1. Environmental Health:
|
"The area of public health that studies how the
environment affects human health."
|
In order to fully appreciate the meaning of environmental health,
we need to examine three terms within the above definition (public
health, environment, and health). We will do that in the definitions
below, but for now, there is a critical relationship we need to
ponder:
environment <----> humans
Certainly the environment effects all organisms, but
environmental health is centrally concerned with the effects on
human health.
3. Public
Health:
A group of disciplines devoted to:
- the prevention of disease
- and the promotion of health
- from the community
perspective.
|
Public Health is an extremely broad collection of professions as
well as disciplines, and it is expanding all the time. Indeed,
environmental health is expanding all the time! However, the above
definition provides us with a philosophical base: the field is
concerned with the prevention of disease and not merely the
treatment of it. Taking what we know about the prevention of disease,
we also promote healthy practices. And finally, we treat much
more than the individual -- we treat the community.
A relatively simple example may help. If a cholera epidemic is
spreading throughout a community, it is not enough (under this
definition) to simply take the victims to a doctor. It's expensive to
rely exclusively on this approach, and some of the victims will die
even when medical treatment is available. However, if we find the
cause of the problem (for example, contaminated water supplies), we
can prevent cholera by promoting healthy practices (for
example, by boiling the water or, better yet, chlorinating the water
supply). As the old saying goes: an ounce of prevention is worth a
pound of cure. Finally, it has to be a community effort to be most
effective -- ultimately it's easier and more effective to chlorinate
the community water supply before it is delivered to the
individual.
4. Health (defined by the World Health Organization in 1948):
|
A state of complete physical, mental, and social
well being and not merely the absence of disease or
infirmity.
|
Under this definition, health is an ideal that is never achieved!
At first, this may sound very negative -- after all, it declares all
humans to be not healthy! But at second glance, this can be an
inspiring definition: it says that we can never take health for
granted. The mere fact that you have no apparent disease or infirmity
is no reason to be complacent. Environmental health professionals are
constantly surveying the environment in search of health risks and
ways to control them.
Another example may help. As of this writing, we have seen limited
follow-ups to the anthrax bioterrorism that followed the 9/11 attacks
on America. Does this mean that we no longer need to be concerned
about anthrax? Hardly. All the experts have said that the anthrax
episodes could happen again, and common sense tells us that we need
to be ever vigilant. I'm not talking about panic or irrational fears,
but about a reasonable and watchful eye over the broad range of risks
in our environment. The good news: this is exactly what
environmental health professionals have been doing for over a
century.
5. Environment:
|
The sum of all external conditions and influences in
human's surroundings, which include biological, chemical,
physical, psychological, and sociological hazards.
|
I have a more informal definition of environment:
anything that is not me.
Notice that this includes not only biological, chemical, and
physical hazards (e.g., microbes, toxic chemicals, or radiation), but
also the psychological and sociological hazards. Sometimes it is the
fear that is more important than the risk itself. Make no mistake
about it. environmental helath professionals have to recognize the
psychological and sociological elements of a risk to be effective in
managing it.
6. Epidemiology:
|
The study of the distribution and
determinants of disease.
|
By determinants I mean the "cause" of
a disease. We do this by examing the distribution rates. Some more
important rates are defined below:
- prevalence = # of existing cases (e.g.,
sick people) divided by the total population
- incidence = # of new cases in a time frame
(e.g., a year) divided by the # of people exposed
We will be discussing a wide range of diseases, but for now there
are three terms to define:
- carcinogenesis: to cause cancer
- mutagenesis: to cause genetic disorders
- teratogenesis: to cause birth defects
7. Interaction of
contaminants:
Finally, we need to be aware that exposures do not
normally occur one at a time, but in combinations. We therefore need
to study the interaction of contaminants. Three terms speak to this
issue:
- synergism: two or more contaminants may act to multiply
the health effects to an extent that would not be predicted simply
by adding them together. For example, both asbestos and smoking
are related to lung cancer, but the combination results in a risk
far higher than would be predicted simply by adding them. I like
to simplify this relationship in the following way:
1 + 1 = 3
- potentiation: A normally harmless agent may combine
with a risky agent to magnify the effect. I express this as:
1 + 0 = 2
- antagonism: finally, there are times when two agents
can cancel each other out, and the effect is far less than you
would predict. I express this as:
1 + 1 = 0
The fundamental problem we face is this: among the literally
thousands of agents to which we are potentially exposed, some may
form synergims, some may form antagonisms, and some may combine
with normally harmless agents to have a potentiation effect. To
sort out these relationships is a daunting task!
