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ACTIVIT Y OVERVIEW
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Wash Your Hands, Please!
V EST IGA
SUMMARY
A powder visible under ultraviolet light is used to simulate microbes. Students place
the powder on their hands and then wash their hands as they do normally. After
examining the results of their hand washing, they design a hand-washing experiment
to reduce the number of microbes on their hands. The role of hand washing in reducing disease transmission is discussed.
KEY CONCEPTS AND PROCESS SKILLS
1.
Creating models is one way to understand and communicate scientific
information.
2.
Most infectious diseases are caused by microbes.
3.
The category of “microbes” includes microorganisms, such as bacteria and
protists, and also viruses, which are not considered to be alive.
4. Effective and frequent hand washing can reduce the transmission of many
diseases.
KEY VOCABULARY
hypothesis
microbe
infectious
qualitative/quantitative data
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Activity 48 • Wash Your Hands, Please!
MATERIALS AND ADVANCE PREPARATION
For the class
2
large ultraviolet (UV) lights
Glogerm™ powder
*
16 AA batteries
*
paper towels
*
sponges
*
nail brushes (optional)
*
access to sinks with running water and soap (or tubs of clean, soapy water)
*Not supplied in kit
If possible, arrange to use a classroom with at least 3 sinks. If such a classroom is not
available, set up buckets or tubs of clean water. Place paper towels around the buckets to reduce the spread of water.
Check to see if your classroom can get dark enough for the powder to be visible under
the UV lights. Turning off the lights and/or closing window shades may or may not
be necessary. If your classroom is too bright to clearly see the powder with the UV
lights, consider setting up a cardboard box “station” under which students can check
their hands with the UV light.
Consider the management of the class using only two UV light sources. You may want
to stagger classes with another SALI teacher to increase the number of available UV
light sources.
If you want to use more Glogerm™ powder than is provided in the kit, you can order
it directly from the company at Glogerm™, P.O. Box 537, Moab, UT 84532. Phone:
1-800-842-6622. Fax: 1-435-259-5930. email: [email protected]. website: http://
www.glogerm.com/order.html
TEACHING SUMMARY
Getting Started
1.
Discuss students’ attitudes and beliefs about hand washing.
Doing the Activity
2.
Provide one member of each student pair with powder as students read the
Introduction and Challenge.
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Science and Life Issues
Wash Your Hands, Please! • Activity 48
3.
Students determine how effective normal hand washing is at removing
microbes.
4.
Students design and conduct experiments to improve hand washing.
Follow–Up
5.
Students share their results.
Extension
Students can make a list of recommendations for a school hand-washing campaign.
INTEGRATIONS
Social Studies
The history of personal hygiene and sanitation would make an interesting extension
to this activity. The class could also consider this issue in a global context: In which
countries do most people have access to clean water and sanitation? Which countries
do not have this and why? What are the implications of the lack of sanitation for infectious diseases elsewhere in the world? What is being done to improve world health?
BACKGROUND INFORMATION
Diseases Prevented By Hand Washing
The Centers for Disease Control and Prevention state “Hand washing is the single
most important means of preventing the spread of infection.” Hand washing can prevent the spread of diseases, including:
•
Diseases transmitted by the fecal/oral route. Most cases of “stomach flu” result
from accidentally eating harmful bacteria or viruses. Food poisoning agents
such as E. coli and Listeria bacteria, as well as the microbes that spread
diseases like polio, giardia, typhoid, salmonella, and cholera, are transmitted
by the fecal-oral route—the pathogen is passed out of the gut, gets onto
hands, and can then be passed on to other people. Even minute particles of
fecal material can transmit these microbes. Washing hands after defecation is
very important. Most hygiene campaigns don’t focus on washing hands after
using the bathroom for privacy reasons. Instead, they focus on washing hands
before food preparation or patient contact.
