ecotoxicologymit.biology.au.dk/~biobaat/ecotoxicology/pdf_filer/fre... · · 2010-09-13all...
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EcotoxicologyEnvironmental medicine
Toxicology Pharmacology
Biochemistry
Histochemistry
Occupational medicineEcologyMicrobiology
Hydrobiology
Pathology
Chemistry
Bioavailability
Uptake
Metabolism
Toxicity
Molecular changesPhysiological changes
Structural damage
Changed behaviour
Reduced fitness
PopulationGrowth, mortality, development time, fercundity
Communitydensity, diversity
Ecosystembalance, production
Discharge of xenobiot-amount-organic / inorganic-vapour pressure-degradability-solubility-Kow Dispersal
-air-water-soil
Elimination
Tolerance-physiological-geneticResistence
Exposure / effectbiomarkers
Effect / healthbiomarkers
Monitoring
Mat
hem
atic
al m
odel
ling
All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.
Paracelsus (1493-1541)
TOXICITY
Compound Median lethal dose mg kg-1
Ethanol 10000DDT 100Nicotine 1 Tetrodotoxin 0.1Dioxin 0.001Botulinus toxin 0.00001
Only the dose makes the poison
Dose - response
The receptor concept
- Toxicity is substance specific
- The response is proportional to the concentration at the receptors
- The concentration at the receptors depends on the dose (absorption)
- The concentration in the animal relates to the concentration in the environment
DOSE - RESPONSE
CONCENTRATION - RESPONSE
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Linear Concentration
Response frequency distribution
In real life response frequencies are usually impossible to measure
2.5 5 10 20 40
Log Concentration
0
10
20
30
40
50
Response frequency distribution
Toxicological endpoints are often log-normally distributed
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1 10 100 1000 10000 100000
Concentration
Num
ber d
ying
in
sub-
popu
latio
n
Cumulative response
Transformation of data
Sigmoid curves difficult to treat mathematically
Wanted: A Linear relationship between dose and response
Dose/concentration is often log-transformed
The response is PROBIT-transformed
The Normal distribution is characterized by its mean
and scatter
Concentration
Freq
uenc
y of
resp
onse
0-1 +1 +2-2
FROM FREQUENCY TO PROBIT
Res
pons
e %
-4 -3 -2 -1 0 +1 +2 +3 +4
50
100
2 (0.1)
3 (2.3)
4 (15.9)
5 (50.0)
6 (84.1)
7 (97.7)
8 (99.9)
0.12.3
15.950
84.197.799.9
Normal Equivalent Deviation (NED):
The proportion of responding animals in terms of standard deviations from the mean of the normal distribution
ex: 15.9% respond: NED = -1
Probit(P) = NED + 5
Dose-response for two chemicals
Log concentration10-4 10-3 10-2 10-1 10 10+1 10+2 10+3 10+4
0.1
2.3
15.9
50.0
84.1
97.7
99.9
Res
pons
e (%
)
The two chemicals have the same LC50
Chem. A: Slowly absorption, fast detoxification
or excretion, delayed toxic effect.
Chem. B: Fast absorption and toxic effect
1 10 50 100 500
Log Dose (mg/kg)
% m
orta
lity
Assessment of toxicity
0
50
100
LD 50= 40 mg/kg
LOED
NOED
Assessment of toxicity
LD50/LC50 Median lethal dose/concentration
ED50/EC50 Median effective dose/concentration
EC10 Concentration affecting 10% of the population
LOEC(D) Lowest observable effect concentration (dose)
NOEC(D) No observable effect concentration (dose)
NEC(D) No effect concentration (dose)
ADI Acceptable daily intake
Safety factor Usually 100. 10 to account for human response variation, 10 for the extrapolation from experimental animals to humans
Essential and non-essential elements
Optimum
Window of essentiality Conc
P No effect
Conc
P
Ex: C, H, O, N, Ca, Na, K, P, Mg, Cl, STrace: Fe, I, Cu, Mn, Zn, Co, Mo, Se, Cr, Ni, V, Ar
Ex: Hg, Cd, Pb
METALS
Hg, Cd, Zn, Pb
PESTICIDES
Insecticides
