Chemical Risk Assessment
H1: Defining the field
Risk vs. Hazard
• Hazard = potential to cause harm (AKA danger)
• Risk = likelihood that harm will occur => Risk depends on hazard & exposure. High
hazard doesn’t always mean high risk (if exposure is low), & vice versa. In real situations,
factors are rarely equal, so relationship must be interpreted carefully.
Risk is expressed as probability (AKA how likely harm is to occur) & during risk assessment we determine if
probability is high or low, we also distinguish:
• Uncertainty = lack of knowledge (AKA gap in what we know) => Can’t be directly measured or assessed.
• Variability = natural differences that we do understand & can measure => Can be assessed using data.
=> These must be treated differently in analysis.
Risk analysis provides method for analyzing uncertainty when making decisions.
• Statistics => Uses available data to estimate outcomes
• Probability => Describes likelihood of specific outcomes
1.1: Exposure to Chemicals
Risk sometimes be higher indoors than outdoors due to pollutants in paint
chemicals, wood preservatives, heavy metals, … => Example: materials like
asbestos in older buildings can pose risks if exposure occurs.
Chemicals originate from products, storage, or waste → released via leaks,
discharge, or transport → Travel through air, water, & soil via processes like
diffusion & transformation (such as degradation) → reach humans through
air, water or enter food chains (plants, animals) & reach us via our diet.
Main pathway of environmental contamination is use of fossil fuels & combustion processes. These release:
• Inorganic gases (such as nitrogen oxides & sulfur oxides) which can form persistent pollutants
• Substances (such as Antibiotics, Hormones & Pesticides) are released into atmosphere & biosphere. Over time,
many of them end up in water & sediments, which can affect drinking water sources.
Humans mainly exposed to chemicals through air (inhalation), water (drinking contaminated water) & food
(contaminants entering food chain). Emerging Concerns are about cosmetics, as many contain nanoparticles (such as
titanium dioxide) & these can penetrate skin pores or enter lung cells through inhalation, which may pose potential
health risks.
Pollutants from air, water, or soil enter via inhalation, ingestion, or skin absorption →
inside body they circulate via bloodstream to organs → may be metabolized → excreted
via kidneys or other pathways.
Biomarkers can be used to trace how chemicals enter & move through body.
1.2: Risk Assessment
Risk assessment = interdisciplinary process used to evaluate chemical hazards & human exposure in order to
determine their resulting risk => Relies on established methods from human risk assessment & environmental risk
assessment to evaluate safety of chemicals.
,Risk assessment is guided by questions:
• What is the exposure & hazard (= danger)?
• What is the risk (= combination of hazard & exposure)?
• What health effects are caused by the pollutant?
In risk assessment we often have limited data, so statistical methods must be adapted. More studies & data improve
reliability, but are not always available.
Risk assessment always involves 2 main components = Hazard assessment & Exposure assessment
Risk assessment follows structured process = Integrated Risk Assessment Framework:
1. Problem formulation to identify hazards
2. Exposure assessment to determine level of contact
3. Effects assessment to evaluate toxicity
4. Dose–response assessment to link dose to effect
5. Risk characterization to estimate overall risk & answers “What is additional risk of health problems in exposed
population?” by combining hazard identification, exposure assessment & dose–response assessment.
6. Results are reported to policymakers (AKA scientists assess risk, but don’t make decisions).
=> Stakeholders participation & management decisions are involved throughout whole process & results used to
support decision-making but don’t replace it.
There is Environmental, Ecological & Human risk assessment). Definitions differ between:
• US:
o Environmental risk = risk to humans from environmental contaminants
o Ecological risk = risk to ecosystems & non-human organisms
• EU:
o Human risk = risk to humans from environmental contaminants (not same as general health risk)
o Environmental risk = risk to ecosystems & non-human organisms
1.2.1: Exposure assessment
Exposure assessment = process of measuring or estimating intensity (= how much), frequency (= how often) &
duration (= how long).
Can involve assessing current environmental exposures & estimating future or hypothetical exposures from new
chemicals. It’s part of earlier steps in risk assessment & answers “How many people are exposed, to which pollutants,
& for how long?”
1.2.2: Dose-Response assessment
Dose–response relationship = how magnitude of exposure to chemical relates to severity of its effects. It answers
question of “What health effects occur at different exposure levels?”
Most dose–response curves are S-shaped (AKA sigmoidal):
• Low doses = little or no observable effect
• Medium doses = effects increase rapidly
• High doses = curve plateaus
Has this shape, cause many chemicals act on receptors in body:
• At very low concentrations → too few receptors are activated → no measurable effect
• At high concentrations → all receptors are occupied → max effect reached (plateau)
Exception could be some carcinogens, which may not have clear safe threshold.
