Occupational Exposure Assessment of Airborne Chemical Contaminants Among Professional Ski Waxers

Abstract

Background:

Ski waxes are applied onto the skis to improve the performance. They contain different chemical substances, e.g. perfluoro-n-alkanes. Due to evaporation and sublimation processes as well as mechanically generated dust, vapours, fumes, and particulates can contaminate the workroom atmosphere. The number of professional ski waxers is increasing, but occupational exposure assessments among professional ski waxers are lacking.

Objectives:

The aim was to assess exposure to airborne chemical contaminants among professional ski waxers. It was also a goal to construct a ventilation system designed for ski waxing work operations.

Methods:

Forty-five professional ski waxers were included. Personal measurements of the inhalable and the respirable aerosol mass fractions were executed in 36 different waxing cabins using Conical Inhalable Sampler cassettes equipped with 37-mm PVC filters (5 µm) and Casella respirable cyclones equipped with 37-mm PVC filters (0.8 µm), respectively. Volatile organic components were collected using Anasorb CSC charcoal tubes. To examine time trends in exposure patterns, stationary real-time measurements of the aerosol mass fractions were conducted using a direct-reading Respicon® sampler.

Results:

Mean aerosol particle mass concentrations of 3.1 mg·m⁻³ (range: 0.2–12.0) and 6.2 mg·m⁻³ (range: 0.4–26.2) were measured in the respirable and inhalable aerosol mass fractions, respectively. Real-time aerosol sampling showed large variations in particle concentrations, with peak exposures of ~10 and 30 mg·m⁻³ in the respirable and the inhalable aerosol particle mass fractions, respectively. The custom-made ventilation system reduced the concentration of all aerosol mass fractions by more than 90%.

INTRODUCTION

Cross-country skiing is a popular winter sport in Europe and is performed in two different styles: Classic cross-country skiing and freestyle ski skating. Various chemical products are used during preparation of the skis, in order to optimize performance. In ski skating style, different types of ski wax glider products are used to reduce the friction between the ski sole and the snow surface. The most frequently used glide wax product groups are powders and solid blocks. In classic style, such products are used only in the front and end parts of the skis, while grip waxes are used in the middle part to increase friction. Several ski wax products are available, designed for different style arts, and snow and weather conditions. Ski sole cleaning products are used after each event to remove the ski wax products. The ski wax glide products are also widely used in other winter sports, such as biathlon, alpine skiing, snowboard, ski jumping, and combined.

The glide wax products contain petroleum-derived aliphatic hydrocarbons (HCs), perfluoro-n-alkanes (PFAs), or polyfluorinated n-alkanes (Gambaretto et al., 2003; Ludwig, 1995; Rogowski et al., 2005; Axell, 2010). The grip waxes are typically mixtures of paraffin waxes, synthetic rubber and oils, and sometimes a mixture of synthetic resins (Axell, 2010). The ski sole cleaning products usually contain petroleum solvents, either neat or in a mixture with limonene (Axell, 2010).

Ski waxes are often applied onto the ski sole by an ironing process at elevated temperatures up to 180°C, resulting in melting, evaporation, and sublimation of the products, prior to mechanical removal of excessive wax products and further processing. Thus, there is a potential for contamination of the workroom air. Despite this potential, only a few small studies of exposure are available. Particle concentrations of up to 2.4 mg·m⁻³ by personal sampling during the melting of paraffin glide wax or up to 9.6 mg·m⁻³ during application of fluorine-containing glide waxes have been reported (Dahlqvist et al., 1992; Liesivuori et al., 1994). A larger model experiment study showed mass concentrations of up to 32.2 mg·m⁻³ in the inhalable aerosol fraction and particle number concentrations ranging from 650000 to 900000 particles·cm⁻³ with particle sizes ranging from 50 to 350nm when applying PFA-based glide wax powders, respectively (Freberg et al., 2013). Thus, the chemical composition of the ski waxing products and the limited information on exposure levels among professional ski waxers support the need for more thorough studies of exposure.

