Ukrainian President Viktor YushchenkoDioxin Poisoning

faza de absorbtie

• Aspecte comparativeo Celular organism.

• Morfologia memebranelor celulare o Bi-strat lipoproteine

• Procese fizico-chimice ce determina transportul transmembranar o Solubilitatea lipide-apa, Kow o Ionizarea (pKa), grupe functionaleo Marimea moleculara si conformatia

faza de absorbtie, 2

• Transportul transmembranaro Difuzie simpla – legea Ficko Filtrare – pori aposio Transportatori

• Locuri de Absorptieo Animale – TGI, cutanat, pulmonar. o Plante – pori stomatali, cuticule, radacini. o Insecte – pori canaliculari, oral. o Pesti – branhii, TGI, cutanat

faza de distributie

• 4 conditii determinanteo Locul actiunii toxicului, depozitarea, metabolismul,

excretia • Cum are loc

o Animale – sange, limfa. o Plante – xylem si / sau phloem

• Bariere toxicologiceo sange/creier. o Placenta (matern - fetal). o Glanda mamara (sange - lapte).

Sea snake neurotoxin

faza de distributie, 2

• Factori ce afecteaza distributiao Afinitatea tesutului pentru xenobiotice. o Curgerea sangelui, legarea de proteineo Ruta de administrare, rata de metabolism

• Redistributiao circuitul Enterohepatic

faza metabolica • Faza I – Bioconversia.

o Factori ce afecteaza toxicitatea si metabolismul. Mediu, genetic

• Faza II – Conjugarea.

Dioxin

factori ce influenteaza toxicitatea expunerea concomitenta

• Aditiv 2 + 2 = 4 o OP (organofosfati) determina inhibitia cholinesterazei.

• Sinergic 2 + 2 = 10 o CCl4 cu etanol determina hepatotoxicitate

• Potentare 2 + 0 = 6 o Isopropanol cu CCl4, promotori tumorali.

• Antagonic 2 +2 = 0 o BAL cu metale grele, antidot. (British anti-lewisite (BAL), the classic heavy

metal antidote )

excretie

• Semnificatie toxicologica. • Excretie Renala• Excretie non-renala

o Biliara, expiratie, secretie gastrica• Aspecte comparative.

o Animale, plante

toxicodinamica

• Activitate Intrinseca:o raspuns

Agonist – substanta fara activitate intrinseca, care blocheaza receptorii, e.g. O2

Antagonist – substanta ce actioneaza impotriva agonsitilor, e.g. CO

Medicamente – Tipic reversibil.Toxice – Tipic non-reversibil.

toxice ale transportului de oxigen• Formarea Methemaglobinei (Fe2+ Fe3+).

o Nitrat (NO3-), nitrit (NO2-).o Naftalina.o Clorat.o Acetominofen.

• Competitia O2 la Fe2+o CO, monoxid de carbono CN-, cianide.

transport o2, hemoglobina: biochimie• Bar-headed goose

Hemoglobina (oxy form)• PDB

pdb http://www.pdb.org/pdb/home/home.do

Transport oxigen Site-uri enzimatice active

transport de electroni

nivele de toxicitate – doza orala la om

spectrul dozelor toxice

principii generale in toxicologie


• Mecanisticao Toxicogenica

• Descriptivao Testarea Toxicitatii

Evaluarea sigurantei Reglementari

• Legislatie


• Toxicologie Criminalistica• Toxicologie Clinica• Toxicologie Mediului

o Ecotoxicologie• Toxicologie dezvoltarii

o Teratologie• Toxicologie reproductiva


• Spectrul Dozelor Toxiceo AGENT DOZA (mg/kg)o Ethyl Alcohol 10,000o Sodium Chloride 4,000 o Ferrous Sulfate 1,500o Morphine Sulfate 900o Phenobarbital Sodium 150o Picrotoxin 5o Nicotine 1o D-Tubocurarine 0.5o Hemicholinium-3 0.2o Tetrodotoxin 0.1o Dioxin (TCDD) 0.001o Botulinum Toxin 0.00001

principii generale in toxicologie Clasificarea Agentilor Toxici: • Toxine – de origine biologica• Toxine – de origine antropogena (produs de om)


• Cai si Locuri de Expunere • Durata si frecventa expunerii

o Acuta – expunere la doza in mai putin de 24 ore Ingestie Dermica Inhalatie Intra-ocular Injectie


