systems safety1 systems safety ー environmental risk assessment ー kazuo furuta (rerc) toxic...
Post on 03-Jul-2020
1 Views
Preview:
TRANSCRIPT
1
Systems Safetyー Environmental Risk Assessment ー
Kazuo FURUTA (RERC)
Toxic substances
Chemicalsn Arsenic, hydrocyanic acid, NOx, SOx, etc.n Natural poisons (mushroom, snake, insect, etc.)n Pesticide (insecticide, herbicide, etc.)n Dioxin, endocrine disruptor, etc.
Heavy metals and mineralsn Lead, mercury, cadmium, etc.n Asbestos
Radioactivity
2
Risk assessment of toxics
Assessment of releasen Location and amount of release
Transportation analysisn Transportation of toxics in environment
Assessment of exposure leveln Exposure of an organism to toxics
Assessment of effectsn Adverse health effects by toxics
Diffusion of matter
A matter is transported from the high-density site to the low-density site by random motion of molecules
Fick’s law
D : Diffusion coefficient
High-d. Low-d.
A
AA
CDx
CDJ
grad−=∂
∂−=
AJ
(1-D)
(3-D)
3
Diffusion equation
∂∂
∂=
∂∂
∂∂
+
∂∂
∂=
∂∂
∂
∂+
∂∂
+∂
∂=
∂∂
rCr
rrD
tC
zCD
rCr
rrD
tC
zC
yC
xCD
tC
AA
AAA
AAAA
22
2
2
2
2
2
2
2
2
1
1
C0
AA CD
tC 2∇=∂
∂
Cartesian
Cylindrical
Polar
Chemical reaction rate
ktAAAAk
tA
0
02
1][][][
+=⇒−=
∂∂
C0
General form of chemical reaction rate
First-order reaction in terms of A
Second-order reaction in terms of A
)exp(][][][0 ktAAAk
tA
−=⇒−=∂
∂
Lba BAk ][][=ν
4
Convection-diffusion model
1-D convection-diffusion model
1-D convection-diffusion-reaction model
zCv
zCD
tC
vCzCDvC
zCD
tCz
zzzavg
∂∂
−∂
∂=
∂∂
+
∂∂
−−
+
∂∂
−=
∂∂
∆∆+
2
2
kCzCv
zCD
tC
−∂∂
−∂
∂=
∂∂
2
2
Environmental chemodynamics
Estimation of transportation paths of toxics from the sources to the living environment
Evaluation of the densities of toxics in the air, water, foods, and soil that people take or make contact with
Evaluation of the intake of toxics considering the physiological features and the lifestylen Oral intake, suction, skin absorption
5
Example scenario of radioactivity transportation by groundwater
地下水位
海への移行
廃棄物充てん土壌
降雨の廃棄物層への浸透
降雨による核種の地下水への移行 海
覆土
灌漑 飼育水 飲用
海岸活動者・汚染された土壌からの直接線・汚染された土壌粉塵の吸入
飲料水摂取畜産物摂取
汚染された土壌
農耕作業、農産物摂取者・汚染された土壌からの直接線・汚染された土壌粉塵の吸入・農作物摂取
養殖水産物摂取
養殖水
地下水が利用されている場合
地下水が利用されていない場合
飲料水摂取(低頻度事象)
井戸水利用
海産物摂取
地下水位
海への移行
廃棄物充てん土壌
降雨の廃棄物層への浸透
降雨による核種の地下水への移行 海
覆土
灌漑 飼育水 飲用
海岸活動者・汚染された土壌からの直接線・汚染された土壌粉塵の吸入
飲料水摂取畜産物摂取
汚染された土壌
農耕作業、農産物摂取者・汚染された土壌からの直接線・汚染された土壌粉塵の吸入・農作物摂取
養殖水産物摂取
養殖水
地下水が利用されている場合
地下水が利用されていない場合
飲料水摂取(低頻度事象)
井戸水利用
海産物摂取
Water in useWater
not in use
Accidental intake
well
Groundwater level
Contaminated soil
Drink waterSea foodsMeat & milk
Sea foods
Sea
Irrigation Stock farming Cultivation Drinking
Packingsoil
Cover
Infiltration of rain
Transfer into groundwater
Exposure by farming· Direct irradiation· Suction of soil dust
Exposure by outdoor activities· Direct irradiation· Suction of soil dust
Transfer to sea
Chemodynamics within body
Organs
Gut (out)Gut (in)
Muscle
Liver
Kidney
Fat
Skin
Blood Blood
Suction
Oral intake Excretion
ExcretionMetabolism
Box model
Lung (in)Lung (out)
6
Types of toxicity
Acute toxicityn Adverse effects caused by single exposure or
multiple exposures in a short time (<24hrs)n Medium lethal dose (LD50)w The dose required to kill half the tested populationw The mass of substance per unit mass of subject (mg/kg)
Semi-acute toxicity (1d~1yr)
Chronic toxicityn Adverse effects caused by repeated exposures
over a longer period (1yr<)
Radiation effects
Types of radiationn α-ray, β-ray, γ-ray, …
Measures of radioactivity and radiationn Radioactivity (Bq), absorbed dose (Gy), dose
equivalent (Sv)
Adverse effects of radiation exposureWhat depends
on dose Threshold Principal effects
Probabilistic Probability of adverse effects (no) Cancer,
genetic disorder
Deterministic Degree of adverse effects yes Cataract, burn,
infertility
7
in vivo / in vitro testing
in vivo testingn Experiment using animals (mice)n Toxicity evaluation of environment
in vitro testingn Experiment using living tissue or cellsn Examination of poisoning mechanism
Issues with experimental methodsn Cost effectivenessn Reliability of outcomesn Extrapolation of outcomes to humans
Epistemological study
Cohort studyn Two groups of samples, exposed and unexposed,
are followed over time on manifestation of effects.
