Identifying Hazards and Communicating Risks

Identifying Environmental Problems

Environmental hazards (see Definition box below: Hazards and risks) contribute to cause a wide range of diseases and environmental factors are involved in the aetiology of virtually every illness. Environmental hazards are often complicated by how ubiquitous they can be and the scale of remediation that may be required to address them, as with soil contamination by effluents, or air pollution. In other instances, a disease caused by specific environmental hazards may respond to a simple solution such as cleaning or wearing protective equipment. Moreover, many patients worry about elements of their environment that have little or no effect on health, so physicians need to be able to distinguish those that are hazardous from those that are not. To diagnose an illness as predominantly environmental in origin, physicians have to include a thorough environmental assessment in their history-taking. Clues that an illness is caused, in part or wholly, by an environmental factor include:

• The patient suspects it
• Local epidemiology: for example, the pattern of illness is atypical; the patient is not in the usual age group; the common non-environmental risk factors are absent; and if the environmental hazard persists the symptoms may not respond to the usual treatments.
• The temporal pattern of the illness suggests it (for example, symptoms improve when the patient goes on holiday and worsen on returning home, or they worsen when the patient is at work and improve at home).
• There is no obvious other cause for the illness
• The signs and symptoms suggest specific toxic substances, such as lead or mercury poisoning.

Simultaneously, physicians must be aware of how climate change can impact the health of their patients and communities. While climate change is not a specific hazard that may be removed from a patient’s environment, physicians are well-placed to provide advice on adaptive measures to lessen the effects of climate on their patients. Many physicians also choose to participate in research and in political action to combat the health effects of climate change.

Once an environmental cause is suspected, the physician should take a detailed environmental history to identify potentially pertinent hazards the patient may have been exposed to, as shown in the box “Taking an environmental history”. All of the patient’s activities and environments should be explored. The chronology of events, patient’s proximity to the presumed source, and whether or not other people are affected should be explored for evidence that supports or discounts the hypothesis of an environmental cause (i.e., establishing Time, Place, and Person).

Once the physician has established that the problem is likely related to a given environment, they should further consider how to engage public health authorities to address their concerns and to ensure that other people are protected. The physician can consult with their colleagues in occupational medicine or in public health and preventive medicine for advice on how to manage a health problem linked to the environment. Indeed, some provinces require physicians to notify their local public health department of particular environmental illnesses or possible outbreaks. In the case of a hazard that is likely to affect the population at large, the public health department is responsible for controlling the problem. The roles of the public health department may include conducting investigations, surveillance and public education; remediation may require intervention or support from other parties. At times, public health departments my proactively advise on the possible health impacts of projects proposed by industry or governments, known as Health Impact Assessment.

In the case of a hazard related to a workplace, employers and workplace health and safety representatives bear a responsibility to investigate and address concerns brought forward by workers. Where this fails, provincial regulatory authorities for workplace health and safety may need to get involved, as described in Chapter 12. In an emergency, as with a case of carbon monoxide poisoning, public security services (fire and police) would coordinate control efforts.

Taking an environmental history³

The following topics cover the basic elements of an environmental history. Asking scanning questions about these different topics using the CH₂OPD₂ mnemonic (see below) may clue you in to something that warrants further discussion.

• Community or neighbourhood sources of hazard: pollution; industry; waste storage
• Home: year of construction, renovations; materials used in construction and decoration; moulds; garden and house plants; use of cleaning products, pesticides, herbicides
• Hobbies and leisure: exposure to chemicals, heavy metals, dusts, or micro-organisms
• Occupation: current and previous occupations; work with known hazards; air quality
• Personal habits: hygiene products; smoking
• Diet: sources of food and water; cooking methods; food fads
• Drugs: prescription, non-prescription, and alternative medications; health practices.

If a scanning question reveals a possible hazard, ask detailed questions to find out as much as possible about the nature and level of the hazard and then check Time, Place and Person:

• Time: When did symptoms begin? When did the exposure begin? When do symptoms get worse? When do they improve?
• Place: Where is the patient when symptoms get worse? Where is the likely hazard? What is the route of exposure through which the hazard reaches the patient?
• Person: Does anyone else have similar symptoms? Who? When? Where?

