Emissions of DEHP‐free PVC flooring

Abstract Degrading 2‐ethylhexyl‐containing PVC floorings (eg DEHP‐PVC floorings) and adhesives emit 2‐ethylhexanol (2‐EH) in the indoor air. The danger of flooring degradation comes from exposing occupants to harmful phthalates plasticisers (eg DEHP), but not from 2‐EH as such. Since the EU banned the use of phthalates in sensitive applications, the market is shifting to use DEHP‐free and alternative types of plasticisers in PVC products. However, data on emissions from DEHP‐free PVC floorings are scarce. This study aimed at assessing the surface and bulk emissions of two DEHP‐free PVC floorings over three years. The floorings were glued on the screed layer of concrete casts at 75%, 85%, and 95% RH. The volatile organic compounds (VOCs) were actively sampled using FLEC (surface emissions) and micro‐chamber/thermal extractor (µ‐CTE, bulk emissions) onto Tenax TA adsorbents and analyzed with TD‐GC‐MS. 2‐EH, C9‐alcohols, and total volatile organic compound (TVOC) emissions are reported. Emissions at 75% and 85% RH were similar. As expected, the highest emissions occurred at 95% RH. 2‐EH emissions originated from the adhesive. Because the two DEHP‐free floorings tested emitted C9‐alcohols at all tested RH, it makes the detection of flooring degradation harder, particularly if the adhesive used does not emit 2‐EH.

Degradation of DEHP-PVC floorings has been extensively studied.
In addition to the relative humidity (RH), other parameters affect flooring emissions. For instance, a rise of pH (alkaline pH, pH > 7) in the concrete slab increases the hydrolysis rate. 27 However, adding a screed layer between the concrete slab and glue/flooring interface will act as a buffer and prevent this rise of pH. 27,28 Temperature also affects flooring emissions, for example, when room temperature increases or when there is a presence of an in-floor heating system. 16,29,30 To prevent premature degradation of plastic floorings, the Finnish protocol RT 14-10984 recommends laying new plastic floorings when the concrete slab surface is <75% RH and bulk is <85% RH. 31 Moreover, selecting low-emitting building material will limit the impact on the indoor air quality. The voluntary Finnish M1 label is a classification intended to help customer discriminate between the building material emissions. 32 It classifies building material from lowest (M1) to highest (M3) emitting. The emissions are tested according to standards ISO 16000-9:2006 and EN 16516:2017 after a 28-day aging period in a ventilated chamber at 50 ± 5% RH and 23 ± 1°C. 33,34 There are various sources of 2-EH emissions: microbes, ethylhexyl acrylate-containing adhesives, and degrading PVC flooringsfor example, containing 2-ethylhexyl plasticisers, or trimellitate, adipate and terephthalate esters plasticisers. [35][36][37] Exposure to indoor 2-EH is not a problem unless the concentration exceeds the irritation potency of 175 µg/m 3 (expressed as RD50 values), which provokes irritation of the respiratory tract and asthma symptoms. 35,38 However, the detection of 2-EH is a strong indicator of DEHP-PVC flooring degradation and indirect proof of occupant exposure to dangerous DEHP as well as to possible microbial growth. 39,40 Alternative plasticisers do not degrade into one major chemical like DEHP does, but produce a mixture of long-chain alcohols. Since the shift to alternative plasticisers, the health risks arising from moisture damage, and possibly microbial growth, are harder to evaluate.
Data on degradation of alternative plasticisers are scarce. 41  In this study, the emissions of two DEHP-free PVC floorings laid at 75%, 85%, and 95% RH were investigated over three years.
Emissions were monitored as 2-ethylhexanol, C9-alcohols, and total volatile organic compounds (TVOC), actively sampled on Tenax TA and analyses with gas chromatography-mass spectrometry. The surface and bulk emissions were simultaneously monitored. The field and laboratory emission cell (FLEC) sampling method was selected to monitor surface emissions as it is the method used to investigate building material emissions by indoor air inspectors and determines how much is emitted from the building material into the indoor air.
The bulk emissions from the plastic floorings were assessed using a micro-chamber/thermal extractor device (µ-CTE) and represent both surface emissions and emissions stemming from the underlying layers of the PVC floorings.

| MATERIAL AND ME THODS
The experimental work was conducted in the laboratory of the Finnish Institute of Occupational Health (FIOH), Finland. Laboratory Services is a testing laboratory T013 accredited by FINAS Finnish Accreditation Service, accreditation requirement ISO/IEC 17025 and the VOC analysis covered by this accreditation.

| PVC-coated concrete slabs
Six concrete slabs were cast into anodized aluminum molds of dimension 280 × 560 × 110 mm. Tubes of 10 mm inner diameter were inserted at 10 mm (surface tube) and 50 mm (bulk tube) below the surface of each cement slab ( Figure 1). Cement-based screed was spread over the surface of the concrete slabs. Two types of PVC floorings were adhered onto the screed with water-based adhesive (approximately 207 g/m 2 ) when the concrete slabs reached 75%, 85%, or 95% RH (measured from the surface tube). The slabs were stored for three years in a clean laboratory under normal room conditions (temperature-controlled room, 21 ± 3°C, no RH data available).