As you will soon discover, my favorite answer to
questions asked in class is "it depends." For example, "Is this
chemical a health hazard?" Well, it depends on
the exposure. "Can this microbe kill you?" It depends on who it
infects. "How should you protect yourself against radiation
exposures?" It depends on the type of radiation (as well as many
other variables!).
If you've already studied statistics, you'll
recognize each of these answers as dependent variables (hence the
phrase "it depends"). To put it more simply, consider the context of
each problem . Amateurs may happily accept simple answers, but
professionals must dig for a deeper understanding. To do this, I
suggest three major models for analyzing our environmental health
issues.
1. Exposure - effect - control
This first context is really just a
restatement of environmental health.
First, we study environmental issues primarily through human exposures.
Second, we study health issues as the major effect of concern.
Third, we differ from various scientific disciplines because we prescribe controls to help solve problems.
This model will help sort out your questions
in chronological order . For example, I generally start each section
by discussing the movement of agents through the environment. Be
patient with your questions about health effects or environmental
controls! We must first understand the sources of our environmental
agents before we can address their health effects or specific
controls.
2. Multi-media models
According to an EPA study in Philadelphia
(some years ago), where was the largest single source of their air
pollution? (Hint: it's not cars, because in this study they
considered each car to be a single source). Give up? Their largest
single source was a wastewater treatment plant! It turns out that it
produced much more than a bad smell! This is a simple example of how
treating one pollution (wastewater) leads to another form of
pollution (air pollution). But why stop there? All of our environment
is inter-linked! Can treatment processes chase pollution in
circles?
Consider the three major phases in nature:
solid, liquid, and gas
water-air: this is represented by the Philadelphia study mentioned earlier. Further examples include:
air-water: acid rain (rain cleans the air but can damage the rest of the environment).
water-solid: sludge refers to the solids left over after wastewater treatment.
solid-water: if we place solid waste into landfills, they may end up leaking into groundwater supplies.
air-solid: various filters can remove particulates from air pollution, but the collected residue may be a nasty solid waste.
solid-air: incinerators can dispose of solid wastes but may create air pollution.
In each case, good intentions for resolving
one problem result in creation of another problem. So, what's the
real problem? It is the nature of humans to be caught in vicious
cycles , and the only way to break from these cycles is to see a
larger picture. In this case, the larger picture is the multi-media
nature of environmental problems.
This leads me to a warning. This class
focuses on separate media of the environment (e.g., air and water).
We must use these conceptual building blocks to introduce various
terms in our profession. However, our true challenge is to go beyond
that.
3. Who, what, when, where, how,
why
Environmental health involves the work of a
detective. We must constantly make diagnoses of environmental
problems and prescribe solutions. The key questions, which we call
interrogatives , are the same for any detective: who, what, when,
where, how, and why.
Who? Who
are the high risk groups? For example, are they the elderly, or
newborns? Who can help us solve the problem? For example, do we need
a lawyer? Teamwork is essential to every environmental health
professional, and the development of a network of professionals is an
important aspect addressed by this interrogative.
Also, the context of environmental health
depends on the participants. Journalists look for the more
sensational elements of a story, but they ask the same
interrogatives. Attorneys, of course, take a more legalistic tone,
but they too use the same interrogatives. Rock musicians, movie and
television actors, and other public figures may also gain attention
by asking these interrogatives, although what may be most notable are
the questions that they don't ask. All play an important role in
environmental issues, and risk communication helps us in addressing
these different groups.