Respiratory problems during ski waxing have been reported in case studies (Strøm and Aleksandersen, 1990; Hansen, 1991; Bracco and Favre, 1998). Also reduced lung diffusion capacity for carbonmonoxide and pulmonary symptoms among a limited number of professional ski waxers have been reported (Dahlqvist et al., 1992; Knöpfli et al., 1992).

Ski preparation for high-performance athletes is usually performed by professional ski waxers employed by national, regional, local, and commercial ski teams. However, the majority are employed in ski resorts, ski shops, and ski wax-producing companies. Also a large number of consumers are regularly exposed during ski preparation for leisure skiing.

Ski waxing cabins used during World Cup competitions most often have no ventilation system, or at best limited general ventilation systems. The competitions take place at different locations with different infrastructure limiting the possibilities to optimize working procedures for the ski waxers. Also the time pressure and the stressful working conditions for the ski waxers reduce the potential for preventive actions and exposure control. Thus, general ventilation systems have only limited preventive potential due to the aerosol emission during the ironing process close to the waxer’s breathing zone.

The use of ski waxing products, as well as the number of products, has increased to a large extent during the last decade, while the chemical composition of the products are continuously evolving (Axell, 2010). Especially the use of fluorinated products has increased lately, and e.g. the well-known persistent organic pollutant perfluorooctanoic acid has recently been determined at elevated levels in the blood of professional ski waxers (Freberg et al., 2010; Nilsson et al., 2010). Thus, there is a need for better knowledge about chemical exposures among professional ski waxers, both with regard to qualitative and quantitative aspects.

The aim of this study was to assess the occupational exposure to airborne contaminants among professional ski waxers during ski preparation in World Cup events. A further goal was to construct and evaluate the efficiency of a custom-made ventilation system designed for ski waxing work procedures. This study is part of a larger study assessing pulmonary health in ski waxers.

METHODS

Study design

Professional ski waxers working for the larger skiing teams participating in the World Cup competitions were invited to participate in the study. Contact with the teams was established several months prior to the examinations. Altogether 7 cross-country teams, 10 biathlon teams, and 3 combined sports teams were approached. All teams accepted the invitation.

From these teams, 47 subjects were asked to participate in the study. All subjects agreed to participate. The number of participating ski waxers from each team ranged from one to seven, recruited from 13 different nations. Two of the ski waxers were excluded because they did not complete the full measurement program. The only criterion for inclusion was being a professional (highly skilled) ski waxer working for one of the international skiing teams. The study was performed over a period of two winter seasons at three different locations in Norway (Trondheim, Beitostølen, and Oslo) during six different events in 36 different waxing cabins.

The study was approved by the Regional Ethical Committee for medical research in Norway (REC South East). Each participant provided an informed written consent to participate in the study.

Sampling strategy

Based on a previous model experiment study (Freberg et al., 2013), personal size-selective aerosol samplers were used to collect both the inhalable and the respirable aerosol fractions. Personal active sampling on charcoal tubes was used to collect volatile organic components (VOC). The sampling equipment were mounted on belts, allowing the samplers to be located in the ski waxer’s breathing zone. The pumps were stopped if the waxers occasionally left the waxing cabin. The sampling times were selected to cover the full work shifts related to ski preparation in connection to the specific day of competition. The sampling times varied between 33 and 486min (mean 197min). Stationary direct-reading size-selective Respicon® aerosol samplers were mounted in six randomly selected waxing cabins, in order to examine time trends in exposure patterns, possible peak exposure scenarios, and particle size fraction distributions (inhalable, thoracic, and respirable aerosol fractions). The Respicon® samplers were located as close as possible to the waxing tables (at 1.6 m height at distance 1–2 m) without interfering with the work execution.

