Live and Let Die? Life Cycle Human Health Impacts from the Use of Tire Studs

Studded tires are used in a number of countries during winter in order to prevent accidents. The use of tire studs is controversial and debated because of human health impacts from increased road particle emissions. The aims of this study are to assess whether the use of tire studs in a Scandinavian studded passenger car actually avoids or causes health impacts from a broader life cycle perspective, and to assess the distribution of these impacts over the life cycle. Life cycle assessment is applied and the disability-adjusted life years indicator is used to quantify the following five types of health impacts: (1) impacts saved in the use phase, (2) particle emissions in the use phase, (3) production system emissions, (4) occupational accidents in the production system, and (5) conflict casualties from revenues of cobalt mining. The results show that the health benefits in the use phase in general are outweighed by the negative impacts during the life cycle. The largest contribution to these negative human health impacts are from use phase particle emissions (67–77%) and occupational accidents during artisanal cobalt mining (8–18%). About 23–33% of the negative impacts occur outside Scandinavia, where the benefits occur. The results inform the current debate and highlight the need for research on alternatives to tire studs with a positive net health balance.

. Input data for calculations applied in the low and high impact scenarios. The low and high impact scenarios are denoted LS and HS, respectively. Descriptions of the parameters are provided in Section 2.1 to 2.5 in the article. WC-Co= tungsten carbide with cobalt, Al=aluminum and DRC=the Democratic Republic of the Congo. Number of tire studs in four studded tires [-] 480 540 The number of tire studs in one studded tire is 119-135.
Ref. [1] Cobalt content in a WC-Co pin [%] 6 10 Ref. [1] System boundary 1: Lives saved in the use phase (DALYuse save) R [-] 0.02 0.05 Compared to non-studded winter tires, studded ones reduce accident rates with 2% on bare roads and 5% on icy or snowy roads. Elvik [3] Nacc [accidents/year] 0.00051 0.0011 Calculated Nacc tot [-] 860 1200 The lowest and highest annual number of accidents with passenger cars using non-studded winter tires in Norway in winter SSB [4] Ntot car [-] 2 700 000 2 400 000 The lowest and highest annual number of total registered passenger cars in Norway during the time period of 2012-2016 were 2 400 000 in 2012 and 2 700 000 in 2016, respectively.

Parameter [unit] Value Comment Reference LS HS
Scar non-studded [-] 0.64 0.46 The lowest and highest annual average share of passenger cars with non-studded winter tires in Norway in the time period of 2012-2016 were 46% in 2014 and 64% in 2016, respectively.
NPRA [6] Ltire [year] 6 7 Winter tires are approximately used for 6-7 years. Swedish Transport Administration [7] DALYcar acc [ This data was given for each individual fatal accident as described in the statistics from the reference. When ranges were given for the age of the affected person (e.g. 35-44 year), the high value (e.g. 44 year) was applied in the LS and the low value (e.g. 35 year) in the HS. For the age group of 75+, Ldeath was set equal to LEXSca in the LS. For exact values, see the reference.
Transport Analysis [8] Nsevere car acc [-] 1 300 1 600 The lowest and highest annual number of persons who got severely injured in passenger car accidents in Sweden during the time period of 2013-2017 were 1 300 in 2017 and 1 600 in 2013, respectively. See information on "Persons killed, severely and slightly injured in road traffic accidents reported by the police by age, group of road users and sex" from the reference.
Transport Analysis [8] 6 The average disability weight of a fracture in the hand, short term, with or without treatment at 0.01 and of a fracture in the neck of femur, long term, without treatment at 0.4 were assumed in the LS and HS, respectively.
Salomon, et al. [10] Lsevere [year] 0.083 0.5 Time of recovery from fractures in general is about 1-6 months. MEDIBAS [11] Nslight car acc [-] 10 000 12 000 The lowest and highest annual number of persons who got slightly injured in passenger car accidents in Sweden during the time period of 2013-2017 were 10 000 in 2014 and 12 000 in 2013, respectively. See information on "Persons killed, severely and slightly injured in road traffic accidents reported by the police by age, group of road users and sex" from the reference.