What? What's the problem? What's the solution? Risk
assessment helps answer these questions, because the real root of
most environmental problems is usually an underlying risk. Risk
assessment also addresses questions of when and where.
When?
When is this a problem? By understanding the timing of an
environmental problem, we can prescribe preventive action. Life cycle
analysis examines the consequences of a product throughout its
lifetime and is especially helpful in analyzing this part of the
problem. Acute problems with a short lifetime are sometimes more
dramatic and easier to understand, but chronic problems dominate our
societies and are more demanding for life cycle analysis.
Where?
Where is this a problem? Our previous discussion that considered a
multi-media perspective is a perfect example of this question.
Furthermore, we can ask "what is the spatial scope of environmental
evaluation?" For example, is it indoors only? If it includes
outdoors, is it regional or global in scope?
How? How
should we analyze this problem? Our choice among analytic methods has
a huge influence on the solutions we prescribe. For example, if a
citizen complains about water quality, is it a chemical question or
is it a psychological question? A psychologist might analyze the
fears and concerns of this citizen, while a chemist would examine
water content. Which approach is right? Well, it depends. If that
citizen is a paranoid schizophrenic complaining of marijuana
contaminating her drinking water supply, then most would agree this
is a psychological problem. (It's hard to believe, but yes, such a
complaint really happened to me some years ago!). However, if
remnants of a documented gasoline spill were making their way towards
a known groundwater supply, then a background in chemistry is
essential. (Yes, this too is another one of my true stories). The
multi-disciplinary nature of environmental health constantly
challenges us with which method is most appropriate. I gave you some
easy examples, but we will soon see that this question is
formidable.
Why? In
enforcement activities, why do we require a given action? The answer
is usually that it's the law! But how do we examine laws? Risk
management offers us insights into this question. What is our
ultimate professional purpose: do we save lives, money, or energy, or
do simply save face? Environmental health professionals would most
likely answer that our purpose is to save lives. An economist would
answer money, and a physicist would answer energy (and make a
powerful argument with the laws of thermodynamics and environmental
sustainability). But politicians, long known for saving face, would
usually have final word in the form of law. All of these answers play
a role.
Risk analysis is a broad term
that represents a collection of approaches and disciplines devoted to
all aspects of risk issues. At a minimum, risk analysis includes 1)
risk assessment, 2) risk
communication, and 3)
risk management (all defined below).
Risk assessment is the characterization of adverse effects from
exposure to hazards. Probably the simplest example of this
characterization is to say "the risk of cancer from a lifetime of
exposure to "chemical X" is greater than one out of a million." More
formally, risk assessment includes four steps defined below:
hazard identification, dose response
assessent, exposure assessment,
and risk
characterization.
Hazard
identification is to determine
whether a particular agent is causally linked to particular health
effects. For example, does this chemical cause cancer?
Dose-Response Assessment is to determine the relationship between the
magnitude of exposure and the probability of occurrence of health
effects in question. For example, one ounce of "chemical X" will kill
50% of laboratory mice.
Exposure Assessment is to determine the extent of human exposure (this
is especially useful both before or after the application of
regulatory controls). For example, after the Clean Air Act revisions
have been put into place, the exposure to the average citizen to
"chemical X" is 50% of the allowable standard.
Risk characterization is to describe the nature and often the magnitude of
human risk, including attendant uncertainty. For example, "chemical
X" may cause cancer deaths in anywhere from 3 to100 people in Los
Angeles over the next 20 years.
Risk communication is an interactive
exchange of information and opinions
among individuals, groups, and institutions regarding risk.
Risk management is the evaluation, selection, and implementation of
alternative risk control actions.
This section simulates what the hypernews pages will look like.
The critical areas (i.e., where to double-click the mouse) are generally in
bold and larger font. My own instructions are added in red font.
1. On any of my course web pages, select "Hypernews,"
and then select the appropriate course.