Case-control studyn Two groups of samples, with and without effects,
are examined on the past exposure history.
Cross-sectional studyn Samples are examined on both the present
adverse effects and the past exposure history.
8
Data processing in epistemology
Risk ratio (Cohort study)R = [a/(a+b)] / [c/(c+d)]
Odds ratio (Case-control study)φ = (a/c) / (b/d)
Effects No effects
Exposed a b
Non-exposed c d
Bias in epistemology
Bias: Factors that impair the validityn Selection bias
– Samples were selected inappropriately.
n Information bias– The collected information were inappropriate.
n Confounding– The groups to be compared are not equivalent in terms
of some factors other than exposure.
Statistical uncertainty
9
Dose-response relationship
Exposure Exposure
Deg
ree
of d
amag
e
Prob
abili
ty o
f da
mag
e
0 0
100
Non-cancer effects Cancer or genetic effects
Threshold
100
Toxicity measures with threshold
No Observable Effect Level (NOEL)n Highest dose with no observable effects
Lowest Observable Effect Level (LOEL)n Lowest dose with any observable effect
No Observable Adverse Effect Level (NOAEL)n Highest dose with no observable adverse effects
Lowest Observable Adverse Effect Level (LOAEL)n Lowest dose with any observable adverse effect
10
Non-cancer risk
Acceptable Daily Intake (ADI)ADI = NOAEL / Safety factor (10)
Tolerable Daily Intake (TDI)n Intake limit of toxic substance with no benefits
Hazard Ratio (HR)HR = Exposure level / AID or Exposure level / TDI
Hazard Index (HI)n When more than one hazards exist
HI = ΣHRi
Carcinogenesis measures
Cancer unit riskn Increase of cancer risk per unit density of
carcinogen for lifetime intake
Cancer potencyn Dose of carcinogen that yields 5% of
cancer probability
Cancer slope factorn Increase of cancer risk per mg of
carcinogen intake / kg body weight-day
11
Environmental risk
Endpointn An event that people want to avoidn Relevant to avoid adverse effects to environmentn Measurable and predictablen Sensitive enough for risk management
Selection of endpointn Which level should be focused on?
Individual, group, public, ecosystem
Allowable risk limit
Absolute risk limitn The risks that exceed the particular limit
must be reduced.Ex. Cancer risk of drink water < 10-5/lifetime
Risk-benefit tradeoffn The risks with a low benefit per unit risk
are the first ones to be reduced. n The risks with a very high benefit per unit
risk should not be reduced.
12
Benefit-risk ratio (B/R)
Unit of riskn Death of one person (B/R = price of life)n Reduction of lifetime (B/R = price of lifetime)
reduced] be to [Riskrisk] the reducingfor requiredCost
ortaken] be to Risk
risk the takingby obtainableBenefit
[
[][
=
=
RB
RB
Example of risk-benefit tradeoff
Regulatory optionsB/R
(mill.yen/man・yr)Ban on Chlordane (termiticide)Ban on mercury in soda productionShift to mercury-free battery cellsRegulation of benzene in gasolineRegulation of NOX in car exhaustRegulation of dioxin from incinerator
Urgent actionPermanent action
4505,700
2202,300
860
791,500
R: 1yr of LLE
13
Cost-benefit analysis
Comparison of B/R with the price of lifen Evaluation from wage difference between
dangerous and undangerous jobsn WTP (Willing To Pay) obtained through CVM
(Contingency Valuation Method)
Points to be discussedn Consideration of vulnerable groupsn Difference between voluntary and involuntary risksn Uncertainties in risk assessment
top related