ENVIRONMENTAL HEALTH

RISK ASSESSMENT
PUBH 4101
 COURSE OBJECTIVES
• Understand the fundamentals of risk assessment
• Apply risk assessment principles to real life cases
• Make risk based management decisions
• Communicate risk to various stakeholders
 WHAT IS RISK ASSESSMENT?
• Hazard identification
• Risk estimation/evaluation
• Risk control or remediation
• (RISK COMMUNICATION)
 FOUR QUESTIONS ON RISK
• What do we have?
• What does this mean? (RISK ASSESSMENT)
• What should we do about it? (RISK MANAGEMENT)
• Who should we tell and what should we tell them? (RISK
COMMUNICATION)
 What is RA?
• Involves hazards and assessments of those hazards
• Physical (includes radiological), psychosocial, biological, ergonomic, chemical
and safety (CCOHS, 2017). In this case, we look at chemical risks due to
environmental contaminants
• Looking at vulnerabilities of the population affected
• Could be the whole population
• Could be a section of the population
• Purpose is to eliminate hazards
• Or minimize when the hazard cannot be eliminated
 Common hazards
• Hazards that are common in every day life to which everyone is
affected
• Can you think of such a hazard?
 Specific hazards
• Specific contaminants have specific hazards
• Some people are more exposed than others
• Geographic
• Work exposures
• Food exposures
• water/outdoor exposures
What are major hazards associated with burning wood?
 Major accidents/incidents
• Series of events
• Can result in deaths, environmental damage and property destruction
• Lives, environment, property is always a concern in Risk Assessment
• Exxon valdez
• Chernobyl
• BP oil
 Risk – 3 questions
1. What can go wrong?
2. How likely is it?
3. What are the consequences?
• Risk Perception
• Can help and hinder
• Landfills, not in my backyard
• Propane tanks vs. Hiroshima
CBC News article dated August 24, 2012
• Fertilizers, herbicides and pesticides Sunrise Propane Explosion

• Acceptable vs. unacceptable

 HAZARD IDENTIFICATION
• What is a hazard?
• How can you determine cause and effect?
• Some linkages were discovered prior to understanding the causative
agent, or being able to measure it.
Risk Assessment
• Individuals will respond differently depending on how well they feel
they understand the hazard
• Influences
• Environmental
• Biases
• Risk is Measured in
• average annual risk per individual
• average lifetime risk per individual
• average number of individuals affected annually in a given population
Activity Odds
Getting cancer 1 in 2 (lifetime)
Struck by lightning 1 in 10,456
Getting heartburn today 1 in 68
Being murdered in USA 1 in 140 (lifetime)
Serious cut while shaving 1 in 5,044 per year
Dying in car accident 1 in 75 (lifetime)
Having car stolen 1 in 159 yearly
Eating a hotdog today 1 in 7
Seeing Elvis this year 1 in 706,850
Being injured by toilet bowl cleaner 1 in 173,972 yearly
Dying falling out of a chair or bed 1 in 513,142 yearly
Dying while running 1 in 10,000 yearly
Dying while playing football 1 in 57,000 yearly
Dying from heart disease 1 in 6 (lifetime)
Risk Assessment Models
 Models
• Used for performing risk assessments. Different models are used for
different areas.
• Not an inclusive list
• Models include qualitative and quantitative information

• Human Exposure Model (HEM) – used for performing RA’s on sources

that emit toxins into ambient air (EPA, 2017)
• Breast cancer risk assessment models (Breast Cancer Research)
• Actuarial risk assessment models
 NAS-NRC (National Academy of
Sciences/National Research Council)
Hazard identification

Dose response assessment

Exposure assessment

Risk characterization
Covello Merkhofer Model – microbial food
contamination
Hazard identification

Release assessment

Exposure assessment

Consequence assessment

Risk estimation
Risk Chain Model – supply and demand

Risk source release

processes

Exposure processes

consequence processes
 EPA Risk Assessment Model
• Risk analysis
• Hazard identification
Risk • Risk estimation

