Download PS64 Are we allowed to...?

ARE WE ALLOWED TO .......?
CLEAPSS runs a  and receives thousands of phone calls, faxes and e-mails a year from school teachers
and technicians with queries about practical aspects of science. For biology topics, the enquiries are very wide
ranging, from “Is it alright to burn a cow pat in the laboratory?” (it is - if you follow the stringent precautions
detailed in a special risk assessment produced by CLEAPSS!), “Is it safe to use Vampire’s blood?” (a fake blood
from theatrical suppliers being painted onto pupils’ skin for a school play), “Can I stick my head in a bucket of
water?” (from a teacher wishing to demonstrate the diving reflex and its effect on slowing the heart rate) to lessbizarre queries about, for example, enzymes, suppliers of stick insects, how to encourage Elodea to give off
bubbles of oxygen on demand and keeping rabbits.
A common thread runs through many of the enquiries and relates to the widespread belief that many biological
activities, animals, tissues and microorganisms are banned or too hazardous to use in schools. In most cases, the
teacher or technician is surprised (and sometimes disappointed!) to hear that there is no ban and that there are
no problems, other than the need to take some straightforward precautions. Given below is a selection of the
most-frequently asked biological queries and the CLEAPSS responses. CLEAPSS members can purchase (or
view free on the CLEAPSS Science Publications CD-ROM or members-only part of our web site) a variety of documents which give further guidance on the issues that are discussed.
Butchers’ bits
Q.
“I know that I can’t dissect eyes, but what about hearts? Does it matter which animal they come from?”
A.
Er, actually, you CAN use eyes. In a nutshell, you can dissect whatever your butcher/abattoir will provide, with one or two provisos. Anything that a butcher sells must have been passed as ‘fit for human consumption’. Now, apart from the student in Lincolnshire who ate the eye he was dissecting, we don’t anticipate
an oral route of transmission of any diseases. Ensuring hands are washed within the lab before leaving the
room will rule out this transmission route. (Materials may, of course, be carrying food-poisoning bacteria.) We
don’t believe that it is necessary to wear gloves; you don’t wear them when preparing meat in a kitchen.
The government has enacted the Specified Risk Materials (SRM) Regulations and these determine the parts of
animals which have been slaughtered that may be capable of transmitting spongiform encephalopathies and
therefore must not be supplied. Only materials from cattle, sheep and goats are currently specified and only
under certain circumstances. In fact, the eyes from sheep and goats are not classed as SRM if the animal was
slaughtered below 12 months. Similarly, eyes from cattle are not SRM if the animals were slaughtered below the
age of 6 months. The eyes from pigs, llamas, ostriches, deer and horses are also not classed as SRM.
Thus anything that you can obtain through normal channels should not be SRM and could therefore be used.
However, you may get more hassle than you need if eyes from cattle are dissected, students go home and tell
their parents what they were doing in science today and parents freak out, complaining to the principal, chair of
governing body, local newspapers etc! You also need to consider the suitability of pigs’ eyes if you have pupils
with religious/cultural objections to handling material from pigs.
Butchers/abattoirs are sometimes not very helpful, as the eyes are difficult to remove (especially from pigs’
heads) and refuse to supply anything. Shop around to try and find a butcher/abattoir that is more obliging.
Hearts, lungs, kidneys etc from any animal are fine but the tops of hearts will often have been cut off, rendering
them useless. You need to cultivate your butcher so that intact hearts are supplied or, alternatively, order several plucks - the heart and lungs together. This way, you can cut out the hearts yourself with long lengths of
vessels and then use the lungs for inflation investigations. Unfortunately, the organs will probably have been
cut into at the abattoir (as part of the inspection process), so choose the least-hacked about specimen for a demonstration. Naturally, we don’t recommend that you directly exhale into the trachea nor use a length of tubing to
breathe down. Because of the elastic recoil of the lung tissue, you might inhale a blast of unpleasant air. Use, for
example, a bicycle pump attached to the trachea to inflate the lungs. Air will almost certainly escape from cut
surfaces of the lung, so it is best to place the lungs inside a large, transparent, plastic bag to stop any aerosols,
contaminated with possible pathogens, from escaping into the laboratory air. [See also section 14.7.2 of the
CLEAPSS Laboratory Handbook on our CD-ROM.]
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© CLEAPSS , The Gardiner Building, Brunel Science Park, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: [email protected]; Web site: www.cleapss.org.uk
Tongue in cheek?
“A new teacher has arrived and is horrified to see that we allow pupils to sample their own cheek cells. He says this
activity has been banned for years. Is he right?”
A.
