H.S. 356B:
Modules
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A. Introduction |
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B. Air Quality |
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D. Wastewater |
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E. Radiation |
Objective: to familiarize yourself with the format of this web course page. This will be necessary to prepare for the environmental health content in the subsequent units.
Check out the following resources for the class:
1. Overview summarizes the course syllabus (for a complete copy, buy the course manual at the CSUN bookstore).
2. Calendar provides dates for tests and activities.
3. Library Resources are various tools available at the CSUN library.
4. Web Resources are web sites related to environmental health.
5. Web search services helps find even more information on the World Wide Web.
6. Listserv may be used for group discussions.
7. Self-assessed tests are sample exams.
8. You can also submit questions or comments to the class discussion list (link to your listserv address) or the instructor at vchsc006@csun.edu.
2:
A Context for Environmental
Health 
Objective: to set a context for my environmental health core lectures. Of course, it can help prepare you for my exams, but it may also help prepare you for future work as an environmental or occupational health professional.
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: wastewater sludge is the solids left over after treatment.
solid-water: if we place solid waste into landfills, all too often
they 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 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.
Objective: to provide a model for analyzing the various risks
associated with environmental health.
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 (defined below).
Risk assessment is the characterization of adverse effects
from exposure to hazards. This includes four steps defined
below: hazard identification, dose response assessment, exposure
assessment, and risk characterization.
Hazard identification is to determine whether a particular
agent is causally linked to particular health effects.
Dose-Response Assessment is to determine the relation
between the magnitude of exposure and the probability
of occurrence of health effects in question.
Exposure Assessment is to determine the extent of human
exposure (this is especially useful both before or after the
application of regulatory controls).
Risk characterization is to describe the nature and often
the magnitude of human risk, including attendant uncertainty.
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.
Assignment: consider a current issue using this model.
Send comments to: entire class
instructor only
1: SOURCES OF PRIMARY AIR POLLUTANTS
Objective: to describe the natural as well as human sources of pollution life cycles.
1. Sulfur oxides:
Also known as SOx, its natural sources include volcanoes,
oceans, and general microbial degradation. Human sources are
primarily from combustion of fuels containing sulfur.
We often refer to crude oils as sweet and sour (sour crude is
high in sulfur, while sweet crude is low).
2. Particulates:
Also known as solid and liquid aerosols, particulates are the
various non-gaseous pollutants in air. Natural sources include
volcanoes, oceans (sea salt), general erosion processes, and
fires. Human sources are primarily from fuel combustion .
3. Carbon monoxide (CO):
CO is colorless, odorless, and tasteless. Due to these
characteristics, CO can be undetected even at dangerous levels.
Natural sources of CO are primarily from the oceans -- mostly
from the partial oxidation of chlorophylls and methane. Human
sources of CO are from incomplete combustion of fuels (from both
motor vehicles and industrial processes). Carbon monoxide is
usually, by mass, the largest of the criteria pollutants.
4. Hydrocarbons:
Hydrocarbons are in various combustible fuels. Natural sources
include bacterial decomposition, and emissions from plants and
animals. Human sources are primarily from the oil industry
(from incomplete combustion as well as evaporation). Since it is
a category (rather than a specific chemical), the source of
hydrocarbons depends on the type of hydrocarbon.
5. Nitrogen Oxides:
Also known as NOx, natural emissions of NOx are mostly from
microbial action. Human sources are from virtually any
combustion process. The heat of combustion combines nitrogen and
oxygen (both naturally present in air) by the following equation:
N2 + xO2 ---> NOx
(NOx is primarily in the form of NO).
6. Lead:
Lead comes from a wide variety of natural and human sources.
Since the development of unleaded gasoline, combustion emissions
of lead have dropped dramatically. Nevertheless, total lead
sources continue to be a major concern.