Practical implications
• DEHP-free floorings emit mixtures of long-chain alcohols instead of 2-EH which is emitted from DEHP-PVC floorings.
• Assessing the degradation of PVC floorings in building is more difficult when they no longer emit 2-ethylhexanol in the indoor air.
Only the lowest emitting building material (M1 classified) was selected in this study, and further specifications are listed in Table 1.

| RH measurements
Vaisala HMI41 humidity and temperature probe (serial number C4910014, Helsinki, Finland) was used to measure the RH. The Vaisala probe was sealed overnight in the tube (with Parafilm M) before reading its value. Between measurements, round bars of 10 mm diameter were inserted into the tubes to prevent moisture leakage. In Finland, the national protocol RT 14-10984 provides guidelines for measuring the RH of a concrete structure. 31 Generally, the RH is assessed from two depths (A and B) determined by the structure thickness (d) and the drying conditions of the structure. 31 In case of a bi-directional drying, the depth measurement B (or "surface" measurement) is B = 0.4 × A and the depth measurement A (or "bulk" measurement) is 20% of the structure thickness (A = 0.2 × d). When the drying takes place in one direction only, the measuring depth B remains unchanged but the measurement depth A is 40% of the structure thickness for a maximal value of 70 mm (A = 0.4 × d, with A max < 70 mm). With PVC floorings, the protocol recommends to glue the flooring when the RH is A < 85% RH and B < 75% RH (with B = 0.4 × A). 31

| Measurement of surface and bulk emissions
The VOC (including 2-EH, C9-alcohols, and TVOC) emissions were monitored with FLEC (surface emissions) and µ-CTE (bulk emissions) 1-36 months after laying of the PVC floorings. The same side of the concrete slab was used to monitor the surface emissions, after wiping down dust (FLEC, Figure 1). The opposite side of the slab was reserved to cut pieces of PVC flooring (4 × 4 cm) to measure the bulk emissions (µ-CTE, Figure 1). To avoid loss of moisture, the missing pieces of floorings were replaced with pieces of aluminum. The surface and bulk emissions were simultaneously monitored.
The emission samples were collected following the FIOH guidelines. FLEC sampling is based on ISO 16000-10:2011. 42 The bulk sampling is based on an in-house method, in which the µ-CTE was set to 25°C. The emission samples were actively sampled on Tenax TA adsorbent tubes and analyzed at FIOH following ISO 16000-6:2011 using F I G U R E 1 Details of one coated concrete slab with the location of the field and laboratory emission cell (FLEC), microchamber/thermal extractor (µ-CTE), and relative humidity (RH) measurements (not on scale, dimensions reported in mm)

| RH
The RH profiles of the concrete slabs are presented in Figures 3, 4, and 5. Laying of the PVC floorings initiated moisture redistribution in the 75% and 85% RH concrete slabs which increased their surface and bulk RH. After the laying and moisture redistribution, the surface and bulk RH of the 75%, 85%, and 95% RH-covered concrete slabs continuously decreased. The PVC 2-covered concrete slabs consistently had higher surface and bulk RH than the PVC 1-covered concrete slabs.

| Emissions from the PVC floorings
The Figures 6, 7, and 8 represent the emissions of C9-alcohols, 2-EH, and TVOC from the covered concrete slabs. The concentrations are reported as toluene equivalents.

| TVOC emissions
The TVOC emission profiles of the 75% and 85% RH-covered con-

| D ISCUSS I ON
C9-alcohols were emitted by each of the covered concrete slabs.
This indicates that the PVC floorings contained the C9-alkyl type of plasticisers (Supplementary material figures S1 and S2). These emissions were expected for the PVC floorings laid at high initial RH (eg >85% RH) since degradation is more likely to occur. The 75% RH slabs also emitted C9-alcohols. Therefore, it was concluded that the two investigated DEHP-free PVC floorings emitted C9-alcohols even at 75% RH. For each of the initial laying RH ranges (meaning: 75%, 85%, and 95% RH), the C9-alcohol emissions increased and fluctuated during the three-year study, although the RH of the concrete slabs constantly decreased. Considering the preliminary results presented in this study, C9-alcohol emissions alone might not be a suitable indicator of moisture damage-for example, in the case of PVC 1 FLEC emissions, the C9-alcohol emission level was just below 100 μg/m 2 .h at 75% and 85% RH, while at 95% RH it was just above that value. It would be hard to conclude whether hidden moisture damage is occurring in the concrete based on C9-alcohol emissions alone.
The 2-EH emissions were attributed to the water-based adhesive acryl dispersion (Supplementary material figure S3). 45 5,57 There are no data on the inhalation toxicity of C9-alcohols, but they have been reported as low toxicity compounds. 58 In conclusion, this preliminary study shows that C9-alcohols were emitted above 75% RH. Even though the study was limited In future, it will be important to study the emissions of a higher number of PVC floorings, but also to determine the effects of the concrete pH level, of using a screed layer, or of the room temperature.

ACK N OWLED G EM ENTS
The

CO N FLI C T O F I NTE R E S T
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.