Types of prevention
Risk assessment
Mgr. A. Peřina, Ph.D.
Dept. of Public Health
Faculty of Medicine, Masaryk University
Health
• A state of complete physical, mental and social well-being and not
merely the absence of disease or infirmity (WHO, 1948).
• Health is neither born nor cultivated in hospitals but it arises and
developes wherever people live, play and work, relax and grow old.
• Pillars of health care:
1. Health education
2. Disease prevention
3. Health protection + health promotion
Health protection and promotion
• Health protection: summary of activities and measures focused on
creation and protection healthy living and working conditions aimed
at the prevention of infectious and non-infectious diseases
• Health promotion: summary of activities helping people to
strengthen and improve their health and control their determinants
of disease
• Sectors involved: health care, environmental sciences , food
production and agriculture, technologies, industry, trade, social care,
transport, culture, state defense forces, schools, sport facilities…
Some examples of prevention:
• Water treatment technologies
• Indoor air quality (lecture rooms, study rooms, entertraiment halls,
hospital rooms etc.)
• Food production technologies
• Product design and product safety (noise, chemical safety etc.)
• Product claims (false claims about able to cure serious illnesses such
us generalized cancer, marketing of breast milk substitutes etc.)
Prevention
Type of prevention Tasks Responsibility
Primary Influencing disease
determinants and reducing
health risks
Health and Social care
services, Environment. sci.,
, Food prod. & Agriculture,
Education etc.
Secondary Preventive examinations,
screening programs
Health care services
Tertiary Treatment of diseases and
mitigation of their
consequences
Health and social care
services, M. of Social
Affairs
Quarterly Mitigate the effects of
unnecessary or excessive
treatment interventions
Health care services
Selected
campaigns of WHO
• BreatheLife mobilizes cities and
individuals to protect people’s and
Planet health from the effect of air
pollution.
• Predominant type of prevention:
primary
• Antibiotic resistance: new
WHO recommendations
are trying to help
maintaining the
effectiveness of antibiotics
used in human medicine
by limiting the
unnecessary use in
animals.
• Predominant type of
prevention: primary &
tertiary
Selected
campaigns of
WHO
Selected
campaigns of
WHO
• „Global Hearts" is an
initiative to averting
the global threat of
cardiovascular disease,
the world's leading
causes of death.
• Predominant type of
prevention: primary &
secondary
Selected
campaigns of
WHO
• "WHO's Global School Health
Initiative", also known as "Health
Promotion School": An initiative to
promote health and education at
local, national, regional and global
level. The aim is to improve the
health of students, school staff,
families and other community
members through schools.
• Predominant type of prevention:
primary
Selected campaigns of WHO
• Global Action Plan
„Healthy enterprise“
addresses all aspects of
workers’ health: primary
prevention of occupational
hazards, protection and
promotion of health at
work, working conditions
and health services for
employees of enterprises.
• Predominant type of
prevention: primary
Selected campaigns of WHO
• SaveLIVES: road safety
package, evidence-based
inventory focusing on
speed limits, transport
infrastructure, vehicle
safety, traffic law and
regulations and actions
increasing the chance of
survival after a traffic
accident.
• Predominant type of
prevention: primary
The preventive
and
therapeutic
components of
medicine are
complementar
y to one
another.
Why to prevent diseases
when we can cure them?
• Effective prevention reduces the incidence and prevalence of serious
diseases.
• In most cases, treatment has side effects that can be avoided by
effective prevention.
• Consistently healthy people are economically active.
• Consistently healthy people are less sensitive to social, cultural and
other differentiation.
• Satisfactory environment fulfills well the functions of production,
recreation and regeneration.
• The zero option means the growing cost of medical technology, the
possibilities of which can be (once) exhausted (eg. antibiotics and
current resistance, organ transplants and ethical issues etc.).
Health risks
assessment
Hazard vs RiskHazard vs Risk
• Hazard
• Characterizes properties of
agents
• Pathogenicity, toxicity...
•Risk
• chance of harmful effects to health
• It is a mathematical function of
hazard.
• P = 0 … 1
• P = 0 % … 100 %
… It may, it could…
Probability
• Meaning in conversation
• Relative frequency of the phenomenon
The result can be predicted on the
basis of a statistical analysis of a large
number of iterations.
However:
• the life expectancy in the population does not
indicate the length of an particular person
• the likelihood of genetic diseases do not indicate
the occurrence of this disease in particular
newborns
Pifalls in risk assessment
• Risk assessment (among others) = hazard analysis +
emotions
• the public knows very little about probability and overestimates its
importance
• experts (mostly) know very little about emotions; experts must be
fully aware of the fact, that
• emotions are measurable, as well as the probability is
• emotions can be affected as well as the probability
• emotions are a legitimate part of the risk
Prioritization of
health risks
• Why?
There are a lot of risks that occur in
the human environment, but only
some of them have a direct impact on
human health.
Risk Assessment
Attention focuses on human!
Hazard identification: can the agent (specific active factor) harm
health?
1. Dose – response relationship: what is the numerical relationship
between the exposure and the effect on health?
2. Exposure assessment: how important is the contact of the
individual / population with the agent?
3. Risk characterization: can the assumption of an adverse effect on
health be confirmed?