Sampling equipment

The inhalable aerosol fractions were collected using Conical Inhalable Sampler sampling cassettes (Casella Measurement, Bedford, UK) equipped with 37-mm PVC (5 µm) filters connected to a SKC sampling pump operated at a sampling flow rate of 3.5 l·min⁻¹ (SKC Universal XR Pump Model PCXR8, SKC Ltd, Dorset, UK). The respirable aerosol fraction was collected using Casella respirable cyclones (Casella Measurement, Bedford, UK) equipped with 37-mm PVC filters (0.8 µm) connected to in-house built PS101 pumps (National Institute of Occupational Health, Oslo, Norway) operated at a sampling flow rate of 2.2 l·min⁻¹. The direct-reading Respicon® sampler was operated at a flow rate of 3.11 l·min⁻¹ (Helmut Hund GmbH, Wetzlar, Germany) (Koch et al., 2002).

Organic vapours were sampled using Anasorb CSC charcoal tubes (SKC 226-01) at a sampling flow rate of 0.05 l·min⁻¹ with SKC Pocket Pumps.

All the aerosol and VOC air sampling pumps were calibrated before and after the collections using BIOS Defender 510-H and 520-L digital flow calibrators (BIOS International Corporation, Butler, NJ, USA).

To measure particle number concentrations according to size, a Scanning Mobility Particle Sizer (SMPS) model 3034 (TSI Incorporated, MN, USA) was used. The SMPS measures continuously the number of particles in the size range from 10 to 487nm.

Analytical methods

The mass of aerosol collected on the filters was determined by weighing the filters before and after aerosol collection using a Sartorius MC 5 Micro Balance weight scale (Sartorius AG, Göttingen, Germany) in a climate-controlled room (20±1°C, 40±2% relative humidity) after conditioning the filters for at least 2 days. The conditions in the climate-controlled room were monitored continuously. Each of the filters was discharged prior to weighing (Po210 α-emitter, Staticmaster™, Nuclear Products Co., CA, USA).

The charcoal tubes were desorbed in 1.5ml carbon disulphide (CS₂) overnight, and the trapped components were determined using an Agilent 5890 gas chromatograph (GC) (Agilent Technologies, Santa Clara, CA, USA) with an Agilent HP-5 (0.32mm × 25 m, 1.05 µm film thickness) capillary column and flame ionization detector (FID), as previously described (Freberg et al., 2013). The air concentrations were calculated from the respective sampled air volumes.

Reagents

PFA-C₆/C₁₀/C₁₂/C₁₆/C₂₀ (≥98%) were obtained from Chiron AS (Trondheim, Norway). PFA-C₂₄ (≥99.5%), N-alkanes (C₆, C₁₀, C_15–20, and C₂₆) and limonene (≥99%) were purchased from Fluka (Buchs, Switzerland). The purity of the N-alkanes (C₆, C₁₀, C_15–19, and C₂₆) were ≥98%, while the purity of the N-alkane (C₂₀) was >97%. Spectrograde 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113) was obtained from Pfaltz & Bauer (Waterbury, CT, USA). GC-grade CS₂ was purchased from Ratburn (Walkerburn, Scotland, UK).

Chemical characterization of ski wax products and air filter samples

Eleven of the most frequently used powder glider wax products from six ski wax manufacturers were characterized with regard to PFA content and distribution, based on information from the waxing team managers. These products are suitable for the most common snow and weather conditions. All 90 filters collected for the personal exposure assessment [both inhalable (n = 45) and respirable (n = 45)] were characterized for PFAs and HCs.

The sampling filters were transferred to 4-ml vials after gravimetric determination and desorbed in 3ml of Freon 113 and sonicated for 15min. An aliquot of the Freon 113 solution was subsequently transferred to a sample vial prior to GC-FID determination (Agilent 7890GC, temperature program: 35–250°C (held 28.5min) at 10°C·min⁻¹, using an Agilent DB-210 capillary column (0.32mm × 30 m, 0.5 µm film thickness). The injection volume was 1 µl. The calibration curves were in the range 1.0–50.0 ng·µl⁻¹ for the PFA-C_{12–16 and 20} and n-alkanes (C_{15–20 and 26}), while the calibration curves for perfluorotetracosane were in the range 2.0–100.0 ng·µl⁻¹. PFA-C₁₈ was quantified based upon PFA-C₁₆ standards. A mass of 20mg of each of the powder glider wax products was dissolved in 10ml of Freon 113, prior to additional dilution in Freon 113 (20×). The PFAs were subsequently determined using the GC-FID method.

