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Whether it’s needing to wear socks to bed or peeling off a pair of sweaty boots for relief, we’ve all experienced the urgency of thermal comfort in our feet. So when it comes to working in hot temperatures where strict PPE is still required, could protective footwear actually be putting workers more at risk?
The Middle East and Africa endure some of the most extreme high temperatures globally, meaning that even the most menial work, if done outside in the high sun, can become incredibly hazardous to health. One of the main dangers being heat stress.
Heat stress is the combination of metabolic heat, environmental factors, and clothing or PPE, that leads to an increased heat storage in the body1. This can then lead to more dangerous heat-related illnesses such as heat exhaustion and heat stroke.
In fact, many hot-climate countries have laws in place against working outdoors at certain hours of the day where the sun is at its most intense. But even the most well-intended guidance, if it doesn’t take into consideration our human behaviour around comfort, will not always be heeded correctly. Workers who are uncomfortably hot are more likely to wear their PPE incorrectly, and the discomfort can have a negative effect on their concentration, which opens the door to errors and accidents.
The Health & Safety Executive (HSE), the UK’s authority on occupational safety and health, formally recognises thermal comfort as a risk to workers, as they state that a lack of thermal comfort can make people behave unsafely and impair their decision making2, which puts both workers and businesses at risk.
But what exactly does thermal comfort mean, and how do you identify it in the workplace or worksite?
Hot and bothered
If comfort can be defined by most dictionaries as a state of being ‘physically relaxed and contented’ then thermal comfort, as described by the HSE, is ‘a person’s state of mind in terms of whether they feel too hot or too cold’. In other words, thermal comfort means being comfortable in the temperature that you’re in.
There are several indicators of thermal comfort, which means businesses have to take into account a range of environmental, occupational and personal factors. These include:
Air temperature
This is your ambient temperature, or the general temperature of the room or worksite. There is no set maximum for indoor temperature, as this greatly depends on the work at hand and can usually be combated with things like air conditioning. Outdoors, air temperature can be determined by the heat index which, for Dubai3, recognises temperatures above 35°C as of significant risk to health and safety.
Radiant temperature
This relates to the temperature radiating from objects that are also heat sources, for example hot machinery, ovens and molten materials. The radiant temperature can have significant effects on the temperature of a workplace, and thus should always be accounted for when assessing thermal comfort.
Air movement and speed
These are pretty self-explanatory. A room with closed windows and doors will offer no airflow, and stagnant air can intensify the temperature of the room and make you feel more stuffy and uncomfortable than if a window was open. The speed at which the air flows is also important, as convection (yes, the same process your oven uses to cook food evenly) can carry heat away from the body through air transfer, even in ambient temperatures. This is called convective heat loss.
Humidity
This is the concentration of water vapour present in the air. The problem with high-humidity environments, is that the high concentration of water vapour present stops sweat being able to evaporate. This is pretty important, as we’ll discover later, as sweat is vital to the body’s thermoregulation. An environment can be considered very humid if the concentration of water vapour is over 80%. Certain PPE can also increase or emulate the effects of humidity by stopping this all-important sweat evaporation.
Clothing and PPE insulation
As just mentioned, certain PPE meant to insulate the wearer from high heat or contaminants, can have an adverse effect by trapping sweat inside the non-permeable material. But wearing too much, or the wrong PPE, can also exacerbate the wearer’s thermal comfort. Layering is a great way of allowing the wearer more control over their body temperature, and where possible, minimising the use of unnecessary PPE can also help. A great way to do this is by regularly assessing the risk level to see what PPE is necessary and what could potentially be swapped out for a more comfortable alternative.
Work rate and metabolic heat
These are two very important personal factors to account for when assessing thermal comfort. Work rate, as you can guess, is the rate at which work is performed. This is important as increased physical activity creates more body heat, and increased body heat means the body tries harder to regulate itself, such as by sweating. Metabolic heat on the other hand, is the heat generated by biological processes in the body, and this can be different for every single person. Factors such as height, weight, fitness and age should all be considered when assessing thermal comfort, as they can affect an individual’s tolerance even when other environmental factors are constant.