Organochlorines (DDT, Lindan, Dieldrin)
Organophosphates (Dimethoat, Diazinon)
Carbamates (Methiocarb, Carbofuran)
Pyrethroides (Deltamethrin, Cypermethrin)
Rodenticides (Warfarin)
Herbicides (“Agent orange”, diquat, paraquat, dinitrophenoles)
Fungicides (Metylbromid, Dazomet, Borax)
POLYCHLORINATED BIPHENYLES (PCB)
Stable, non-reactive fluids (hydraulic- and coolant fluids, plastic paints)
POLYKLOREREDE DIBENZODIOXINER (PCDD)
By-products of burning PCBs and pesticide manufacturing
OIL PRODUKTS
Polyaromatic hydrocarbons (PAHs) - naphtalene, benzo(a)pyrene
ENDOCRINE DISRUPTORS
Alkylphenolpolyethoxylates, Bisfenol A, DDE, PCB, farmaceutikals, 17α-ethinylestradiol
CHLORIDE PHENOLS
Polychlorinated phenols (wood preservatives, bleaching agents)
TRIBUTYLTIN
Ship paints
DETERGENTS
Washing powder
Important xenobiotics
Cl
Cl Cl
Cl
Cl
Cl
3,3,4,4,5,5- HexachlorbiphenylPCB
p,p,DichlorDiphenyl TrichlorethaneDDT
ClCl C
ClCl Cl
C
H
Cl
Cl Cl
Cl
O
O2,3,7,8-tetra-chlorodibenzodioxin
Dioxin
N CH3CH3 N
Paraquatherbicide
Cl
ClOH
Cl2,4,5-Trichlorphenol
Bleaching agent
N
N
CH3
CH3
CH3
CH
OPS
C2H5OC2H5O
DiazinonOrgano phosphate
3,4-Benzo(a)pyrenePAH
OH
OH
CH3
17β- EstradiolHormone
p,p,DichlorDiphenyl Trichlorethane
DDTH
Cl
Cl C
Cl
Cl
Cl
C
HISTORICALSynthetized first time in 1874Insecticide properties discovered in 1939
- alter ion transport in axons - convulsionStable in nature – low mammal toxicity – cheap productionControl of malaria started in 1944
Ceylon 1946: 2.8 mill. cases - 13.000 died1963: 17 cases - 0 died
Saved about. 5 mill lives (100 mill serious cases)Now forbidden in most countries
Evolution of resistance and persistence in natureAccumulation of DDT and metabolites in food chainsEgg shell thinning
Half-lives for Cl-pesticides
0 2 4 6 8 10 12
Years
1
10
100% remaining in soil
DDT
Dieldrin
EndrinLindanAldrin
Cl
Cl
Cl
ClOClCl
Dieldrin
DDT/DDE in terrestrial systems
0 5 10
Year
0
5
10
15m
g D
DE
kg-1
Farming land treated with 9 kg DDT ha-1
DDE i earthworm
Reduction in Scandinavian Peregrine falcon populations
1940 1950 1960 1970 19800
1
2
Migratory birds/dayNumbers of migratory birds counted at Falsterbo in southern Sweden
DDT is highly lipid soluble
103 104 105 106 107
n-octanol:water distribution coefficient
10
100
1000
104
105
BC
F
2,2',4,4',5,5'-PCB
2,3,4'-PCB DDD
DDT
DieldrinEndrin
HCH
DDT biomagnification
Loss of organic matter through respiration
Fat solublepersistent chemical
DDT spreads globally in the atmosphere to water and soil
High lipophility ⇒ accumulates in adipose tissue
Air 0.000004
Attmospheric dust 0.04 mg/kg
Rain water
0.0002
Untilled soil ? Fresh water
0.0002
Salt water
0.0002
Agricultural soil 0.000004
Insects ?
Plants 0.05
Invertebrates in soil 4
Water plants 0.01
Invertebrates in water 0.001
Plankton 0.0003
Plant- & Insectivorous birds 2
Plant- & Insectivorous mammals 0.5
Fresh water
Fish 2
Salt water
Fish 0.5
Carnivorous mammals 1
Carnivorous Birds 10
Vegetables 0.02
Meat 0.2
Humans 6
Resistance against DDT
strain 1 strain 2 strain 3
LD50 (mg DDT/kg) 12-15 93-100 2500-3500
DDE produced (ug DDE/flue/time) 0 1.0 -1.5 3.8 - 5.2
Resistance in 3 fly strains
Genetic activation of the enzymatic metabolism of
DDT to DDE and faster elimination
DDT DDD
ClCl CH
Cl ClCCl
ClCl CH
H ClCCl
Metabolism of DDT
Non-reactive chlorine atoms - DDT og DDE degrade slowly
Degraded photochemically and microbially in nature
Partly metabolized in higher organisms (depending on enzyme systems)
DDT and DDE accumulate in adipose tissue
DDA (and DDD) are excreted by the kidneys
ClCl C
Cl ClC
H
Cl
ClCl CH
ClCl CHDDT
H ClCCl
DDD
Cl ClCH
CO OH
DDA
Cl ClC
DDE
PCBs, Dibenzofurans and Dioxins
5
2' 3'
4'
5'6'
1
23
4
6
1'
