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t_Articles
Putting activities into perspective
Life is inherently full of risks. We face risks every day whether
it's by crossing the street, eating food or catching a plane. Yet this
shouldn't interfere with everyday activities or prevent someone "taking
on the day." Although most of us are familiar with common hazards such
as driving a car or taking part in high-risk sports, it can often be
difficult to decide which risks to worry about or avoid and which ones
to accept.
One key challenge is getting good science-based information about the
relative risks of different activities, especially when it comes to a
very personal and pleasurable activity -eating and drinking. Public
concern about risks associated with food often exceed concerns for other
health and safety hazards despite government assurances. The public also
tends to misjudge the relative risks from food safety issues, ranking
pesticide residues as posing a much greater threat to human health than
not achieving a healthful diet. Yet nutritionists and public health
educators will tell you that the biggest health risk facing most people
is a lack of exercise coupled with a poor diet. So what are the real
risks from foods and beverages? Although precise estimates of
food-related risks are not yet available, we can think rationally about
food safety and appropriate health-promoting (or risk-reducing)
behaviors. Health professionals, journalists and other communicators can
empower consumers as they sort through the many risks they face by
helping people think more broadly about risk issues and about food
safety risks in the context of other health and safety hazards.
Consistency between public and expert opinion is necessary to ensure
that the greatest public health risks receive adequate attention and
that both science and public values are included in decisions about food
safety. This article helps provide a framework for putting food safety
risks in perspective and discusses various ways in which risk
information is presented. The goal is to help communicators and health
professionals illustrate more clearly the relative risks of food safety
and other public health issues.
Understanding risk
"Most of us have little experience thinking about the size or
magnitude of different risks. Although we have an intuitive sense that
some risks are smaller or larger than others, research shows that people
tend to underestimate relatively large risks, such as heart disease and
heart attacks, and overestimate relatively small risks such as botulism,
a foodborne illness" caused by a bacteria, said George Gray, Deputy
Director for the Center for Risk Analysis at Harvard School of Public
Health. "Public misperceptions may be driven in part by what we hear and
read, but a lack of understanding about risk magnitudes and how to
interpret risk information also influences them," he said.
Judging the size of a risk can be more relevant if the risk is
compared to other, more familiar activities that inherently carry risk.
For example, consider the fact that the annual risk of dying in India
from motor vehicle accidents in 1998 was about 221 in 1 million. This
means that in a total population of one million, 221 are expected to die
from a traffic accident in any given year (keeping in mind it does not
mean that 221 people will die since in reality, greater or fewer people
may die).
Is this a big risk? Table 2 shows that each year, the average risk of
dying from motor vehicle accidents in India is more than 2 times higher
than the risk of drowning. In contrast, this risk is 13 times lower than
the annual risk of dying from coronary heart disease and nearly 10 times
lower than the risk of dying from a parasitic or infectious disease.
Thus, driving a car poses a significant risk when compared to other
public health hazards yet it still trails behind several leading causes
of death.
In China, the risk of dying from cardiovascular disease is also the
greatest risk (2,350 per million) and is one-and-a-half times higher
than the risk of dying from cancer and more than 16 times higher than
the risk of dying in a traffic accident.
Table 1: RISK ANALOGUES
A risk of 1 in 1,000,000 is about equal to:
- the chance of flipping a coin and getting 20
heads in 20 consecutive tries.
- the chance of rolling a dice and getting 7
sixes in 7 consecutive rolls.
- the chance of dying from taking one flight on a regularly
scheduled airliner.
- 30 seconds in a year.
A risk of 1 in 100,000 is about equal to:
- the chance of flipping a coin and getting 16
heads in 16 consecutive tries.
- the chance of rolling a dice and getting 6 sixes in 6 consecutive
rolls.
- the chance of dying from taking 10 flights on regularly scheduled
jet airliners.
- 5 minutes in a year.
A risk of 1 in 10,000 is about equal to;
- the chance of flipping a coin and getting 13
heads in 13 consecutive tries.
- the chance of rolling a dice and getting 5 sixes in 5 consecutive
rolls.
- the chance of dying from taking 100 flights on regularly scheduled
jet airliners.
- 53 minutes in a year.
Table 2: RISK COMPARISONS
Annual risk of dying in India and China per million
persons
| |
India
|
China |
|
Total population (000) |
982,223,000 |
1,255,698,000 |
|
Total deaths (000) |
9,337,000 |
9,296,000 |
| |
Death per M per yr
|
Death per M per yr |
|
Cardiovascular disease
|
2871 |
2350 |
|
Parasitic & infectious
diseases |
2159 |
363 |
|
Cancer |
665 |
1462 |
|
Respiratory infections |
1004 |
263 |
|
Diabetes |
104 |
49 |
|
Nutritional deficiency |
102 |
44 |
|
Accidents (all) |
736 |
526 |
|
Road Traffic Accident |
221 |
143 |
|
Drowning |
94 |
108 |
|
Fire |
137 |
20 |
|
Poisoning |
33 |
54 |
(Based on mortality data in "The World Health Report,
1999 - Making a Difference", WHO, 1999)
Putting risk into perspective
While data on foodborne risks are limited, it is estimated that most
food-related hazards result from harmful bacteria such as E.Coli and
Salmonella. Figures for Asia are difficult to obtain as they tend to be
included with deaths from total unintentional poisonings, which include
chemical and viral contamination of foods. These figures are 33 and 54
deaths per million in India and China respectively.