“cutting off vital sweat evaporation from our feet could contribute to the body’s overall experience of heat stress”
But what does this all have to do with safety footwear? Well, with around 7,000 nerve endings, our feet are incredibly sensitive to touch, pressure, pain and temperature4. And our brain acts as our thermostat in the sense that it sends signals to let us know when we need to put on a pair of socks for warmth or take off our shoes for relief, for example. Because feet are so sensitive, we perceive these signals with much more urgency and immediacy to fulfil whatever the brain is telling us to do, and this can be largely influenced by the factors listed above. It’s all because of how important our feet are to the body’s thermoregulation.
Understanding thermoregulation
Feet play a key part in our body’s thermoregulation. As part of our body’s way of regulating its own temperature, it produces sweat which, when it evaporates away, helps to cool us down. This is known as evaporative cooling. Given that our feet have more sweat glands than the rest of the body, 25% of that sweat escapes from our feet alone5.
In fact, evaporative cooling is an adaptation many species native to hot climates have to survive extreme temperatures. The cooling effect happens as heat energy is used up by the sweat to turn into a vapour. If the sweat can’t evaporate, we can’t cool down. Instead, moisture builds up on the surface of our skin, softening our skin barrier and making it very hot and uncomfortable, which can become a breeding ground for nasty bacteria and fungus.
So, cutting off vital sweat evaporation from our feet could not only cause a lot of discomfort and contribute to the body’s overall experience of heat stress, but could lead to other health issues such as athlete’s foot and fungal nail infections.
Safety vs comfort
Given all we’ve explored so far, it would make sense that comfort could impede your safety when it comes to working in the right shoes. Afterall, we’re more inclined to follow rules if they make life easier for us. But is comfort something that safety shoe manufacturers consider to great lengths, or are safety footwear standards just too stiff to budge on the matter?
To get to the bottom of the safety vs comfort debate, I asked Simon Courtney, Divisional Manager for Personal Protective Equipment (PPE) at SATRA, about the testing and certification process of safety footwear and to what extent it values the comfort of the wearer.
“There are a few rudimentary comfort related tests in the International/European safety footwear, including a heel energy absorption test and a water vapour permeability absorption test on upper materials. However, these are limited and have significant drawbacks. For example, the water vapour permeability and absorption test is carried out on samples of outer and lining materials and is usually taken from sheet material and not from completed footwear due to the difficulty of obtaining adequate samples from potentially very small regions.
“In theory the sheet material will give results which may change when the material has been sewn into the footwear, and hence pierced or attached with adhesive, potentially adding a layer of non-permeable material. The move to a whole shoe test would be better as it would approach testing holistically, e.g. using something like ‘SATRA STM 567 Endofoot (for advanced moisture management testing — AMMT)’6.”
Of course safety is the priority when thinking about getting a product certified. Safety is very broad, and many standards exist to test and certify very specific areas of protection, such as electrostatic discharge and fire or chemical resistance. But as Simon puts it, “the standards are the minimum that a supplier must do to put a product on the market, although they may choose to do additional testing to assess comfort properties should they wish. Users would normally expect that footwear with a greater degree of protection, or protection from several risks, may be less comfortable than footwear that does not. While something like a fireman’s boot may not be as comfortable as a sandal, the wearer would expect this to be the case.
“I think it is possible for the footwear to be comfortable from a cushioning point of view but from a temperature point of view this may be difficult in hot weathers when the level of protection is needed.”
In these cases, it is important to look at other areas of comfort to balance out the wearer’s experience. For example, ensuring that the footwear is the right size and is as lightweight as possible can help to counteract some of the extra exertion a too-large, heavier shoe would impose on the wearer.
When getting to the crux of comfort’s role in safety testing, Simon had a very interesting take. “It is hard to define comfort as it is different for each person and will also relate to their expectations of the footwear.” He explained, “we sometimes define comfort as an absence of discomfort.”
Cool control measures
So what can we do when the situation doesn’t allow for much adaptation for comfort? If you can’t compromise on certain footwear requirements for safety reasons, let’s look at what you can do instead.