• Sub-acuto Mai putin de o luna indiferent de cale de expunere si repetitie

• Sub-cronico Expunere la doza intre 1-3 luni

• Cronico Expounere peste 3 luni pana la toata durata vietii


• Spectrul efectelor toxice o Reactii Alergice o Reactii idiosincratice (pseudo-alergice) o Reactii imediate vs intarziateo Reactii Reversible vs ireversibleo Reactii Locale vs sistemice


• Interactiunea subst. chimice:o Actiune aditiva

2 + 3 = 5o Sinergica

2 + 2 = 20o Potentare

0 + 2 = 10o Antagonism

4 + 6 = 8


• Tipuri de antagomnismo Functional

Efecte opuse asupra aceleasi functii fiziologiceo Chimic

Chelatori ai metalelor o Dispositional

Modificari ale expunerii, distributiei sau excretieio Receptor

Blocant

lectii invatate 1

• intrebare: toate substanetele sunt toxice daro Produsii naturali nu sunt otravitori deoarece au efecte beneficeo Substanetle chimice de sinteza sunt mult mai toxice decat

substantele care se gasesc in mod natural in mediu o Toxicitatea atat a substantelor naturale cat si a celor sintetice

depinde de dozao Doua subtante chimice au aceeasi toxicitate daca au aceeasi

LD50

lectii invatate 2• Pe baza ariei suprafetei expuse, clasificarea dozei per unitatea

de arie: o Soarece, sobolan, iepure, porc de guineea, pisica, maimuta, caine, om

toxicologie (abstract)• Expunere + Hazard = Risk• Toate substantele pot fi toxice• Doza determina raspunsul • Doza sb determina pathway-ul, durata si frecventa

expunerii• Absorptia, distributia, metabolismul & excretia

(ADME)• The extent of the effect is dependent upon the

concentration of the active compound at site of action over time

• Bioactivation: compounds to reactive metabolites• Individual variation of the organism will affect ADME

dose (intake) x toxicity = risk

• The does makes the poison• Dose/intake are exposure• That is:

o no matter how dangerous the toxicanto no risk without exposure

risk

• Technicalo # of people that

will be injured, become ill, or die

• Non-Technicalo Upsetting,

frightening, or enraging

risk assessment

• A process or method by which we assess the nature and magnitude of risk.

• hazardous waste disposal and chemicals• new and existing technologies• site facilities• set priorities• develop cleanup goals

• Risk- the likelihood or possibility of suffering injury, disease, or death from a hazard

• Hazard-a source of risk, refers to a substance or action that can cause harm

• a hazard can not constitute a risk unless there is exposure

• 1983 NRC Report- Risk Assessment in the Federal Government: Managing

the Process• 1. Hazard identification• 2. Dose-response assessment• 3. Exposure assessment• 4. Risk characterization

congressional commission on risk assessment – risk assessment and risk management in regulatory decision-making (1997)

hazard identification

• Determining whether a chemical, under plausible circumstances, may cause harm to human health or the environment

types of information

• 1. Epidemiological studies• 2. Animal bioassays• 3. In vitro tests• 4. SAR analyses

• Animal Bioassays• acute studies• subchronic studies• chronic studies

• Acute studies• single exposure, multiple doses• observed up to 14 days• LD50, LC50

subchronic studies• Repeated exposures, 5 to 90 days• variable exposure routes• 3 doses• NOEL, LOEL vs. NOAEL, LOAEL• determine MTD

chronic studies• Several doses- MTD, 1/2 or 1/4 MTD, 0• majority of lifetime (2 years rodent)• lower doses, larger N = subtle effects• long time, high cost

exposure assessment• Estimate or directly measure the quantities of chemicals

received by individuals, populations, or ecosystems• no risk without exposure• output is quantitative, used in Risk Charterization

questions to answer

• Which chemicals reach target?• How much exposure?• In what way?• For how long?• Under what circumstances?

• Biomonitoring- measuring a chemical or its byproducts in tissues or fluids as an indicator of exposure (exposure vs effect)

• rarely done- expensive, limited tests• time issues

ambient monitoring

• Monitoring contaminants in media (soil, air, water, etc.) to estimate exposure point concentrations (EPCs)

• when inadequate, often use modeling

• Goal of modeling or ambient monitoring

• calculate an intake or dose for organism

• Dose (intake, exposure) x Toxicity = Risk

intake = c x cr x efd bw x at

• I is intake or dose• C is chemical concentration• CR is contact rate• EFD is exposure frequency and duration• BW is body weight• AT is averaging time

• These equations are used to calculate doses from exposure pathways

• values for inputs are as realistic as research allows (Exposure Factors Handbook)

• but many uncertainties exist

• At GAEPD, evaluate Reasonably Maximally- Exposed Individual (RME)

• not a worst case scenario• may be appropriate to contrast with exposure estimates

calculated from central tendency estimates• Probability Density Functions (Monte Carlo simulations)

total dose (intake) = sum of all doses from individual pathways

• chronic versus intermittent exposures?

