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Chilly Soles

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this is an article that is being published in a Health & Safety journal, which is the aftermath of all the publicity we got in over 20 newspapers,

also 15 radio stations and now being followed up by 2 T.V. stations...

viewtopic.php?f=30&t=6626

 

 

 

Chilly Soles

Introduction

“If it gets any colder can we shut the door?” Said Adam.

 

Martin Connellan considered this. Adam had a point. It was cold inside the cobbler’s shop but then the weather was exceptional. December 2010 was the coldest since records began. Along with the rest of the country Bromsgrove in Worcestershire was shivering in sub-zero temperatures more suitable to Siberia than the UK.

 

Like any good employer Martin worked his way down the hierarchy of controls. Eliminating the task was clearly not an option. The cobblers and key cutting shop was his livelihood and provided a living for his three young staff. The work had to continue, even during the week between Christmas and the New Year.

 

But what about engineering controls to contain the hazard?

 

“We have an electric fire mounted on the wall at the back of the shop,” says Martin. “Although this copes with most situations on this day the outside temperature was exceptionally low. My thermometer told me that although the temperature in the shop was well above freezing, it was struggling to get near the comfort zone. But, unfortunately, the shop is so small there is literally no room to put another heater.”

 

Why not simply shut the shop door?

 

“The shop is only 17’ by 20’ ”. Says Martin. The retail counter is only 6’ from the door. If one customer is already inside it is very difficult for another customer to open the door to get in. With the door open wide the shop can at least hold a couple of customers.”

 

There was another reason for keeping the door open. In the workshop immediately behind the counter Martin’s staff use glue to fix soles back onto shoes. The glues are not classified as harmful and most of their smell was gobbled up by the shop’s ventilation.”

 

“Keeping the door open helped remove the residual odour,” says Martin.

 

Organisational controls such as job rotation did not provide a total solution although there were some possibilities. The shop also offered a key making service. While the glue tended to be warm the keymaking machines were quite cold. There may have been scope for rotating staff around these jobs but this would not be easy because of the random way in which the work came in.

 

This brings us to personal protective equipment; this should always the last option to be considered but all too often is not the least.

 

“I went out immediately and bought them all lumberjack coats,” says Martin. “They already had fingerless gloves.”

This would have been the end of the story had Martin’s friend, James Kerwin not walked into the shop. James Kerwin is a registered clinical hypnotherapist.

 

“Martin does a lot of charity work.” explains James. “Unfortunately, he is very nervous about the public speaking this entails. I use hypnotherapy to build his confidence.”

 

And so it was that a new control measure was tried out. James hypnotised the staff into feeling warmer.

 

“It was martin’s suggestion and probably meant more as a joke,” says James. “The two lads in the shop were very cynical but we gave it a try.”

 

When most people think of hypnotism they conjure up images of swinging clocks and trances. This was nothing like that. It was more like a conversation.

 

“A lot of it is to do with suggestion,” explains James. “I said how nice it would be if were warm. I asked them if there was a radiator in the shop what control they would set it to.”

 

It was so much like a normal conversation that when it was over the reaction of the subjects was the same.

 

“I was not hypnotised.”

 

But they certainly felt warmer.

 

“It definitely helped,” says twenty year old David Gary. “I actually took off my lumber jacket. And when I got home I opened some of the windows.”

 

Twenty seven year old Adam Hood subsequently came into work in a Hawaii 5-0 style shirt and sun-glasses.

 

David says he would be interested in learning self-hypnosis but did concede that it would never replace “wrapping up and keeping warm.”

 

But is there a danger that hypnotising people into thinking they are warm can lull them into a false sense of security so that they actually suffer damage from the cold?

 

“No.” James is quite definite about that. “The sub-conscious will never allow anyone to harm themselves.”

 

The media got hold of the story and various versions appeared over Christmas. One suggested that Martin and his staff were working in temperatures of -13⁰C with no heating at all within the shop.

 

 

 

 

Of course working in a cobblers shop is not traditionally listed as one of those occupations incurring significant exposure to the cold. Occupations which fall more naturally into this category include divers, cold store workers and postmen. Table 1. gives a more comprehensive list.

The principles of heat loss

The human metabolism is like a miniature furnace. Or more accurately it is like a collection of miniature furnaces, all generating heat. These individual “furnaces” include the heart, the brain and the liver. The main source of heat, however, is skeletal muscle. Even at rest this can account for up to 30% of the body’s heat production. During hard exercise skeletal muscle can produce, at least for a short period, up to 40 times the amount of heat produced by the rest of the organs put together.

