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Chemistry is comprehensible This is a story about the effects of toxic substances.

Chemical substances, which we don't want in our body are called toxic. Our body itself is made of chemical substances and its survival depends on many different substances. At first this sounds very confusing, because there are so many substances in our environment. There are a few among them whose effects are not desirable for us. For that reason the development of our biology has given us many tricks to protect us from unwanted chemical substances and their effects.

grosser Kreislauf The science of poisons, toxicology, is unfortunately not easy to understand. This is not because of the complicated topic, but because of the history of toxicology, which was mystified by magic at the times of alchemy. Later on it was a subsidiary subject of pharmacology and because of the medical phrases not very comprehensible.
This text was developed for the instruction and further education of the fire brigade and the internal education of industrial workers, who handle dangerous chemicals.
Produktionskreislauf From the idea of ecosystems I developed an easy model that might make the science of poisons comprehensible:
I compare the poisons invading the ecosystem man with foreign substances that invade a different complex system. Such systems are for example a production plant, a hospital, a school or a fire station. 

The consideration/analysis/in-depth-look is divided in four parts:

 1. How does an organism protect itself from the invasion of unwanted substances ?
2. How does an organism control the mass exchange ?
3. Which effects can unwanted substances have on an organism after they entered ?
4. How does an organism protect itself from foreign substances, that have already entered the system ?

Biokreislauf This text is a parallel story, which I present with suitable objects and transparencies.
In the text the parallels are marked by different colours.
The comparisons are often not perfect in style and formulation. Uwe Hillman made the drawings for the text. They often form series of drawings that are more exciting to watch with an overhead projector than in the text.
As a reader you have to picture yourself a lecture! This text is meant to be a mnemonic aid, to have a better recollection of the lecture.

 The special effects of single substance groups are only briefly mentioned in the lecture to maintain an overview over the whole field of toxicologists. For details you can use numerous books (for example Max Daunderer). 

Here begins our story about LIVING WITH POISON
Read the text once with the red colour and a second time with the green colour.

 A presentation of the effects of an the protection from toxic substances, which is explained by an example of unwanted foreign 

substances for man : take a look in the mirror, you have a skin for protection, a mouth to take up substances with, an organic interior and a biological, integrated defense system.
people for a production plant, the drawing may not look like the factory or the school we are in right now, but the principle always remains the same

Part One : The boundary

 The organism has a boundary that separates him from the outside world. He uses it to protect himself against everything that may invade him from the outside. With

 the skin / the factory fence

 all usual things, that shall not enter the organism, are averted. The experience that has been made up to now, namely 

the biological evolution / a trained architect

 has structured the boundary in a way that enables it to fulfil its task with the least possible expense.

factory fence
1. The stability

 In some spots the demand on the boundary is extremely high, therefore the structure is stronger:

 horny skin, fingernails crash barrier, stronger fence, higher fence

 2. Injury

 In some cases the stability of the boundary is not strong enough for unusual influences, an injury is possible:

 a cut from a knife / pincers make holes

3. Repair

 The organism has to initiate repair activities. We will come back to that in Part Four:

 erythema (reddened skin) indicates better blood circulation, pus is secreted
workers with tools arrive

 Fast, temporary protection helps remove the wound:

 plaster / barriers

Possible invaders, like

 bacteria, dirt / walkers, troublemakers

 can be rejected at the same time.

repairing the fence
4. Maintenance

 With such a boundary problems come along:

 skin can age, dry out and tear
the fence can rust and break

 Constant care helps prevent problems and small parts of the boundary are replaced regularly.

ageing fence
5. Defenseless

 Problems also exist with substances, things or objects that cross the boundary without leaving noticeable wounds.

 Many chemicals are resorbed by the skin. Petrol, aromatic hydrocarbons, alcohol, pesticides, ... are marked with the symbol for danger "h" meaning skin resorbtive.
Mice or wasps are not rejected by normal fences. The same is true for a cloud of nitrous gases from an accident in the neighbouring factory.

 6. Short time reinforcements

 If it is known, which unusual stresses are to be expected for the boundary of the organism, additional protection can be put up. The additional protection is determined by the experiences the organism has made until now. These experiences can misjudge the danger: the protection is overestimated or too weak.

 gloves against the cold, slop, chemicals, heat
aprons lead aprons, protective suits, headrest
barriers, building stronger posts

Maus freut sich

Part Two : Mass transfer

 The boundary protects the organism, but it has to take part in the life surrounding it, it is inevitably ecologically connected with other organisms. Therefore the boundary is specifically pervious. Special installations supervise the exchange:

 The mouth is protected by the senses. If we bring a substance in the vicinity of the mouth, the sense of touch transfers information, the eyes evaluate it, the nose with its sense of smell will, immediately in front of the mouth, report if the substance smells suspicious. The contact with the lips, the feeling we have while chewing, the control of the taste, all is made use of and the information is collected, correlated and judged.
The factory entrance is protected by a guard. He has a surveillance camera, a very good view, some phones, an alarm and a fast connection to the company management.