Climate Change and Health

From the population health perspective, the World Health Organization ranks ranks climate change as the top global health threat, projected to cause an estimated 250,000 additional deaths annually from 2030. Depending on the patient’s presenting complaint, physicians may also  consider how climate change is contributing. Extreme weather events may lead to an increase in injuries, exacerbations of underlying cardiovascular or respiratory diseases, heat-related illnesses, or enteric diseases if electrical or water infrastructure is damaged.⁴ Longer, warmer, and drier seasons may influence the food security of patients. Physicians may also encounter changing patterns of vector-borne diseases, such as Lyme disease, due to longer and warmer seasons that extend the natural habitats of vectors such as tics.⁵  Physicians should also recognize that some of their patients will be disproportionately impacted, such as those who are medically vulnerable or socially marginalized. As with other environmental hazards, physicians should help patients identify ways to reduce their risk of adverse health effects due to climate change. Figure 10.1 illustrates the multiple routes through which climate change may affect human health.

Figure 10.1: Routes through which climate change affects health (adapted from Mobilizing Public Health Action on Climate Change in Canada, Figure 3.

Wildfires and the climate crisis

Public Health Approaches to the Climate Crisis

Climate change is an important public health priority. The public health response involves a two-pronged approach of mitigation to address the immediate impacts of climate change, and adaptation to build long-term resilience against future climate-related challenges (see Figure 10.2).

Mitigation involves efforts to slow, stabilize, or reverse climate change primarily by reducing greenhouse gas emissions: a form of primary prevention. Mitigation strategies involve two key actions: reducing the sources of greenhouse gases and enhancing the natural sinks that absorb and store these gases, such as the lake, wooded areas, and soil.

Adaptation focuses on anticipating and preparing for the effects of climate change, representing secondary and tertiary prevention strategies. Climate change adaptation seeks to reduce vulnerability to the detrimental effects of climate change and to seize any potential benefits. This may  involve conducting health vulnerability and adaptation assessments to identify at-risk populations and to evaluate the resilience of health systems. These assessments help to understand the health impacts of hazards such as heatwaves and infectious diseases, and to develop strategies to enhance infrastructure, to improve disease surveillance, and to promote community resilience.

This combined approach will guide targeted actions to minimize adverse health impacts and improve preparedness for a changing climate. This should provide ecosystems with the time they need to adapt to a changing climate. Mitigation includes ensuring that food production and economic development proceed in a sustainable manner. Policies must maintain a balance between addressing current needs and preserving the health of our planet for future generations.

Figure 10.2: Illustration of strategies for climate change mitigation and adaptation (adapted from Sandink & MacLeod (7))

Toronto’s climate change mitigation plan

Disasters and disaster preparedness

The Medical Council defines a disaster as “a serious disruption of the functioning of a society, causing widespread human, material, or environmental losses that exceed the ability of the affected society to cope using only its own resources.” While disasters often follow natural hazards, not all natural hazards cause disasters. For example, flash flooding of unfarmed land is not considered a disaster – it’s just weather. But if it occurs in a low-income neighbourhood without flood resilient housing and impacts thousands of inhabitants, it would be a disaster. Disaster exposure is usually quantified as number of people or assets affected. When complete prevention of exposure is not possible, it can be mitigated through the implementation of early detection systems and disaster preparedness programs.

Common categories of hazard that may lead to a disaster include:

1. Natural hazards
   1. Weather & climate change (including anthropogenic): extreme weather events, droughts, wildfires, flooding; earthquakes
   2. Infectious disease outbreaks and pandemics
2. Hazards deriving from human systems
   1. Technological hazards: industrial or structural failures; infrastructure disruption; electricity or water system failures
   2. Chemical, biological, radiological, nuclear hazards (unintentional or intentional); food contamination
   3. Social: civil unrest; cybersecurity; weapons; armed conflict; terrorism
3. Multi-Hazard: combinations of the above.