Probably not - but the story is complicated. When AIDS first arose, questions were asked in the House
about taking blood samples in schools and, following these, the DES issued recommendations that the “taking
of blood and cell samples should cease”. As a result, most LEAs issued instructions to schools effectively outlawing blood and cheek-cell sampling. But why did the DES include cheek cells along with blood? At the time,
the technique of obtaining cheek cells was often described as a “scrape preparation”. In the minds of the DES
mandarins, this conjured up the image of pupils using scalpel handles, microscope slides etc to gouge into their
mouths, with consequent large amounts of blood spurting out along with the cheek-cell samples.
Q.
For some time, the Institute of Biology, CLEAPSS and ASE argued that cheek cells could be sampled safely if a
gentle technique, using a cotton bud to avoid scraping, was used. However, it was not until the publication of
Safety in Science Education by the DfEE that official government guidance on cheek cells was effectively reversed,
indicating that the use of cotton buds was now ‘permitted’ together with appropriate precautions to treat
contaminated items with disinfectant or by autoclaving. Unfortunately, schools still remember the ‘old’ ban and
many LEAs have never officially revised their earlier instructions. [Refer to section 14.4.2 of the CLEAPSS
Laboratory Handbook on our CD-ROM.]
Blood, sweat and tears (and spit, and urine)
Q.
“I know I can’t use human blood and saliva but can I collect tears for lysozyme studies?”
A.
You certainly can, if your employer hasn’t outlawed human body fluids (see above). Just bop a student on
the nose for a plentiful supply (only joking). (Finger nails are also a good source of lysozyme apparently.) But,
actually, neither saliva nor urine has ever featured in a DES/DfE/DfEE/DfES ‘ban’. Schools have assumed that
if cheek cells mustn’t be used, then saliva is also a no-no. And urine is so unpleasant, its use can’t be permitted,
can it?
Not so, (unless you work in some areas where the employer has issued restrictions). In fact, saliva is a more
reliable (and safer, and cheaper) source of amylase than preparations made from purchased, powdered
enzymes, extracted from plants, fungi or bacteria. Diastase is loaded with sugar, so control investigations of
starch digestion into sugars, testing with Benedict’s solution, are a real problem. Bacterial amylases often go on
working when they are boiled, undermining a teacher’s attempts to investigate denaturing with heat. We know
of entire science departments which have developed allergies to all the amylase particles floating about in the
air after an intensive series of Sc1 investigations. Of course, a few simple precautions with saliva are needed. No
class spitoons please, to which all students contribute. Each student must produce his or her own saliva sample,
rinse out test tubes etc afterwards and all glassware should be placed into a washing-up bowl of sodium
hypochlorite for half an hour or so before being washed up in the normal way.
Urine may not be very nice to handle (though it’s probably sterile anyway) but there is no reason why it can’t
be investigated, for example, to study its chloride content, related to dietary intake. The same precautions as
with saliva seem appropriate (with used samples being taken by students to the loo for disposal and then a
hypochlorite soaking of laboratory glassware, just to be on the safe side).
But human blood must surely still be off limits? Well, actually no. The DfEE Safety in Science Education advice,
while hardly recommending that wholesale blood sampling should recommence, states that it is for an educational employer to decide whether to permit the practice. (After all, compare sixth-form investigations using
finger-prick samples taken under sterile conditions with an average game of rugby. Which is the more hazardous in terms of the transmission of blood-borne viruses? And yet sports such as rugby promote healthy exercise
and are only to be encouraged, aren’t they?) A realistic assessment of risks should often allow human blood
sampling by responsible students (probably sixth formers) under tightly-controlled conditions. Several colleges
and foundation schools (for whom the employer is their governing body) now investigate human blood in lab
practicals. Some community schools have approached their employers (the LEA) and been granted permission
for some students to take their own blood samples. CLEAPSS and the ASE (in Topics in Safety) have published
procedures for taking blood samples safely. [See sections 14.4.1, 14.4.3, 14.4.4 and 14.4.5 of the CLEAPSS
Laboratory Handbook on our CD-ROM.]
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© CLEAPSS , The Gardiner Building, Brunel Science Park, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: [email protected]; Web site: www.cleapss.org.uk
Giant African land snails
“I’ve recently read that these animals can cause meningitis. What should I do with the colony we have maintained in
the school for several years?”
A.
Continue to enjoy studying these snails without any worries. The recent reports in the USA, circulated on
the Internet (and also statements made by the DES many years ago) have caused much confusion. In some parts
of the world (typically the Far East), the giant snail, Achatina fulica, may be infected by a parasite that normally
inhabits the lungs of mammals, such as rats. In some circumstances, the parasite may transfer from the snails to
humans, causing illness with symptoms not dissimilar to meningitis (though no bacteria or viruses causing
meningitis are involved). Giant African snails, bred in captivity in this country, cannot be carrying the parasite.