Types of hazard (will be discussed in more detail in specific
seminars)
• Biological agents
• Pathogenic microorganisms (see epidemiological seminars)
• Non-pathogenic microorganisms related to health
• Toxins as by-products of decomposing and primarily non-pathogenic microflora
(fungi and aflatoxins)
• Chemicals
• Irritating, toxic, mutagenic, teratogenic and carcinogenic effects
• Physical factors
• Noise, vibration
• Nonionizing and ionizing radiation: Special features of therapeutic use: benefit /
risk ratio
• Microclimate, unilateral strain of muscle groups
Types of dose-response relationship
• Agents with deterministic health effect: depends on dose
• Usually at infection known as the minimal infective dose
• Many of chemical substances
• High dose of ionizing radiation
• Agents with stochastic health effect: depends on a chance; one illness/death
per one thousand people, per one million people, per ten million people?
• Chemicals with carcinogenic or teratogenic effects
• Low dose of radiation
• However: dose in environment is not equal to dose in tissues (see next slide)
Exposure assessment
• Potential dose
• It corresponds to the concentration of the agent in the environment (i. e. in air,
water, food, soil), converted to a unit of mass, volume or area of the matrix.
• Applied dose
• It depends on the speed of diffusion and capacity of receptor.
• Ingestion, inhalation, contact with skin or mucous membranes
• Comment: besides the concentration, the duration of exposure can also determine the size of
the effect.
• Effective dose
• Defined by the concentration of agents in the target organ
• How to measure the exposure plausible? (see next slides)
Exposure assessment – methods
• Indirect methods
1. Environmental monitoring: The amount of agent in the matrix multiplied by the
average matrix intake by the exposed person:
• Average lung volume (22 m3/person/day)
• Average water consumption per person (1,9 liter/day)
• Amount of food consumed per person (e.g. Food pyramid)
• The average length of stay in the swimming pool
• Inaccuracy! Interindividual differences are significant!
2. Exposure scenario or questionnaire survey: A rough estimation of the exposure
can be specified, most often in a well defined population group (typically school
pupils, members of the army ...)
Estimation of
individual
exposure
based on the
food pyramid
may be difficult.
Exposure assessment – methods II.
• Direct methods
are preferred but are generally less accessible.
• Personal monitoring
• 24 hrs recall, double portion method…
• Personal dosimetry - healthcare workers
• Biological monitoring
• Biomarkers of exposure (DNA adduct in tests of genotoxicity)
• Biomarkers of effect (measurable pathophysiological changes in organs)
• Biomarkers of sensitivity (measurable susceptibility to health impairment)
Risk characterization
1. Harmful to health has not been confirmed
2. Exposure to harmful factor reduces the level of well-being (health in
a broader sense)
• Example: The source of environmental noise has forced the use of space
(more demanding activities are moved to a quieter part of the building).
3. Exposure to a harmful factor poses a threat to health in the longer
term, with the factor being considered at most as one of several
disease factors (long-term and multifactorial health effects)
4. Exposure to harmful agents poses an immediate threat to human
health or lives
• (See the Czech “methanol affair“ in 2012.)
Epidemiology (non-infectious)
• Method of work used to study the distribution of determinants of
diseases in the population.
• Epi demios (Greek) = Among the people
• Descriptive, analytical, experimental and interventional epidemiology
use statistical methods; a separate field of biostatistics is being
developed.
• The way how to study stochastic health effects
• Problems: transferability of results
• Internal validity of epidemiological studies
• Hill's criteria of causality (Sir Austin Bradford Hill, 1897 –
1991)
Strength of association: Even a weak association does
not rule out causality if it is weakened by
unrecognized confounders
Consistency: Inconsistency with other epidemiological
studies does not exclude causality, the effect may
only occur under special circumstances
The causality does not assume the specificity of the
effect
The temporality (time sequence) of exposure and
effect is a prerequisite!
Epidemiology in health risk
assessment I.
Hill's criteria of causality ….continuation
Biological gradient: its absence does not exclude
causality, many dependencies can be J-shaped
Biological plausibility: the inability of
pathophysiological explanation of the phenomenon
may be just the result of the current scientific
knowledge
Coherence: Incompatibility with "established" theories
does not exclude causality
Experimental evidence: its absence does not exclude
causality, as the experiment can also be prevented by
ethical reasons
Analogy: its absence can only be a manifestation of a
lack of scientific imagination
Epidemiology in health risk
assessment II.
Public Health and qualitative research
• Be aware that a state of complete physical, mental and social well-being
cannot be expressed by a statistic only! Health is relationship too!
• Qualitative research always just as a complement to epidemiological
methods of work It enables us to understand the social, cultural, economic
and behavioral aspects of (public) health
• Epidemiological methods: “How many? How much?”
Calculation of frequency, confidence intervals, the probability of the
estimation error (magic “p-value“)
• Qualitative research: how and why?
From the Latin word “Qualis” (= How? What?)
Verbal analysis of relationships and contexts
Health risk assessment in doctor’s
everyday practice
Not only in prevention, but also in the diagnosis and treatment of diseases,
doctors should ask the following questions (according to the US EPA):
What symptoms can be causal in terms of exposure to environmental
or occupational hazards?
Is there a safe exposure level for the selected agent?
Is there a possibility that some people will be exposed to significantly
different exposure doses?
Is it an exposure of an increasingly vulnerable (susceptible) population
group (such as children, pregnant women, sick people, the elderly,
people with occupational exposure)?
Conclusions
• Lost health can be restored medically.
But:
• Creation of health, health protection and health promotion
in some ways exceeds the capacity of clinical medicine.
• The basis for the protection and promotion of health is a
health risk assessment process built on a scientific basis.
• Principles of health risk assessment are very useful in clinical
practice.