Send comments to: entire class
instructor only
2: HEALTH EFFECTS FROM AIR
POLLUTANTS 
Objective: to consider the basic evidence in evaluating health effects. Such methods are
discussed in greater detail in other classes (e.g., air pollution, toxicology, and risk analysis).
1. Acute episodes:
Occupational exposures , often at much higher concentrations
than community levels, can provide evidence of health effects.
One major problem is extrapolating this evidence from a
population of relatively healthy workers to a general
population that includes the very young, the very old, and the
very sick. These special populations are usually not found
in a worker population, yet they are much more vulnerable.
Acute community episodes are another sub-category. The most
notorious examples of acute community episodes include London,
Donora PA., and the Meuse Valley in Belgium (for a more
complete list, see Salvato, p. 769). In each of these
episodes, sudden and severe changes in pollution (usually from
inversions) were followed by sudden and severe changes in
mortality rates. These episodes tell us a great deal about
higher concentrations, but the challenge is to extrapolate
what this means at lower concentrations and chronic exposures.
2. Toxicological studies:
In the previous category, we typically start with an increase
in health effects and try to associate that with the higher
community concentrations. In this category, by contrast, we
can start with well defined exposures (e.g., concentrations of
recognized toxics in the air), and then test animals for dose
response relationships. Ultimately, we want to extrapolate
what this means to humans.
There are various problems with toxicological studies that are
best left for other courses to discuss. However, some obvious
issues include:
1) the differences between humans and other animals, and
2) most air pollution is chronic (i.e., low concentrations)
and mixed (not just one pollutant but many, and they may have
synergistic interactions).
More subtle is the issue that most test animals are quite
homogeneous, while humans are far more heterogeneous.
Therefore, it can be difficult to translate what animal
evidence means to the most sensitive humans.
3. Chronic studies
Much of these principles are covered in your studies of
epidemiology and statistics. We generally start with effects
and look for relationships with chronic exposures (e.g., in
epidemiology, this could be a retrospective study).
A statistical approach can use regression analysis to
establish associations between tiny increases in exposures and
tiny increases in effects. Because the increases and their
relationships are not readily apparent, we need the tools of
statistics to test these associations.
These studies can be very powerful and useful, but they have
their own set of limitations. For example, they are more
expensive to conduct, they take more time to establish
definitive evidence, and they are subject to many confounding
variables that are the focus of epidemiological study.
What have these studies told us? To summarize, tiny
increases in pollution are associated with:
1) increased incidence of colds and sore throats; and
2) increased mortality, especially in sensitive persons
(e.g., "COPD" stands for Chronic Obstructive Pulmonary
Diseases, which include asthma, bronchitis, emphysema, and
lung cancer.)
The most important principle in using these three areas of
evidence is that they can be used to corroborate each other. For
example, if independent toxicological and epidemiological studies
both suggest health effects, we have much greater confidence in
our conclusions than if we relied on only one approach to
evidence. Also, the weaknesses of one approach may be assisted
by the strengths of another approach.
Review Questions
1. Contrast the 3 categories of evidence of health effects.
2. Describe 2 sub-categories of evidence from acute episodes.
3. Discuss 2 problems with animal toxicological studies.
4. Name 2 effects associated with small increases in air pollution.
5. Why do we need more than one category of evidence in studying
health effects?
Send comments to: entire class
instructor only
3: CONTROLS OF AIR POLLUTANTS 
Objective: to analyze natural and manmade controls of air pollution.
Natural Controls
Just as we considered natural sources of pollution, we should
also consider natural sinks :
1. rain washes out pollutants;
2. gravity settles out particulates; and
3. wind can disperse pollutants.
On the other hand, these very same forces can act to accumulate
pollutants:
1. rain can become acid rain;
2. gravity can increase exposures at ground level; and
3. wind can trap pollutants horizontally.
