Artificial Turf and Fibre Wear: The need for a balanced view

As the artificial turf industry faces yet another challenge it is

important that we do not allow the facts to become obscured by this

emotive issue. As recent rumblings from EU focus groups are now

showing interest in fibre wear this topic gains traction in the public

domain, a deeper dive into the topic is warranted. This article

attempts to bring a balanced perspective keeping the emotions in

check.

Let’s begin with the basic premise of fibre wear: When plastic

filaments age they can spilt, erode, and shed from the parent

filament, smaller pieces of plastic which have broken off can find their

way off the field of play, further these ‘fragments’ can be classified as

microplastic particles if they are the correct size category to fall into

this description. The potential for microplastics to be generated by

artificial turf is what is causing some concern with Government

Agencies, NGB’s and NFP organisations following the focus by the EU.

Put very simply artificial turf comprises of, three components, namely:

a backing cloth, also known as primary backing; plastic filaments,

which simulate the appearance of grass; and latex or polyurethane

adhesives, which anchor plastic filaments to backing cloth. There are,

of course, variations on this theme, though, typically, this is how

artificial turf is assembled.

As artificial turf ages, like all plastics it can become brittle: the fibre

can crack, splitting, and discoloration are also frequent outcomes.

When artificial turf reaches the end of life, it is replaced and ideally

can be recycled or repurposed into other products which can then be

reintroduced into the sports sector as ‘new’ products.

The mechanisms which cause artificial turf to age are well known, as

illustrated in the graphic. Wear from foot traffic, ongoing

maintenance, and weathering are the most impactful contributors to

fibre ageing. However, as is the case for all plastics, the plastic also

deteriorates due to UV damage and oxidation.

So why is there alarm associated with artificial turf fibre wear? The

ageing process is not kind to turf. The finger is firmly pointing at those

plastic filaments. Somehow, as the theory goes, simulated grass

blades degrade, thereby potentially shedding smaller fragments of

yarn which can find their way in some circumstances off the playing

surface. Though perhaps a popular and compelling hypothesis, there

exists virtually no science to validate this theory or indeed evidence to

prove this is a problem. Observations have been made of broken fibre

on aged pitches – these are mainly field hockey installations which

have a much higher ration of yarn to infill than the popular 3G pitch.

What is more, site-based observations would suggest the breakdown

of plastic filaments is not a major polluter or an unmanageable hazard

for the industry to control.

In a reality check which is entirely necessary in this debate: strong

and durable, plastic filaments are built to sustain heavy traffic by

studs and cleats. The fibres are also resilient to weathering albeit they

do weather – its plastic after all! As the pitch approaches end of life, it

is possible that those fibres used to form grass blades will start to

deteriorate. Here, the probability of fibre wear increases, as does the

potential for fragments to break off the filaments and part company

with the parent filament. Ongoing maintenance of fields can mitigate

this form of fibre erosion to a significant extent and there are

machines available which hoover up and filter infill thus removing

broken filaments of yarn in doing so, they can be very effective in

‘cleaning the infill of yarn’.

What happens to the fibres?

Plastic yarn filaments can be crushed and split, and they can be

subjected to wear and tear via studs, blades, or cleats. Intact

filaments do not shed smaller particles of plastic until such time as

either aging or erosion precipitates the potential splintering and

fragmentation.

In the case of wear and tear, which can cause yarn fibres to split, finer

filaments can break off and find their way into the infill. As the field

continues to mature over time and with extended use, UV

damage/oxidation of the polymer can occur, causing smaller pieces of

the filaments to become dislodged. Ordinarily, these fragments will

remain trapped in the infill, but they can also migrate to field

perimeters, there to be deposited in the adjacent landscaping or

exceptionally washed into surrounding drainage.

How

How much plastic are we talking about?

While no conclusive, scientific data exists to quantify fibre loss from a

typical artificial turf pitch, several small-scale studies have attempted

to quantify it. Whereas one branch of research equates a loss of pile

height with a loss of fibre, another juxtaposes the weight of “worn”

yarn filaments alongside the weight of “unworn” yarn filaments.

