Environ. Sci. Technol. 2009, 43, 7824–7830
Release of VOCs and Particles During Use of Nanofilm Spray Products ASGER W. NØRGAARD,† KELD A. JENSEN,† CHRISTIAN JANFELT,‡ FRANTS R. LAURITSEN,‡ PER A. CLAUSEN,† AND P E D E R W O L K O F F * ,† The National Research Centre for the Working Environment, Denmark, and Faculty of Pharmaceutical Sciences, University of Copenhagen, Denmark
Received July 1, 2009. Revised manuscript received August 31, 2009. Accepted September 1, 2009.
Here, we present emission data on VOCs and particles emitted during simulated use of four commercial nanofilm spray products (NFPs) used for making easy-to-clean or selfcleaning surfaces on floors, ceramic tiles, and windows. The aim was to characterize the emitted VOCs and to provide specific source strength data for VOCs and particles released to the air during use of the products. Containers with NFP were mounted on a spray-stand inside a closed stainless steel chamber with no air exchange. NFPs were sprayed in amounts corresponding to 1 m2 surface toward a target plate at a distance of 35 cm. Released VOCs were measured by a combination of air sampling on Tenax TA adsorbent followed by thermal desorption GC/MS and GC/FID analysis and real time measurements using a miniature membrane inlet mass spectrometer. Particles were measured using a fast mobility particle sizer and an aerosol particle sizer. A number of VOCs were identified, including small alcohols, ketones and ethers, chlorinated acetones, a perfluorinated silane, limonene, and cyclic siloxanes. The number of generated particles was on the order of 3 × 108 to 2 × 1010 particles/m3 per g sprayed NFP and were dominated by nanosize particles.
Introduction Nanofilm spray products (NFPs) are a relatively new type of industrial and consumer products for surface coating. Most of the NFPs induce nonstick properties when applied to surfaces. The NFPs are available for a wide range of different surfaces, e.g., bathroom tiles, floors, textiles, and windows. Some NFPs are designed to mimic the nonstick and selfcleaning abilities known from the leaves of the lotus plant (1). The NFPs are sprayed onto a surface, and a thin film is formed by self-organization during evaporation of the solvent (2). The film arises from the sol-gel process (3, 4) involving series of hydrolysis and condensation reactions between organo-functionalized silanes and in some cases nanoparticles of, e.g., metal oxides or silica. The result is an interconnected rigid network of functionalized organo siloxanes. The process is similar to the preparation of silica * Corresponding author phone: +45 39165272; fax: +45 39165207; e-mail:
[email protected]. † The National Research Centre for the Working Environment. ‡ University of Copenhagen. 7824
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 20, 2009
sols by polymerization of silicon alkoxides by addition of water and acid catalyst (3). The identity and concentration of all ingredients added to the commercial products do not appear in the product information available from the distributors. Consequently, the current knowledge of the chemicals added to the products is limited and insufficient for risk assessment. Previous studies assessing potential exposure, risk, and health effects have been carried out for cleaning and water proofing agents (5-7) some of which may contain compounds that are somewhat similar to those in the NFPs. Water proofing agents for leather and textile containing mixtures of fluorinated polymers (e.g., fluoro acrylate) and isoparaffinic hydrocarbons have caused several outbreaks of acute respiratory symptoms (6). Use of an early type of NFP, Magic Nano, resulted in several outbreaks of lung injury in Germany in 2006, which caused the manufacturer to withdraw a pressurized spray can product for ceramic tile coating. The airway effects have been reported in a recent bioassay study (8), the casual agents, however, remain unknown. To understand such side effects it is important to know the volatile and particle exposure in detail. Such data is still not available. The aim of this study was therefore to investigate the VOC and particle emissions during use of four different and common NFPs available on the Nordic, German, and UK markets.