Responding to Disasters

Disasters could be thought of as potentially recurring events and managing disasters is generally presented as a cycle of phases that include:

• Prevention: actions taken to stop a potential emergency or disaster from occurring (e.g., efforts to combat climate change; diplomacy to prevent wars; food and water safety standards; hazardous material safety standards).
• Mitigation: based on risk assessment, actions taken to lessen the cause or the impact of a disaster that cannot reasonably be prevented (early warning systems; creating fire breaks in forests; adequate drainage; earthquake proofing buildings).
• Preparedness: planning, training, and educational activities to ensure appropriate actions are taken within the components of prevention and mitigation, and where necessary, ensure an effective response to, and recovery from disasters (e.g., a tabletop exercise simulating roles in the event of a widespread fire).
• Response: activities before, during and immediately after a disaster when regular operations are suspended (e.g., search and rescue missions). The goal is to mount a coordinated and effective response at the outset of the emergency to prevent loss of life, injury or other health impacts, property damage, loss of services, social and economic disruption, environmental damage.
•  Recovery: restoration activities that occur alongside a return to regular operations, such as rebuilding damaged structures (building back better), provision of financial, physical and emotional support.

These are commonly shown in a circular diagram in which recovery feeds back into improving preparedness and future mitigation plans.⁸ Effective public health systems continuously anticipate and prepare for potential hazards, so are always in some phase of the disaster management cycle. Ontario Public Health, for example, publishes guidelines for assessing risks from infectious diseases and other potential hazards.

The emergency response cycle in practice

Several practical components and tools are typically involved in an emergency response. For example, a Hazard Identification and Risk Assessment (HIRA) system. This assesses the probability and impact of  hazards, and may identify high-level planning implications for data collection or surveillance. Ontario Public Health, for example, publishes guidance on completing a HIRA.

As part of preparedness, and before mounting a response, organizations may develop an Emergency Response Plan (ERP), which is a document that outlines the policies, procedures, roles and responsibilities of agencies, to coordinate action. For example, the Ontario provincial emergency response plan describes the multiple ministries and other organizations involved. It outlines an organizational structure, legislated responsibilities, and lines of communication.

Several tools or approaches may be utilized during the response phase. For example, once a disaster is declared, an Incident Management System (IMS) provides guidelines for standardizing responses to an incident, covering personnel, facilities, equipment, financing, procedures, and public information communications. An Emergency Operations Centre (EOC) is a centralized facility for the overall coordination of a response, including information exchange and coordination. A Continuity of Operations Plan (COOP) outlines how the continued delivery of critical functions and services will be maintained in the event of a disaster. Most disasters are managed at the local or provincial levels, but due to the extraordinary authority that may be required to mount a large-scale response to an emergency, two federal laws may be invoked:

1. The Emergency Management Act delineates the roles and responsibilities of federal Ministries, such as those of the Ministry of Public Safety and Emergency Preparedness, which include coordinating emergency response activities between provincial/territorial actors and governments.
2. The Emergencies Act is used during national emergencies to allow the federal government extra temporary powers only when necessary to protect the health and safety of Canadians. In this way, the Emergencies Act may conflict with the Charter of Rights & Freedoms.

Reducing Risk

The three main activities in addressing health problems possibly linked to environmental hazards are risk assessment, risk management, and risk communication. The clinician addresses these when discussing environmental disease with a patient; a public health officer applies them in responding to community wide problems.

Risk assessment

Risk assessment involves a series of steps in evaluating the likelihood of occurrence and probable severity of health effects due to a hazard. Please note that ‘Risk assessment’ for the purpose of environmental or occupational hazards is a different approach than the ‘Hazard Identification and Risk Assessment’ discussed above in the context of emergency preparedness. Various agencies assess hazards, including occupational health agencies, environmental protection agencies, and public health authorities. Clinicians confronted with a case of disease with possible environmental links might use some of the following risk assessment steps to arrive at a diagnosis.