Muscular activity is therefore one of the most important ways in which a body can regulate its temperature.

And the body does need to regulate its core (i.e. internal) temperature. Survival depends upon it. Ideally, the core temperature should be 37⁰C. This is our optimum operating temperature need to maintain this temperature to within plus or minus 1⁰ C. Straying too far either side of this range can is fatal.

It is fortunate therefore that we have built in physiological mechanisms for keeping our body’s core at the required temperature. Elements of this system include:

• Heat sensors: these are located in two different locations; in the skin and in the core. The sensors in the skin are simply nerve endings. But it would be a mistake to think of these as neurological thermometers. More usefully they detect the flow of heat and the direction of that flow. The deeper heat sensors are located within the core of the body.

• Control nerve; this is the key to controlling our core temperature. It is located an area of the brain known as the hypothalamus. It controls the diameter of small blood vessels which in turn regulates the blood flow. This is important because as well as carrying oxygen around the body the blood also carries heat. The heat control nerve can also make us shiver, thus causing the muscles involved to generate more heat.

 

The control nerve operates through various mechanisms. These effector mechanisms include the endocrine and autonomic systems and help orchestrate the body’s response to the thermal environment. For example:

 

• The nerve centre can restrict blood supply to the skin. This cuts heat loss through the skin but can cause frostbite in areas deprived of blood. The system may therefore open these vessels to prevent this. However, should severe cold conditions persist, supply to the periphery will be closed completely. Surface tissues will be sacrificed in order to protect the core.

• Sweating is very effective at getting rid of unwanted heat. We sweat approximately 650 ml per day of anyway. When sweat reaches the surface of our skin it will evaporate and the cooling associated with evaporation is a very effective cooling mechanism.

• Shivering. Cold induces shivering. It does this by inducing a reflex action which causes a muscle to contract once it has become slightly stretched. This in turn can cause another muscle attached to the same joint to stretch or contract in the opposite direction. This effect is enhanced by cold and as it continues we notice the effect known as shivering. From a practical point of view shivering can increase the amount of heat produced by up to 400%.

• Voluntary muscle action. Shivering is an involuntary muscle action. But as a cold environment reduces core temperature we will want to become more active; for example jumping up and down. This activity generates heat to help us keep warm.

• Change in metabolic rate. Unlike some animals our metabolism does not slow down sufficiently so that we can hibernate through the winter. This is a shame because, given the last two winters in the UK hibernation would be a tempting prospect. However, Australian aborigines and the natives of Tierra del Fuego, South America, do seem able to reduce their basal metabolic rate to the extent that they can sleep comfortably in cold conditions down to zero.

Heat Balance

As shown above, the human body has a sophisticated system of thermal regulation. This aims to keep our core temperature constant. Achieving this requires a balance between the heat generated within the body and the heat lost. This is summed up by the following equation:

S = M + R ± C ± K -E

Where:

 

S = heat loss or heat gain by the body.

M = metabolic heat generated by body

R = heat gained or lost by body through evaporation.

C = heat gained or lost by body through convection

K = heat gained or lost by body through conduction

E = heat lost by body through evaporation of sweat

 

Note: Where heat is gained the term in the equation is positive. Where heat is lost by the body the term in the equation is negative.

 

Of these effects, the most significant for heat gain is muscular activity, which, as we have seen, increases the heat produced by the metabolism. For heat loss the most significant is the evaporation of sweat. Because air is such a poor conductor of heat, loss or gain through this mechanism is probably the least significant. However, its importance increases where the body is in contact with another medium e.g. water.

 

Convection becomes important in air if there is wind. By taking heat away from the body wind exerts a cooling effect. It can also increase the rate of evaporation of sweat which also increases the cooling effect.

 

For example, a wind speed of 10 ms-1 will make a temperature of -1⁰C equivalent to a temperature of -18⁰C. This temperature is known as the wind chill equivalent temperature. This particular example is applicable to cold naked fingers. In other words, the risk of cold injury to cold naked fingers at a temperature of -1⁰C in a wind speed of 10 ms-1 is equal to the risk of cold injury at -18⁰C in a wind speed of 0 ms-1 . A table showing wind chill equivalent temperatures can be found in HUNTER’S DISEASES OF OCCUPATIONS1. The table itself is derived from the work of Siple and Passell2. More recently a new wind chill index has been developed and is used in BS (EN) ISO 110793

 

Effects of cold on the human body

Two useful terms are used in the assessment of the effects of cold. These are:

• Cold stress: this is the thermal load to which the body is subjected.