• aggregate

dose-response assessment

• Intake x Toxicity = Risk• often must extrapolate from animal

studies• two important assumptions

o1. Thresholds for non-cancero2. No thresholds for cancer

Dose-Response Relationship:

2

3

4

0 1 DOSE

RESPONSE

0-1 NOAEL2-3 Linear Range4 Maximum Response

DOSE DETERMINES THE BIOLOGICAL RESPONSE

As the dose increases…. so does the response

thresholds exist for most biological effects

• Doses exist below which no adverse effects are observable in a population of exposed individuals

thresholds do not exist for carcinogens.

• Any level of exposure to the chemical corresponds to some non-zero increase of inducing genotoxic effects.

non-cancer evaluation

• Reference Dose- an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily or continuous exposure for human populations, including sensitive subgroups, that is likely to be without appreciable risks of deleterious effects occurring in a lifetime.

rfd = noael or loaelufs x mfs

• NOAEL OR LOAEL for critical effect

uf 1 to 10 to account for:

• Variation in humans• extrapolation from animals to humans• subchronic instead of chronic• LOAEL instead of NOAEL

assumptions

• Population threshold exists• RfD estimate represents subthreshold

doses• preventing critical effect protects

against all effects

cancer evaluation

• EPA’s guidelines published in 1986• weight of evidence- all human and animal

‘86 scheme

• Group A- known human carcinogen sufficient human data• Group B- probable human carcinogen

o B1- limited human, sufficient animal datao B2- inadequate human, sufficient animal data

• Group C- possible human equivocable animal data

• Group D- not classifiable inadequate or no data

• Group E- evidence of noncarcinogenicity

current practice

Data (usually animal) fit with model to extrapolate into low dose rangeEPA uses Linearized Multistage Model

lms• Accommodates nonlinearity at high

doses• Constrains results to linear form at

low doses• Based on current understanding of

cancer as multistage process

lms• Output in form of “slope factor” • Represents steepness of dose-response curve (larger

number = more potent)• Slope factor represents upper bound (95th percentile) caner

risk per unit dose

risk characterization• Where all components of

assessment are brought together in a quantitative evaluation and transparent qualitative discussion

• Integrate information from Haz ID, Dose-Response, and Exp Assess

• discuss overall quality, degree of confidence in estimates and conclusions (uncertainty)

• describe risk to individuals and populations (extent, severity, probable harm)

• Calculating risk (numeric) and hazard indices

• Non-cancer- hazard quotient, hazard index

• HQ = intake/ RfD• Both intake and RfD have units of mg/kg-

day

• HQ < 1.0 – no detrimental effects• HQ > 1.0 – potential for effects to

occur• HI is sum of HQs• Summing based on assumption of

additivity of effects

cancer risk

• Calculate “theoretical lifetime”• Cancer risk from estimated exposure or intake• Excess or additional risk• Upper-bound on risk

risk = intake x sf

• Intake units of mg/kg-day • SF units of 1/(mg/kg-day)• Risk is unitless (probability)• Sum cancer risk for all chemicals

risk char discussion

• Confidence in key site-related chemical identity and conc. relative to background

• Describe types of cancer and health effects, distinguish between known effects in humans versus animal derived or predicted

• Confidence in quantitative tox info used to estimate risk, and qualitative info on chemicals not included in assessment

• Confide in exposure estimates for key pathways and inputs

• Magnitude of cancer risks and non-cancer HIs

• Major factors driving risk (chem., pways, and pway combinations)

• Major factors reducing certainties and the significance of uncertainties (ex. adding risk over chemicals and pways)

• Exposed population characteristics

risk = hazard + outrage(the non-technical side)

• Voluntary vs. Involuntary• Natural vs. Industrial• Familiar vs. Exotic• Dreaded or Not

web resources

• www.epa.gov/ncea/raf/cancer.htmo Draft revised guidelines for carcinogenic risk assessment

(1999)• www.epa.gov/iris/

o Methylmercuryo Polychorinated biphenyls

concepte in toxicologietoxicologia produselor alimentare ramona suharoschi 10.10.2011

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