Ventilation intervention study

The custom-designed ventilation system was equipped with a suction aluminium cap air unit (220×26cm), with the active suction slot of 4mm along the circuit circumference of the cap. The suction hood was mounted ~30cm above the waxing table, with ergonomic friendly design allowing vertical adjustments. The system was driven by an air ventilation fan with a capacity of 1.500 m³·h⁻¹ (220V), resulting in a negative air pressure of 1.6 hPa in a typical waxing cabin (45 m³). A scheme of the custom-made ventilation system is shown in Fig. 1.

1.

Specifications of the custom-made fume hood ventilation system mounted above the waxing table. The hood can be regulated vertically in order to optimize ergonomic work positions.

To evaluate the effect of the ventilation system, an intervention approach was applied, by comparing the generated aerosol concentration when preparing a series of 15 pairs of skis, with and without the ventilation in use. This procedure was performed during application of a representative powder and a solid block glide wax product separately.

One professional ski waxer performed all of the waxing in the experiment. The waxing iron and the skis were cleaned after each work operation, and the room was ventilated and allowed to reequilibrate between the experiments. The personal sampling of the inhalable and the respirable aerosol mass fractions and the generated particle number concentrations were counted using a SMPS as previously described (Freberg et al., 2013).

Statistics

In cases of skewed distribution, the distributions were log transformed. For these variables, the geometric mean (GM) is presented. Otherwise the arithmetic mean (AM) is given. Group differences were assessed by Student’s t-test for independent samples. Least square regression analysis was carried out to assess the relationship between two independent variables, yielding Pearson’s correlation coefficient as the measure of association. A two-tailed significance level of P < 0.05 was accepted as the level of statistical significance. The data were assessed using the Statistical Package for Social Sciences (SPSS), version 19.

RESULTS

Exposure assessment

‘The personal aerosol measurements’ showed mean particle concentrations of 3.1 mg·m⁻³ (range: 0.2–12.0) and 6.2 mg·m⁻³ (range: 0.4–26.2) in the respirable and the inhalable aerosol fractions, respectively (Table 1). The correlation between the inhalable and the respirable particle masses on the filters (µg) was highly significant (Pearson’s R = 0.96; P = 0.01).

Table 1.

The concentrations of particles and volatile organic components assessed by personal sampling in 45 ski waxers^a

	Respirable (mg·m−3)	Inhalable (mg·m−3)	Aliphatic hydrocarbons, C5–C13 (ppm)
Meanb	3.1	6.2	4.3
Minimum	0.2	0.4	0.01
Maximum	12.0	26.2	35.5.
SD	2.8	5.9	6.1

^aThe mean measurement time was 198min (range: 33–486min).

^bArithmetic mean.

When comparing the exposure levels among ski waxers preparing ski for the cross-country national teams (both classic and ski skating styles) with ski waxers working for biathlon and combined national teams (only ski skating style), the measured particle mass concentrations were significantly lower (P = 0.02) for the cross-country waxers, both in the respirable and inhalable aerosol fractions (Table 2).

Table 2.

Particle concentrations (mg·m⁻³) in ski waxers from biathlon and combined teams and cross-country teams

	Biathlon and combined (N = 19)			Cross-country (N = 26)
	Meana	Range	SD	Meana	Range	SD
Respirable	4.4b	0.21–12.0	3.2	1.8b	0.4–5.9	1.8
Inhalable	8.6c	1.09–26.2	6.6	3.9c	0.4–17.0	4.8

^aArithmetic mean.

^b,c denotes P = 0.02 for comparisons of concentrations with the same letters.