Man-made controls
When natural controls are insufficient, manmade controls are
needed. It's impossible to give a complete list of air
pollution controls within this class, so I offer the following
generic classification. These nine generic alternatives can
be derived from basic systems theory (i.e., input, process, output).
input process output
isolation 1 2 3
treatment 4 5 6
substitution 7 8 9
Using cars as an example, gasoline is the input, engines are the
process, and exhaust is the output. Strategies for reducing air
pollutants are to isolate, treat, or substitute these factors.
Therefore, items 1-9 are defined below with some examples (some
of these examples will be explained in lecture).
1. isolate the input: gas rationing
2. isolate the process: PCV valves
3. isolate the output: national parks
4. treat the input: unleaded gas
5. treat the process: tune-ups
6. treat the output: catalytic converter
7. substitute the input: electric cars
8. substitute the process: bicycling
9. substitute the output: carpooling
Which method is the best? It depends, of course, on costs,
reliability, and other economic/technological factors.
Review :
1. Explain natural controls of air pollution.
2. Use systems theory to analyze indoor air pollution.
4: Gasoline and Engines 
Objective: to explain different components of crude oil, and explain their relationship with octane rating, knocking, and engine compression ratio.
Source
The source of gasoline is petroleum (also known as "crude oil" or
"fossil fuel"). Petroleum is formed over millions of years from
decayed plants and animals. Processing of the crude oil is based on
distillation (generally in huge towers), which separate
components by their volatility (longer chain hydrocarbons tend to
have higher boiling point). These components include (starting with
the lowest boiling point):
1. natural gas 4. aviation gasoline 7. kerosene
2. liquefied gas 5. auto gasoline 8. fuel oil
3. petroleum ether 6. naphtha 9. lubricating oils
Processing :
Among the above components, auto gasoline carries a huge
consumer demand. Therefore, various processing steps can
increase the gasoline yield. For example:
1. Cracking refers to the breaking down of long chains.
2. Polymerization is connecting of smaller chains.
3. Alkylation builds slightly larger chains and helps increase
octane rating (see below).
Output from Engines
Several terms relate gasoline structure to engine performance:
1. Knocking refers to ignition at wrong time. In general, aromatic
hydrocarbons have the best antiknock properties, and straight
chain hydrocarbons are worst. However, knocking may be a
function of many things, and so we rate anti knocking properties
by a measure called octane.
2. Octane is a measure of the tendency to produce knocking.
According to a 0-100 scale, n-heptane has a rating of 0, and
iso-octane has a rating of 100.
3. Within engines, the compression ratio is a critical measure.
By squeezing the air-fuel mixture during combustion, this high
compression increases the efficiency of engines but increases
knocking. In other words, high compression engines needs higher
octane fuels.
In the past, we increased octane by adding tetraethyl lead.
This technique was relatively cheap but ultimately dangerous because
of the health issues surrounding lead. Today, we build octane with such
additives as ethanol and MTBE.
Review :
1. List some of the distillation components of petroleum.
2. How can we increase the gasoline yield from petroleum?
3. Explain knocking, octane, and compression ratio.
Objective: 1. To identify pollutants from gas stoves and space heaters.
2. To identify controls for these indoor air pollution exposures.
1. Gas Stoves
Most American homes rely on gas stoves. By itself, this does not necessarily
translate into an indoor air problem. However, a survey in New York City
found that half the population used gas stoves for supplemental
heating (turning on the stove to warm the house or apartment).
This habit translates into increased exposures.
What kind of exposures? Incomplete combustion releases
hydrocarbons and carbon monoxide. Furthermore, combustion
releases nitrogen oxides. Depending on other conditions,
particulate exposures can be significant, too.
Simple dispersion usually reduces the pollutants within an hour,
but ventilation techniques are critical. In one experiment,
investigators installed a new stove and turned two burners on
full for 35 minutes. With a standard ventilation fan above the
stove, there was no significant problem. However, when the fan
was not turn on, levels reached 2/3 of the federal standards for
carbon monoxide. This is assuming no outdoor air pollution.
The lessons are simple: 1) keep equipment in good repair,
2) do not use it in inappropriate ways, and 3) turn on the fan.