Steps in risk assessment for clinicians and public health officers ⁹

1. Hazard identification: Are environmental or occupational hazards involved? What are they? How likely are people to be exposed and what will the effects be?
2. Dose – Response assessment: Given the patient’s level of exposure, is the hazard likely to cause these types of symptoms in this type of patient? What are the dose response curves for different routes of exposure (inhalation, ingestion, etc.)?  
3. Exposure assessment: to what extent is the patient or population exposed? Is the exposure to the hazard sufficient to cause these symptoms? Which population groups are likely to be at most risk of health effects?
4. Risk characterization: How much has the hazard contributed to the patient’s condition? What is the risk from this hazard for this specific population?

Risk assessment, Step 1: Hazard identification

The first step identifies the agents possibly responsible for the problem. Each hazard is defined by its ability to cause adverse effect, under what conditions and to which population groups. Hazards are classified as biological, chemical, physical, ergonomic, psychosocial, or related to safety. Table 10.1 gives examples of the various types of hazard and their possible health effects.

Table 10.1: Examples of the various types of environmental agents and their associated health effects

When we think of exposure to environmental hazards, we can consider the different media that hazards can exist in, such as air, water, soil and in food. It is through consumption, inhalation and or contact with environmental media that exposure to hazardous substances occurs. Hazards may affect health directly, or indirectly when they produce a change that puts a person or population at risk, as seen with climate change. Table 10.2 lists some of the common hazards.

Table 10.2: Examples of hazards in the environment

Indoor hazards that cause health problems include household chemical products, carbon monoxide, radon, mould, lead, and consumer products (cosmetics, perfumes, hygiene products). Second hand smoke is still a problem in some households.

The clinical picture may indicate what kind of hazard to assess for. Airborne irritants can cause itchy or sore eyes, runny nose or coughing. Irritants that come into direct contact with the skin can cause dermatitis. Allergens can cause numerous manifestations of allergy including dermatitis, asthma, allergic rhinitis. Asphyxiants cause different respiratory problems depending on the type of asphyxiant. For instance, as a chemical asphyxiant, carbon monoxide blocks oxygen transport. Other inert gases can still accumulate in high concentrations displacing oxygen in the air. Certain ingested or absorbed substances may damage organ systems in pathognomonic ways. For instance, severe lead poisoning causes neurological changes, abdominal pain, or anaemia, whereas poisoning with mercury typically produces tremors, among other neurological symptoms. Mesothelioma is linked to exposure to asbestos.

The effects of a hazard may be delayed, sometimes for years. This is especially true of cancer-causing agents. Because of the time-lag, identifying hazards of this type and proving the effect can be difficult. Identifying this type of hazard and evaluating claims about it can be difficult. Furthermore people can be exposed to more than one hazard, each contributing to their health problem. For instance, in the case of a person who works in construction and who smokes, it can be difficult to assess the relative contributions of occupation and smoking to his chronic lung disease.

If an outbreak of a disease of environmental origin is suspected, public health officials will collect initial information on the possible sources. Once a case definition (see CASE DEFINITION in Glossary) is established, cases are sought and information is collected on when and where they were exposed, when they started showing effects, and demographic characteristics and predisposing factors (Time, Place and Person). Information from all cases is then collated to produce a picture of the distribution of cases in time and place (see Chapter 11: Detection and control of outbreaks).

Risk assessment, Step 2: Dose-response assessment

This step describes the potential health effects of a hazard at different levels of exposure. As far as possible, effects on molecular, biochemical, cellular and organ systems are described. A chemical hazard may only cause health problems when in a specific form: small amounts of ingested elemental liquid mercury are unlikely to cause adverse health effects, although mercury vapor and organic and inorganic mercury compounds have known adverse health effects. The route of entry into the body may also be an important determinant of the damage caused: the risk of toxic effects from the ingestion of asbestos is considered to be low,¹⁰ whereas inhaled asbestos causes asbestosis, mesothelioma and other cancers.¹¹  Furthermore, a person’s response to a hazard is mediated by the factors that influence the hazard’s toxicokinetics and toxicodynamics (See Definitions: Kinetics and dynamics). The individual’s genetic makeup and metabolic state as well as environmental factors moderate the toxicokinetics and toxicodynamics, so susceptibility to damage by a hazard varies from one person to another; malaria offers an example.