Beat the heat
The first step should always be to remove the heat source where possible. If you’re outside, this means avoiding work at peak hours of the day. Many localities have their own laws on this, with work actually prohibited between certain hours. Ensure you’re adhering to local laws at all times.
Rest and remove
Rest scheduling is a practice in most industries involving strenuous or hot environments. Where possible, increase worker’s rest periods, provide shaded rest areas, and allow workers to remove or change PPE whilst resting.
Cotton on
Research has shown that, although foot sweat doesn’t affect the thermo-physiological responses of wearing footwear, it can negatively affect the comfort of the wearer7. Socks are a great barrier between shoe and foot which help to absorb the moisture off the skin, relieving the discomfort from feelings of wetness. Socks made with natural fibres such as cotton or bamboo, have natural moisture-wicking properties which can offer more effective and prolonged comfort compared to socks made of polyester or other synthetic fibres with less absorption. Workers can always carry a change of socks with them to swap over during rest breaks. This can greatly reduce the chances of foot related health problems such as skin infections.
Try tepid
Tepid water helps to alleviate some of the heat stress experienced by our feet. In the same way sweat works, tepid or cool water can carry away the body’s heat from the surface of the skin, which in turn improves blood circulation, alleviating any potential swelling. Allowing workers to wash or soak their feet in tepid water could quickly alleviate foot heat stress. Workers should avoid using cold or ice-cold water, as the sudden drop in temperature can shock the body into contracting blood vessels which will be counterproductive to heat loss.
Shop around
As with any PPE, it’s best to do your research and look for options which are going to offer better comfort to the wearer. Where possible, you should look for breathable and lightweight materials for optimal comfort. Some manufacturers also offer innovative materials, and cushioned or breathable in-sole options. But, always be wary of workers customising their own shoes without consulting the manufacturer or a medical professional, as in-soles can actually do more harm than good if used incorrectly8. Make sure you’re getting the correct size too – comfort starts with the right fit!
Why don’t roads melt in Dubai?
Climate warming has brought about rising concerns for the safety of people all over the world. The summer of 2022 broke records across the globe. For countries not acclimated to the hot weather, like the UK, the 40°C heat caused widespread disruption, even melting the tarmac on some roads and putting train rails at risk of buckling9. The same summer saw parts of the Middle East hit upwards of 50°C, which, at that heat, becomes a public health emergency10.
Much like the roads that are built to withstand higher temperatures, the Middle East has several laws and regulations built into their infrastructure to be able to handle work at high temperatures. No industry is exempt from protecting their workers from heat stress, and by understanding thermal comfort, how to assess it, and how it ties in with heat stress, you can ensure that your business is not only being compliant, but that your workers are able to work safely and comfortably, which is a win-win situation.
When it comes to safety footwear for the hot environment, as Simon had mentioned, additional testing for comfort is an option for both suppliers and manufacturers alike. It may just be one of the distinguishing factors to look out for when you next procure footwear for your workers.
It’s important to remember that there is constant research and development underway by manufacturers to provide the best and latest solutions to end-users. Whether it’s the latest in sole technology, or innovative new materials that are more durable yet breathable, perhaps there is a future where even the most stringent safety footwear can be both safe and comfortable. In the meantime, ensure you’re doing the most to protect the workers you have.
References
- www.cdc.gov/niosh/newsroom/feature/working-in-heat.html
- www.hse.gov.uk/temperature/thermal/#metabolic
- www.dm.gov.ae/wp-content/uploads/2022/08/DM-HSD-GU38-MHSW2_Technical-Guidelines-for-Management-of-Heat-Stress-at-….pdf
- www.perthpodiatrist.com.au/feet-are-sensitive-soles
- www.passaicfootandankle.com
- www.satra.com/test_equipment/machine.php?id=67
- doi.org/10.26174/thesis.lboro. 12030174.v1
- www.hsmemagazine.com/article/middle-eastern-footwear-issues/
- www.theguardian.com/business/2022/jul/19/why-does-britains-tarmac-melt-and-its-rails-buckle-in-heat
- edition.cnn.com/2022/08/19/middleeast/climate-change-heat-humidity-mime-intl/index.html