Only recently-imported animals might be a source of the parasite and, since the giant African snails breed prolifically, there is a plentiful supply of UK residents, eliminating the need for imports. Also the parasite only infects
humans when affected snails are eaten; a fate unlikely for the majority of the snails kept in British schools.
[Refer to the CLEAPSS Guide L197 on our CD-ROM.]
Q.
A microbial miscellany
“Escherichia coli is obviously too dangerous to use, but which bacteria are OK for work in schools?”
“My teacher insists that it is safer if pupils completely seal their agar plates after setting them up. Is she right?”
“Are we allowed to take samples from door knobs, the floor, the pupils’ fingers and hair?”
“Isn’t 37 °C the best temperature at which to incubate bacteria?”
A.
[These are just a sample of the many enquiries we receive about microbiology. For a full treatment of this
subject, CLEAPSS members should refer to section 15.2 of our Laboratory Handbook (also on the CD-ROM).] But
here goes on these particular enquiries... .
i) OK, E. coli can cause various diseases but you won’t be using a pathogenic strain (such as 0157; remember
meat pies in Lanarkshire?). In schools, the K12 strain is used and this is not hazardous to human health. It may
have the same name as all the other E. coli types that hit the headlines but it is a quite different organism. There
are many other ‘safe’ bacteria from the educational suppliers but E. coli grows very quickly and more reliably
than several others. It is the bacterium to choose when studying the effects of antibiotics because it is resistant to
penicillin and sensitive to streptomycin. In one agar plate, you can show both effects at the same time. (But
don’t mix the bacteria with the agar in a pour or lawn plate more than an hour or so before the antibiotics are
added. Otherwise, the bacteria will have started to increase before the antibiotics arrive and will have no effect.
ii) Completely sealing an agar plate around the circumference with tape before it has been incubated might
seem like a good idea: after all, there may be nasties in there and they mustn’t get out. Unfortunately, it’s a bad
idea. Petri dishes are ventilated and allow air to circulate. Many bacteria require oxygen to grow and, with a
completely-sealed plate, will not develop - possibly ruining the experiment. But worse are the anaerobic conditions that are created in the sealed dish. Only bacteria that grow in the absence of oxygen will flourish but such
anaerobes are likely to be rather unpleasant bacteria. By total sealing, instead of making the agar plate safer, the
opposite is achieved - if the seal is broken. We know of one pupil who stole his agar plate and dabbed the agar
surface on the noses of other students! Before incubation, agar plates should only be taped closed with a couple
of strips of sellotape. After incubation, however, completely sealing agar plates is not such a bad idea, particularly when all the students can’t be trusted not to prise open their Petri dishes and unknown, environmental
microbial samples will have grown.
iii) Whether to sample from various places around the school to investigate what might be lurking depends
very much on the teacher’s risk assessment of the behaviour and responsibility of the pupils. Sampling, for
example, the door knob of the toilets may harvest a bumper crop of coliforms and provide a testimony of the
inadequacy of many people’s hand-washing skills. What is sampled from the floor will depend very much on
what may be on the soles of everyone’s shoes! A teenager with ripe acne might have a fine collection of Staphylococcus aureus on his/her finger tips. The surface of a hair from the head, however, is probably quite a clean
environment but perhaps not so for one extracted from the inside of the nose. A safe (but boring) response is
not to sample from anywhere in the environment but this will deny the opportunity of interesting / motivating
work and discussions of the importance of good hygiene may not have much impact. If agar plates are sealed
with tape around their circumference after incubation (see above), the seal remains intact and the plates are
ultimately autoclaved before disposal, risks of infection from unknown pathogens are extremely low. In many
classes (but not all), such activities can be entirely safe. It all depends on the teacher’s risk assessment.
iv) 37 °C is certainly a great temperature for many bacteria; they will grow much more reliably and quickly than
at, say, 20 °C. But it is, of course, also human body temperature, so incubating agar plates at 37 °C will ensure
that what grows inside the Petri dishes can also thrive inside us. All model risk assessments for microbiology
work in schools recommend that microbes should be incubated at ambient temperatures, to reduce the chances
of isolating pathogens. The advisability of growing bacteria at the higher temperature will again be dependent
on the risk assessment and the likelihood of inadvertent accidents or deliberate foul play.
Q.
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© CLEAPSS , The Gardiner Building, Brunel Science Park, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: [email protected]; Web site: www.cleapss.org.uk
Nuts!
Q.
“Is the burning peanut investigation banned?”