,Parameters
• No Observed Adverse Effect Level (NOAEL) = Highest dose at which no harmful effects are observed
• Lowest Observed Adverse Effect Level (LOAEL) = Lowest dose at which harmful effects are observed
• Max response level = Point where increasing dose no longer increases effect (AKA reach plateau)
Dose–response relationships can be applied to individuals & populations (average response across many individuals)
Mixture Effects (or Cocktail Effect) => Dose–response curves usually determined for 1 chemical, but in reality humans
exposed to mixtures of chemicals. This can lead to additive effects or synergistic effects (= stronger combined impact)
Exposure vs. sensitivity distribution:
• Left curve = how much of population is exposed to different concentrations
• Right curve = how sensitive organisms are to those concentrations.
• Overlap = potential risk.
Safety thresholds & uncertainty factors are used to estimate acceptable exposure levels &
protect vulnerable populations.
1.2.3: Risk Characterization
Specific step in risk assessment, that estimate overall risk & answers “What is additional risk of health problems in
exposed population?” by combining hazard identification, exposure assessment & dose–response assessment.
Typically uses probability. Results are reported to policymakers (AKA scientists assess risk, but don’t make decisions).
1.3: Risk management
1.3.1: Management
Risk assessment provides scientific advice & technical support for decision-making. Risk management is where
decisions are made by policymakers & helps guide decisions such as:
• Prioritizing hazards
• Permitting releases of chemicals, waste & effluents, new organisms, international trade (is important in this
industrial society)
• Remediation & restoration of polluted environments
• Land use management (such as agriculture, urban or residential use) => Example: using groundwater VS surface
water for irrigation
• Species management (Fisheries, Forestry, Wildlife)
• Setting damages with economic or monetary compensation
Risk management is continuous process (AKA cycle repeats to ensure ongoing improvement & adaptation): Assess
risks → evaluate their significance → manage through actions or policies → monitor outcomes → repeat
1.3.2: Precautionary principle
Precautionary Principle used when there are potentially serious or irreversible risks, even if scientific certainty is
incomplete.
• Main principles:
o Early detection through research & monitoring
o Reduce environmental burdens
o Promote clean production & innovation
o Cooperation between stakeholders
, o Take preventive action before full scientific proof
• Guidelines for when Applying Precautionary Principle
o Proportionality => Measures should not exceed what is necessary (no need for 0 risk)
o Non-discrimination => Similar situations should be treated similarly
o Consistency => Measures should align with existing policies in similar cases
o Cost–benefit analysis of action vs. no action
o Scientific review => Decisions should be updated as new data becomes available
Example: DDT => Insecticide banned or restricted in many regions (such as in EU), but still used in some areas to
control malaria-carrying mosquitoes. Here there is trade-off in risk management for environmental & health risks due
to DDT use VS major public health risks due to malaria.
1.3.3: Chemicals & Society
Chemicals are essential for economic development & modern society. In EU ~100.000 chemicals exist, from which
<3000 have been tested for risks. REACH Regulation aims to close knowledge gaps about chemicals by requiring
companies to provide physicochemical, toxicological & environmental data => No data = no market (AKA chemicals
not sold without safety info).
1.4: Historic Perspective of Contaminant Levels in Receiving Waters
Biological Oxygen Demand (BOD) = amount of oxygen required by microorganisms to break down organic matter in
water => It’s indicator of water pollution (especially in rivers)
• high BOD → more oxygen consumed → less oxygen available for aquatic life → harm or kill aquatic organisms
Eutrophication = excess of nutrients in water (N, P, S)
• Nutrients enter water → algal bloom → Algae die → Bacteria decompose them & by doing that they consume
large amounts of oxygen → oxygen depletion → causes trophic cascade
Main sources of eutrophication are agriculture, fertilizers & pesticides => Pesticides vs. Biocides
• Pesticides = used mainly in agriculture
• Biocides = used in non-agricultural settings (such as disinfectants, preservatives)
How environmental monitoring has evolved => Concentration on Y-axis = level needed to produce biological effect
• pre-1960s => bacteria & basic indicators like BOD.
• 1970s => nutrients & eutrophication.
• 1980s–1990s => metals & persistent organic pollutants (such as DDT, PCBs).
• 2000s–present => emerging contaminants like pharmaceuticals, endocrine
disruptors (EDCs), PFAS, & microplastics.
Increasing sensitivity in detection & expanding concern over lower concentrations of
more complex pollutants. Many pollutants act at very low concentrations, so there
is need for advanced detection methods (such as mass spectrometry, which is very
sensitive but expensive).