Data from the United States shows that there is an approximate annual
risk of dying from foodborne illness of 36 in 1 million based on the US
population of 260 million. This is 7 times greater than the risk of
dying from tuberculosis in the US each year and 100 times greater than
the risk of dying from floods. On the other hand, this risk is 78 times
lower than the risk of dying from heart disease, 57 times lower than the
risk of dying from cancer and 4 times lower than the risk of dying from
motor vehicle accidents. Even the mere act of eating food poses an
annual risk of dying from choking of 5 in one million. Of course, the
risk of not eating can also be substantial!
While these comparisons help put the magnitude of risk into
perspective, they do not convey the level of uncertainty associated with
formulating risk estimates or provide information on how the risk of a
specific activity is distributed within a population. For example, the
risk of dying from a motor vehicle accident is known with greater
certainty than the risk of dying from harmful bacteria in food, since
the cause of death is easier to identify (and quantify) when it is a car
accident versus a foodborne illness death. In addition, the elderly are
at much greater risk from cancer or heart disease than are younger
persons, while the reverse is true for automobile accidents. The
acceptability of risk also requires the consideration of other important
factors. For example, driving a car or hang gliding are voluntary
activities that provide many perceived benefits, thereby increasing the
acceptability of these risks for many people.
"Beside thinking about risk in a broader context, it is important to
be aware of the various ways in which risk formation is presented. Risks
can refer to a variety of health outcomes including death, cancer and
non-fatal injuries or illness, and risk rankings may differ depending on
which outcome is used," said Gray. For example, although the risk of
dying from foodborne disease ranks relatively low compared to other
public health hazards, the risk of foodborne illness may rank much
higher where the outcome is not death. Indeed, it is estimated that up
to 81 million cases of foodborne illness occur in the United States each
year. A parallel example is comparing the risk of death from bacteria
with the risk of illness from bacteria. According to Gray, risk
information may also be framed according to different consequences such
as the number of deaths in a population or the estimated loss of life
expectancy (the number of years taken away from a life). Further, risk
estimates may be based on exposures that occur in a given year (annual
risk) or cover the duration of one's lifetime (lifetime risk).
Relative or absolute: a distinction that makes a difference
The distinction between relative risk and absolute risk is also
important. "Relative risk puts risk in comparative terms and indicates
the ratio of risk among individuals who are exposed versus non-exposed
to a particular hazard," explained Gray. Relative risks greater than 1
mean that exposed per-sons are more likely to experience a health effect
than non-exposed persons, while relative risks less than 1 suggest the
exposure has a "protective" effect (for example, consuming fruits and
vegetables has been found to reduce the risk of certain cancers).
Absolute risk refers to the actual risk of an occurrence - the chance
of a specific outcome occurring. For example, suppose that a study shows
that a man who brushes his teeth only once a day is 50 per cent more
likely to lose all of his teeth in the next ten years than others who
brush their teeth twice a day. Yet, the absolute risk of the man losing
all his teeth may only be one per cent. In this case, the relative risk
makes the problem seem more important than it may be in reality. On the
other hand, relative risk can also make a problem seem less important
than it really is so it is best to consider both types. "In practice,
relative risks are more useful for identifying the result of various
health outcomes or behaviours, while absolute risks are better suited
for evaluating the actual impacts of a risk on a specific population,"
said Gray.
Food for thought
Like everything we do, consuming food and beverages poses some degree
of risk. Although everyone is entitled to choose which chances they want
to accept or avoid, personal actions to reduce foodborne and other risks
should be based on informed decision-making and science rather than
allowing reports of outbreaks to lead one to believe the risk is greater
than it is. Certain behaviours, such as eating fewer fruits and
vegetables to avoid potential exposure to pesticides, can also lead to
potential negative consequences such as a reduced intake of essential
vitamins and minerals. "While there is no 'right' answer for how to
judge food safety risks," said Gray, "thinking about food-borne hazards
in the context of other hazards can help shift attention away from the
'wrong' risks and toward those that pose the greatest threats to public
health and safety."
Table 3: WHAT DO WE FEAR?
Research on how people interpret risk has reported some interesting
findings. For example, it has been found that:
- People tend to overestimate the danger of rare events, such as a
plane crash, yet underestimate dangers of more common events like
driving a car. Yet motor vehicle accidents are responsible for far
more deaths every year than plane crashes.
- People tend to assume that if they can control a situation they
are safer. The high number of traffic accident fatalities shows this
is an erroneous assumption.
- People are less likely to fear the risk of an unhealthy lifestyle
than levels of pesticides in foods. Yet the statistics show that
people are far more likely to die from lifestyle-related diseases such
as coronary heart disease and cancers than they are from pesticide
residues.
- People tend to be less likely to fear natural disasters -
typhoons, earthquakes, floods - than man-made disasters.
- People are more worried by dramatic but infrequent events such as
plane crashes than by "boring" risks like slipping on a wet floor.
(H.A Cohl, "Are We Scaring Ourselves to Death?" St Martins Griffin,
1997)
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