A low dose of some substances may be beneficial for a person, yet a higher dose is toxic. For instance, fat soluble vitamins, such as A and D, are essential for health, but too much of either is toxic (see ‘Hormesis’). Sunlight in small doses increases the production of Vitamin D, while in high doses it can cause skin cancer. Some hazards, such as heat and noise, must reach a threshold level before damage occurs. Others, including many cancer-causing agents, are presumed to cause damage even at the lowest measurable levels. The chronic effects of some agents, such as X-rays, are cumulative over a lifetime, while the acute effects of other agents, such as anesthetics, may only be temporary without ongoing exposure.

For information on hazardous substances, clinicians can look to the scientific literature, check with the local public health department or call the toxicology or poison centre. If the probable source of the hazard is an industrial product, information is likely to be available via the Workplace Hazardous Materials Information System (WHMIS5), which sets out the labelling requirements for the hazards shown in Table 10.3. The product label also indicates if a ‘Safety Data Sheet’ is available for the product. This sheet contains further details about the hazard, how to handle it safely and what to do in an emergency.¹⁴

Table 10.3: The Workplace Hazardous Materials Information System Symbols ¹⁵

Acute toxicity, skin corrosion, eye or respiratory damage, and specific organ toxicity

	Gas or chemicals under pressure
	Flammable gases, aerosols, flammable liquids & solids, etc.
	Oxidizing gases, liquids, or solids
	Respiratory or skin sensitization, mutagenicity, carcinogenicity, reproductive toxicity and target organ toxicity and aspiration hazard
	A general warning covering several of the previous hazards: Acute toxicity, skin corrosion, eye or respiratory damage, and specific organ toxicity
	Biohazardous infectious materials
	Corrosive materials; agents causing skin corrosion or eye damage
	Self-reactive substances & organic peroxides

Risk assessment, Step 3: Exposure assessment

Exposure assessment is the step that quantifies the exposure of a person or population to a hazard. The levels of some hazards can be directly measured, either in the environment or in the people exposed. More often, however, exposure must be estimated from a careful history of the patient’s activities, as well as an inspection of the environment. Details of activities, working practices, and processes during which a person is likely to be exposed must be examined to determine how and how much the person was exposed to the hazard.

When the problem may have been caused by an agent that produces delayed effects, such as a carcinogen, the exposure history should trace exposures back twenty years or more. Occupational disease can occur in retired people; in workers, it can be caused by previous employment.

Risk assessment, Step 4: Risk characterization

Risk characterization describes the likelihood that a hazard will affect a specific person or population; it also estimates the size or severity of the effect. In this step, the information obtained during the previous steps is summarized and collated. The epidemiological triad (see Chapter 2, Figure 2.8) can be used to assemble the information on what the hazard is, where it comes from, how the environment allows it to come into contact with the host, and the host’s susceptibility to the hazard in order to arrive at a conclusion on who is at what level of risk. Table 10.4 illustrates what needs to be considered in this step.

Table 10.4: Examples of various host, agent, and environmental risk factors for selected categories of health problems

Following the risk assessment process, risk management should be considered. The risks for an individual and for a population should be balanced against the costs and risks of intervening. In individuals it might be a choice between the risk of asthma and the loss of a beloved pet or, if the risk is work-related, it could be a choice between staying healthy or staying employed. For the population as a whole, risk management includes a balanced look at all of the benefits and harms associated with a given hazard. Some benefits of the presence/use of the hazard, assuming it is appropriately controlled, may include consumer products that are essential and employment for those who are part of production, while the risks may include adverse health effects in workers and for those in the community who may be inadvertently exposed to that given hazard due to a failure of controls

Occupational Hazards

Most people spend a substantial part of their life at work, and encounter a variety of hazards depending on the work that they do, often over a period of years. In some occupations, specific hazardous agents must be used, putting workers at risk of occupational diseases associated with them. In taking an exposure history, physicians could use a mnemonic such as WHACS.¹⁸  Ask four simple questions:

• “What sort of work do you do?”
• “How do you do it?”
• “Are you concerned about any of your exposures on or off the job?”
• “Co-workers or others exposed?”
• “Satisfied with your job?”