H1: Defining the field
Risk vs. Hazard
• Hazard = potential to cause harm (AKA danger)
• Risk = likelihood that harm will occur => Risk depends on hazard & exposure. High
hazard doesn’t always mean high risk (if exposure is low), & vice versa. In real situations,
factors are rarely equal, so relationship must be interpreted carefully.
Risk is expressed as probability (AKA how likely harm is to occur) & during risk assessment we determine if
probability is high or low, we also distinguish:
• Uncertainty = lack of knowledge (AKA gap in what we know) => Can’t be directly measured or assessed.
• Variability = natural differences that we do understand & can measure => Can be assessed using data.
=> These must be treated differently in analysis.
Risk analysis provides method for analyzing uncertainty when making decisions.
• Statistics => Uses available data to estimate outcomes
• Probability => Describes likelihood of specific outcomes
1.1: Exposure to Chemicals
Risk sometimes be higher indoors than outdoors due to pollutants in paint
chemicals, wood preservatives, heavy metals, … => Example: materials like
asbestos in older buildings can pose risks if exposure occurs.
Chemicals originate from products, storage, or waste → released via leaks,
discharge, or transport → Travel through air, water, & soil via processes like
diffusion & transformation (such as degradation) → reach humans through
air, water or enter food chains (plants, animals) & reach us via our diet.
Main pathway of environmental contamination is use of fossil fuels & combustion processes. These release:
• Inorganic gases (such as nitrogen oxides & sulfur oxides) which can form persistent pollutants
• Substances (such as Antibiotics, Hormones & Pesticides) are released into atmosphere & biosphere. Over time,
many of them end up in water & sediments, which can affect drinking water sources.
Humans mainly exposed to chemicals through air (inhalation), water (drinking contaminated water) & food
(contaminants entering food chain). Emerging Concerns are about cosmetics, as many contain nanoparticles (such as
titanium dioxide) & these can penetrate skin pores or enter lung cells through inhalation, which may pose potential
health risks.
Pollutants from air, water, or soil enter via inhalation, ingestion, or skin absorption →
inside body they circulate via bloodstream to organs → may be metabolized → excreted
via kidneys or other pathways.
Biomarkers can be used to trace how chemicals enter & move through body.
1.2: Risk Assessment
Risk assessment = interdisciplinary process used to evaluate chemical hazards & human exposure in order to
determine their resulting risk => Relies on established methods from human risk assessment & environmental risk
assessment to evaluate safety of chemicals.
,Risk assessment is guided by questions:
• What is the exposure & hazard (= danger)?
• What is the risk (= combination of hazard & exposure)?
• What health effects are caused by the pollutant?
In risk assessment we often have limited data, so statistical methods must be adapted. More studies & data improve
reliability, but are not always available.
Risk assessment always involves 2 main components = Hazard assessment & Exposure assessment
Risk assessment follows structured process = Integrated Risk Assessment Framework:
1. Problem formulation to identify hazards
2. Exposure assessment to determine level of contact
3. Effects assessment to evaluate toxicity
4. Dose–response assessment to link dose to effect
5. Risk characterization to estimate overall risk & answers “What is additional risk of health problems in exposed
population?” by combining hazard identification, exposure assessment & dose–response assessment.
6. Results are reported to policymakers (AKA scientists assess risk, but don’t make decisions).
=> Stakeholders participation & management decisions are involved throughout whole process & results used to
support decision-making but don’t replace it.
There is Environmental, Ecological & Human risk assessment). Definitions differ between:
• US:
o Environmental risk = risk to humans from environmental contaminants
o Ecological risk = risk to ecosystems & non-human organisms
• EU:
o Human risk = risk to humans from environmental contaminants (not same as general health risk)
o Environmental risk = risk to ecosystems & non-human organisms
1.2.1: Exposure assessment
Exposure assessment = process of measuring or estimating intensity (= how much), frequency (= how often) &
duration (= how long).
Can involve assessing current environmental exposures & estimating future or hypothetical exposures from new
chemicals. It’s part of earlier steps in risk assessment & answers “How many people are exposed, to which pollutants,
& for how long?”
1.2.2: Dose-Response assessment
Dose–response relationship = how magnitude of exposure to chemical relates to severity of its effects. It answers
question of “What health effects occur at different exposure levels?”
Most dose–response curves are S-shaped (AKA sigmoidal):
• Low doses = little or no observable effect
• Medium doses = effects increase rapidly
• High doses = curve plateaus
Has this shape, cause many chemicals act on receptors in body:
• At very low concentrations → too few receptors are activated → no measurable effect
• At high concentrations → all receptors are occupied → max effect reached (plateau)
Exception could be some carcinogens, which may not have clear safe threshold.
