Should horses run on tyres?

Horses require year-round exercise even when the conditions outdoors disagree. It’s not that horses particularly mind a bit of mud, but difficult weather conditions can raise the risk of injury and limit options for exercise. The multimillion-pound equestrian industry has adopted technological solutions to address this problem, but those proving most popular raise significant but little-appreciated environmental concerns.

Before we get started, non-equestrian readers will need to understand a couple of pieces of terminology:

• an ‘arena’ is like a sports-pitch for horses. Most commonly, arenas are rectangular areas of around 20x40m although they can be much larger.
• a ‘gallop track’ is like a cross-country running course for a horse, generally at least 3m wide and anything from 800m to a few miles in length. They are largely used for race horses and sports horses.

All weather tyres

In the past, arenas were generally surfaced with grass, sand or woodchip – each material having its own drawbacks. The most popular surface today is a recycled material – shredded vehicle tyres. End of life tyres are in plentiful supply and are difficult and costly to dispose of safely. That makes using them as a surface material very affordable, and a means of recycling a problematic waste.

In addition, the surface doesn’t lose its integrity through biodegradation, like wood chip. It won’t become muddy or slippery in wintery or wet conditions like grass. It’s also less prone to freezing, and it is springy, making it safer to fall on. All in all, a lot of practical advantages.

To make up the surface, tyres are processed into small rubber fragments and mixed with sand to form a soft, grippy surface. This is laid over drainage channels, allowing you to exercise your equine companion in all weathers. On paper, it looks like a win for recycling, and a win for horse owners.

This use of tyre-derived rubber as an “unbound material in sports surfacing” is a recognised end of waste solution. Take the worn tyre off the car and it becomes waste; reprocess it into a sports surface such as an equestrian arena, and according to the Environment Agency it’s no longer waste. However, one of the criteria for a product classifying as ‘end of waste’ under Article 6 of the Waste Framework Directive is that it poses no harm to the environment or human health. Is that the case with tyre-derived surfaces in equestrian settings? I’m not convinced.

Laying down rubber

Tyres are made from a mix of synthetic and natural rubbers, along chemicals such as sulphur, textile and metal reinforcements and fillers such as carbon black and silica. Surfacing arenas, all weather bridleways and gallop tracks means introducing large volumes of post-consumer polymers into the rural environment.

One might argue that, so long as this plastic-type material is contained, that isn’t too much of a problem. However, there are some potential issues.

• Numerous studies have found that tyres also produce somewhat worrying leachates, although the technical advisory group to the project that put together a quality protocol for tyre recovery found that leachate was minimal after 30 days exposure to the environment. However, 30 days of leaching on or near agricultural land still seems somewhat risky.
• Especially in warmer weather, there seems to be a risk that tyre-based surfaces result in people and equines exercising in elevated concentrations of tyre dust. Research indicates that at the levels found near busy roads, tyre dust could be damaging the respiratory health of athletes. Negative effects have been suggested for those regularly exposed to silica sand arenas, and tyre dust could pose similar problems. Surprisingly, my research has turned up no studies investigating the impact of rubber surfaces on equine health. A couple of comments from asthmatics on horse forums, saying they avoid rubber arenas, is all I’ve found.

In practice, though, tyre rubber doesn’t stay put. Much like the tyre it once was, it’s on the move. There are likely to be numerous routes, but I’ll highlight three.

Leaking tyres

While arenas are often fenced, helping to contain the rubber, they regularly require top-ups. One likely vector is the horses’ hooves: as horse owners know, they’re good at picking things up and need ‘picking out’ regularly. Horses travelling in and out of the arena will transport some material in their feet to the yard and stables, from where it can be dispersed around the farm – whether directly, or via mucking out and a sojourn in the muck heap.

Equestrian question: are shredded tyre surfaces the best overall option for arenas and gallop tracks? Photo: Alice Thomson.

In the case of gallop tracks, where the surface is rarely contained, one only needs to watch to see the problem. A galloping racehorse on a deep footing can generate a large amount of kick back from the surface with chunks of tyre rubber spreading to the surrounding grassland. Gallop tracks often cross gradients, providing ideal conditions for escaping rubber to travel.

Smaller plastic particles can escape by other means. At the moment, I have a very lovely light-grey horse to ride. Riding him in the arena in the wet results in a creature with very black legs; so I hose him down to return them to his normal colour. It recently hit me that what I’m washing off is probably a mix of water and fine, carbon black-dyed tyre dust. Rinsing it off means the material entering the wastewater system, and is potentially en route to the ocean.

How much leakage might we be talking about? Unfortunately, numbers are hard to come by, but an estimate is possible. According to the British Equestrian Federation there are 1,037 facilities with an outdoor arena in the UK. Whilst rubber is now the most popular surface, some still use woodchip, sand, or carpet fibre surfaces and there’s no data indicating the percentages.

Assuming (conservatively) that half use rubber chip, and that the average size is 20x40m, that translates into around 20-35 tonnes of rubber per arena, or up to 17,500 tonnes in all. There is probably a strong correlation between top-up levels and leakage. I understand that, while top up requirements vary due to maintenance and use regimes, a typical figure might be a 10-12% top up every six years – or a yearly leakage rate of around 2%. Tentatively, that would mean up to 350 tonnes escaping from arenas each year, equivalent to around 50,000 tyres. That excludes the greater losses from gallop tracks, all-weather race tracks, and bridleways.

The widespread popularity of equestrian sports means this is a global problem. Places like Singapore and Dubai may be higher risk candidates for loss of material than the UK.  The Singapore turf club alone has 3,000 tonnes of polytrack (a mixture of rubber chip, sand and synthetic fibre) stored for future top-ups. Perhaps it should consider changing its name?

Changing tyres

Since rubber surfaced arenas are a new phenomenon and raise important environmental concerns, what’s to stop us simply phasing them out? There are certainly some trade-offs to consider.

• If equestrian facilities are forced to use more expensive surfaces, it will put up the cost for riders.
• Since alternative surfaces are less weather-proof, it could mean fewer days of safe riding, and greater risk of injury.
• Some alternatives, such as shredded carpet, other synthetic fibres, granulated PVC and combinations of these, come with many of the same environmental concerns.

Despite the benefits of tyre-derived rubber as a surface, it seems there is a case for reviewing whether its use in equine arenas and gallop tracks should count as “end of waste”.

Given the leakage, the residence of plastic in the environment and the potential for it to reach rivers and – ultimately – the sea, the use of tyre-derived rubber (and probably also carpet fibre) for equestrian arenas and gallop tracks does seem to be causing environmental harm.

The possibility of leachate reaching agricultural land and the health risks to humans and horses due to tyre dust inhalation also require further investigation.

In the meantime, to minimise risks, equestrian facilities could consider:

• Ensuring manufacturers weather the rubber in advance, so as to reduce leaching.
• Installing kerbs, fences or other means of containment alongside gallop tracks, especially on gradients and near watercourses.
• Looking at the potential to set up wash-down areas for cleaning horses, and filtering the waste water to capture escaping rubber.
• Monitoring top-ups and reviewing how leakage can be minimised.
• Changing behaviour to minimise transport – for example, picking out horses’ feet before leaving the arena or separating rubber from droppings removed from the arena.

Measures like this could help to minimise the environmental impacts of using tyre rubber – and other plastic surfacings, such as carpet fibre and granulated cable sheathing, which seem to pose no fewer problems – and could make the equestrian industry think again about whether synthetic surfacing is really the best option