A.
Not unless your employer has issued restrictions. However, the consequences of going ahead if a student
with a severe nut allergy is affected could be severe. Schools will usually know if a student is allergic and there
should be a system in place to alert the science department. If burning peanuts is still to be done, the student
must be nowhere near the lab in which the activity takes place and the lab must be thoroughly cleaned and
ventilated afterwards. Thought must be given to who will be entering the lab after this particular lesson; small
amounts of peanut debris left behind could trigger an allergic reaction in a sensitive individual.
All these precautions are rather a hassle in a busy department and there are alternatives to peanuts which
schools claim are just as useful. These include Cheesy Wotsits, Monster Munch, dog biscuits, spaghetti and honeycoated banana chips! [Refer to the CLEAPSS Laboratory Handbook section 9.4.2, on our CD-ROM.]
To sleep? Purchance to dream!
“I’ve been told that it’s not permitted anymore to use ether to anaesthetise Drosophila. Is this true? I’ve had to stop
genetics work with these fruit flies.”
A.
Another myth! Clearly, ethoxyethane (diethyl ether) is a hazardous chemical; its extreme flammability
and its narcotising effect if inhaled in large quantities aren’t helpful. (But note, our noses are very efficient at
detecting ether in the air at levels way, way below those which put everyone to sleep!) It is not difficult to
ensure that there are no naked flames around when using it, that there is good ventilation in the lab and that the
amounts dispensed are small to limit evaporation into the air. In fact, there are alternatives. A proprietary
anaesthetic, called FlyNap, uses (slightly) less hazardous chemicals but if you get any of it on your fingers, the
smell is disgusting and seems to last for days! You could also try chilling the flies in a fridge (keep the bottles on
their side or the flies fall into the food goo) and then tipping them onto a freezer block just removed from the
deep freeze. Cover the freezer block with a fine-mesh hankie or similar. The flies stay immobile for quite some
time. [Refer to CLEAPSS Bulletin articles 106 and 107 on our CD-ROM.]
Q.
Students on drugs
Q.
“Can I investigate the reaction time of my students after they take different numbers of Proplus tablets?”
A.
Hmm! I’m not sure that senior management or parents will take too kindly to your efforts to deliberately
alter the behaviour of your students by giving them drugs. That’s how such 50 mg doses of caffeine might be
perceived. However, if you do something similar by asking them to drink cups of coffee or cola in the school
canteen etc (no drinking allowed in the lab, of course!), I suspect that no-one will raise any objections. You can
use decaff for the controls and, to make the investigations quantitative, instead of delivering doses in milligrams, the units will be level teaspoons! [See section 11.8.1 of the CLEAPSS Laboratory Handbook on our CD.]
A frog he would a-wooing go
Q. “I’ve been told it’s illegal to bring frog spawn into school from a local pond. Is this correct?”
A.
No! unless your local pond is host to fully-protected species of amphibians - the Natterjack toad and the
Great crested newt. For common frogs and toads, the only protection offered to these animals under the Wildlife
and Countryside Act is that it is an offence to remove the animals and sell them without a licence. This may
surprise you but the common species are not endangered to the extent that the fully-protected amphibians are.
We would, however, recommend that only tiny amounts of spawn are taken, the animals are properly reared to
an advanced stage and released back into their original habitat. Would you like me to send you our guide on
tadpoles? (But it’s also on our CD-ROM: Guide L206!)
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CLEAPSS is an organisation offering an advisory service supporting practical science (and technology) in schools, colleges, etc. It is
largely funded by subscriptions from members. Currently, every one of the 180 education authorities in England, Wales, Northern Ireland
and the various islands is a member and so all their schools have free access to our services. (A sister organisation, SSERC, operates in
Scotland.) The vast majority of independent schools, post-16 colleges and teacher-training establishments are associate members, as are
many curriculum developers, field study centres, museums and learned societies. There is a particular focus on health & safety.
CLEAPSS produces a large number of publications for members, ranging from termly newsletters for primary and secondary schools, a
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1000-page Laboratory Handbook, Hazcards , Recipe Cards and many leaflets and booklets. Much of this is now available on CD-ROMs.
The members’  takes about 6600 calls per year. CLEAPSS also runs about 180 courses per year, mostly 1-day. We are represented on several committees of the British Standards Institution and maintain a close dialogue with the Health & Safety Executive, the
Qualifications & Curriculum Authority, professional bodies and others with an interest in science education.
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© CLEAPSS , The Gardiner Building, Brunel Science Park, Uxbridge UB8 3PQ
Tel: 01895 251496; Fax: 01895 814372; E-mail: [email protected]; Web site: www.cleapss.org.uk