2. Home heating
Most American homes use natural gas for heating. Usually, it is centralized
heating with external venting, and therefore poses no significant indoor air
problem. However, many problems can arise with the use of portable "space
heaters." Improperly vented, they can be significant sources of
carbon monoxide and nitrogen oxides. Kerosene heaters (normally
reserved for outdoor use) can release the same pollutants along with sulfur
oxides.
Even the traditional fireplace can be a significant source. Ever
curl up by the fireplace and, as time passes, start to feel
relaxed and maybe a little sleepy? It could be initial symptoms
of carbon monoxide exposure! If it is followed by a headache,
the evidence is even stronger.
Of course, I am not suggesting we ban fireplaces or all space
heaters. However, simple recognition of sources followed by
common sense application of controls (such as ventilation) can
be our most important tools in controlling indoor air pollution.
6: Hypernews 
Objective: The purpose of this assignment is twofold: 1) to gain experience using the Hypernews format to exchange information as an alternative to the listserv, and 2) to analyze various aspects of air quality.
1. Enter our hypernews site, read the instructions and then enter your comments. 2. If you have any questions or problems, send email to Dr. Hatfield.
Objective:
SOURCES :
The earth contains about 326,000 cubic miles of water. Most of it is in the oceans (about 97%). However, water goes through phase changes (solid, liquid, gas), and its movement is ultimately driven by the sun. For example, the oceans ultimately supply the following 3 sources:
USES :
The U.S. supplies billions of gallons/day in water, but most of it is lost to:
Average U.S. water use has been steadily increasing, although not all of it has been for drinking. Typical uses include:
Average home uses include:
Various fittings can save about 6-12 % in the average home (from toilets, showers, and laundry).
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews Click on the following California sources for more information:
2: The Safe Drinking Water Act
(SDWA)
PRE-SDWA:
The U.S. Public Health Service originally issued standards for drinking water. They developed the primary and secondary standards that were covered in our last lecture.
SDWA:
1974 saw the passage of the Safe Drinking Water Act (SDWA). Several things were fundamentally different about this law:
The primary federal agency that oversees water quality is the Environmental Protection Agency. However, a number of federal agencies are involved with various aspects of water quantity and quality, including:
Progress in adding standards was slow, however, as scientists in 1974 were just beginning to detect many of the synthetic organics that find there way into water.
1986 AMENDMENTS:
Congress gradually became disenchanted with the EPA's progress, which led to the 1986 SDWA Amendments. This law required addition of 83 contaminants by 1989, and required adding 25 contaminants to the list every 3 years thereafter. Examples of new standards from this law include various VOCs in water, and inorganics such as aluminum, nickel, and beryllium. At the same time, the new law designated "best available technologies" for water treatment.
1996 AMENDMENTS:
The 1996 SDWA amendments canceled the schedule of 25 new standards every three years, and in its place set up a mechanism to set standards based on the occurrence and assessed risks of contaminants. The law also authorized $1 billion in federal grants to individual states for upgrading water treatment systems. Research programs were set up for a consortium of American and Mexican Universities (especially for states on the Mexican border), for estrogen screening programs, and for general research.
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews Click on the following for more information on:
Objective: The purpose of this assignment is:
Hard water is water that contains hardness minerals (e.g., calcium, manganese and magnesium) above 1 GPG (grain per gallon). 1 GPG is equal to 17.1 PPM of water hardness as defined by Standard Methods. Hard water is not as efficient or convenient as "soft water" for bathing, washing (dishes, clothes or cars), shaving, and many other uses. For example:
If the hardness is over 3 GPG, softening can usually save enough to pay for the cost and maintenance of a water softener. Water softeners can also remove copper, iron, and other minerals. De-ionization is a more extensive form of water softening that removes anions as well as cations.