Experimental Section Materials. Four kinds of NFPs were investigated in this study: One for coating of nonabsorbing floor materials (NFP 1), one for coating of ceramic tiles (NFP 2), one for glass coating with photo catalytic titanium dioxide (NFP 3), and one multipurpose coating product (NFP 4). NFPs 1, 2, and 3 are delivered in hand pump spray bottles and NFP 4 in a pressurized can. According to the material safety data sheets (MSDS) supplied by the distributor, NFP 1 contains 2-propanol (solvent) and unspecified fluorosilane; NFP 2 contains ethanol (solvent), methanol and unspecified siloxanes; NFP 3 contains ethanol and titanium dioxide; NFP 4 contains propane/butane (propellant) and kerosene. Amounts needed for treating surfaces are 10-40 mL/m2 depending on the product. The selected NFPs are believed to be relatively representative for nonwater based NFPs. A few other products taken off the shelf with similar brand names and applications emitted VOCs similar to those found for the NFPs of this study. The following authentic standards were used for verification and quantification of identified compounds: 1-propanol (99%), 1-chloro-2-propanone (96%), 1,1-dichloro-2-propanone (96%), 1,3-dichloro-2-propanone (95%), 2-butanone (99.5%), 3-methyl-2-butanone (98.5%), 3-hexanone (96%), 3-octanone (98%), octamethylcyclotetrasiloxane (98%), decamethylcyclopentasiloxane (97%), methyltripropoxysilane (97%), chloromethyltriisopropoxysilane (96%), 1H,1H,2H,2Hperfluorooctyltriethoxysilane, isopropyl acetate (99.5%), 1,1diethoxyethane (98%), and a kerosene reference standard in hexane were all obtained from Sigma-Aldrich in Denmark (Brøndby, DK). 1H,1H,2H,2H-perfluorooctyl trimethoxysilane (95%) and 1H,1H,2H,2H-perfluorodecyl trimethoxysilane (95%) were obtained from Apollo Scientific (Cheshire, UK). Spraying and Air Sampling. The NFP spray tests were carried out in a closed aerosol chamber (0.66 m3) made of stainless steel (Figure 1a and 1b) equipped with two fans (air flow: 410 m3/h) to ensure mixing. The chamber tightness was evaluated using 25 ppm butane as tracer. The test showed constant concentrations (1.2% ppm for a 90 min period as 10.1021/es9019468 CCC: $40.75
2009 American Chemical Society
Published on Web 09/18/2009
FIGURE 1. (a) Schematic of the 0.66 m3 stainless steel chamber used for the experiments. (b) The steel grid seen from above. Fans, target plate and holders for spray apparatus and sample tubes are in fixed positions. measured using a ppbRAE photo ionization detector (RAE systems, San Jose, CA). For spraying, the NFP containers were mounted in an automatic actuator to facilitate remote controlled spraying. An amount needed for coating 1 m2 surface (∼8 g for NFPs 1-3 and 13.6 g for NFP 4) was sprayed horizontally toward a stainless steel target plate (46 cm × 28 cm) mounted at a distance of 35 cm from the spray nozzle. The NFP was released over a maximum period of 25 s. Air and particle sampling were performed at a position 20 cm behind the spray nozzle (Figure 1b) by the use of fresh 1/8” Teflon tubes (60 cm) connected to adsorbent tubes and the MIMS outside the chamber. Air samples (200 mL) for GC and GC/MS analysis were taken from the chamber using PerkinElmer Tenax TA tubes and a flow controlled pump (100 mL/min) (Gillian Gilair5, Sensidyne, U.S.). Two samples were taken within the first 5 min after the release of NFP and additional samples were taken with 10 min intervals throughout the experiment. The MIMS was operated continuously for about 20 min. The temperature and relative humidity was monitored by two Gemini Tinytag data loggers (Gemini data loggers ltd., West Sussex, UK) placed inside the chamber. The average temperature and relative humidity in all four experiments were 25 ( 2 °C and 23 ( 2% RH, respectively.
