How about the "severity"?
OK, here is a scientific statement of risk: "About 1
out of 750 unprotected workers with high exposure to vinyl chloride
develop angioscarcoma (a rare liver cancer)." Although I
was not very specific about what I meant by "unprotected"
and "high," it states the probability and severity
of a harm. (I guessed at the 750, the rest is true.)
The word hazard is a very general
term meaning some unsafe or dangerous, situation or thing. We
use the term "hazard" and its adjective "hazardous"
frequently, but neither are precise and should be avoided in
technical descriptions of "risk."
How about skydiving. Let's say the chances of being hurt while
skydiving are: one minor injury per 500 jumps and one serious
injury or death per 10,000 jumps. Is this a statement of risk?
. Before you click on the little buttons with the "?"
you should try to formulate an answer to the question. Hope
we all agreed about that that. (I made up those numbers too,
but let's assume they are true.) Now would you describe skydiving
as "safe?" Here we may
not agree. Thousands of skydivers pay lots of money to jump out
of airplanes. They admit there is a chance of them getting hurt,
but enjoy the exhilaration of falling thousands of feet, and
feel the risk is well worth it. They describe the sport as "safe."
Do you? (I don't.)
Think about it. We agree on the risks of skydiving,
but do not agree if it is "safe." That is often
the case. Why? The definition of "safe"
is,
Absence of unacceptable risks.
(Or its equivalent, the presence of only acceptable risks.
You can restate that defining "unsafe" similarly.)
So now, when you read or hear that something is "safe,"
you should immediately ask yourself .
Again, safe and unsafe are words we often use, but they are very
subjective.
While we are defining, let us contrast the words "injury" and "disease."
An injury usually occurs at
a definite time and place. Most injuries are caused by a sudden
release of energy. There is a clear cause and effect. A worker
falls down and breaks her arm. The fall happened at a particular
time and place. The fall is a transfer of potential energy, the
height of the body's center of mass over the ground, into kinetic
energy of the falling body.
A disease is ill health.
The time the disease is acquired is often vague. Many diseases
have periods of incubation or latency. There is often a lack
of clear cause and effect.
In the field of industrial health and safety, safety
is the prevention of injuries and industrial
hygiene is the prevention of (workplace caused) disease.
So the term "industrial hazard" might include threats
of injury and/or disease. For example: gasoline is both a safety
hazard (fire) and a health hazard (narcosis, skin irritation,
and perhaps cancer).
Next. Last Slide Learning
goals