O
1
7
82
3
4 6
9 O2
34 6
91
7
8
O
DioxinsPCBs Dibenzofurans
Cl
Cl Cl
Cl
O
O
2,3,7,8-tetra-chlorodibenzodioxin
DIOXIN
Dioxins are generated as unwanted by-products by:
The production of herbicides - ex 2,4,5-T (Seveso accident)
Heating of the fungicide pentachlorphenol
OH
Cl
Cl
Cl
ClCl
Cl
Cl
Cl
Cl
OH
Cl
Cl
Cl
OCH2COOH
Cl
Cl
Cl
NaOH
180ºC
CICH2COOHNaOH
Cl
Cl Cl
Cl
O
O230ºC
Tetraklorbenzene 2,4,5-Trichlor phenol2,3,7,8-tetra-chlorodibenzodioxin
Waste combustion of e.g. phenol compounds, PCB and PVC at too low temperature (< 1200ºC)Exhaustion gasses from leaded petrol (halogenated hydrocarbons)Chlorine bleaching of paper (e.g. Trichlor phenol)
Dioxines’ distribution, metabolism and harmful effectsAtmospherically and aquatic distribution leads to global pollution
3 10 25 50 100 150 km
7000
6000
5000
4000
3000
2000
1000
pg T
CD
D/g
glø
deta
b)
Concentration of 2,3,7,8 TCDD in sediment-transect at a Swedish paper mill
Dioxins are present in most aquatic organisms (pg)Very lipophilic – accumulate in adipose tissue2,3,7,8-TCDD is considered the most toxic synthetic compound
LD50 µg/kgGuinea pig 0.6Rat 22Chicken 25-50Monkey 70 .
Toxicological mechanism partly unknown
Loss of weight and death after 1-7 weeks
Teratogenic (embryonic injury)
Carcinogenic
Environmental data for dioxin
Log Kow 6.8
Log BCF’s fish 3.2-4.4
snail, dafnia 4,3-4.4
algae 3.6-3.95
Volatisation1/2 life soil, sediment >50 YEARS
Source: EPA (USA)
2,3,7,8-TCDD ‘acute’ toxicity
Experimentalanimal
LD 50
(µg/kg)
rat 22 ♂rat 45 ♀Guinea pig 0.6♂Guinea pig 2.1 ♀rabit 10-115chicken 25-50dog 100-3000monkey 70mouse >150hamster 1157-5000frog >1000
Acute symptoms: liver damage, thymus damage, significant weight loss, death occurs between 1 and 7 weeks after intake
Current views on Dioxin effects
No effectsUrinary systemInconsistent evidenceImmunological findings
Compelling evidence but not completely consistent
Thyroid function
Inconsistent findings, but reports from Vietnam and Seveso. Not depression
Neurological, Psychological findings
InconsistentRespiratory system effects
Positive association in high dose studies, not entirely consistent
Cardiovascular disorders
Inconsistent but found in agent orange studies
Diabetes
Inconsistent but compelling evidenceReproductive disorders including outcome
Accepted?Increase in cancer incidence, including reproductive cancers
Temporary effect but provenInduction of liver enzymes (AHH)Proven associationChloracne
Consistency of evidenceEffect
Many sp. High dosesOvarian dysfunctionRatsReduced circulatory
androgensRatsReduced spermatogenesisMonkeys, Rats, Mice Low concentrations, chronic exposure
Endometriosis (Uterus epithelium cysts outside the uterus)
Rats, High dosesAnovulation, suppression of oestrous cycle
Many sp. High dosesInfertility and fetal lossSpecies, commentsEffect
Reproductive effects seen in experimentalanimals after dioxin exposure
A cancer promoting pathway for dioxin
TCDD + AHH Activated product
(Adduct)
Unwinding enzymes
Excision
ResynthesisRepair
Mistake Mutation
Cancer
Ahh activity can be used to determinerelative toxicity in complex mixtures
TCDD
TCDD
+
TCDD
mRNA
AHH
DNA
Ah
Aryl hydrocarbon hydroxylase
TCDD
TCDD
TCDD Ah
Ah
Relationship between AHH-inductionand general toxicity
2 3 4 5 6 7 8
Weight loss (-log ED 50)
4
5
6
7
8
9
10
11AH
H-in
duct
ion
(-log
EC
50)
DioxinFuran
Substitution pattern Conversion factor ng/g fat TEQ
PCDD2,3,7,8-tetraTCDD 1 2,3 2,31,2,3,7,8-pentaTCDD 0,5 4,8 2,41,2,3,6,7,8-hexaTCDD 0,11,2,3,7,8,9-hexaTCDD 0,1 6,4 0,641,2,3,4,7,8-hexaTCDD 0,1 35 3,51,2,3,4,6,7,8-heptaTCDD 0,01 41 0,41octaTCDD 0,001 132 0,13
total PCDD 9,3
TCDD-equivalents(Toxic equivalent quotient)