The chamber was ventilated for at least 2 h after each experiment, followed by cleaning of both chamber and target plate using 96% ethanol on a cotton cloth. All experiments were initiated with determination of the chamber background using both MIMS and Tenax samples. Real Time MIMS Analysis. A portable miniature mass spectrometer, the Mini10 (9-12), equipped with a heated tubular membrane inlet was connected to the aerosol chamber for real time monitoring of VOCs emitted during the spray process. A detailed description of the Mini10 and its performance with heated membrane inlet has been published elsewhere (13). The Mini10 operates at a pressure of 10-5 - 10-4 mbar, which often results in [M+1]+ ions due to chemical ionization taking place inside the ion trap. In short, the membrane inlet was a 37 mm long polydimethylsiloxane (PDMS) tube (0.66 mm ID, 1.19 mm OD) from Technical Products Inc. (Decatur, GE) and, positioned inside the vacuum space of the mass spectrometer and connected to the outside via two 1/16” stainless steel tubes. Air from the aerosol chamber was pumped through the inside of the PDMS tube at a flow rate of about 1 L/min. Before entering the PDMS tube, the sample air passed through a heated steel tube (100 °C) in order to increase diffusion of chemicals through the membrane. Nonpolar VOCs diffuse through the membrane into the mass spectrometer, where they are ionized, separated by mass, and detected. The Mini10 was scanning in the range m/z 50-550 at a scan speed of 5/second; the software was set to average over 200 scans. The use of a PDMS membrane for sample introduction does not result in artifact siloxanes in the MIMS equipment (14). GC/MS and GC/FID. The Tenax TA tubes were analyzed using a PerkinElmer ATD 400 thermal desorber (TD) coupled to a PerkinElmer Turbomass GC/MS or a HP 5890 GC/FID. Desorption was carried out at 250 °C for 20 min. For general ATD 400 operational details, see Klenø et al. (15). The column used for both GC/MS and GC/FID was 60 m × 0.32 mm with 0.25 µm film thickness (Varian Chrompack Sil-19). The oven program was as follows: Initial temperature at 35 °C held for 2 min, ramp 1: 5 °C/min to 120 °C held for 0 min, ramp 2: 10 °C/min to 250 °C held for 2 min. Helium was used as carrier gas at a flow of 1.5 mL/min. Liners and detectors were kept at 200 °C. The MS was scanned in the range m/z 50-600 for EI experiments. For CI experiments the scan range was m/z 70-600 with isobutane as ionization gas at a pressure of ∼1 × 10-4 bar. Compounds observed by GC/MS were identified by search in the NIST 08 mass spectral library (16) and comparison with authentic standards if available. Criteria for positive identification of compounds were satisfactory match (match >800 and probability >70%) in NIST 08 and a retention time of ( 0.02 min to that of an authentic standard. Quantification with GC/FID was carried out using six-point calibration curves made from three individually weighed solutions of authentic standards in methanol. In cases where no standard could be obtained, the FID responses were estimated from those of similar compounds: The response factor of diisopropoxymethane was estimated from 2-ethyl hexanol; cyclohexasiloxane and cycloheptasiloxane were estimated from cyclotetrasiloxane and cyclopentasiloxane; 1H,1H,2H,2H-perfluorooctyl triisopropoxysilane was estimated from 1H,1H,2H,2H-perfluorooctyltrimethoxy- and 1H,1H,2H,2Hperfluorooctyltriethoxy-silane. The concentrations listed in Table 1 are the average of four consecutive air samples taken within 40 min. The quantification limit was e5 µg/m3 per g released product for most of the identified compounds. Particle Measurements. Particles were measured using a TSI FMPS model 3091, which measures the electrical mobility particle size (Dm) in 32 channels with midpoints ranging from 6 to 523 nm. The FMPS was operated with the column heater at 50 °C and sampling was conducted through the standard FMPS cyclone model 1031083 (d50 ) 1 µm). To ensure VOL. 43, NO. 20, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
7825
TABLE 1. Identified VOC/SVOCs for each NFP; CAS numbers are in Brackets. All Concentrations Are Measured by TD-GC-FID and Shown as µg/m3 per g Released Product and Reported As the Average of Four Samples NFP 1 a
1-propanol 71-23-8) 1,1-diethoxy ethanea (105-57-7) diisopropoxy methaneb (2568-89-0) 2-butanonea (78-93-3) 3-methyl-2-butanonea (563-80-4) 6-methyl-3-heptanonea (624-42-0) 1-chloro-2-propanonea (78-95-5) 1,1-dichloro-2-propanonea (513-88-2) 1,3-dichlor-2-propanonea (534-07-6) isopropyl acetatea (108-21-4) octamethylcyclotetrasiloxanea (556-67-2) decamethylcyclopentasiloxanea (541-02-6) dodecamethylcyclohexasiloxaneb (540-97-6) tetradecamethylcycloheptasiloxaneb (107-50-6) 1H,1H,2H,2H-perfluorooctyl triisopropoxysilanec limonenea (138-86-3) methyl cyclopentanea (96-37-7) 2-methyl hexanea (591-76-4) 3-methyl hexanea (589-34-4) heptanea (142-82-5) octanea (111-65-9) nonanea (111-84-2) decanea (124-18-5) undecanea (1120-21-4) dodecanea (112-40-3) tridecanea (629-50-5) tetradecanea (629-59-4)
139 ( 13 49 ( 10
123 ( 11 46 ( 6 9(3 24 ( 3