• Cold strain: this is the response of the body to cold stress. Examples would include shivering, peripheral vasoconstriction and piloerection (the hairs standing on end in order to more effectively retain heat). Increased cold stress can result in local damage to peripheral tissues (e.g. frostbite to the fingers) or, ultimately, hypothermia and death.

Injuries caused by the cold

Exposure to sub-zero temperatures causes the extremities to become chilled. The cold will affect fingers and toes most. Next are the nose cheeks and ears. Freezing of the local tissues is termed freezing cold injury. When tissue fluids freeze damage is caused by the high concentrations of electrolytes left in any remaining liquid.

Frostnip is commonly used to describe mild freezing. Provided full recovery occurs within 30 minutes of starting the re-warming no further treatment should be necessary. The affected areas of skin will feel leathery.

Superficial frostbite: this is a more severe injury than frostbite. Here, recovery is not so rapid, the thawing process is extremely painful requiring analgesic or even morphine and surgery may be necessary. Those with impaired blood circulation, e.g. those with diabetic vascular disease, are at increased risk from frostbite.

Deep and complicated frostbite: occurs where muscles and deeper tissues freeze. It can cause whole limbs to freeze solid. This is highly unlikely in normal occupational situations. Re-warming must be well controlled. Warm the individual too rapidly and the sudden release of potassium from dead cells could kill them.

Long term effects of freezing cold injury: Freezing cold injury can sometimes lead to long term effects. These include cold sensitisation, chronic pain, residual neurological defects such as loss of touch, joint pain, stiffness and skin and nail abnormalities.

Non freezing cold injury (NFCI): this type of injury results from long exposures to cold, but not necessarily freezing temperatures. Contact with, or immersion, in cold water is an effective cause of NFCI. Water is a good conductor of heat, much better than air. It can therefore conduct heat away from the skin causing temperatures above freezing to become harmful. Examples include Trench foot. Blood vessels in the skin contract to reduce the escape of heat from the body. The foot can become waterlogged and very susceptible to even slight injury or infection. Another long term effect is cold sensitisation.

Hypothermia

Hypothermia occurs when the body’s core temperature falls below 35⁰C (the normal temperature is around 37⁰C). It can happen when it is so cold that the body’s heating mechanisms fail to cope. Wind and evaporation can accelerate hypothermia. Evaporation occurs when the body is wet, either through rain, immersion in water or sweat.

Immersion in cold water can itself cause hypothermia. As mentioned above, water in contact with skin is more effective at removing heat than air in contact with the skin because it is a better conductor.

The physiological effects of falling core temperature are summarised below:

 

35⁰C – loss of manual dexterity, e.g. unable to strike a match.

32⁰C – loss of consciousness

26⁰C – death from heart failure resulting from hypothermia

Controlling the risks from cold

• Elimination of the task

Mechanisation has considerably reduced the need for manual work to be carried out in refrigerated warehouses in the food industry. Often, the only people to be found in these areas now are maintenance engineers.

• Controlling the environment

 

Almost by definition it is not feasible to vary the temperature of indoor environments. They are cold for a purpose. Nor is it practical to create a “heat refuge” in say, a cold store where staff can spend some time warming up.

 

As far as outdoor cold working environments are concerned, it could be argued that global warming is a major step towards controlling the risks posed by the cold. More seriously, however, “heat shelters” could be built in outdoor environments to give workers a temporary refuge from the cold.

 

Further guidance on working in cold environments can be found in BS 79154 and the more recent BS EN ISO 157435

 

• Consideration of the individual

The physiological mechanisms for dealing with thermal stress work less well in older people. These mechanisms can also be compromised by alcohol and drug abuse. It is also important to check with the pharmacist whether any prescribed drugs could also compromise these mechanisms. General fitness also helps individuals cope with thermal stress. Obesity can be a handicap. It can make thermal clothing harder to don. And the increased insulation provided by the fat can actually result in heat stress for cold worker required to carry out physical work in thermally protective clothing.

Careful consideration should be given to those with conditions which may make them more susceptible to the cold. Examples include vibration white finger, Raynaud’s disease, impaired circulation, skin grafts and previous adverse effects to cold exposure. Ideally, such individuals should not be exposed to the cold.