The stationary direct-reading Respicon® measurements performed in one of the waxing cabins during each of the six World Cup events showed that the aerosol concentrations varied substantially within the work shift, illustrated by occasional peak exposures up to around 10 and 30 mg·m⁻³ in the respirable and inhalable aerosol fractions, respectively. However, the mean concentrations over the work shifts in the six waxing cabins were 1.07 mg·m⁻³ (range: 0.15–2.26) and 1.62 mg·m⁻³ (range: 0.26–3.23) in the respirable and the inhalable aerosol mass fractions, respectively. Figure 2 shows typical real-time aerosol particle mass concentration profiles over a work shift.

2.

Variations in particle concentrations in a waxing cabin using a direct-reading Respicon® sampler during a 7-h work shift. The races started at 10:00 AM and 12:45 PM.

The volatile organic compound measurements showed that the main compounds in the VOC samples were aliphatic HCs with carbon chains between C₅ and C₁₃, with a mean concentration of 4.3 ppm (range: 0.01–35.5). Limonene in concentrations above the limit of detection (>0.003 ppm) was determined in 29 of the 45 samples, with a mean level of 0.4 ppm (range: 0.02–2.6). Low concentrations of other solvent vapours were occasionally measured in a limited number of samples ranging from 0.002 to 0.003 ppm toluene (n = 5), 0.02 to 0.98 ppm ethanol (n = 5), and 0.11 ppm ethylbenzene (n = 1) (not tabulated).

Chemical characterization of ski wax products and air filter samples

The analyses of 11 commonly used glider wax powders showed that PFA-C₁₆ was the dominating component in most of the powders (Table 3). Two of the waxes contained PFA-C₁₆ only, while the other powders also contained PFA-C_12–24 in various amounts, but mainly C₁₄ and C₁₈.

Table 3.

Relative mass of different PFAs (C₁₂–C₂₄) in 11 analyzed powder glide ski waxes (%;w/w)

	C12	C14	C16	C18	C20	C22	C24
A	Nd	Nd	97.0	Nd	Nd	Nd	Nd
B	Nd	Nd	98.8	Nd	Nd	Nd	Nd
C	Nd	Nd	43.1	25.5	13.6	4.6	1.4
D	Nd	1.9	42.3	25.2	15.0	5.3	1.3
E	4.5	Nd	49.5	20.5	11.5	3.1	1.3
F	8.2	15.8	65.3	7.5	3.7	0.3	Nd
G	6.0	2.8	33.9	23.7	14.4	4.6	2.1
H	2.4	10.3	67.3	4.9	2.4	Nd	Nd
I	25.2	39.4	20.5	5.7	2.0	Nd	Nd
J	23.2	36.6	24.5	5.5	2.0	Nd	Nd
K	18.3	29.1	21.5	11.9	6.0	1.1	Nd

Nd = Not detected. Deviation from 100% when summing the individual components in the products indicates the presence of other components in the products that was not analyzed.

No exact information on the products used on the day of air sampling was available because the teams use wax mixtures which they do not want to disclose. Nevertheless, the components recovered from the collected air sampling filters were in general similar to those determined in the 11 most commonly used powder wax products. Neat HC and PFA compounds accounted for on average 70% of the total mass (µg) on the filters (range: 25–100%), with a distribution of 75:25 between PFA and HC components, respectively. Thus, the PFA components represented on average ~50% of the total mass on the sampling filters. The correlation between the total mass on the filters and the summed masses of PFAs and HCs was high (Pearson’s R = 0.99; P < 0.01) (Fig. 3).

3.

The association between the masses of HCs and PFAs and the total mass on 45 air filters collected from the workroom air.

Efficiency of custom-made ski waxing ventilation system

The custom-made ventilation system was evaluated during waxing sequences of 15 pairs of skis with powder and solid block glide waxes. The particle concentration was reduced by 95% (P = 0.02) in the inhalable and respirable aerosol fraction during the application of powder glide wax compared with identical application sequence at non-ventilated circumstances (Table 4). For the solid block glide wax, the concentration was reduced by 92% (P = 0.01) and 88% (P = 0.02) in the inhalable and respirable aerosol fractions, respectively.

Table 4.