•
Diseases spread by the indirect transmission of droplets and other body fluids. Hand
washing removes “transient” microbes such as flu, strep, and cold viruses
Teacher’s Guide
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Activity 48 • Wash Your Hands, Please!
found in droplets. Because these diseases may be spread indirectly by
hands freshly soiled by respiratory discharges of infected people, illness
may be avoided by washing hands after coughing or sneezing. Hands
contaminated with urine, saliva, or other moist body substances can
spread infections like schistosomiasis, typhoid, Epstein-Barr virus, and
Staphylococcus infections. These germs may be transmitted from person
to person or indirectly by contamination of food or of inanimate objects
such as toys or patient-care supplies.
Sexually transmitted diseases and diseases transmitted by vectors (such as malaria and plague) are not prevented by hand washing.
Hand-Washing Techniques
A large percentage of bacteria on the hands are found under the nails. Others are
found in the sweat and hair pores. Although it takes about 5 minutes of washing
to remove 99% of the transient organisms, studies have shown that 15 seconds
of vigorously rubbing soapy hands together was found to be sufficient for removing most pathogens. When hand-washing compliance was improved in intensive
care units, there was a large reduction in hospital infections. The incidence of
diarrhea in two-day care centers where staff routinely washed hands was half that
observed in two control centers during a 35-week study period.
Antimicrobial soaps do not seem to significantly reduce the amount of transient
bacteria on hands when compared with ordinary soap. Most pathogens are
removed by the wetting action of any soap combined with the physical friction
of rubbing the hands together for at least 15 seconds. Over-use of antimicrobial
soaps may encourage the growth of resistant bacteria. Antimicrobial agents are
recommended in surgical settings where the risk of infection is most extreme.
Alcohol-based hand sanitizers such as Purell™ and Dial™ have been found to
be reasonably effective at killing bacteria and are useful in settings where regular hand washing is inconvenient.
Use of paper towels removes more microbes by friction. Use of a communal
towel tends to re-contaminate hands.
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Science and Life Issues
Wash Your Hands, Please! • Activity 48
Other Methods of Disease Prevention
•
Sanitation and clean water. The quality of the U.S. water supply and the
sanitation infrastructure are usually sufficient to prevent transmission of most
fecal organisms. Water-related disease outbreaks occur occasionally. In other
parts of the world, sanitation and clean water are among the most pressing
public health needs. Diarrheal illness (often transmitted through poor
sanitation) causes millions of deaths each year, particularly to children who
are just weaned. Although hand washing, even with unclean water, has been
found to reduce the rate of diarrheal illnesses, it is secondary to improving
sanitation as a public health measure.
•
Vaccination. Vaccination programs have been extremely effective at reducing
and nearly wiping out diseases such as polio, but not all infections have
preventive vaccines.
•
Use of sterile gloves. Most gloves have microscopic tears in them. For this
reason, surgeons and operating room personnel have found it necessary to
continue to scrub their bare hands.
REFERENCES
Centers for Disease Control and Prevention. “Hand Washing—The Semmelweis
Lesson Forgotten?” report, 1994.
Leavitt, J.W. Typhoid Mary. Boston: Beacon Press, 1996.
Teacher’s Guide
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Wash Your Hands, Please! • Activity 48
TEACHING SUGGESTIONS
GETTING STARTED
1.
Discuss students’ attitudes and beliefs
about hand washing.
3.
Students determine how effective normal
hand washing is at removing microbes.
Show students how to do a two-handed handshake
with their partner, as described in Step 3 of the Procedure. Be sure to demonstrate with a student who
has not been given the powder. Either direct students
Ask, When, how, and why do you wash your hands?
to go to the UV light stations or circulate with the UV
Students can either write and turn in their respons-
lights so students can see where the powder is on
es on paper or discuss the question in small groups
their hands. Instruct students to wash their hands as
before sharing their ideas with the class. Most peo-
they would normally. Be sure to emphasize this
ple will say that they wash their hands better and
point—the goal is not to remove the greatest number
more often than they actually do. Bring out reasons
of “microbes” but to see how effectively a student’s
why people sometimes don’t wash their hands well
normal hand-washing procedure removes microbes.
or don’t bother washing their hands at all.
