Use in Scandinavia
The negative impact is dominated by worn particles emitted to air during the use of studded tyres here in Scandinavia (67–77 percent).
Nokian Tyres criticises our study and claims the following, according to, among others, the magazine Teknikens värld, which we quote below in italics:
“Due to wear, studded winter tyres emit large particles that have a diameter of at least 10 micrometres (PM10). It is problematic that the study is based on the assumption that people are constantly exposed to PM10 particles.”
In its reply, the company does not acknowledge that through wear studded tyres also emit smaller particles that adversely affect health. According to Ferm and Sjöberg (2015), the use of studded tyres gives rise to 20–50 mg of airborne particles that are 2.5–10 micrometres in size (PM2.5–PM10) per vehicle-kilometre. It is these particles, ranging in size from PM2.5 to PM10, that we have included in our calculations – they are linked to various health problems such as heart and lung diseases. Additionally, we have only included particles from wear during the winter half of the year when studded tyres are actually used. Everyone is not always exposed to this wear, which is why an average absorption of particles (up to 10 micrometres) for the European population (Goedkoop et al., 2013) was used in the study.
“Even those who drive vehicles with non-studded winter tyres benefit from studded tyres which make the road surface rougher, giving non-studded tyres better grip.”
This effect has been taken into account in the statistics that we use regarding the reduced number of accidents through the use of studded tyres instead of non-studded tyres (Elvik, 1999).
“A ban on using studded tyres would not improve the environment or public health, conversely the situation would worsen because decreased use of studded tyres would increase the need for sanding, which is a major source of particles.”
Our study shows that public health is adversely affected through the use of studded tyres. According to our knowledge, there is also no direct link between reduced use of studded tyres and increased sanding. We see several additional potential alternatives to studded tyres, such as electronic anti-skid systems and durable asphalt. But all these need to be studied further from a life cycle perspective in order to investigate both advantages and disadvantages and to enable a statement to be made about their potential as alternatives to studded tyres. At present, we cannot assess the health effect of the alternatives. The statement above has therefore not been proved.
“In the debate on winter tyres it is important to highlight both road safety and environmental aspects without being biased towards either studded or non-studded tyres.”
We agree. In this study we have concentrated on the impact of studded tyres on human health. Both negative and positive. Here, we have approached the issue neutrally and evaluated all differences between studded and non-studded tyres that we have been able to identify as relevant in the context.
The result from our calculations shows that particle wear on roads from the use of studded tyres contributes substantially to negative impact on people’s health, and exceeds the positive effect in Scandinavia in the form of saved lives. We are working within a relatively large range, where cautious figures must be compared to each other, and high estimates in a corresponding way.
For Sweden this means – if we make a high estimate – 770 life years saved, thanks to the studs, and about twice as many life years lost due to particle wear alone. If we make a low estimate – 60 life years saved in Sweden – the negative health effects of particle wear may be about seven times higher than the positive effects.
Production of studs
According to our study, the production phase causes 23–33 percent of the negative impact on health, nearly all of which is outside Scandinavia.
“The studs contain extremely small quantities of cobalt, and only on the cemented carbide stud pins to strengthen them. The cemented carbide pins on a studded tyre contain in total about 5 grams of cobalt.”
In our calculations we have assumed that a studded tyre contains a maximum of 5 grams of cobalt.
“The tyre industry uses nearly exclusively, up to 95 percent, recycled cemented carbide.”
Recycled cemented carbide has also had an impact on people’s health in the mining sector. In our calculations we have used a degree of recycling comprising 10–14 percent of cemented carbide, based on the average global recycling for tungsten, which is the main component of cemented carbide (Graedel et al., 2011; Leal-Ayala et al., 2015). If the tyre industry has a higher degree of recycling, this is good news. We welcome information from Nokian Tyres which could in that case support this statement.
“Cobalt does not only exist in the Democratic Republic of the Congo (the DRC), mining also takes place in Finland, for example.”
Global production of cobalt is dominated by the DRC, accounting for 50 percent (USGS, 2017), which is why in our calculations we presuppose that all mined cobalt comes from there. If we instead assume that 50 percent of mined cobalt comes from the DRC – and in an extremely simplified way assume that the rest is produced in countries where safety and health data from the mining industry can be represented by such data in the USA – the total negative health impact linked to the use of studded tyres decreases by 4–10 percent. We know that this is a certain underestimate of the health impact.
We are therefore sure of our conclusion that studded tyres, generally, also take lives in areas that do not have wintry weather, and that this accounts for roughly a third of the negative impact on health. A manufacturer claiming otherwise should trace their own resource flows and show that they deviate from those prevalent in the market.
Cobalt in general
To conclude, several actors have reacted to the fact that the use of cobalt in studded tyres is small in relation to other uses, such as in electronics and vehicle batteries.
Yes, this is of course true. But in this particular study we are focusing on the health effects of studded tyres. The problems of cobalt – and the human suffering connected to the mining – are also significant in this comparison. This is what we are saying.
It does not mean that we are making light of the serious problems caused by cobalt overall. On the contrary.
Chalmers recently organised the world’s first conference on the subject of battery recycling. In conjunction with this, battery researcher Martina Petranikova highlighted in the media the need to recycle cobalt and other materials. In March a colleague demonstrated the possibility of recycling cobalt and other materials from motor vehicles to achieve a less wasteful material turnover in society. In an earlier study our group also looked at alternatives to replace cobalt with materials based on the more common element carbon (Arvidsson and Sandén, 2017).
We must also understand that many major areas of application contain great potential for utilising cobalt material again and again. However, not in studded tyres (Furberg et al., 2019). In the wear of the studs, most of the cemented carbide is emitted into the environment and is lost from the cycle that we humans can use – in principle, dispersed forever.
Anna Furberg, Sverker Molander and Rickard Arvidsson