Effects of a custom-made ventilation system, showing the percentage reduction in measured aerosol particle mass concentrations and number particle concentrations during the application of powder and block gliders onto 15 pairs of skis each (mean time for each work operation: 38min, range: 33–42)

	Respirable aerosol fraction (mg m−3)a			Inhalable aerosol fraction (mg m−3)a			Particle concentration (particle numbers cm−3)b
	VS:offc	VS:on	% reduction	VS:off	VS:on	% reduction	VS:off	VS:on	% reduction
PGd	8.96	0.44	95*	14.1	0.73	95*	472000	61200	87***
BGd	2.68	0.33	88*	3.72	0.30	92**	71000	17000	76****

^aArithmetic mean.

^bGeometric mean.

^cVS = Ventilation system.

^dPG = Application of powder glide wax; BG = Application of solid block glide wax.

*P = 0.02. **P = 0.01. ***P < 0.01. ****P < 0.001.

The particle size distribution and number concentration were measured by SMPS during the waxing sequences. The particle number concentrations (particles·cm⁻³) were 87% (P = 0.003) and 76% (P < 0.001) lower for the powder glide wax and the solid block glide wax products, respectively, when the ventilation system was in use. The majority of the particles measured, regardless of whether the ventilation system was turned on or off, varied in size (GM) between 50 and 130nm for the powders and between 150 and 350nm for the block glide waxes, respectively.

DISCUSSION

Exposure assessment

Due to the highly competitive environment, the ski waxers did not want to disclose individual formulas of their wax mixtures or application methods. Thus, we have sparse information on the participating ski waxer’s specific work operations, division of work tasks, work intensity, and specific ski waxing products in use during the sampling period. This limits the potential for detailed comparisons between individual ski waxers, ski waxing locations, and ski waxing teams. The general picture is, however, that most of the ski waxers performed all relevant work procedures. The exposure levels measured in this study therefore represent an average of most ski waxing work procedures during ski waxing for world class professional competitions.

To our knowledge, only one small field study of personal exposure to glide waxes among professional ski waxers exists. They reported levels up to 9.6 mg·m⁻³ during application of powder gliders among three waxers (Liesivuori et al., 1994). However, the glide wax product range and chemical content have changed substantially since then. We have, however, recently investigated in detail the exposure levels associated with different individual ski waxer work operations in a controlled experimental study (Freberg et al., 2013). Application of glide wax powders was identified as the individual work operation being the major contributor to the aerosol generation, illustrated by average inhalable and respirable mass concentrations of 32.5 and 18.6 mg·m⁻³ (GM), respectively. The application of solid block glide waxes and grip waxes yielded mean mass concentrations between 0.15 and 0.40 mg·m⁻³ (Freberg et al., 2013).

The exposure levels measured in this study are on average one-fifth of the air concentrations measured when powder glider waxes were applied intensively in our experimental study, and approximately one order of magnitude higher than the exposure levels related to the intensive application of solid block gliders only. Thus, it is reasonable to assume that work operations in relation to application of powder glide waxes are the dominating source of exposure during this study.

The ski waxer work intensity varies throughout the work shift. Some of the work can be executed before the competitions, while most of the work usually is carried out as close as possible to the race start, in order to take advantage of updated information on snow and weather conditions and ski testing results. Thus, it was of interest to measure variations in exposure by direct-reading measurements in order to identify possible peak exposures. The large variations in exposure with two major exposure sequences are illustrated by two subsequent races taking place at 10:00 AM and 12:45 PM, respectively (Fig. 2). The peak exposure period started ~1h prior to the start in both races. The lower aerosol concentrations measured during the ski preparation for the second race are probably because some of the initial ski preparation for the second race was conducted at the same time as the preparation for the first race. It is reason to believe that application of powder glide waxes substantionally contributed to these two peak concentrations, which has been reported recently (Freberg et al., 2013). Furthermore, the direct-reading Respicon® samplers were mounted in a distance of 1–2 m from the waxing tables, and it can be assumed that the measured peak concentrations might have been even higher if personal sampling had been carried out.

