Do Tire Studs in Cars Save or Take Lives? A Life Cycle Assessment on Human Health Impacts

Conference poster, 2017

Tire studs are being used during winter in a number of countries worldwide in order to ensure a more secure and reliable mobility in those countries. For example, more than 60% of the passenger cars in Sweden use studded tires during wintertime. A tire stud consists of a body made out of aluminum and a pin, which consists of cemented tungsten carbide with cobalt (WC- Co). This is an extremely hard and tough material that improves the driving conditions on slippery winter roads. In this way, human health impacts associated with traffic accidents and fatal crashes are reduced. On the other hand, the use of tire stud pins causes human health impacts since inhalable particles worn from the road can lead to respiratory and cardiovascular diseases. Other factors, including emissions of toxic substances and occupational health hazards during the production of tire studs, also contribute to negative health impacts. Emissions from ore tailings during mining are known to release considerable amounts of toxic metals and the high energy use during WC-Co production indicate the possibility of notable emissions related to energy production. Furthermore, tungsten is a conflict mineral and thereby contributes, among other factors, to civil warfare in e.g. the Democratic Republic of the Congo. Cobalt is not defined as a conflict mineral but is also mined in that region. The aim of this study is to answer the question of whether the use of tire stud pins results in net health improvements or not. This was assessed by conducting a cradle to grave life cycle assessment (LCA) focusing on human health impacts related to the use of tire stud pins. All processes from the extraction of tungsten and cobalt, to waste management of tire studs, were considered. The impact category human health was operationalized by the disability adjusted life years (DALY) indicator, and a sensitivity analysis was conducted for relevant parameters, including the varying tungsten content of tire stud pins. An explorative scenario accounting for human health impacts related to tungsten being a conflict mineral was also employed. This was done in order to investigate if the results would be affected applying a wider system boundary. This study can support societal decisions related to tire studs, including both requirements and prohibitions, by evaluating from a life cycle perspective to what extent tire studs succeed with their intended purpose. Their purpose of enabling a more secure mobility in colder countries by saving lives and avoiding injuries.