,Parameters
• No Observed Adverse Effect Level (NOAEL) = Highest dose at which no harmful effects are observed
• Lowest Observed Adverse Effect Level (LOAEL) = Lowest dose at which harmful effects are observed
• Max response level = Point where increasing dose no longer increases effect (AKA reach plateau)
Dose–response relationships can be applied to individuals & populations (average response across many individuals)
Mixture Effects (or Cocktail Effect) => Dose–response curves usually determined for 1 chemical, but in reality humans
exposed to mixtures of chemicals. This can lead to additive effects or synergistic effects (= stronger combined impact)
Exposure vs. sensitivity distribution:
• Left curve = how much of population is exposed to different concentrations
• Right curve = how sensitive organisms are to those concentrations.
• Overlap = potential risk.
Safety thresholds & uncertainty factors are used to estimate acceptable exposure levels &
protect vulnerable populations.
1.2.3: Risk Characterization
Specific step in risk assessment, that estimate overall risk & answers “What is additional risk of health problems in
exposed population?” by combining hazard identification, exposure assessment & dose–response assessment.
Typically uses probability. Results are reported to policymakers (AKA scientists assess risk, but don’t make decisions).
1.3: Risk management
1.3.1: Management
Risk assessment provides scientific advice & technical support for decision-making. Risk management is where
decisions are made by policymakers & helps guide decisions such as:
• Prioritizing hazards
• Permitting releases of chemicals, waste & effluents, new organisms, international trade (is important in this
industrial society)
• Remediation & restoration of polluted environments
• Land use management (such as agriculture, urban or residential use) => Example: using groundwater VS surface
water for irrigation
• Species management (Fisheries, Forestry, Wildlife)
• Setting damages with economic or monetary compensation
Risk management is continuous process (AKA cycle repeats to ensure ongoing improvement & adaptation): Assess
risks → evaluate their significance → manage through actions or policies → monitor outcomes → repeat
1.3.2: Precautionary principle
Precautionary Principle used when there are potentially serious or irreversible risks, even if scientific certainty is
incomplete.
• Main principles:
o Early detection through research & monitoring
o Reduce environmental burdens
o Promote clean production & innovation
o Cooperation between stakeholders
, o Take preventive action before full scientific proof
• Guidelines for when Applying Precautionary Principle
o Proportionality => Measures should not exceed what is necessary (no need for 0 risk)
o Non-discrimination => Similar situations should be treated similarly
o Consistency => Measures should align with existing policies in similar cases
o Cost–benefit analysis of action vs. no action
o Scientific review => Decisions should be updated as new data becomes available
Example: DDT => Insecticide banned or restricted in many regions (such as in EU), but still used in some areas to
control malaria-carrying mosquitoes. Here there is trade-off in risk management for environmental & health risks due
to DDT use VS major public health risks due to malaria.
1.3.3: Chemicals & Society
Chemicals are essential for economic development & modern society. In EU ~100.000 chemicals exist, from which
<3000 have been tested for risks. REACH Regulation aims to close knowledge gaps about chemicals by requiring
companies to provide physicochemical, toxicological & environmental data => No data = no market (AKA chemicals
not sold without safety info).
1.4: Historic Perspective of Contaminant Levels in Receiving Waters
Biological Oxygen Demand (BOD) = amount of oxygen required by microorganisms to break down organic matter in
water => It’s indicator of water pollution (especially in rivers)
• high BOD → more oxygen consumed → less oxygen available for aquatic life → harm or kill aquatic organisms
Eutrophication = excess of nutrients in water (N, P, S)
• Nutrients enter water → algal bloom → Algae die → Bacteria decompose them & by doing that they consume
large amounts of oxygen → oxygen depletion → causes trophic cascade
Main sources of eutrophication are agriculture, fertilizers & pesticides => Pesticides vs. Biocides
• Pesticides = used mainly in agriculture
• Biocides = used in non-agricultural settings (such as disinfectants, preservatives)
How environmental monitoring has evolved => Concentration on Y-axis = level needed to produce biological effect
• pre-1960s => bacteria & basic indicators like BOD.
• 1970s => nutrients & eutrophication.
• 1980s–1990s => metals & persistent organic pollutants (such as DDT, PCBs).
• 2000s–present => emerging contaminants like pharmaceuticals, endocrine
disruptors (EDCs), PFAS, & microplastics.
Increasing sensitivity in detection & expanding concern over lower concentrations of
more complex pollutants. Many pollutants act at very low concentrations, so there
is need for advanced detection methods (such as mass spectrometry, which is very
sensitive but expensive).