Common, non-specific work-related diseases include dermatitis, asthma, and musculoskeletal disorders. It is also accepted that mental health can be influenced by excessive work demands, lack of decision latitude, concerns with lack of support, workplace harassment and workplace violence among other things.

Table 10.5: Some examples of occupational disease

Injuries do not occur randomly; groups at particular risk of occupational injury include:

• • New and young workers lacking in work experience or safety training—particularly those in temporary or summer jobs;

• • Workers obliged to work long hours at a fast pace. This could include piece-workers or those working on production lines;

• • Workers given work responsibility without the authority or control necessary to meet that responsibility; and

• • Workers in certain high-risk industries such as construction and forestry.

According to Canadian federal and provincial laws, specific services must be provided for the protection of workers (see Chapter 12, Occupational Health Services) and for compensating those who are harmed as a result of work.

Risk Management

Derived from energy engineering, the Source-Path-Receiver model outlines approaches to controlling risks. The source refers to the equipment or process that is directly responsible for a hazard. The hazard could be a form of energy (acoustic, thermal, etc.), or it could be a substance such as toxic fumes or dusts. The path is the conveying medium (air, water, etc.), while the receiver is the human being, the worker. Strategies to reduce risk can target the source of the hazard, the path, or the receiver, whether the risk involves a person or a population.

.

As complete elimination of risk is generally not possible, risk management aims to reduce the risk from a hazard without causing another problem. The ‘Hierarchy of Controls’ lists approaches from the most effective to the least, generally working from the source toward the receiver. The most effective approach is Elimination, followed by Substitution, then Engineering controls, Administrative or legislative controls and, finally, Personal Protective Equipment.¹⁹

Upstream strategies aimed at the source are especially relevant for climate change; examples include education on how to reduce one’s carbon footprint, green energy production, or regulations to decrease industrial greenhouse gas emissions. Other strategies aimed at the source can modify or substitute the hazard (for example, replacing asbestos with other materials). Engineering strategies include enclosing the source if it cannot be removed.

Modifications to the path include environmental changes: closing windows to prevent smog from entering the home, or using bed nets to prevent transmission of malaria. Community level interventions may include cooling centres during extreme heat events or climate resilient building codes.

Strategies aimed at the receiver alter individual (or population) susceptibility to the risks of hazards. Examples include immunization against infectious disease, improving the nutritional status of disadvantaged children, and counselling for behaviour change. Personal safety equipment is mandated in many occupations.

Haddon’s matrix and injury prevention

Dr. William Haddon combined the epidemiological triad (see Chapter 2, Figure 2.8) with a time dimension to create Haddon’s matrix, which sets out the factors that determine the level of risk associated with a hazard and the severity of its effects, in order to identify modifiable risk factors for injury.²² It is commonly applied to the analysis of road traffic collisions, as illustrated in Table 10.6. In this example the host is the person injured (driver or other), while the agent is the equipment that determines how much energy (mechanical or thermal) is transmitted to the host. The environment refers to the physical and social environments in which the injury occurs. The time axis distinguishes factors that operate before the injury (e.g., recent snow that made the road slippery) from those that operate at the moment of injury (e.g., the driver was wearing a seat belt). Other factors operate following the collision (e.g., bystanders knew CPR).

Table 10.6: Illustration of Haddon’s matrix applied to a motor vehicle collision

The matrix is now being used in other situations, including the assessment of medical errors. The matrix has the advantage of giving the full picture of the problem instead of focussing blame on individuals; it leads to a more constructive consideration of ways to reduce this type of error. Table 10.7 illustrates a situation in which potassium was used instead of saline for dissolving a drug that was then administered intravenously, causing severe cardiac arrhythmia, leading to the collapse of the patient.

Table 10.7: Illustration of Haddon’s matrix applied to an incident of erroneous intravenous administration of potassium

 As a way to enhance patient safety, completing the matrix identifies hazards as well as protective factors. The protective factors, such as nurses monitoring patients while they administer injections, calling promptly for help, and quick response of the cardiac team should be reinforced, while the risk factors—storage and packaging of solutions, poor lighting, inadequate supervision, and harassment by other team members—can be rectified. (To prevent this type of mistake, most hospitals do not store potassium on the ward.)

