Introduction
 
Objective: to provide definitions that are 
                   the foundation to the the practice of environmental health. 
               

1. Environmental Health:

"The area of public health that studies how the environment affects human health."

In order to fully appreciate this definition, it is not enough to look at it in isolation! There are three terms within the above definition (public health, environment, and health) that need further definition. 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 take this approach, and some of the victims will die even when medical treatment is available. 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). 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 not seen any 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 ("sick people") divided by the total population
• incidence: # of new cases in a time frame dvided 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!