Transport Analysis [8]
DWslight [-] 0.008 0.008 The average disability weight of other injuries of muscles and tendons (consisting of sprains, strains and dislocations other than shoulder, knee or hip) at 0.008 was assumed for both the LS and HS.
Ref. [10] Lslight [year] 0.042 0.5 Time of recovery from a sprained ankle is about two weeks to half a year which was assumed to be valid for sprains in general.

MEDIBAS [11]
Ntot car acc [-] 10 000 9 100 The total number of passenger car accidents were obtained by summing the number of such accidents causing fatal or severe personal injury with the number of slightly injured passenger car drivers (the latter was used as an assumption for the total number of passenger car accidents with slight personal injury due to limited data). See information on "Road traffic accidents with fatal or severe personal injury reported by the police including persons killed or severely injured, by involved type of traffic elements" and "Persons killed, severely and slightly injured in road traffic accidents reported by the police by age, group of road users and sex" from the reference. Ref. [12] Ii [e.g. kg CO2 eq to air]

Many different
Many different LCIA data for typical non-Chinese WC-Co production was provided from ref. [17] and LCIA data for aluminum production (tire stud bodies) was obtained from ref.
[18] applying allocation by cut-off, the ReCiPe 2008 method and the hierarchist perspective for "aluminium production, primary, ingot, RoW". The weight of a tire stud body is approximately 0.85g [2]. i = climate change, ozone depletion, human toxicity, photochemical oxidant formation, particulate matter formation and ionizing radiation. LCI data for typical non-Chinese WC-Co production was provided from ref. [17] and LCIA data for aluminum production (tire stud bodies) was obtained from ref.
[18] applying allocation by cut-off, the ReCiPe 2008 method and the hierarchist perspective for "aluminium production, primary, ingot, RoW". The weight of a tire stud body is approximately 0.85g [2]. See further Section 2. People involved in heterogenite mining [20], which is the most abundant cobalt mineral in Katanga in the DRC where about 50% of the global cobalt production takes place [21].

Furberg, Arvidsson and
Elgstrand and Vingård [20], Decrée, Pourret and Baele [21] Sfatal acc [-] 0.025 0.025 In general, fatal accidents in artisanal mining occur to 2.5% of the miners involved in a year. This was assumed to be valid for artisanal cobalt mining specifically.
ILO [22] LEXDRC  USGS [24], KP [29] 2. Data for Production System Accidents Figure S1. Flowchart for the included foreground and background processes in the production system of tire studs. APT=ammonium paratungstate, WC=tungsten carbide and WC-Co=tungsten carbide with cobalt.  Table S3. Ecoinvent processes and industrial categories applied for inputs and outputs in the foreground and background system. Note that no Ecoinvent process was available for Alamine 336, why a literature source was applied following ref. [17]. Furthermore, note that a specific calculation was conducted for the artisanal mining of cobalt, see Section 2.4 in the article. Some products are not given an industrial category but are still shown here since they were needed for further calculations.

Product Ecoinvent process [18] Industrial category [19]
Alamine 336 Alamine 336 production according to Vahidi Table S6. Contributions to health impacts. The low and high impact scenarios are denoted LS and HS, respectively. DALY=disability-adjusted life years, DALY tire stud =the net DALY of the tire studs in a studded Scandinavian passenger car, DALY use save =years saved by using studded tires instead of non-studded winter tires during winter, DALY total lost =years lost by using studded tires during winter, DALY use em =years lost due to use phase emissions of road particles, DALY prod em =years lost due emissions in the production system of tire studs, DALY prod acc =years lost due to accidents in the production system of tire studs and DALY conflict =years lost due to revenues from cobalt mineral mining. DALY total lost is the sum of DALY use em , DALY prod em , DALY prod acc and DALY conflict . DALY tire stud is equal to DALY use save minus DALY total lost .

Resulting Contributions to Health Impacts
Parameter