assessment • Option Evaluation

• Development of options
• Option analysis

• Decision
Risk • Implementation
management • Monitoring and evaluating
• review
 Goal of Risk Assessment
• ID hazards or potential hazards
• ID users and/or tasks
• Determine level of risk (low and acceptable vs. high and
unacceptable)
• Evaluate potential controls (elimination, substitution, admin controls,
PPE etc.)
• Develop a report
• Implementation and review
 Risk Perception
• A personal or group assessment of the potential for negative
consequences
• Perceived vs. actual
• Over-react to things that are: intentional, offend our morals, immediate
threats, spectacular and rare, earthquakes, terrorism, risks in situations you
can’t control
• Under-react to things that are: accidents, natural phenomena, long term
threats, things that occur slowly and over time, common risks, slipping on the
floor, street crime and risks you’re willing to take
• Worry more about anthrax than influenza
• Two planes brought down by lightning
 Risks and Consequences
• Propane use
• Pest/weed control
• Nuclear power
• “at some point, the benefit of having nuclear electrical power was found to be
greater than the risk of a nuclear reactor meltdown.”
• Driving vs. flying
• Risky driving vs. small chemical plant
 Considerations
• What are all the known hazards
• What are all the possible events involving these hazards
• Have these events occurred before
• How frequently have these events occurred
• What happens when these events occur
• How severe are the consequences of these events
• How hard is it to clean up the mess left by the event
• Who ultimately pays for the cleanup
• What values does the organization consider important
 Important to remember:
• Never dismiss a consequence until it is proven to be not credible
• Consider all credible consequences
• All actions have consequences
• Healthy eating/exercise
• Driving intoxicated
• skydiving
 19th Century Linkages:
• London smog and respiratory disease
• celibacy and breast cancer
• tobacco snuff and nasal cancer
• chimney sweeps and scrotal cancer
• arsenic and cancer
• slum living and illness (generally)
• sunlight and skin cancer
• aromatic amines and bladder cancer
• contaminated water and cholera
 RISK ESTIMATION
• Qualitative
• How will the contaminant or activity adversely affect human health?
• Is it a large risk or small risk?
• size of impact, number of people affected, likelihood of effect
• Probability and severity
 RISK ESTIMATION
• Quantitative
• How much does the contaminant or activity adversely affect human health?
• shorter life
• illness
• altered quality of life (disabling, etc)
• Measure the contaminant
• Determine dose-response relationship
 Lab risk assessment

Generation Generation
Generation Rate - Change Minimum Fume
Hazard - Quantity - Method Location
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generation rate for General order and
the peak hazard contained by volume of all method for any location for any Frequency of change Risk Rating Band Requirement based
any hazard contained cleanliness of the lab
ECD hazards hazard contained by hazard contained by in the ECD
by ECD on ANSI Z9.5
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- - - - - - -
 Sensitivity or
Evaluation Criteria Rating Weight Multiple Weighted Risk Score
Importance

Hazard 4 10 40 43%

Quantity 4 3 12 13%

Potential or Rate of Generation 4 5 20 22%

Method of Generation 4 1 4 4%

Generation Location 4 1 4 4%

Dynamic or Potential for Change 4 2 8 9%

Housekeeping 4 1 4 4%

Total Weighted Risk

Totals 28
Score
92 100%
Risk Score Range for each Risk Control Band (Based
on Tolerance of Risk)