Active versus passive interventions

Interventions to reduce risks are categorised according to the participation required of the person at risk. Active interventions rely on continued compliance by the person at risk, whereas passive interventions are applied once only, or else their effects last for some time. In general, passive interventions are more effective because people do not have to remember to use them. For instance, administration of influenza vaccine (passive) confers immunity for the whole influenza season, whereas hand-washing (active) must be repeated several times a day. An airbag (passive), once installed in a car, stays there until it is needed, whereas seat belts (active) must be put on every time. Even in well-managed workplaces, people’s compliance with the use of personal safety equipment can be poor. For example, ear protectors can be hot and uncomfortable, and may mask auditory danger signals, so that reducing environmental noise levels is preferable, where possible. Safety harnesses can impede mobility, but in some situations they can be replaced by guard rails or safety cages.

Risk Communication

Once a risk has been identified and quantified and methods of reducing it have been found, the information has to be communicated to people at risk to allow them to understand their risk and take steps to mitigate it. Good communication exchanges information in a way that the recipient understands what the sender intends. A useful model of interpersonal communication is shown in Figure 10.4. It distinguishes six elements in the communication process: the message, the messenger, the encoding, the channel, the decoding, and the recipient.

The message

How risk is perceived depends on factors beyond the simple statistical level of risk; perception varies according to the nature of the hazard (the exposure) and according to its possible effects (the outcome). Factors that increase the perception of danger are listed in Table 10.8.

• Involuntary
• Not under personal control
• Unnatural (e.g., terrorist attack)
• Unfamiliar
• Mismatch between risk and benefit (people who suffer the consequences experience no gain from the activity)
• No trust in the institutions involved
• Media attention

• Catastrophic (instead of chronic)
• Affects children or future generations
• Unknown or uncertain outcome
• Affects identifiable people, not statistics
• Dreaded outcomes (e.g., cancer)
• Immediate (vs. delayed)
• Irreversible
• Media attention.

These characteristics can transform a statistically minor risk into a major perceived risk. For example, in the U.S., the risk of death per mile travelled in a car is about 10 times the risk of death per mile travelled in a commercial airplane. Despite this, people overestimate the risk of death from an airplane crash (confusing case fatality with overall risk). News of an airplane crash is widely publicized, whereas car crashes are much less newsworthy. From Table 10.8, the difference in reaction reflects the unfamiliarity of the event and the fact that it is beyond the traveller’s control, and the death toll from an airline crash is generally in the hundreds. By contrast, road traffic fatalities are frequent, under the control of road users, and each only affects a few people. The table also offers some insight into why some people may be concerned about small environmental risks and yet underestimate the risk of behaviours such as smoking. Similarly, one may consider items from Table 10.8 to discuss why the risks of climate change may be underestimated.

Finally, the message may be obscured by indirect language and resulting uncertainty. Clinicians should be as precise as possible when giving information:

• Words can be ambiguous and their meaning can vary: terms such as high or low risk are unclear. Clinicians should make certain that their patients understand the precise meaning of the possible outcome and the course of action suggested.
• However, if numbers are used instead of words, be aware of potential misunderstandings. Expressing a risk should always include a time frame. A 10% chance of death from a lung cancer over a lifetime is not the same as a 10% chance in the next five years. A 20% chance of loss of function could be interpreted as a 20% reduction in function, or that 20% of people will have complete loss of function, or that 20% of people will have some loss of function.
• Furthermore, be aware of the biases inherent in a positive versus a negative framing of statistics (see the next section).

Framing the message

In relation to communication and decision-making, framing refers to the way in which information on risk is presented. Crucially, minor variations in the way options are presented can have a major impact on a person’s choice.²⁵

Emphasis on gain versus loss

People tend to be averse to loss and will do more to avert a perceived loss than they will to achieve a gain: see the Nerd’s corner.