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews Click on the following for more information on:
4: Alternatives to
Chlorination
Objective: The purpose of this section is to analyze the alternatives to chlorination for their advantages and disadvantages (relative to traditional chlorination). A "+" means the alternative has a relative advantage over chlorination, and a "-" has a relative disadvantage relative to chlorination.
A. General considerations:
+: All the alternatives will reduce microbes and THM's
-: All the alternatives tend to cost more than chlorination
B. The alternatives:
1. Chloramines:
+: chloramine residual is more stable
-: chloramines need longer contact times
chloramines may add taste and odor
dialysis patients are susceptible
2. Chlorine dioxide (ClO2):
+: ClO2 more effective in disinfection
ClO2 destroys many taste and odor compounds
-: ClO2 must be generated on site
no reliable test for the residual
3. Iodine:
+: Iodine more effective in disinfection
Iodine has little reaction with organics
Iodine safe to transport
Iodine leaves a traceable residual
-: expensive
taste and odor
4. Ozone (O3):
+: Ozone more effective in disinfection
Ozone destroys many taste and odor compounds
-: Ozone must be generated on site
Ozone has no residual protection
5. U.V.:
+: no added taste or odor
-: interference by turbidity
viruses are especially resistant
no residual protection
6. Heat:
+: good for emergencies, no taste or odor added
-: impractical for large scale
no residual protection
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews
5: California Swimming
Pools Standards 
Objective: The purpose of this assignment is understand some of the minimum legal requirements for public pools in California for:
Disinfection
1. Free chlorine residual: at least 1 ppm is required. This is to be achieved by automatic hypochlorinators (units which provide for continuous chlorination) that are listed by NSF (the National Sanitation Foundation).
2. pH: must be between 7.2 to 8.0. If necessary, soda ash can be added to raise the pH. More typically, the pH naturally rises from the use of hypochlorites.
3. Other disinfectants: others may be used, provided that they are registered with the EPA for disinfectant use, and that they provide a protective residual.
Clarification
4. Turbidity: the drain must be visible (this is, of course, the deepest point)
5. Filters: filtration units are similar in concept to units discussed for water treatment (e.g., diatomaceous earth filters)
6. Turnover time: this is the time it takes for a unit to filter the complete volume of a pool. The minimum legal standard in California is once every 6 hours for pools, and once every 1/2 hour for spas.
Safety
7. Lifesaving equipment: life rings must be at least 17 inches in diameter, with a line (rope) that is long enough to span the maximum width of the pool. Rescue poles (long poles with body hooks) must be at least 12 feet long.
8. Posted signs: if there is no lifeguard, a sign must be posted stating "Warning -- No Lifeguard On Duty."
9. Access: access to the pool must be limited by fencing (at least 4 ft. high) with gates that must be self closing and self latching.
Other
10. Records: there must be daily records of maintainence (including chlorine levels, pH, etc.).
11. Spas, hottubs: high temperatures can be especially risky to the elderly; the powerful suction at the bottom of spas can also, in some cases be, risky. Numerous agents can be a risk in spas, including Pseudomonas aeruginosa (causing rashes), and Naegleria fowleri (causing PAM, or primary amoebic meningoencephalitis).
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews For more information, try: Swimming Pools
Objective: The purpose of this assignment is to analyze soils in terms of the content (elements), horizons, profiles, soil types, and biological components. This section also analysis types of wells.
1. The earth's crust is composed of the following elements (given in the order of average % of soil content):
O2: 46%, Si: 28% (mostly
SiO2),
Al: 8%, Fe: 5%;
Ca, Mg, Na,
and K:
11%;
all
others: about
1.5%
2. Horizons are horizontal layers of different soils. Examples of the different layers include:
Horizon
A: top soil:
zone of maximum bioactivity
Horizon
B: sub soil:
zone of eluviation (washing in)
Horizon
C: parent
material:
Horizon
R:
consolidated bedrock:
3. Profiles refer to different patterns of soil horizons. For example, the topsoil may be very thin or even missing in some soil profiles.
