356A MODULES

A01: Introduction -- part I

A02: Introduction -- part II

A03: Communicable Disease Concepts

A04: Communicable Diseases

A05: Food Safety I

A06: Food Safety II

A07: Pests

A08: Vectorborne Diseases

A09: Pesticides

A10: Solid Wastes

A11: Hazardous Wastes


 

Introduction -- part I

  1. Definitions
  2. Context
  3. Risk
  4. Hypernews

 

 

 

 

 

 


Definitions

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!

 

 


  

A Context for Environmental Health  

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  

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.

 


 

HYPERNEWS 

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 ]
 
  1. 356a by Tom Hatfield, Jan 03, 16:32
  2. 356b by Tom Hatfield, Jan 03, 16:33
  3. 553 by Tom Hatfield, Jan 03, 16:34
  4. 353 by Tom Hatfield, Jan 03, 16:34
  5. 469 by Tom Hatfield, Jan 03, 16:40 <----- click here for 469
 
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469

     Forum: Hatfield's Hypernews 
     Date: Jan 03, 16:33 
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This is for 469 hypernews.

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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)
 
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