Those with disabilities can also be vulnerable. For example individuals with mobility impairment have lower average metabolic rates. Their bodies are therefore less likely to counteract cold environments. This needs to be taken into account when issuing thermal protection.

Spinal injuries can have dramatic effects on an individual’s ability to respond to cold. This is because the injury can prevent blood vessels near the surface from dilating and contracting. This in turn prevents them from responding to heat or cold and they get colder or hotter quicker than non-impaired colleagues.

All of these individual factors have to be taken into account in risk assessing individuals for work in cold (and hot) environments.

• Acclimatisation

Physiologically, acclimatisation or training in cold environments is actually of little actual benefit. However, anecdotally, such training can help psychologically. It helps individuals develop behaviour patterns to help deal with the cold.

• Personal Protective Equipment

Selecting the right clothing to protect against the cold is a major challenge. Conflicting demands have to be met. The degree of thermal insulation provided by clothing increases with its thickness. But too many bulky layers become unwieldy. It also takes a lot of time and effort simply to put them on and take them off.

If physical work is carried out (e.g. lumberjacks in the forest) then too much clothing can result in sweat. This in turn wets the clothing and reduces its ability to provide effective insulation. Evaporation of the sweat in turn leads to more cooling.

Gloves of course make any intricate work using hands difficult. The fingerless gloves used by Martin and his employees in the cobbler’s shop are a compromise.

To make matters worse, below 0⁰C gloves are not effective enough. Mittens must be worn which further impair dexterity.

Where gloves need to meet more than one requirement further problems can arise. For example, staff cutting meat in a cool room require metal inserts in their gloves to protect against cutting. Unfortunately metal is a good conductor of heat and so will make the hands even colder.

All these factors make the selection of thermal clothing a difficult task. Further guidance is given in BS EN ISO 110796. Specifications for gloves for use against the cold can be found in BS EN 5117.

Further reading

Comprehensive coverage of all aspects of the thermal environment can be found in a British Occupational Hygiene Society (BOHS) publication The Thermal Environment8. This should be read in conjunction with a recent addendum9, published in 2009.

The HSE web-site provides comprehensive guidance on thermal comfort which includes a short section on cold stress. This can be found at http://www.hse.gov.uk/temperature/infor ... stress.htm.

 

 

 

 

 

 

References

1. HUNTER’S DISEASES OF OCCUPATIONS, 10th edition, (2010) page 529

2. Dry atmospheric cooling in sub-freezing temperatures. Siple PA, Passell CP. Proceedings of the American Philosophical Society (1945).

3. BS (EN) ISO 11079 (2007) Ergonomics of the thermal environment – Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects BSI London.

4. BS 7915 Ergonomics of the Thermal Environment – Guide to the Design and Working Practices for Cold Indoor Environment (1998)

5. BS EN ISO 15743:2007 Ergonomics of the thermal environment Cold workplaces. Risk assessment and management.

6. BS EN ISO 11079: 2007 Ergonomics of the thermal environment – Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects.

7. BS EN 511:2006 Specification for protective gloves against the cold.

8. TG12 The Thermal Environment (second edition), 1996 A Youle, Et al. published by the BOHS.

9. TG12 The Thermal Environment Addendum to the second edition 2009, A Youle, Et al. Published by the BOHS.

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by rlj » Thu Jan 06, 2011 5:03 pm

 

FFS Martin I ain't reading all that, lifes too short.

 

LOL

 

it is all health & safety - also a good advertisement for our shop!

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Lee » Thu Jan 06, 2011 8:52 pm

 

I read it all, Martin that's brilliant. Hows trade been this week?

 

we have had some fantastic days since Christmas, today better than a 'normal' Saturday :D better that it is my day off! :D

 

before Christmas the SNOW killed us! :( the Saturday just before was a disaster for the whole of my town, the market packed up and closed before 11 am to give you an idea of the effect of the weather - were forecast more tomorrow, but hopefully it wont be anything like it was. this afternoon I was telephoned from a national radio station in USA for a live chat - which was great fun. this story is the biggest thing I have ever been involved in there is not an hour that goes by without a comment.

petercoulson » Thu Jan 06, 2011 6:55 pm

 

I think Martin needs some better weather to get out on the bike, far too much time on his hands

 

your right there Pete, but my calculation is just another 6 weeks to go! :D then all of us will be out again..

I know that is optimistic but I always am! :D

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