 If an invading substance awakens suspicions, there are certain countermeasures:

 the mouth closes, the breathing stops / the door is shut

 The control at the passage points is problematic in five cases:

clever disguise
1. The unwanted substance goes by unnoticed.

 carbon monoxide is odourless
a person sneaks by under the window

 2. The unwanted substance disguises itself as, is confused with customary substances.

 lead carbonate tastes like sugar, hydrocyanic acid smells like bitter almonds.
ID cards are faked and the troublemakers wear the same clothes as the factory workers

 3. Unfamiliar substances arrive in large amounts and too quick.

 a cloud of methylisocyanate, toxic smoke
a mass demonstration or a bus with 60 people in front of the factory entrance.

don´t let the bedbugs bite
4. The unfamiliar substance hides in a large amount of known substances.

 fishbones, cherry stones or mushroom poisoning often go by unnoticed with other food.
single strangers hide in the stream of workers leaving after work

 5. The protective functions are paralyzed

 Pain, a cold, heavy smoking or alcohol deaden the senses.
sulfur hydrogen stuns and smells sweet afterwards.
the guard is asleep.

the general surgeon warns
Part Three: Interior effects

 Now it happened, the foreign, unwanted substances invaded the organism. Six different results will be looked at:

 1. Harmless substances

 The substances don't disturb the interior, they are unnoticed, don't cause any damage and leave the interior at a favorable moment, without calling any attention to them.

 single cherry stones, sand, placebos
single passers-by 

sunday morning
The harmless substances will cause problems, if their number grows too large. Then we become aware of them:

 eating many cherry stones
many passers-by occupy the access road

take a walk on the wild side
2. General chaos

 Some foreign substances cause unspecific damage. The organism notices that something is wrong, but the usual activity is not disturbed.
Those are all general disturbances of well being. They are no reason to see a doctor, who would probably diagnose "unspecific civilization disease".

 feeling uncomfortable, insomnia, indigestion, the cardivascular system is not at maximum capacity, lack of concentration.
A strangers crooks the pictures, dismantles a doorhandle, loosens the banisters, pleats the carpet, boards up five windows, steals the toilet paper and saws off the legs of all the chairs. The activity of the company goes on. These small disturbances don't scare anybody and everybody accepts the challenge to continue the work.

 Only when productivity rises will the organism start to collapse, because now the small disturbances show their effects:

the boss is in
In cases of stress or too much work the reduced resistance is displayed.
In cases of deadlines or alarms small defects cause bigger accidents and shut down the activity.

 If we notice, that our organism can't handle the unspecific damages caused by additional loads, then we can:

 Take a cure and clean up our interior. With medical care we can regenerate our health as far as possible.
In the factory holidays or at an activity stoppage the staff has time to clean up the interior of the factory. The renovations restore the activity, if possible, to the old level.

 Unspecifically acting foreign substances can still harm the organism if they enter in large amounts.

 radioactive radiation or city air
If too many light bulbs are missing or all doors are broken, the activity of the factory can't continue.

a job for the cleaner
3. Specific poisons

 Substances in the organism might also have very specific effects. Specialist only need a minimal concentration to find the right switch and harm the organism.

 lead blocks enzymes, phosgene works as war gas, the arrow poison curare or the extremely poisonous dioxins are very specific
an electrician finds the master switch in no time

the switch
We know several different mechanisms of impairment. Here are two of them:
The foreign substance blocks the transport systems:

carbon monoxide, cyanide or sulfur hydrogen react with haemoglobin in the blood cells and block the oxygen transportation, respiration will cease.
all forklift trucks are occupied with useless things or obstructed. The resulting lack of supplies causes the production to stop.

some chemistry The foreign substances are mistaken for substances that belong to the organism, but they can't satisfy the demanded functions. The organism is no longer viable.

 compounds of barium are chemically similar to compounds of calcium, but they can't take over their functions, for example when transporting of nerve signals (for that reason soluble barium compounds are used as rat poison).
left-wound screws are delivered to the production site instead of the right-wound screws that are needed there. They do not fit and the screw threads will be destroyed if someone actually tries to use them.

where´s Waldo 4. Chronic effects

 Until now, we have looked at effects that can be recognized very soon. Beside acute poisonings there are also the chronic poisonings. If we absorb foreign substances in small amounts and they gather in the organism (accumulation), they suddenly, after a waiting (latency) period or an extreme physical demand, become effective. The organism gets visibly sick.

 PCB accumulates in body fat, cadmium in the kidney. Other chronic poisonings show their effect only after a long time, like arsenic (18 years) or cadmium (30 years).
troublemakers in a factory hide in the broom closet or in the mezzanine of a hospital and act at the same time.

experts at work 5. Synergies

 When several different foreign substances have invaded the organism synergies can occur. In that case the effect of those substances is worse than the sum of the single effects would be.