4. Soil types: soils are made of combinations of three different grains:
sand: coarse grained (> .05 mm)
silt: medium grained (.05 - .002 mm)
clay: fine grained (< .002 mm)
Finally, loam is a combination of all the above: 40% silt, 40% sand, 20% clay.
5. Humus refers to the organic material in soil
6. Biological components include such diverse components as:
nematodes, fungi (molds), protozoans, algae, actinomycetes, and various bacteria.
7. Wells fall into at least three basic categories:
dug wells: relatively shallow, hand excavated wells that are easily contaminated (diameter of 3-30 ft.).
driven wells: constructed by driving a steel point into the ground (diameter of 1 to 4 inches).
drilled wells: constructed by using various types of drills. This is generally the safest and most efficient of wells (diameter between 2-48 inches)
Test your knowledge with a: quiz
Send your questions (or read others) to: hypernews For more information, try: Soils and wells
Objective: The purpose of this section is to define:
and to derive an equation to help predict these conditions.
A cross
connection is
any physical connection between wastewater and potable water, with
the potential for backflow. Backflow is any force pushing the wastewater towards potable
water. In other words, a cross connection can result in contamination
of drinking water, and it is a fundamental concern for environmental
health professionals. In order to understand backflow, we start with
an equation that should be familiar to all physics students:
P =
F/A where P =
pressure, F = force, and A = area
Pressure is typically
measured in psi (pounds per square inch) with two
scales:
psi a
(absolute scale) and psi g (gage scale)
Psig is what we see on pressure gauges, and psia is the larger,
absolute pressure in pounds per square inch. This may seem confusing
at first, so consider two examples:
1. If we open a gauge at sea level (which releases the pressure), it may read zero, but we know that gravity is pushing down at about 14.7 pounds per square inch. Thus, psig = 0, but psia = 14.7
2. If a pump sucks all the air from a closed container (i.e., a perfect vacuum), the gauge will start reading negative numbers. Thus, we know that in a perfect vacuum at sea level, psia = 0 (by definition), but the gauge will read psig = -14.7 In each example, psig = (psia - 14.7).
Using these units, we can now define backsiphonage as backflow that occurs in a negative psig (i.e., backflow caused by sucking liquids). In contrast, backpressure occurs in a positive psig (i.e., backflow caused by a higher pressure fluid forcing itself against a weaker pressure fluid).
We can study
backsiphonage by deriving an equation for the pressure of a water
column at any height. Consider the pressure for one cubic foot of
water. Since once cubic foot of water weighs 62.4 pounds, and this
cube of water rests on an area that is 1 sq. foot, we can calculate
the psi reading with the equation P = F/A:
P = F/A = 62.4
lbs. / 1 sq. ft. = 62.4 lbs. / 144 sq. in. = .433 psi
Next, for two cubic
feet (one on top of the other), we double the weight resting on the
same square foot:
P = (62.4 lbs.
/ 1 sq. ft.) * 2 = .866 psi
Finally, for any
number of cubic feet:
P = (62.4
lbs/sq. ft.) * H (where H is the height in feet)
To generalize this equation for any water column (Pw):
1) divide 62.4 lbs. by 144 square inches (62.4 / 144 = .433),
2) add any other existing pressure in the system (P), and we then get the general equation: Pw = (.433*H) + P
VARIABLES:
|
P = pressure (psi) |
psig = lbs./square inch (gage) |
|
F = force (lbs.) |
water = 62.4 lbs./cubic ft. |
|
A = area (square inches) |
Pw = pressure in a water column (psi) |
|
psia = lbs./square inch (absolute) |
H = height of water column (in ft.) |
PROBLEMS
1. If a 100' building has 20 psi at the top floor, what is the pressure at the bottom?
|
H = 100' |
|
P = top = 20 psi |
|
Pw = ? |
2. If the pressure drops by 30 psi, what are the new pressures at the top and bottom floor? (hint: the pressure drops by exactly 30 psi throughout the system)
Objective: This section analyzes wastewater in terms of its major sources.