Low Tolerance Medium Tolerance High Tolerance Risk Level

0 -4.6 0 -9.2 0 -18.4 0

4.7 -9.2 9.3 -23.0 18.5 -46.0 1

9.3 -18.4 24 -36.8 46 -64.4 2

18.5 -50.6 36.9 -69.0 64.5 -82.8 3

50.7 -92.0 70 - 92.0 82.9 -92.0 4

 RISK CONTROL/REMEDIATION
• Determine which risks can be controlled
• Determine available resources
• Review most effective method of controlling a risk. Consider:
• legal mandate
• cost effectiveness
• public reaction
• sociologic considerations
HAZARD IDENTIFICATION
What type of toxicity may occur?
Is this toxicity relevant to humans?
 Site Investigation
• Walk through
• Disease statistics/incidents
• Complaints
• Media coverage
 Workplace Walk Through Survey
• Workplace
• access SDS for site
• determine chemical usage areas
• visually check locations of chemicals
• determine other “hazardous areas”
• is ventilation functioning?
• where are areas of employee concerns?
• etc.
 ILLNESS/INJURY STATISTICS
• Information on the occurrence of disease or injury may be available
• Epidemiological studies
• Statistics Canada
• Local rates of disease
• Hospital reports
 COMPLAINTS
• General public complaints about issues
• Worker complaints
• Media coverage
 CHARACTERIZE THE HEALTH HAZARD
• Hazard classification/identification
• Toxicological studies
• Epidemiological studies
 HAZARD IDENTIFICATION
• Toxicity can be characterized by different perspectives
• Systems; nervous, immune, reproductive, endocrine, etc
• Organs; lung, liver, kidney, skin, eye, etc
• Diseases; cancer, birth defects, pneumoconiosis, etc
 HAZARD CLASSIFICATION
• Hazardous agents can be classified as
• carcinogens
• mutagens
• neurotoxins
• developmental/reproductive
• Based upon a “weight of evidence” assessment
• Classifications must be judged with care
 HAZARD IDENTIFICATION
• Chemicals vary greatly in types of toxicity they produce
• No single measure of toxicity can be adequate to characterize all
possible toxic outcomes
 HAZARD IDENTIFICATION
• Substances do not have “all or nothing” toxic properties
• those classified to be one or more of the types of toxic agent do not
necessarily have a proven cause-effect relationship (often cautious)
• those not classified are not judged to be safe
• Hazard classification is a classification of potential
 HAZARD IDENTIFICATION
• Risk assessment judges the hazard potential in relation to exposures
and dose-response relationship to determine likelihood (chance,
probability) of harm
 HAZARD IDENTIFICATION
• Weight of evidence approach considers:
• quality of each relevant study
• quality of data
• specifics of study design
• overall strengths and limitations
• knowledge about principles of each study
• experience and judgment for the interpretation of data
 HAZARD IDENTIFICATION
• Human studies are the best, but
• limited availability for env. exposures
• ethics preclude env. human experiments
• observational nature limits control
• not able to be preventive (predict hazard before human exposure)
• poor quality exposure data (generally)
• encounter unrecognized bias and confounding
• limited statistical power
 HAZARD IDENTIFICATION
• Animal studies offer advantages of:
• lab control
• can be predictive
• existence of some agreement between animal studies and human
• can test exposure patterns (routes, duration, frequency)
• can determine dose response relationships
• can fill gaps in human data
 HAZARD IDENTIFICATION
• Animal studies have disadvantages;
• need to extrapolate results to humans
• need to be on practical scale (high dose to see effect), then have to
extrapolate to low dose human exposure
• In vitro assays and structure activity relationships provide support but
cannot confirm human toxicity
 HAZARD IDENTIFICATION
• Hierarchy of value:
• human>animal>in vitro>theoretical
• Hazard identification should include statements of:
• confidence in conclusions
• alternative conclusions
• evident data gaps
• identification of assumptions
 Hazards
• Well known hazards?
• Carcinogens
• Mutagens
• Neurotoxicants
 CARCINOGENS (CEPA)
• Group I - Carcinogenic to humans
• data from epidem. studies indicate causal relationship
• Group II - Probably carcinogenic to humans
• inadequate epidem. evidence but sufficient animal study info.
• Group III - Possibly carcinogenic to humans
• Group IV - Unlikely to be carcinogenic to humans
• Group V - Probably not carcinogenic to humans
• Group VI - Unclassifiable (not enough info)
 CARCINOGENS
• New US EPA carcinogen guidelines (1996)
• weight of evidence classes for Human Evidence
• Category 1 - conclusive causal
• Category 2 - plausible causal assoc. suggested
• Category 3 - conclusive causal assoc. cannot be judged
• Category 4 - conclusive assoc. does not exist
 CARCINOGENS - US EPA Guidelines
• Weight of evidence for mechanisms of action:
• explained by body of research accepted scientifically
• experimental evidence supports the agent acting by the mechanism
• observed animal effects must be relevant to humans
• agent affects carcinogenesis linearly at low exposure (dose and response)
 Carcinogens
• Chemicals in tobacco
• Arsenic
• What else?
• Carexcanada.ca
 MUTAGENS
• Agents capable of causing genetic effects by damaging genes or
chromosomes
• links to cancer
• activation of protooncogenes to oncogenes
• inactivation of tumour suppressor genes
 MUTAGENS
• more than 100 bioassay systems for testing mutagenicity
• Ames salmonella assay is most famous
• Used to determine the mutagenic potential of new drugs/chemicals
• Has to do with histidine to show which are mutagens
• no one test can detect full spectrum of genotoxicity
 TOXICOLOGICAL APPROACHES
• Toxicology is the study of the adverse effects of chemicals on the
body
• Science - based on observation and experiment
• Art - based on interpretive and predictive activities
• Health risk assessment relies on the science, but is an application of
the art of toxicology
 DOSE RESPONSE