For example, if
you were taking my risk class (H.S. 469), you would click on
"Hypernews" and
get the following
screen:
- This site is
used for various activities within
Hypernews.
-
- Messages [
Display
All ] [
Outline
All ]
-
- 356a
by Tom Hatfield, Jan 03, 16:32
- 356b
by Tom Hatfield, Jan 03, 16:33
- 553
by Tom Hatfield, Jan 03, 16:34
- 353
by Tom Hatfield, Jan 03, 16:34
- 469 by Tom
Hatfield, Jan 03, 16:40
<-----
click here for 469
-
- [ Add Message ]
to: "Hatfield's Hypernews"
- [Members] [Admin
Mode] [Show Frames] [Help for HyperNews at
hyper.vcsun.org (group:/thatfield)1.10 ]
|
2. We continue with the 469 site as an example. If you wanted to add a message to this site, you would
click on "Add Message" as indicated below:
469
Forum: Hatfield's Hypernews
Date: Jan 03, 16:33
From: Tom Hatfield <vchsc006@csun.edu>
|
This is for 469
hypernews.
|
[ Next-in-Thread ] [ Next Message ]
Messages [ Display All ] [ Outline All
]
1. For test messages, click here. by Tom Hatfield, Jan 22, 19:55 <----- (click here to enter
2. Click here for general questions. by Tom Hatfield, Jan 22, 19:57 the subsections)
[Add Message] to: "469" <------------------------------------ (click here to "Add message"
to this section)
[Members] [Admin Mode] [Show Frames] [Help for HyperNews at hyper.vcsun.org (group: /thatfield) 1.10 ]
|
3. Enter the appropriate information only where indicated below with red arrows,
Be sure to skip all the other entries. Also, be sure to enter your name!
Hypernews may describe it as "optional," but it is essential if you wish
to receive credit for your assignments in my classes!
Edit Message
You are adding a Message to: "Module 7A" Your
message should be related to the subject named above. If it is
not, please do not add your message here.
Instead, first find the appropriate page and add your message
there. If you just want to test this system, please do it on the
Test Forum. If you are a frequent contributor to forums at this
site, you should become a member. If you are unfamiliar with
HyperNews at hyper.vcsun.org (group: /thatfield), please see the
instructions for details.
From (User ID or Email address, if you are a
member of HyperNews at hyper.vcsun.org (group: /thatfield)):
Password at HyperNews at hyper.vcsun.org (group:
/thatfield):
If you are not a member of HyperNews at hyper.vcsun.org
(group: /thatfield), please enter the following instead.
Email Address (required if you want to be
notified):
<----- click
here and type in information
Your name (optional):
<----- click
here and type in information
Title (describe your message, no HTML tags
allowed):
<----- click
here and type in information
Choose a format for your message:
- Word Processor: Wrap long
lines, break lines at hard Returns, preserve leading blanks and
tabs, and use a fixed-width font. URLs and email addresses will
be made into links.
- Smart Text: Format paragraphs
separated by blank lines. If you begin any lines with spaces or
tabs, the whole paragraph will not be formatted. Lines
beginning with a common prefix (for instance, ">")
are also unformatted. URLs and email addresses will be made
into links.
-
- Enter your message here:
<----- click in box and type in message
<----- click here when you're done
Please preview your message before posting. The preview page
shows your message the way it will appear to readers. You may
post your message from the preview page or return to this page
to edit it (use your browser Back button to get back
here), then preview again and send. To cancel your message,
just don't submit it.
4. If you're satisfied with the preview of your message,
post it by clicking as indicated below.
-
-
5. You can now see your posted message. If you return to the previous hypernews
pages, be sure to "reload" so that your addition will be seen.
Your title
should be here
- Forum:
469
Re: Chapter 7 (Tom Hatfield)
Re: Module 7A (Tom Hatfield)
Date: Sep 28, 09:58
From: <Anonymous>
|
Your
message should be here.
|
|