 Synergies are disastrous, because there is little research concerning them and the threshold values for toxic substances are gained from the effects the substance has on a healthy organism that is not harmed by other poisons.

Research has been done with miners of the Johannistalgruben to test the effect of radioactivity and tobacco smoking
a specialist for alarm systems is joined by a specialist for safes to rob a bank. Neither could do it alone.

taming lions 6. Accompanying substances

 Substances whose toxic effects are known can be neutralized if they are escorted by other substances. Through the socialisation of certain substances who always appear at the same time, the harmful effect of these substances will be eased.

 In our diet many problem substances exist, that are used as flavour or as basic substances (like sugar). However there are also many accompanying substances that neutralize the harmful effects. Joined with vitamins and enzymes the effects of sugar are unproblematic, as single substance its effects can be "toxic".
an infant will cause no problems in a department store if it is joined by its mother. A handicapped person can be guided to the right spot in the factory by a helper. Here he can do regular work.

good company Part Four: Defense systems

 Organisms have gathered experiences concerning and adjusted to the appearance of foreign substances causing damage in their interior. Learning by experience (trial and error) is the same for architects as it is for evolution.

 Two important mechanisms are available to the organisms. The immune system and redundancy.

schooldays 1. The immune system

 The immune system is supposed to resist intruding substances. It has been developed by evolution and is available at birth. White blood corpuscles defend against bacteria infections in a wound.

 Vaccinations can increase the existing immune system.
The factory security office or the workshop are supposed to defend against and repair damages. They are built and equipped with the latest technical knowledge and equipment. Workers, who are well trained and educated, and equipment that is up to date are available to the factory security office.

toolatetoolate A defense system can sometimes be overburdened. It can't repair the damage with its own means, help arrives from the outside:

 When we have large scale burnings or several infections at once we are given drugs (antibiotics).
If too many disturbances occur we call the fire brigade, technicians or other factories for help.

 Outside help can be very effective, but often side effects that harm the organism occur:

 Acetylsalizilacid helps against headaches but damages the stomach lining.
The fire brigade extinguishes the fire but destroys parts of the production plant with its equipment.

While the immune system is working, the activity of the organism is often decreased. Parts of the organism are shut down or managed at reduced activity. After the damage is repaired the organism needs a certain time to regain its usual fitness.

 During a sickness we lie in bed quietly, afterwards we need time to regenerate, rehabilitate or take a cure.
While the repairs are going on, the activity is reduced to parts of the factory. After that there are trial periods, starting routines and test runs.

 The defense system can become ineffective or break down. Outside help is needed to replace the immune system, but there are problems with possible side effects.

 In case of leukemia or HIV drugs can help prevent infections for a while.
All workers of the factory security office are sick and stay at home. Temporary guards take over their tasks, but work not as professionally.

caught in the act
The defense system can also act up. It repairs damages, where none exist and gets everything mixed up. The last chance then is to paralyze the whole immune system. For the reconstruction outside help is necessary:

 An allergic reaction is a mistake, which for example reddens the skin at an uncritical, not endangered spot. The skin is supplied with a lot of blood and signals (itches) report a bad wound. Because in reality there is no wound, this mistake is very annoying.
Cortisone paralyzes the endogenous immunity, drugs that replace the immune system are needed for the time of recovery.
The factory guards arrest innocent workers and stop the production. After the dismissal of all guards, the production can restart, but a different factory has to ensure protection while the factory security office is reconstructed.

the sick and the dying
2. Redundancy

 The second important mechanism that is used by an organism to protect itself against damages is that some functions are multiple or have more capacity than they normally need (redundancy).
While damaging an ecosystem, we often experience that the system seems to have no problem for a long time, until suddenly, out of the blue, the whole system collapses. The reason for this surprising behavior may be redundancy.

The pulmonary volume, the kidney capacity, the liver size, the amount of blood, ... are proportioned very generously. If through sickness (for example scar tissue in the lungs or tar from cigarettes) parts of this extra capacity are blocked, we don't notice anything. Not until further damage is done, which can be relatively small, and exhausts all reserves we become aware of an enormous damage.
A company has five phones but effectively only needs one for the work to continue. If four phones break down from age or disorder, the activity can go on unimpaired. Not until the last phone breaks (an event that has been handled the previous four times) the activity breaks down.

 Extra capacity can be useful for the organism, but it makes our usual cause-effect-analysis difficult, when we are searching for toxic substances that are responsible for a visible damage.


 The story about the effects of toxic substances surely has to be enlivened with examples and experiences from the listeners. Still the story is a strong simplification and the examples should not pretend to be an argumentation.
Our everyday life with toxic substances is most of the time easier and safer when we know why we should protect ourselves in a certain way. The instruction "don't smoke during certain activities and wear protective gloves" will often not be followed, for the simple reason that it has not been properly explained. This short story about "Living with poison" may help. 

gealterter Zaun

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