The default option

The option that is presented as the usual choice is more likely to be chosen than one presented as the alternative.

Numbers versus proportions

Data expressed as proportions tend to be seen as relatively benign, whereas data expressed as a frequency tend to engage people much more. (This is the relative versus absolute presentation mentioned in Chapter 2).

The messenger

People respond more to the attitude of the messenger than to their status as a professional or authority. People tend to disregard information given by a recognized expert if they show a lack of caring or empathy (Figure 10.5). Therefore, to get a message across to a patient, a clinician needs to show a caring attitude rather than trying to impress with science.

The recipient

The recipient is an active participant in communication. The recipient’s prior knowledge, beliefs, attitudes and experience affect their understanding of the message (see Nerd’s corner People and their perceptions). When communicating with patients, a clinician needs to assess the patient’s state and adapt the message accordingly.

The channel

The usual channel for clinical communication is the spoken word: clinician and patient talk to each other. However, words can be supplemented with visual aids, such as posters, leaflets, and, occasionally, videos. The recipient must have access to the channel of communication: written materials may not reach people who have difficulty reading.

Encoding and decoding

Information must be coded before it can be passed on. For communication to be successful, the messenger and the recipient must share a common understanding of the code. Even though a clinician speaks the same language as the patient, differences in socio-economic milieu, education and experience can limit their shared understanding of terms. When a physician discusses an appendectomy with a patient, the physician is talking about a routine procedure that the patient is likely to recover from in a few days. The patient, on the other hand, is hearing about an alarming and unique experience that is likely to be painful, will leave a permanent scar, and will disrupt life for, at the very least, several days.

When communicating with their patients, clinicians should:

• Use words and concepts that their patients can understand;
• Speak directly: say “I recommend that you do this…” rather than “You may consider doing this…”. The former is unambiguous whereas the latter uses ‘mitigation’ or softening of the instruction, perhaps out of politeness. But this is harder for the patient to interpret: is my doctor telling me something important, or is it just a passing comment?
• Remember that clinicians are familiar with medical conditions and procedures, whereas their patients are not and that the patient’s perception is clouded by apprehension;
• Modify their tone and body language to conform to the common code, bearing in mind that gestures may mean different things in different cultures. Some people feel that it is polite to look an interlocutor in the eye, others find it threatening.

Risk information is often presented as numbers or graphs. Most people can grasp the information in these forms, but there are a number of points to remember when using numbers to communicate information:

• People don’t come in halves
  People are more at ease with whole numbers, so fractions and decimal places should be avoided. Few estimates of risk or of therapeutic benefit are so precise that they merit decimals.
• Numerator and denominator
  People tend to focus on the numerator and ignore the denominator. A disease that afflicts ten people in a hundred tends to be seen as less common than one that afflicts a hundred people in a thousand. When discussing a single risk with a patient it can be helpful to express it in several ways: 10%, or one in ten, or ten in a hundred. However, when asking people to compare risks of different outcomes, one should keep the denominator constant. It is difficult for most people to understand the difference between one in five risk of one outcome and a 25% risk of another outcome. They will find it easier if a 20% risk is compared to a 25% one or if a one in five risk is compared with a one in four risk.
• Relative and absolute risk
  Relative risks may be particularly difficult to interpret because people rarely know the context. Although hormone replacement therapy doubles the risk of breast cancer, it causes only eight additional cases of breast cancer in 10,000 woman-years. For an individual woman, doubling the risk does not greatly increase her absolute risk because the baseline risk is so small. But on a population level, a doubling of the risk may be significant. It is advisable to use only absolute risks when communicating with individuals, because proportional changes may often obscure a lack of substantive importance.²⁷ (See Chapter 5 for a discussion of relative and absolute risk).

When discussing risk with a patient, the information should be communicated in different ways, using both positive and negative framing, to help the patient arrive at a fully informed decision.

An effective message contains more than simple information; it also implies what the recipient should do with the information. For example, after discussing the risks and benefits of exercise with a patient, a clinician should conclude by relating this information to the patient’s personal situation and making it clear that the patient should take more exercise.

Self-test Questions

References

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