If necessary, provide students with additional direc-
Have students brainstorm why hand washing is
tions for keeping water spills under control.
important. Students may remember that flu and
Darken the room if necessary, and have students
colds can be transmitted through airborne droplets
complete Part One of the Procedure.
and from droplets on hands and surfaces. Other diseases, such as the plague and HIV/AIDS, cannot be
prevented by hand hygiene.
DOING THE ACTIVIT Y
2.
Discuss Analysis Questions 1 and 2 before moving
on to Part Two. Follow up these questions by asking,
What could have caused the differences in the
amount of microbes left behind? Students may
mention: the amount of time spent rubbing hands
Provide one member of each student pair
together; how hands were rubbed together; use of a
with powder as students read the
nail brush; water temperature; type of soap
Introduction and Challenge.
(antibacterial/ordinary, moisturizing/ordinary, bar
Have students read the Introduction and Challenge
on page C-85 in the Student Book either in small
groups or individually. As students read, circulate
soap/liquid soap); method of drying; differences in
skin moisture; differences in the initial amount of
powder; etc.
and sprinkle a couple of shakes (less than a quarter
Ask, Could some powder still be on your hands,
teaspoon) of powder on the hands of one student in
even though it didn’t show up with the UV light?
each pair. Use the powder sparingly, making sure to
How could that be? Where might it be? Bring out
allow enough for three classes to carry out their
the idea that there needs to be a certain amount of
investigations. Have the students who received the
powder for it to be visible; in other words, a thresh-
powder spread the “microbes” all over their hands
old has to be reached. Some powder may be in pores.
(front and back) and gently scratch their palms to
Many real microbes can survive under skin flakes, in
get some powder under their nails.
pores, in hair follicles, and under fingernails.
Teacher’s Guide
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Activity 48 • Wash Your Hands, Please!
4.
Students design and conduct experiments
dents to list ways in which healthy bodies resist or get
to improve hand washing.
rid of microbes. They may mention the skin, the acid
n Teacher’s Note: You may wish to assess students on
either element (“Task Management” and “Shared
Opportunity”) of the GROUP INTERACTION (GI) variable during this part of the activity. Alternatively, you
can use the “Recording Design or Procedure” element
of the D E S I G N I N G
TIONS
AND
CONDUCTING INVESTIGA-
(DCI) variable to assess students’ experiments.
You may wish to have students sign up to investigate different variables (such as water temperature,
amount of soap, length of hand washing, etc.), or
just let them investigate the variable they are most
in the stomach, hairs and mucus in the nose, tears
that wash the eyes, and a healthy immune system.
Extension
Students can make a list of recommendations for
a school hand-washing campaign.
The class can use the results of the experiments as
described in the Student Book. If students plan on
carrying out their recommendations, they may
need to consider:
•
within the school: Are they material and
interested in. Since students are likely to want to try
facilities problems or hand-washing attitudes
improving everything at once, remind them about
and behavior?
designing experiments—they should be controlling
all variables except for the one being tested.
The most urgent hand-washing problems
•
The school’s facilities and materials for hand
washing in bathrooms and food preparation
Some students may require help with deciding what
and eating areas: Is there enough soap and
results they could record and how to record them.
paper towels? Are the bathrooms so
Encourage students to think of how they could
unpleasant that people won’t use the hand-
record some kind of quantitative result, as well as
washing facilities? How about the school
qualitative result.
kitchens? Do they have the necessary sinks,
Let students design and carry out their experiments.
soaps, and towels? Students can use the
Encourage them to repeat their experiments if you
evidence they have gathered through
have time and enough powder.
experimentation and reading to present
their ideas.
FOLLOW–UP
5.
•
Students may wish to develop posters, a video,
Students share their results.
a newsletter, and/or a website as media to
Ask each group to share what variable they investigated, their experimental design, and their results.
Ways in which to change people’s behavior.
inform, persuade, and train people to wash up.