The average air particle concentrations were significantly higher in the ski waxers working for biathlon and combined national teams compared with the ski waxers working for the cross-country teams. Biathlon and combined styles only use the ski skating technique, while cross-country use ski skating and the classical style. Only gliders are used during ski skating, while a mixture of gliders and grip waxes are used in cross-country. It is therefore reasonable that ski waxers in biathlon and combined styles had higher exposure to particles than ski waxers in the cross-country teams. The high degree of secrecy resulting in sparse information on the actual products in use, the work task division between the ski waxers within the teams, and working procedures in general limits the potential for further analysis and comparisons between individual waxers, locations, etc.

There exist to our knowledge no occupational exposure limit (OEL) for PFA fumes. The OEL for paraffin wax fume in Norway is 2 mg·m⁻³ in the inhalable aerosol mass fraction (National Work Environment Authority, 2013). It might be reasonable to compare with this OEL because several of the ski waxing products (especially solid block glide waxes) also contain similar paraffin wax compounds. The reported inhalable personal mean aerosol mass concentration in this study exceeded the Norwegian OEL for paraffin wax fume with more than 200% (P < 0.001).

However, as demonstrated in this study with high PFA levels in the 11 ski wax glider products and in the workroom air samples, the major sources of contamination are PFAs. Furthermore, a recent study has shown that fluorine-containing ski waxes may also contain traces of perfluorinated carboxylic acids (PFCAs), and increased blood levels of a range of PFCAs in the blood of professional ski waxers have been detected (Freberg et al., 2010). Information on toxicological effects of PFAs is in general not yet well documented, but several studies have addressed concerns about perfluorinated compounds and human health hazards (Lau et al., 2007; Tsai, 2009; Environment Canada 2012; Borg et al., 2013).

The VOC exposure levels measured in this study are within the VOC concentration range measured during the model experiments (Freberg et al., 2013). The limonene concentrations measured in this study are in agreement with the concentrations measured previously when using a limonene-containing product only, while the alkane concentrations in general are slightly lower. In practice, ski wax removal products are used only in limited time frames and mostly at the end of the work shift, and the calculated mean VOC levels were well below (P < 0.001) the OELs in Norway (25 ppm for the aliphatic HCs and limonene).

Custom-made ski waxing ventilation system

In contaminated workroom atmospheres, exposure reduction by ventilation is in general to be preferred over personal protective equipment. The use of point ventilation is difficult due to the long length and narrow width of the skis. Furthermore, respirators are difficult to use in practice during ski waxing.

Several different variables were identified as important factors in the construction of the custom-made ventilation system. The system should be ergonomically user friendly and should not influence negatively on the work tasks to be executed. Secondly, it was a goal to construct a transportable system that easily could be mounted. Due to the low densities of the powder waxes, the critical step in the construction was to balance the need for efficient ventilation along the whole length of the ski without blowing away the applied glider wax powder prior to ironing. On the other hand, the high area of the suction cap unit, as well as the capabilities for ventilation of ultrafine particles, was requiring high air flows.

The solution to these needs was to construct the suction unit cap with broader width than the ski sole and to make restrictions in the air flow by allowing suction only in a small slot along the circuit circumference (Fig. 1). A combination of a cap length and width of 220 and 26cm, respectively, combined with a slot width of 4mm (∼200cm² suction area), provided a good combination between applicable air streams, mechanical requirements, and ergonomic needs. Furthermore, the angle of the suction unit side walls at the slot relative to the base line of the suction unit was critical, and an angle of 37° provided most efficient ventilation based on visual evaluation using generated smoke. This is in accordance with the literature (Perry, 1963). A cap width of 26cm was required in order to not be in conflict with powder glider wax sprinkling processes, while a length of 220cm (~20cm longer than the longest skis in use) was required in order to obtain also efficient ventilation longitudinally.

The ventilation cap unit was allowed to be vertically adjusted. A distance of 30cm was identified as the lowest possible distance to the ski sole in order not to be in conflict with the powder application. This distance was also in accordance with ergonomic needs and was not in conflict with the practical ski waxing work operations.