As discussed with drinking water, our knowledge about the sources of wastewater constitutes a major diagnostic tool that helps determine how we manage wastewater. This knowledge, combined with wastewater testing, can give Environmental Health Professionals a major role in this area.
1. Point sources of wastewater are discrete and identifiable sources that are divided into domestic and industrial sources. Domestic sources include residences and small businesses. Compared with industry, these are relatively small sources. As a result, a major issue in this category is the collection of wastewater (i.e., it is a major expense when added up for the entire community). Nationwide, about 80% of domestic wastewater is sent to sewerage systems, and about 20% to private systems (e.g., septic tanks). Industrial sources are relatively large sources that include such sub-categories as the chemical, pharmaceutical, oil, mining, and metal industries. Because of their size, these sources are generally easier to collect, but harder to treat (e.g., their chemical content can vary tremendously). Of course, collection is not always easy: a special sub-category includes the shipping industry, and shipping accidents can occur during transport (e.g., the Exxon Valdez).
2. Non-point sources are diffuse and generally occur from water runoff. Because they are spread over large areas, they tend to be more difficult to control, and in recent years they have gained greater attention from legislators. They are divided into agricultural, urban, and atmospheric sources. Agricultural sources include farms, which can contribute fertilizers, pesticides, soil erosion, and plant and animal wastes to water runoff. Collectively, they usually constitute the largest source of pollutants to water, and the erosion contributions are being worsened by the deforestation occurring in various parts of the world. Urban sources include the storm water systems that collect water from the gutters of streets in towns and cities. The true scope of the problem from urban sources is still not very well understood, but it is clearly a major contributor. Atmospheric sources include air pollution's contribution during precipitation (e.g., acid rain). We do not discuss it in detail here because we have already covered it in a previous section. Nevertheless, it is a classic example of the multi-media role of wastewater pollution.
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Objective: What are the major sources of radiation exposure? It depends on obvious factors such as occupation and area of residence, but it also depends on more subtle factors such as medical history and travel habits. To sort out these factors, the EPA conducted a survey in 1980 and derived average levels in the U.S. for two major categories: natural and artificial sources.
NATURAL SOURCES (also called background levels) sum to about 100 mrems/year. They include the following sub-categories.
1. Terrestrial sources include all land based sources. U.S. community levels range from about 15 to 100 mrem/year. Globally, levels are as high as 2 rems/year (e.g., parts of Brazil). Various materials contribute radiation, including granite, coal (especially in the western U.S.), and clay (brick homes have typically twice the radiation of wood homes). The most serious radiation exposure from terrestrial sources is usually radon, because it is a gas (i.e., inhalation exposure).
2. Cosmic radiation (also called extra-terrestrial sources) originates from deep space, from such sources as our own sun (a minor contribution) and supernovas. Primary cosmic radiation is mostly protons, some electrons, and various atomic fragments. When these sources hit our atmosphere, their impact creates secondary cosmic radiation, composed of mostly gamma rays, electrons, mesons, and neutrinos. Cosmic radiation varies from 40-160 mrem/year depending on three major factors:
1) altitude (e.g., one plane flight cross country can contribute 1 mrem, and Denver has about twice the cosmic radiation of L.A);
2) latitude (cosmic radiation is attracted to our magnetic poles); and
3) air pressure (as pressure increases, cosmic radiation decreases at ground level).
ARTIFICIAL SOURCES sum to about 80 mrem/year on average.
1. Medical procedures are the major source, with a single chest X-ray contributing an average 200 mrem. Dental x-rays are far less than chest x-rays.
2. Nuclear power plants contribute, on average, about 1 mrem/year. However, this is only for residents closest to the facility. Of course, this does not include other concerns such as nuclear accidents and nuclear waste disposal.