Either way, these studies confirm that only very small quantities of

fibre break off from yarn filaments over time. Furthermore, the timing

of these assessments, most notably what year measurements are

taken in the life of a pitch, can greatly affect the outcomes of these

studies.

Where do these smaller yarn fragments end Up?

The pathway appears to be straight down into the infill to be retained

and contained therein. We know this because the empirical evidence

demonstrates that infill holds yarn fragments. Historically regular

maintenance operations which involve cleaning the infill also collects

yarn fragments, dust etc from the pitch. Yarn has been observed in

the arisings taken during maintenance.

Can the fragments find pathways through the infill, artificial turf backing and into the sub-base and drains?

There is no data to suggest that small fragments of yarn can infiltrate

the base structures and drainage system. Turf systems incorporate

many barriers to inhibit the percolation of smaller particles from

surface to drain, including sand infill which acts as an excellent filter,

the carpet backing, shock pad, levelling layers, sub-base, separator

membranes, and drainage media around pipes. Taken together, these

multiple layers serve as a considerable filter, impeding the entry of

deleterious materials into the drainage system and then transported

into watercourses.

What about nano particles?

When evaluating the finer dust collected from 10-year-old fields, there

is no evidence to support the theory that fibres generate nano

particles. From observations made on samples collected of the yarn

fragments within the infill the fibre appears to breakdown to particles

<50 microns in size. Virtually all the fine fractions in a recovered infill

are small particles of rubber and sand, as observed in this typical

photo showing particles <63 microns. There are yarn fragments, but

they are relatively large in comparison to the sand and rubber

fragments.

Are

Are fragments dispersed in the wind?

It is possible that winds could blow smaller yarn fragments off the

pitch and into the surrounding landscaping. To date, no research has

been conducted to investigate the potential for this. Relatively

speaking, the percentage of small fragments transported off a pitch

by wind will be very small indeed, but we await hard evidence to

verify and quantify this.

Are fragments washed away?

Conceivably, small fragments of yarn could be washed off the pitch

and onto surrounding hard standings if installed, and into drains. This

phenomenon has been mostly observed in older (end of life) pitches

used for hockey, particularly those involving short-pile products or

non-filled (water based) turf. Again, we await substantive research on

this to provide any quantitative data on this potential aspect of yarn

breakdown.

What about turf with no infill?

Many manufacturers of artificial turf systems for sports produce long

pile systems with no infill thus avoiding the inclusion of infill which

contains microplastics. In general, these turf systems containing 4 to 5

x the yarn of filled turf systems. An industry-wide insistence on the

use of durable yarns, extending from manufacturers and vendors to

owners and end-users, will go a long way to minimize any problems

that these heavy fibre-based turf systems may have been perceived

to have.

Maintenance Practices

Maintenance can dramatically reduce the amount of dust and yarn

fragments found in a pitch. Regular, planned maintenance, which

includes cleaning the top layer of the infill over a screen and filter, will

decrease the amount of detritus accumulating in the infill. Regular

maintenance is now regarded as routine for artificial pitches, so

ensuring sites are equipped with suitable maintenance equipment will

go a long way to controlling the materials associated with fibre loss

and perhaps eliminate, the migration of yarn fragments off the pitch

and into the environment.

Comments

Scientific data related to the topic of yarn fragmentation and

migration is very difficult to obtain. Anecdotal evidence is based on

personal observation, and to some extent introduces subjectivity into

the debate. However recent presentations on this topic have grossly

over-estimated fibre loss and the misrepresentation of fibre wear as a

potential environmental crisis. Direct observation using infill sampling

and high-power microscopy corroborate the fact that small quantities

of yarn fragments do find their way into infill; these fragments tend to

break off the parent filament, particularly with end-of-life pitches. No

doubt, sizing particles and gauging their potential to find their way

into the environment will be a critical component of any scientific risk

assessment. Even so, the quantity of small microplastic particles

generated from yarn breakdown is predicted to be very low, especially

when assessed gravimetrically. Common sense should prevail in this

regard, and further independent studies will verify that yarn

breakdown is an issue that the artificial turf industry can control.