• Quantitative basis for toxicology is the dose response

• Dose measures are derived from the dose response curve
• generic dose response - change in an indicator
• individual graded response - form or severity of adverse effects as a function of dose
• population quantal response - predict if an effect occurs in response to an agent
 DOSE RESPONSE
• used to assess effects of exposure of chemicals
• vast amount of info on carcinogens
• neither dose nor response is easily quantified
• exposures vary over time
• health effects vary in frequency and severity
• time delay between cause and effect
• type of effect may change with dose
 DOSE RESPONSE - General Rules
• at low exposure, no effects seen regardless of exposure duration
• at slightly higher exp., subtle effects seen in small proportion
• as dose increases, greater proportion of the popn will respond with
subtle effects, small proportion will have severe effects
• as dose further increased, incidence & severity increase
 DOSE RESPONSE - General Rules
• at high dose, nearly whole population will have severe effects, some
with even more severe
• nearly any risk agent at high enough dose will cause death
 Dose Response - General Information
• dose expressed in terms of cumulative exposure or rate per unit time
• response scale depends on the nature of the response
• severity
• probability
• time until occurrence
• estimate “excess risk” (above that of background risk)
 Dose Response Relationship
• can be derived from statistical analysis of observations
• regression analysis of actual events
• adjust for sensitive population
• derive from animal studies
• careful about extrapolations
• estimates only
• use conversion factors
 Dose Response Models
• Simple dose response model
• tolerance distribution models
• mechanistic models
• time to response models
• pharmacokinetic models
INTERPRETATION
• Statistical inference
• relies on statistical analysis of data
• are responses stat. significant?
• must insure statistical power is adequate for intended purposes
• must distinguish statistical significance from biological significance
 Simple Dose Response Model
• relates single measure of dose to single measure of health response
• eg. exposure to number of deaths
• can be zero threshold or threshold
 ANIMAL TOXICITY TESTING
• Acute toxicity testing objectives
• assess intrinsic toxicity and potency
• identify target organs
• estimate duration of effects
• determine effective dosage ranges for long term studies
 ANIMAL TOXICITY TESTING
• Acute toxicity testing objectives
• assess species susceptibility
• establish reversibility
• determine mechanisms
• determine toxicokinetics
• meet regulatory requirements
 TOXICITY CONSIDERATIONS
• Exposures • Responses
• acute • immediate
• subchronic • delayed
• chronic • Severity
• mild, reversible
• serious, irreversible
• life-threatening
Review
Plan a Risk Assessment
• Who/What/Where is at risk?
• Individual
• General population
• Lifestages such as children, teenagers, pregnant/nursing women
• Population subgroups - highly susceptible (for example, due to asthma,
genetics, etc.) and/or highly exposed (for example, based on geographic area,
gender, racial or ethnic group, or economic status)
What is the environmental hazard of
concern?
• Chemicals (single or multiple/cumulative risk)
• Radiation
• Physical (dust, heat)
• Microbiological or biological
• Nutritional (for example, diet, fitness, or metabolic state)
• Socio-Economic ( for example, access to health care)
Where do these environmental hazards come
from?
• Point sources (for example, smoke or water discharge from a factory;
contamination from a Superfund site)
• Non-point sources (for example, automobile exhaust; agricultural runoff)
• Natural sources
How does exposure occur?

• Pathways (recognizing that one or more may be involved)

• Air
• Surface Water
• Groundwater
• Soil
• Solid Waste
• Food
• Non-food consumer products, pharmaceuticals
• Routes (and related human activities that lead to exposure)
• Ingestion (both food and water)
• Contact with skin
• Inhalation
• Non-dietary ingestion (for example, "hand-to-mouth" behavior)
What does the body do with the
environmental hazard?
• how is this impacted by factors such as age, race, sex, genetics, etc.?)
• Absorption - does the body take up the environmental hazard
• Distribution - does the environmental hazard travel throughout the body or
does it stay in one place?
• Metabolism - does the body break down the environmental hazard?
• Excretion - how does the body get rid of it?

• What are the health effects?

• Example of some health effects include cancer, heart disease, liver disease
and nerve disease.
How long does it take for an environmental
hazard to cause a toxic effect?
• Does it matter when in a lifetime exposure occurs?
• How long?
• Acute - right away or within a few hours to a day
• Subchronic - weeks or months (for humans generally less than 10% of their lifespan)
• Chronic - a significant part of a lifetime or a lifetime (for humans at least seven years)
• Intermittent
• Timing
Is there a critical time during a lifetime when a chemical is most toxic (e.g.,
fetal development, childhood, during aging)?