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Types of ionizing radiation:
Direct (charged particles)
1. alpha Helium atoms stripped of their electrons
particles: low penetrating power; strong ionizer
2. beta electron particles
particles: moderate penetrating power; moderate ionizer
3. other charged
particles: single protons, charged fragments, etc.
Indirect
4. gamma rays: electromagnetic radiation from nucleus
high penetrating power; weak ionizer
5. X-rays: electromagnetic radiation from electrons
high penetrating power; weak ionizer
6. neutrons: 1 proton, 1 beta particle, 1 neutrino
Units of Measurement
activity (of source): radioactive decay ("disintegrations")
7. Curie: (Ci) rate from one gm of natural radium-226/second
= 37 billion disintegrations/second
8. Becquerel: (Bq) = 1 disintegration/second
exposure: ionization in air
9. Roentgens: (R) = 1 esu/cc of air = 773,400 esu/kg
10. Exposure
unit: 1 coulomb/kg = 3,789 R = 3 billion esu/kg
absorbed dose: energy absorbed
11. RAD: radiation absorbed dose
(100 ergs/gram of absorbing material)
12. Gray: (Gy) = 100 RADS
dose equivalent: biological effect
13. REM: roentgen equivalent man = RADs x RBE
14. RBE: relative biological effectiveness (a ratio)
15. LET: linear energy transfer (energy transferred/unit length)
16. Sievert: (Sv) = 100 REMs
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Objective: To provide a few examples of the positive applications of our
knowledge of radiation.
1. Iodine-131 tracers: "radioactive cocktail"
A. beta radiation
1/2-life = about 8 days
B. used to study thyroid activity and thyroid treatment
(thyroid concentrates iodine)
note: 99.9% eliminated in about 80 days
2. NAA (neutron activation analysis): "atomic fingerprint"
A. bombard sample material with neutrons
B. measure frequency and intensity of resultant gamma radiation
C. used to measure trace quantities of pollutants
(e.g., heavy metals)
3. Americium-241
A. beta radiation
1/2-life = about 400 years
B. on end of lightning rods, increases attraction
C. also used in smoke detectors:
ionizes air between two electrodes (creates current)
smoke interferes with current, thereby activating alarm
risk of cancer is negligible and outweighed by risk of fires
4. Cobalt-60
A. cheapest form of gamma radiation
B. used in cancer treatments, food irradiation
5. Carbon dating (Carbon-14)
A. how carbon-14 is created in air:
cosmic rays include neutrons:
N + N ---> C + H
in air, C-14 is at stable concentration in CO2
exception -- 20th century activities:
atomic bomb testing
increased CO2 levels
B. how Carbon-14 is used to date materials (e.g., paper)
plants take in CO2 (photosynthesis)
when plants are alive, in equilibrium with environment
upon plant death, C-14 undergoes beta decay (e.g., paper)
1/2-life = 5,760 years
carbon dating accurate up to 50,000 years
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1. Non-ionizing electromagnetic energy
radiation: that cannot ionize,
but may cause health effects
Starting with the highest frequencies:
2. Ultraviolet
exposure: sun, industrial equipment, tanning booths (!)
effects: sunburn, skin cancers
fever, nausea
cataracts, retina damage
controls: clothing, sunglasses, suntan lotions
3. Visible light
exposure: normally no risk
eclipse can cause retinal burn
lasers (light amplification by stimulated
emission of radiation)
effects: burn hole in retina (even at low quantities)
controls: various filters, glasses
4. Infrared
exposure: quickly detected
effects: burns, cataracts, retina damage
controls: special clothing and shielding
5. Microwaves
exposure: radar, T.V., radio, microwave ovens
effects: heating (cooked tissue),
interferes with pacemakers,
association w/ cataracts, cancer, birth defects
controls: distance, materials
6. Electromagnetic fields
exposure: power transmission lines
electric blankets, toasters, hair dryers,
T.V., video display terminals, etc.
effects: not proven !
controls: prudent avoidance (?)
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