•
How students will know if the campaign is
Analysis Question 3 can then be used as a follow-up
effective. Students should decide the measure
and to assess student understanding. Score students’
of “effectiveness.” It could be simple, like how
answers with the U NDERSTANDING CONCEPTS (UC)
much soap or paper towels the custodians
variable. You could extend this question by asking stu-
replace in a week before the campaign
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Science and Life Issues
Wash Your Hands, Please! • Activity 48
compared to the week after the campaign.
removes most of the microbes, based on results
Students may be able to track student
from our hand-washing experiment.
absences before and after the campaign. It
may even be possible to figure out how many
4.
How well do powdered “microbes” model real
microbes? Explain.
absences were due to illness.
Strengths of this model include the particulate
SUGGESTED RESPONSES
nature of the powder, which models individual
TO ANALYSIS QUESTIONS
microbes; the ease with which the powder is
spread by contact; and the fact that the powder
Part One: Washing Your Hands
1.
is invisible in small quantities. The powder may
Where on your hands did you find the most
not have modeled how well real microbes
“microbes” (white powder)?
attach to human skin (i.e. the “stickiness” factor). There are far fewer powder particles than
Most students are likely to find the most pow-
microbes, and each particle is much larger than
der left under nails, in cuticles, in hair follicles,
a microbe. Nor did the powder “microbes”
at the base of the hand, and around jewelry.
2.
demonstrate the effectiveness of antibacterial
Based on your results in Part One, how well
soap, which may kill, instead of remove, bacte-
did
ria. In addition, the powder has only a single
washing
your
hands
remove
“microbes”?
consistency and cannot model the variability
among microbes.
Most students will find that washing their
hands did remove a lot of the powder, possibly
Many scientific studies of hand washing have
more than they thought it would.
used culture techniques that require a person to
touch an agar plate before and after hand wash-
Part Two: Improving Hand Washing
3.
Why is hand washing important? Use
ing to see how many cultures are produced each
time. It is a reasonable, but not perfect, model.
UC
your knowledge of microbes and the results
of this activity to explain your answer.
5.
Imagine that your school has decided to launch a
hand-washing campaign. You are in charge of
A complete and correct level 3 response follows:
designing the campaign and evaluating its effec-
Hand washing is very important. Microbes are
tiveness.
very small and cannot be seen with just your
eyes. Some microbes cause infectious diseases
a. Why might people resist changing the frequency
and the way in which they wash their hands?
such as colds and the flu. Evidence from our
experiment shows that shaking hands spreads a
lot of microbes from one person to the next.
Washing hands before or after shaking hands
Students can speculate on their own reasons
and their friends’ reasons, or they could conduct an informal survey. Answers may include:
people are often busy; sinks are inconveniently
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Activity 48 • Wash Your Hands, Please!
placed; soap and towels may be lacking; and
dents may consider comparing illness rates
people may not realize how important hand
from different years, as there is a natural
washing is to their health and the health of
increase in illness during winter. Students could
their friends and family.
conduct surveys of attitudes toward hand washing or the self-reporting of hand washing.
b. Explain how you could persuade people to
change their hand-washing behavior.
Replenishing soap and towels, keeping bathrooms clean, adding sinks or soapless hand sanitizers at convenient locations, etc. may
6.
Read the recommendations for hand washing for
surgeons and food handlers on the next page. Why
do both sets of guidelines stress rubbing or scrubbing the hands?
increase hand washing. Students may also sug-
Students’ own results may have suggested that
gest some form of education campaign to make
the amount of friction related most strongly to
hand washing a higher priority for people.
the amount of powder removed from their
c. What type of data could you collect (both before
and after the campaign) to determine if the handwashing campaign was effective?
Observing more hand washing among students
is not easy to do. Towel or soap use could be a
measure of hand-washing frequency. Tracking
the number of infectious illnesses before, during, and after the campaign is also possible. Stu-
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Science and Life Issues
hands. This is the finding of many hand-washing studies involving the use of culture techniques to track real microbes.
The function of soap is to help dirt particles lift
off the skin. It is a wetting agent. Hand washing
with vigorous rubbing but without soap is still
fairly effective. Rinsing will wash the loose particles and microbes down the sink.